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7.6: Effects of Volcanic Eruptions on Humans and on Earth Systems

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• Steven Earle
• Vancover Island University via BCCampus

Humans have a love-hate relationship with volcanoes. For many reasons humans are attracted to areas with active volcanism, but for several others that we’ve already discussed, they would be wise to stay away.

The key reason that humans like living around potentially active volcanoes is that the soil tends to be fertile, and thus there is the potential to grow enough food to live. For example, some parts of the area around Mt. Merapi in Indonesia (Figure 7.0.1) can support subsistence populations of 8 to 10 people per hectare. [1] In comparison, the typical farm in the United States can feed just under 1 person per hectare ( US Farm Bureau ).

Volcanic soil is good for a number of reasons. One is that volcanic ash and rock fragments are rich in volcanic glass and under weathering conditions glass breaks down quickly to clay minerals so that productive soil can form within 200 to 300 years in favorable climates. [2] Another is that the clays that form from volcanic parent materials are effective at holding onto nutrients such as phosphorous. A third is that volcanic lava or tephra are typically quite rich in some important plant nutrients, such as magnesium and sulphur. Volcanic regions all over the world are know for their fertile soils. Some examples, apart from Indonesia, include the volcanic areas in Italy, much of northern New Zealand, Japan, Hawaii, parts of Africa, and much of the Caribbean.

Volcanoes are also valued for their scenic beauty and recreational opportunities. An example is the Mt. Garibaldi area of southwestern British Columbia (Figure 7.6.1), but there are hundreds of other scenic volcanoes around the world, some of which are immense tourist and hiker attractions (Figure 7.6.2). Many volcanoes are also venues for a wide range of winter sports, and for hot springs, spas and mudbaths. Volcanic regions are also an excellent source of geothermal heat for both electricity and district heating, and of hydroelectric energy from streams.

Many volcanoes are also venues for a wide range of winter sports, and for hot springs, spas and mudbaths. Volcanic regions are also an excellent source of geothermal heat for both electricity and district heating, and of hydroelectric energy from streams. Figure 7.6.3 provides an overview of some of the ways that humans interact with volcanoes, and some of the risks associated with living nearby.

Volcanism and Earth Systems

As already noted in Chapter 1 and Chapter 3 , volcanic eruptions contribute to the Earth’s systems in important ways. For starters, it is widely believed that the water in the Earth’s oceans is at least partly derived from volcanism, and the Earth would not have much in the way of systems without water.

Some of the key roles of volcanic eruptions in Earth systems are as follows:

• Cycling solids (mostly silicates) from depth in the mantle and the crust to surface,
• Cycling volatiles (water and gases) from depth, and thereby influencing organisms and the climate,
• Ejecting both solids and volatiles high into the atmosphere,
• Cycling thermal energy from depth,
• Creating solid surfaces (e.g., islands) that will be colonized by organisms, and
• Creating sloped surfaces (mountains) that influence weather and climate patterns, and will be eroded and weathered.

All of these products subsequently contribute to other Earth system processes in myriad ways.

Media Attributions

• Figure 7.6.1 Photo by Isaac Earle, used with permission, CC BY 4.0
• Figure 7.6.2 Mt. Fuji Summit by Derek Mawhinney, public domain image via Wikimedia Commons, https://commons.wikimedia.org/wiki/F...uji_Summit.jpg
• Figure 7.6.3 Steven Earle, CC BY 4.0
• Dahlgren, R., Saigusa, M., & Ugolini, F. (2004). The nature, properties and management of volcanic soils. Advances in Agronom y, 82 , 114-183. https://doi.org/10.1016/S0065-2113(03)82003-5 ↵
• (Dahlgern et al., 2004) ↵

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Causes of Volcanic Eruptions

Volcanic eruptions are awe-inspiring natural phenomena that have fascinated and perplexed humanity throughout history. These explosive events, driven by the Earth’s internal processes, shape landscapes and impact ecosystems in profound ways. Understanding the causes of volcanic eruptions is crucial for both scientific exploration and mitigating potential hazards associated with volcanic activity.

A volcanic eruption refers to the sudden release of magma, ash, and gases from the Earth’s interior through vents or fissures on the surface. This dynamic process can result in the formation of new landforms , such as mountains, craters, and lava plateaus. Volcanic eruptions vary widely in scale, ranging from minor effusive flows to catastrophic explosive events that can alter global climate patterns.

Significance of Studying Volcanic Eruptions:

Studying volcanic eruptions holds immense significance for several reasons. First and foremost, it provides crucial insights into the Earth’s internal dynamics, helping scientists unravel the mysteries of our planet’s composition and evolution. Additionally, understanding volcanic activity is essential for assessing and managing potential risks associated with eruptions, such as lava flows, pyroclastic flows, and ashfall, which can pose threats to human life, infrastructure, and agriculture.

Furthermore, volcanic eruptions play a pivotal role in shaping the Earth’s surface and influencing ecosystems. The deposition of volcanic materials enriches soils, fostering unique biodiversity in volcanic regions. The gases released during eruptions can also contribute to atmospheric processes, influencing climate patterns on both local and global scales.

Types of Volcanic Activity:

Volcanic activity manifests in various forms, each with distinct characteristics and consequences. The two primary types of volcanic eruptions are effusive and explosive.

• Effusive Eruptions: These eruptions involve the relatively gentle release of magma, often resulting in the flow of lava. Lava may emerge through fissures or vents, forming shield volcanoes or lava plateaus. Effusive eruptions are typically associated with low-viscosity magma, allowing it to flow more freely.
• Explosive Eruptions: Characterized by violent and sudden releases of pressure, explosive eruptions eject ash, gases, and volcanic rocks into the atmosphere. This type of eruption can result in the formation of composite volcanoes, calderas, and pyroclastic flows. Explosive eruptions are often linked to high-viscosity magma, which traps gases and builds up pressure beneath the Earth’s surface.

In summary, understanding the causes and mechanisms behind volcanic eruptions is crucial for scientific inquiry, risk assessment, and environmental management. By delving into the intricacies of volcanic activity, researchers can unravel the mysteries of our planet’s dynamic processes and develop strategies to mitigate the potential impact of volcanic events on human communities and the natural environment.

Earth’s Interior Structure

Magma formation, tectonic plate boundaries, volcanic hotspots, volcanic triggering mechanisms, historic volcanic eruption.

The Earth’s interior is composed of several distinct layers, each characterized by unique physical and compositional properties. These layers, from the outermost to the innermost, are the crust, mantle, outer core, and inner core. The study of the Earth’s interior structure is known as seismology, and it relies on the analysis of seismic waves generated by earthquakes to infer the properties of these layers.

• The Earth’s outermost layer is called the crust.
• It is relatively thin compared to the other layers, ranging from about 5 to 70 kilometers in thickness.
• The crust is divided into two types: continental crust, which forms the continents, and oceanic crust, which underlies the ocean basins.
• Composed primarily of solid rocks, the crust is rich in silicate minerals .
• Beneath the crust lies the mantle, extending to a depth of about 2,900 kilometers.
• The mantle is predominantly composed of solid rock, but it can exhibit semi-fluid behavior over geological timescales, allowing it to flow slowly.
• This layer experiences convection currents, driven by heat from the Earth’s interior. These currents play a crucial role in the movement of tectonic plates.
• Below the mantle is the outer core, extending from a depth of approximately 2,900 to 5,150 kilometers.
• The outer core is composed mainly of molten iron and nickel . The liquid state of these metals is inferred from the inability of shear waves (a type of seismic wave) to travel through it.
• The movement of molten iron and nickel in the outer core generates Earth’s magnetic field through a process called the geodynamo.
• The innermost layer of the Earth, extending from a depth of about 5,150 kilometers to the center at approximately 6,371 kilometers, is the inner core.
• Despite high temperatures, the inner core remains solid due to intense pressure.
• Composed mainly of iron and nickel, the inner core’s solid nature is inferred from the behavior of seismic waves.

The transitions between these layers are not sharp boundaries but rather gradual changes in temperature, pressure, and material properties. The Earth’s interior is a dynamic system with heat flows, convection currents, and other processes that contribute to the planet’s geological activity and surface features, such as earthquakes, volcanic eruptions, and the movement of tectonic plates. Seismological studies, in conjunction with other geological and geophysical methods , continue to enhance our understanding of the complexities of the Earth’s interior structure.

Magma formation is a process that occurs beneath the Earth’s surface, where rocks melt to create a molten mixture of minerals. This molten material, known as magma, is a key component in the formation of igneous rocks and is often associated with volcanic activity. The process of magma formation involves a combination of heat, pressure, and the composition of the Earth’s mantle.

Here are the primary factors and processes involved in magma formation:

• Heat is a fundamental factor in magma formation. As one descends deeper into the Earth, temperatures increase. The heat needed for magma formation comes from several sources, including the residual heat from the planet’s formation, radioactive decay of certain elements in the Earth’s mantle, and heat generated by the movement of molten material.
• Pressure also plays a role in magma formation. As rocks descend into the Earth’s interior, they encounter higher pressures. This pressure can suppress the melting of rocks, even at elevated temperatures. However, when rocks move to shallower depths or experience a decrease in pressure through processes like tectonic plate movement or mantle upwelling, they are more likely to melt.
• The composition of rocks is a critical factor in magma formation. Different minerals have different melting points. Rocks are composed of various minerals, and when the temperature exceeds the melting point of certain minerals within a rock, those minerals will begin to melt, contributing to the formation of magma. The composition of the magma depends on the minerals present in the original rocks.
• The presence of water also influences magma formation. Water can lower the melting point of rocks, making it easier for them to undergo partial melting. Water is often introduced into the mantle through subduction zones, where oceanic plates sink beneath continental plates, carrying water with them.
• Upwelling of magma from the mantle is another process that contributes to magma formation. Mantle plumes, which are hot, buoyant upwellings of material from deep within the Earth, can lead to the melting of rock and the generation of magma. This is thought to be a significant factor in the formation of hotspot volcanoes.

Once magma is formed, it can rise towards the Earth’s surface due to its lower density compared to the surrounding solid rock. The ascent of magma can lead to volcanic activity, where it may erupt onto the surface as lava, ash, and gases.

Understanding the processes of magma formation is crucial for comprehending volcanic activity and the Earth’s dynamic internal processes. Researchers use various methods, including laboratory experiments, field studies, and seismic observations, to investigate and model the conditions under which magma is generated within the Earth.

Tectonic plate boundaries play a fundamental role in the causes of volcanic eruptions. The Earth’s lithosphere is divided into several large plates that float on the semi-fluid asthenosphere beneath them. The interactions between these plates at their boundaries create conditions conducive to the formation and eruption of volcanoes. There are three main types of plate boundaries associated with volcanic activity: divergent boundaries, convergent boundaries, and transform boundaries.

• At divergent boundaries, tectonic plates move away from each other. As plates separate, magma from the mantle rises to fill the gap, creating new oceanic crust through a process known as seafloor spreading.
• The rising magma can breach the ocean floor, leading to the formation of underwater volcanoes and mid-ocean ridges. These volcanic eruptions are typically characterized by effusive lava flows.
• Convergent boundaries involve the collision or subduction of tectonic plates. When an oceanic plate collides with a continental plate, or when two continental plates converge, the denser oceanic plate is usually forced beneath the lighter continental plate in a process called subduction.
• As the subducting plate sinks into the mantle, it undergoes partial melting due to the increase in temperature and pressure. The melted rock (magma) rises through the overlying plate, leading to the formation of magma chambers beneath the Earth’s surface.
• The magma can eventually reach the surface, causing explosive volcanic eruptions. These eruptions are often associated with the formation of volcanic arcs and can be particularly violent due to the viscosity of the magma and the release of trapped gases.
• At transform boundaries, tectonic plates slide past each other horizontally. While transform boundaries are not typically associated with large volcanic mountain formations, they can contribute to the formation of volcanic activity under certain circumstances.
• Frictional forces at transform boundaries can generate heat, and localized melting may occur, leading to the formation of magma. Volcanic activity at transform boundaries is usually less intense compared to convergent boundaries.

In summary, the movement and interactions of tectonic plates at plate boundaries are central to the causes of volcanic eruptions. Whether plates are diverging, converging, or sliding past each other, the associated geological processes create conditions conducive to magma formation and the release of volcanic activity. The diverse nature of volcanic eruptions around the world can be attributed to the dynamic interactions at these tectonic plate boundaries.

Volcanic hotspots are areas on the Earth’s surface where volcanic activity is unusually high, often resulting in the formation of volcanic features such as magma plumes, basaltic lava flows, and volcanic islands. Unlike volcanic activity at tectonic plate boundaries, hotspots are thought to be stationary relative to the moving tectonic plates. The exact mechanism behind the formation of hotspots is still a subject of scientific investigation, but they are believed to be associated with mantle plumes—hot, buoyant upwellings of molten rock originating from deep within the Earth.

Key characteristics and features of volcanic hotspots include:

• The prevailing theory suggests that volcanic hotspots are caused by mantle plumes—long, narrow columns of hot rock that rise from the boundary between the Earth’s core and mantle. As these plumes reach the mantle’s upper boundary, they can induce melting, creating magma chambers.
• Unlike most volcanic activity associated with tectonic plate boundaries, hotspots are often considered to be relatively stationary. This leads to a chain of volcanic activity, with older volcanic structures becoming progressively younger as they move away from the hotspot.
• Hotspots can generate volcanic chains or trails of islands, seamounts, and volcanic features as tectonic plates move over them. The Hawaiian Islands are a classic example of a hotspot volcanic chain.
• Hotspot activity beneath oceanic crust can result in the formation of volcanic islands. As magma rises to the surface, it can build up layers of solidified lava, forming islands. Over time, as the tectonic plate moves, a chain of islands is created.
• Hotspot volcanic chains often exhibit a gradient of geological ages, with the youngest volcanic structures located above the current position of the hotspot. The older volcanic islands or seamounts in the chain are progressively eroded or subside below sea level.
• The Hawaiian-Emperor seamount chain is a well-known example of a hotspot track. The Yellowstone hotspot, located beneath Yellowstone National Park in the United States, is another example that has resulted in significant volcanic activity.

It’s important to note that the exact nature and origin of mantle plumes and hotspots are still areas of active research, and scientific understanding of these phenomena continues to evolve. Hotspots provide valuable insights into the dynamics of the Earth’s mantle and contribute to the geological diversity observed on the planet’s surface.

Volcanic eruptions can be triggered by various mechanisms, and while the exact causes can be complex and multifaceted, here are some key triggering mechanisms:

• Subduction Zones: In convergent plate boundaries, where one tectonic plate is forced beneath another (subduction), intense heat and pressure can cause the subducting plate to melt, leading to the formation of magma. This magma can then rise to the surface, triggering volcanic eruptions.
• Rifting: At divergent plate boundaries, where tectonic plates move apart, magma from the mantle can intrude into the gap, leading to the creation of new crust. This process, known as rifting, is associated with volcanic activity, particularly along mid-ocean ridges.
• Mantle Plumes: Hot, buoyant upwellings of molten rock from the Earth’s mantle, known as mantle plumes, can lead to the formation of hotspots. As the plume reaches the crust, it can induce melting, creating magma chambers that feed volcanic activity. The movement of tectonic plates over hotspots can create chains of volcanic islands.
• Geothermal Energy Extraction: Human activities, such as geothermal energy extraction, can sometimes induce volcanic activity. The extraction of fluids from geothermal reservoirs can alter the pressure conditions in the subsurface and potentially trigger volcanic eruptions.
• Dome Instability: Volcanic domes are formed by the extrusion of lava with high viscosity. The weight of the lava on the dome can lead to instability, causing partial or complete collapse. The collapse can release trapped gas and magma pressure, leading to explosive eruptions.
• Tectonic Earthquakes: Earthquakes, especially those associated with tectonic activity, can sometimes trigger volcanic eruptions. The seismic activity can cause changes in pressure and create fractures in the Earth’s crust, facilitating the ascent of magma.
• Gas Overpressure: The accumulation of gas within a magma chamber can lead to increased pressure. If the gas pressure surpasses the confining strength of the rocks, it can trigger an explosive eruption.
• Meteorite Impact: Although rare, a large meteorite impact on the Earth’s surface has the potential to generate enough heat and pressure to melt rocks and initiate volcanic activity.
• Glacial Retreat: Changes in ice volume due to glacial retreat can influence volcanic activity. The removal of the weight of glacial ice may lead to decompression melting in the underlying mantle, contributing to volcanic eruptions.

Understanding these triggering mechanisms is essential for assessing volcanic hazards and mitigating potential risks associated with eruptions. Volcanic monitoring systems, geological studies, and advances in seismology contribute to ongoing efforts to comprehend and predict volcanic activity.

1. Mount Vesuvius, AD 79:

• Event: The eruption of Mount Vesuvius in AD 79 is one of the most infamous volcanic events in history. It buried the Roman cities of Pompeii and Herculaneum under a thick layer of ash and pumice .
• Causes: Mount Vesuvius is located near the convergent boundary of the African and Eurasian tectonic plates. The eruption was a result of the subduction of the African plate beneath the Eurasian plate, leading to the accumulation of magma beneath the surface.
• Lessons Learned: The catastrophic impact of the Vesuvius eruption underscores the importance of understanding the geological setting of volcanic regions. It also emphasizes the need for effective evacuation plans and early warning systems for populations living near active volcanoes.

2. Krakatoa, 1883:

• Event: The eruption of Krakatoa in 1883, located between the islands of Java and Sumatra, resulted in one of the most powerful volcanic explosions in recorded history. The eruption led to tsunamis, global climate effects, and the collapse of the island.
• Causes: Krakatoa’s eruption was caused by the collapse of the volcanic island due to a combination of magma chamber overpressure and tectonic activity in the Sunda Strait.
• Lessons Learned: Krakatoa highlighted the far-reaching consequences of volcanic eruptions, including tsunamis and atmospheric effects. It emphasized the importance of international cooperation in monitoring and mitigating global impacts.

3. Mount St. Helens , 1980:

• Event: The eruption of Mount St. Helens in 1980 in the state of Washington, USA, was a highly destructive event. The eruption resulted in the lateral collapse of the volcano’s north flank and the release of a massive debris avalanche.
• Causes: Mount St. Helens is located at a convergent plate boundary where the Juan de Fuca plate subducts beneath the North American plate. The eruption was triggered by the release of pressure from the magma chamber and the collapse of the unstable north flank.
• Lessons Learned: The eruption highlighted the need for improved monitoring of volcanic precursors, such as ground deformation and gas emissions. It also emphasized the importance of land-use planning to mitigate the impact on surrounding communities.

4. Pinatubo, 1991:

• Event: The eruption of Mount Pinatubo in the Philippines in 1991 was one of the largest volcanic eruptions of the 20th century. It had significant global climatic impacts.
• Causes: The eruption was triggered by the injection of magma into the volcano’s chamber, leading to increased pressure. The climactic eruption released a large volume of ash and sulfur dioxide into the stratosphere.
• Lessons Learned: Pinatubo highlighted the potential for volcanic eruptions to influence global climate. The monitoring and study of volcanic gas emissions gained increased importance in assessing potential impacts on the atmosphere.

5. Eyjafjallajökull, 2010:

• Event: The eruption of Eyjafjallajökull in Iceland in 2010 disrupted air travel across Europe due to the release of volcanic ash into the atmosphere.
• Causes: The eruption was caused by the interaction of magma with ice, leading to explosive activity. The ash cloud created aviation hazards and prompted widespread airspace closures.
• Lessons Learned: The Eyjafjallajökull eruption underscored the vulnerability of air travel to volcanic ash. It highlighted the need for improved communication and coordination between volcanic monitoring agencies and aviation authorities.

Implications for Future Monitoring:

• Advances in satellite technology, ground-based monitoring systems, and improved understanding of volcanic precursors are crucial for early detection and warning.
• International collaboration and information-sharing are essential for managing the impact of volcanic events, especially those with global consequences.
• Public awareness and education about volcanic risks and evacuation plans are key components of preparedness.
• Ongoing research into volcanic processes, including gas emissions and magma behavior, contributes to better forecasting and risk assessment.

These case studies demonstrate the diverse causes and impacts of volcanic eruptions and highlight the ongoing efforts to learn from past events for more effective monitoring and mitigation in the future.

In conclusion, the causes of volcanic eruptions are multifaceted and often stem from dynamic processes within the Earth’s interior. The interplay of geological forces at tectonic plate boundaries and other volcanic features such as hotspots contributes to the diverse and spectacular volcanic activity observed around the world.

Tectonic plate interactions, including subduction, divergence, and lateral sliding, play a pivotal role in triggering volcanic events. Subduction zones, where one plate descends beneath another, can lead to the melting of rock and the formation of magma. Divergent boundaries, where plates move apart, allow magma to rise from the mantle, creating new crust. Transform boundaries, where plates slide past each other, can generate heat and localized melting.

Mantle plumes and hotspots provide another mechanism for magma generation. These upwellings of hot rock from the Earth’s mantle can create stationary points of intense volcanic activity, forming volcanic island chains and contributing to the geological diversity of the planet.

Human activities, such as geothermal energy extraction, can also influence volcanic activity, albeit on a smaller scale. Additionally, external triggers like meteorite impacts and climate-related factors, such as glacial retreat, may contribute to volcanic events.

Historic volcanic eruptions serve as valuable case studies, offering insights into the complex causes and far-reaching consequences of such events. Lessons learned from events like the eruption of Mount Vesuvius, Krakatoa, Mount St. Helens, Pinatubo, and Eyjafjallajökull underscore the importance of understanding volcanic hazards, implementing effective monitoring systems, and developing strategies for risk mitigation.

Advancements in seismology, satellite technology, and the study of volcanic gas emissions contribute to ongoing efforts to monitor and predict volcanic activity. Public awareness, education, and international collaboration are essential components of preparedness and response to volcanic events.

In navigating the intricate processes that lead to volcanic eruptions, the scientific community continues to deepen its understanding, striving for improved forecasting, risk assessment, and the development of strategies to safeguard communities living in volcanic regions. As we move forward, the pursuit of knowledge about the Earth’s dynamic interior remains crucial for enhancing our ability to coexist with the natural forces that shape our planet.

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• BOOK REVIEW
• 22 April 2024

How volcanoes shaped our planet — and why we need to be ready for the next big eruption

• Heather Handley 0

Heather Handley is an associate professor of volcanic hazards and geoscience communication in the Department of Applied Earth Sciences at the University of Twente in Enschede, the Netherlands.

You can also search for this author in PubMed   Google Scholar

Lava erupts from a volcano in Iceland, part of a series of eruptions that began last year. Credit: Anton Brink/Anadolu via Getty

You have full access to this article via your institution.

Adventures in Volcanoland: What Volcanoes Tell Us About the World and Ourselves Tamsin Mather Abacus (2024)

Unlike Alice in Alice in Wonderland , volcanologists cannot fall down a deep rabbit hole to discover what goes on in the bowels of the Earth. Instead, they scour the surface and examine the chemistry of emitted gases, lava and rocks ejected during eruptions. Only by combining many clues can researchers learn where and how molten rock (magma) forms, how it ascends from the mantle below Earth’s crust and what triggers volcanic eruptions.

In Adventures in Volcanoland , volcanologist Tamsin Mather takes readers on a journey to some of the world’s most notorious and active volcanoes — from Mount Vesuvius in Italy to Masaya in Nicaragua. Her eloquent and enchanting book, which is rich in analogies and anecdotes, weaves together geological, historical and personal stories to explain how volcanoes work, how they have shaped our planet and how they have been understood through history.

Santorini’s volcanic past: underwater clues reveal giant prehistoric eruption

Volcanoes’ captivating power clearly entrances Mather, as it does me. And volcanoes make volcanologists work hard to uncover their secrets. Mather explains how researchers, equipped with the geochemical equivalent of a stethoscope, listen to the beating pulses of volcanoes. Scientists can also capture volcanoes’ ‘breath’ — toxic gases that often enshroud Mather as she works and that eat away at her clothes. Mather describes navigating through thick jungle in Guatemala to collect samples of lava while volcanic blasts hurled plumes of ash into the sky. Repairs to broken equipment had to be improvised using duct tape and superglue. Mather once resorted to using an inverted children’s paddling pool to collect gases fizzing up inside the caldera of Santorini volcano in Greece . The effort is worth it, Mather explains, to help volcanologists to answer big questions, such as how eruptions alter the climate and our environment, and how they affect life on Earth.

Volcanologists must exploit a vast array of knowledge, from planetary-scale shifts in Earth’s carbon cycle to the analysis of trapped gases in microscopic beads of glass. They must put eruptions in geological context, on timescales from Earth’s formation more than four billion years ago to the rapid radioactive decay of gases emitted by magma (such as radon-222, with a half-life of just under four days).

Each rock tells a story

Mather describes human experiences of volcanic eruptions, including her own time spent staring into churning lakes of molten rock, a “roiling, red and restless” fiery sea. She first encountered volcanoes and their hazards as a child, when she visited Vesuvius and the former Roman towns of Pompeii and Herculaneum. In ad 79, several scorching (350–550 ºC), fast-moving clouds of ash, pumice and gases surged down the flanks of Vesuvius, with devastating consequences for the people below, including hundreds who had taken refuge at the waterfront in Herculaneum, waiting to flee by boat.

In pictures: lava flows into Icelandic town during volcanic eruption

Today, tourists standing at the excavated pre-eruption shoreline are presented with an intimidating wall of volcanic deposits. After the eruption, the land surface gained up to 20 metres of elevation, and the coastline moved seawards by one kilometre. And all this happened in a geological blink of an eye.

Looking down from the crater rim of Mount Vesuvius towards the urban sprawl of metropolitan Naples, now home to around three million people, it’s sobering to consider just how the city will respond to the next large eruption of the slumbering volcano. It’s hard to know when that will be, but managing a future evacuation will be a colossal task for the authorities.

To prepare and plan, it is essential to better understand the hazards of volcanic regions. By ‘reading the rocks’ deposited by volcanoes, layer upon layer over thousands or millions of years, volcanologists can unravel the frequency, style and magnitudes of past eruptions. For example, rock stripes exposed in the walls of the Santorini caldera reveal how the catastrophic 1600 bc Minoan eruption unfolded; underwater studies of rocks point to other events that were much larger than previously thought. The consequences of another large eruption in the Eastern Mediterranean would be grave.

The Hunga Tonga-Hunga Ha’apai volcano in the South Pacific. Credit: Maxar via Getty

Volcanic and sedimentary rocks, along with signals from deposited sulphate in ice cores, hold clues about how eruptions have altered conditions across our planet. The impacts can be temporary or permanent. Plumes of sulphur dioxide gas can trigger short periods of global cooling called volcanic winters, such as the one following the 1815 eruption of Tambora in Indonesia. Lengthy outpourings of lava can form large igneous provinces — huge accumulations of volcanic rocks, such as the Siberian Traps. In the past, such events might have led to significant changes in planetary conditions that affected the course of life on Earth. As Mather points out, four out of the five largest mass extinctions overlapped approximately in time with volcanic activity that formed large igneous provinces, which would have pumped out vast amounts of carbon dioxide over millions of years.

Plan for big eruptions

All this raises the question of how prepared we are for the next large-scale volcanic eruption. Not very, I would argue. Humans have short memories — the COVID-19 pandemic showed us that, only 100 years after the severe influenza pandemic that began in 1918, we were still not ready.

Monitoring of volcanoes has advanced tremendously, with support from satellites in space , but they can still catch us off guard. For example, the powerful 2022 eruption of Hunga Tonga–Hunga Ha‘apai in Tonga was unexpected and had global ramifications. A shockwave and tsunamis reached the coasts of North and South America, resulting in an oil spill and two drownings in Peru. Tsunami warnings and evacuation orders were issued in Japan, and beaches closed in Australia. Water vapour launched into the stratosphere by the blast could temporarily boost global temperatures.

Tonga volcano eruption triggered ‘mega-tsunami’

Population growth, technology dependency and the increased complexity of global systems have put the world at catastrophic risk from volcanic eruptions. Today, more than 800 million people in more than 85 countries live within 100 kilometres of an active volcano. An eruption near densely populated areas would have disastrous immediate impacts. Pyroclastic flows — fast-moving mixtures of hot gas, ash and rock fragments — could wipe out entire cities. Metres-thick ash falls would devastate crops and overwhelm power lines, water-treatment facilities, ventilation and heating systems, machinery and more. Farther away, flights might be grounded, power grids and undersea cables could be damaged and food security and supply chains could be affected, spreading economic losses.

With little regard for international borders, large eruptions’ far-reaching impacts would require a rapid and coordinated national and international response. Yet, global preparedness for the impacts of volcanic eruptions is lacking. There is no international United Nations treaty organization for ‘operational volcanology’ (systematic monitoring of volcanoes and assessment of risk). There’s no global coordination on issuing cross-border volcanic hazard warnings that address the full range of threats: pyroclastic flow, tephra fall (deposits of lofted rock fragments), lava flow, lahar (volcanic mudflow), volcanic gases, rafting pumice, drifting ash, tsunami and lightning.

Tambora-size eruptions occur somewhere in the world once or twice every millennium on average, and every 400 years in the Asia Pacific region. It’s not a matter of if, but when.

Adventures in Volcanoland reminds us that we should all keep careful watch on the world’s volcanoes. They are more than alluring natural landmarks. They are powerful drivers of processes on our planet that are crucial to understand. Volcano enthusiasts, those interested in the history of this adventurous science and those questioning our place in the world will find much to enjoy in this absorbing book.

Nature 628 , 713-715 (2024)

doi: https://doi.org/10.1038/d41586-024-01179-1

Competing Interests

The author declares no competing interests.

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Essays About Volcanoes: Top 5 Examples and 10 Prompts

Do you need to write essays about volcanoes but don’t know where to start? Check out our top essay examples and prompts to help you write a high-quality essay.

Considered the planet’s geologic architects, volcanoes are responsible for more than 80% of the Earth’s surface . The mountains, craters, and fertile soil from these eruptions give way to the very foundation of life itself, making it possible for humans to survive and thrive.  

Aside from the numerous ocean floor volcanoes, there are 161 active volcanoes in the US . However, these beautiful and unique landforms can instantly turn into a nightmare, like Mt. Tambora in Indonesia, which killed 92,000 people in 1815 .

Various writings are critical to understanding these openings in the Earth’s crust, especially for students studying volcanoes. It can be tricky to write this topic and will require a lot of research to ensure all the information gathered is accurate. 

To help you, read on to see our top essay examples and writing prompts to help you begin writing.

Top 5 Essay Examples

1. short essay on volcanoes by prasad nanda , 2. types of volcanoes by reena a , 3. shield volcano, one of the volcano types by anonymous on gradesfixer.com, 4. benefits and problems caused by volcanoes by anonymous on newyorkessays.com, 5. volcanoes paper by vanessa strickland, 1. volcanoes and their classifications, 2. a dormant volcano’s eruption, 3. volcanic eruptions in the movies, 4. the supervolcano: what is it, 5. the word’s ring of fire, 6. what is a lahar, 7. why does a volcano erupt, 8. my experience with volcanic eruptions, 9. effects of volcanic eruptions, 10. what to do during volcanic disasters.

“The name, “volcano” originates from the name Vulcan, a god of fire in Roman mythology.”

Nanda briefly defines volcanoes, stating they help release hot pressure that builds up deep within the planet. Then, he discusses each volcano classification, including lava and magma’s roles during a volcanic eruption. Besides interesting facts about volcanoes (like the Ojos del Salado as the world’s tallest volcano), Nanda talks about volcanic eruptions’ havoc. However, he also lays down their benefits, such as cooled magma turning to rich soil for crop cultivation.

“The size, style, and frequency of eruptions can differ greatly but all these elements are correlated to the shape of a volcano.”

In this essay, Reena identifies the three main types of volcanoes and compares them by shape, eruption style, and magma type and temperature. A shield volcano is a broad, flat domelike volcano with basaltic magma and gentle eruptions. The strato or composite volcano is the most violent because its explosive eruption results in a lava flow, pyroclastic flows, and lahar. Reena shares that a caldera volcano is rare and has sticky and cool lava, but it’s the most dangerous type. To make it easier for the readers to understand her essay, she adds figures describing the process of volcanic eruptions.

“All in all, shield volcanoes are the nicest of the three but don’t be fooled, it can still do damage.”

As the essay’s title suggests, the author focuses on the most prominent type of volcano with shallow slopes – the shield volcano. Countries like Iceland, New Zealand, and the US have this type of volcano, but it’s usually in the oceans, like the Mauna Loa in the Hawaiian Islands. Also, apart from its shape and magma type, a shield volcano has regular but calmer eruptions until water enters its vents.

“Volcanic eruptions bring both positive and negative impacts to man.”

The essay delves into the different conditions of volcanic eruptions, including their effects on a country and its people. Besides destroying crops, animals, and lives, they damage the economy and environment. However, these misfortunes also leave behind treasures, such as fertile soil from ash, minerals like copper, gold, and silver from magma, and clean and unlimited geothermal energy. After these incidents, a place’s historic eruptions also boost its tourism.

“Beautiful and powerful, awe-inspiring and deadly, they are spectacular reminders of the dynamic forces that shape our planet.”

Strickland’s essay centers on volcanic formations, types, and studies, specifically Krakatoa’s eruption in 1883. She explains that when two plates hit each other, the Earth melts rocks into magma and gases, forming a volcano. Strickland also mentions the pros and cons of living near a volcanic island. For example, even though a tsunami is possible, these islands are rich in marine life, giving fishermen a good living.

Are you looking for more topics like this? Check out our round-up of essay topics about nature .

10 Writing Prompts For Essays About Volcanoes

Do you need more inspiration for your essay? See our best essay prompts about volcanoes below:

Identify and discuss the three classifications of volcanoes according to how often they erupt: active, dormant or inactive, and extinct. Find the similarities and differences of each variety and give examples. At the end of your essay, tell your readers which volcano is the most dangerous and why.

Volcanoes that have not erupted for a very long time are considered inactive or dormant, but they can erupt anytime in the future. For this essay, look for an inactive volcano that suddenly woke up after years of sleeping. Then, find the cause of its sudden eruption and add the extent of its damage. To make your piece more interesting, include an interview with people living near dormant volcanoes and share their thoughts on the possibility of them exploding anytime.

Choose an on-screen depiction of how volcanoes work, like the documentary “ Krakatoa: Volcano of Destruction .” Next, briefly summarize the movie, then comment on how realistic the film’s effects, scenes, and dialogues are. Finally, conclude your essay by debating the characters’ decisions to save themselves.

The Volcanic Explosivity Index (VEI) criteria interpret danger based on intensity and magnitude. Explain how this scale recognizes a supervolcano. Talk about the world’s supervolcanoes, which are active, dormant, and extinct. Add the latest report on a supervolcano’s eruption and its destruction.

Identify the 15 countries in the Circum-Pacific belt and explore each territory’s risks to being a part of The Ring of Fire. Explain why it’s called The Ring of Fire and write its importance. You can also discuss the most dangerous volcano within the ring.

If talking about volcanoes as a whole seems too generic, focus on one aspect of it. Lahar is a mixture of water, pyroclastic materials, and rocky debris that rapidly flows down from the slopes of a volcano. First, briefly define a lahar in your essay and focus on how it forms. Then, consider its dangers to living things. You should also add lahar warning signs and the best way to escape it.

Use this prompt to learn and write the entire process of a volcanic eruption. Find out the equipment or operations professionals use to detect magma’s movement inside a volcano to signal that it’s about to blow up. Make your essay informative, and use data from reliable sources and documentaries to ensure you only present correct details.

If you don’t have any personal experience with volcanic eruptions, you can interview someone who does. To ensure you can collect all the critical points you need, create a questionnaire beforehand. Take care to ask about their feelings and thoughts on the situation.

Write about the common effects of volcanic eruptions at the beginning of your essay. Next, focus on discussing its psychological effects on the victims, such as those who have lost loved ones, livelihoods, and properties.

Help your readers prepare for disasters in an informative essay. List what should be done before, during, and after a volcanic eruption. Include relevant tips such as being observant to know where possible emergency shelters are. You can also add any assistance offered by the government to support the victims.Here’s a great tip: Proper grammar is critical for your essays. Grammarly is one of our top grammar checkers. Find out why in this  Grammarly review .

Maria Caballero is a freelance writer who has been writing since high school. She believes that to be a writer doesn't only refer to excellent syntax and semantics but also knowing how to weave words together to communicate to any reader effectively.

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Review of the U.S. Geological Survey's Volcano Hazards Program (2000)

Chapter: 7 principal conclusions and recommendations, 7 principal conclusions and recommendations.

This chapter summarizes the principal conclusions and recommendations developed elsewhere in this report. Major conclusions are printed in italics and recommendations in bold.

The VHP is comprised of a dedicated scientific and technical staff that has a wealth of practical experience, coupled with good theoretical understanding of underlying volcanic and hydrologic processes. To help society prepare for and deal with the effects of volcanic eruptions, the VHP uses five interrelated approaches: (1) long-term hazard assessment, (2) monitoring baseline measurements that allow premonitory changes to be recognized, (3) crisis response when a volcano is erupting, (4) topical studies of geologic processes that allow for better understanding of the causes and consequences of volcanic hazards, and (5) communicating with civil authorities and the surrounding communities about the results of their studies. These five approaches all aim to help society respond to the dangers posed by volcanoes. Another way to view these activities is to consider a continuum of three overlapping types of societal response to eruptions: research (knowledge acquisition), operations (knowledge application), and outreach (knowledge translation). Research provides the basic information and concepts that underlie the various methods of volcano data collection and interpretation.

The committee was asked to address two questions: (1) Do the activities, priorities, and expertise of the VHP meet appropriate scientific goals? (2) Are the scientific investigations and research results throughout the program effectively integrated and applied to achieve hazard mitigation? The committee’s views with respect to these questions are summarized below and at the end of Chapters 2 , 3 , and 4 .

Basic research in the VHP, although reasonably well integrated, is being threatened by budgetary and personnel constraints, which may diminish the program’s ability to meet appropriate scientific goals. If

these problems are not solved, the program will likely be forced to reduce levels of in-house basic research and/or to increase collaboration with non-USGS scientists. Hazard assessment, while traditionally strong in geologic mapping, radiometric age dating, and related activities, has to be strengthened in modeling and probabilistic approaches if the program is to continue to meet appropriate scientific goals. Existing hazard assessment activities at individual volcano observatories are effectively integrated and applied to hazard mitigation issues. The one-volcano, one-scientist projects under way at some volcanoes, although scientifically appropriate, may not be effectively integrated with each other or with the VHP as a whole.

Continuing budgetary pressures place four types of constraints on the VHP’s ability to monitor volcanoes. (1) Aging equipment is not replaced soon enough (or at all), increasing the chances of failure during a crisis. (2) The VHP’s traditional role as the developer and tester of new monitoring equipment and techniques is jeopardized. (3) The number and extent of regular instrumented surveys, which are crucial for the success of any monitoring program, are restricted. (4) Personnel familiar with new techniques are not hired. If the current situation is not reversed, the VHP may not be able to field the best instruments or to maintain its traditional high standards for monitoring. These issues apply to varying degrees to all of the monitoring methods used by the VHP, and if they are not addressed in the near future, the program runs the risk of not being able to meet appropriate scientific goals. On the other hand, the monitoring methods currently employed in the VHP seem to be well integrated and applied to achieve hazards mitigation.

Crisis response procedures at VHP observatories are well integrated and applied to hazards mitigation. The VDAP, while evoking strong praise from the committee, has to be strengthened, in both personnel and budget. The committee urges wider involvement of VHP personnel in VDAP activities, which—besides providing depth to the VDAP—would permit a wider circle of scientists to gain firsthand experience with volcanoes in crisis. Data gathered during international volcano crises must be better archived and, where appropriate, published. The committee realizes that data acquisition and use can be a sensitive issue with foreign governments and organizations but urges that protocols be explored to improve the ways in which data from one overseas crisis might be better integrated and applied to the next crisis. Existing outreach products of the VHP were judged by the committee to be of

high quality and effective in mitigating volcano hazards. This effectiveness can be increased by developing ways for the VHP to retain proceeds from the sale of its products and by removing impediments that limit the involvement of midcareer VHP personnel in their preparation and dissemination.

It is difficult to separate the contributions to basic volcanological knowledge made by VHP scientists from those made by their colleagues in other parts of the USGS, other government agencies, universities, other countries, and the private sector. Nonetheless, throughout much of the second half of the twentieth Century, members of the present-day USGS Volcano Hazards Program were national if not global leaders in the formulation of ideas about how volcanoes work.

The committee did not review individual VHP research projects, nor did it conduct an in-depth assessment of the research component of the program. However, the committee feels strongly that USGS management must ensure that most, if not all, basic research projects are directed toward program goals. Such assurance can come from internal USGS programmatic oversight and from careful structuring and enforcement of the annual performance plans of individual research scientists.

Basic research in the VHP is being threatened by budgetary and personnel constraints, which may diminish the program’s ability to meet appropriate scientific goals. One of the most important long-range issues that the VHP must face is deciding how central in-house basic research will be to its mission in the future. Such research is also being done at universities, government labs, and non-U.S. institutions. Thus, one might argue that the VHP could forgo its basic research activities without this having a major impact on the state of knowledge of volcanic processes. On the other hand, eliminating this program element altogether would likely damage the intellectual vitality of the VHP and make it more difficult (if not impossible) for the program to hire topflight young scientists. The committee believes that if the VHP is faced with continuing budget shortfalls, it could elect to reduce fundamental research activities and redirect scarce resources to monitoring and crisis response functions, which it is uniquely positioned to do (see Chapters 2 and 3 ). However, these savings would come at a high cost. The ability of

the VHP to respond to volcanic crises would be compromised by a lack of expertise in hazard assessment or volcano process studies.

One possible solution would be for VHP members to collaborate more on research projects with scientists outside the USGS, particularly those from universities and from laboratories of other government agencies. More active collaborations, coupled with an extramural grant program for academic researchers overseen partly or completely by the VHP, would help ensure that more investigations that are directly relevant to the program’s mission would be carried out.

HAZARD ASSESSMENT

Volcano hazard assessment aims to determine where and when future volcano hazards will occur and their potential severity. This kind of appraisal provides a long-term view of the locations and probabilities of large-scale eruptions and related phenomena, such as volcanic debris avalanches and tsunamis. The extensive range of hazards that must be evaluated requires the combined knowledge of a broad array of scientists, including geologists, hydrologists, geotechnical engineers, atmospheric physicists, and statisticians. Because assessment is inherently interdisciplinary, the VHP needs access to a very diverse set of expertise, either within its own ranks or through collaborations with outside groups.

Geologic mapping, stratigraphy, geochronology, and physical volcanology provide the backbone of volcanic hazard assessments by revealing past trends in eruption timing, volume, and explosivity. Historically the USGS has done an excellent job of incorporating geologic data into its assessments. The committee commends VHP efforts to integrate findings of geologic studies into volcanic hazard assessments. An ongoing challenge is to more effectively quantify geologic data in ways that optimize their use in such assessments.

Although mapping and dating of volcanic deposits can provide a good framework for hazard assessment, mechanical models of physical, chemical, and hydrologic processes help refine forecasts of the types and magnitudes of future eruptions. Both numerical models and laboratory simulations can relate the boundary conditions on a volcano to the likely consequences of any incipient eruptive activity. Although there has been some VHP participation in the development of these models, especially those related to hydrologic and sedimentologic phenomena, most have

been created by non-USGS scientists. The committee encourages the VHP to include more theoretical modeling of volcanic phenomena in its hazard assessments.

Because it is impossible to predict eruptive behavior with certainty, particularly for dormant volcanoes, most hazard assessments are inherently probabilistic in nature. Use of three approaches to hazard assessment—mapping and dating, theoretical modeling, and probability calculations—by the VHP reflects the training of its participants. Probabilistic approaches are relatively recent additions to the VHP assessment repertoire, but they have received more attention lately because of their obvious utility in communicating with civil defense authorities and the general public. The committee strongly encourages the VHP to develop a balanced assessment program that takes advantage of the full range of techniques available to volcanologists today.

Assessment priorities vary from observatory to observatory, reflecting local differences in the nature of the volcanic hazard and the expertise of the resident scientists and technicians. Volcanic ash interaction with jet aircraft poses the greatest danger from Alaskan volcanoes, because ingestion of ash can result in engine damage or failure. Although responsibilities for monitoring and crisis response in Alaska are shared among the VHP, the NWS, and the FAA, only AVO is capable of (1) establishing the historical context of future explosive eruptive activity, (2) providing advance warning of an impending eruption, and (3) conducting ground monitoring that can confirm an eruption is actually in progress. Because of the nature of these dangers, AVO has placed greater emphasis on monitoring and crisis response than on long-term hazard assessment. Only a few of the Alaskan volcanoes have even rudimentary hazard maps. The expense and logistical difficulties associated with access in Alaska preclude the kind of comprehensive mapping strategy carried out by CVO and HVO. Recent AVO-coordinated mapping campaigns at selected Alaskan volcanoes carried out by teams of USGS, other government, and university geoscientists have expanded the coverage of hazard assessment products. The committee concludes that basic yet rapid assessment of the eruptive histories of as many of the Aleutian volcanoes as possible is necessary to guide prioritization of the placement of instruments used to provide warnings to pilots and other nearby infrastructure.

If faced with a continued flat budget, the VHP must find ways to carry out its mission more efficiently. The committee recommends that

the VHP initiate a form of collaborative prioritization with respect to hazard assessment. This might include a broader application of the team approach now being used at AVO and CVO. In addition to prioritization, volcano hazard assessment within the VHP would be improved by greater consistency of data collection, storage, presentation, and interpretation.

To be effective, monitoring must be done before, during, and after eruptions and must be integrated with carefully designed communication schemes. It requires the type of long-term commitment of time and resources that academic and industry scientists generally cannot make. Furthermore, the quality of monitoring depends on the amount of experience of the participating scientists. For these reasons, the VHP is uniquely qualified within the United States to carry out volcano monitoring.

The combined seismic-deformation approach, which has traditionally been the core of VHP monitoring, tracks phenomena to provide ample warnings of impending eruptions on most volcanoes. The report Priorities for the Volcano Hazards Program 1999–2003 (USGS, 1999) argues for an expansion of some existing networks and upgrading of overall instrument capability. The committee endorses these plans because they are directly applicable to the scientific goals of the VHP and will help to achieve hazard mitigation.

Although there are pros and cons for making data available on a real-time or near real-time basis, the committee believes that the advantages of public access outweigh the disadvantages. The committee therefore recommends that VHP observatories take measures to make their data available on a near real-time basis.

The committee was favorably impressed by AVO’s attempts to install seismic networks (either large or small) on as many Aleutian volcanoes as possible. The committee believes that a team approach for monitoring and studying Aleutian volcanoes from various perspectives should be expanded in the near future so that AVO can provide airlines and other constituents with adequate advance warning of impending eruptions.

The collection of volcanic gas data is another essential monitoring tool that complements seismic and geodetic information. The committee was disturbed to learn of the paucity of gas geochemical expertise and utilization within the VHP. The program should reestablish in-house capacity to use and develop both conventional and novel methods for measuring and interpreting volcanic gases. New ground-based instruments for remote sensing of CO 2 and other gases are currently being developed outside the USGS. These instruments have major technical advantages over existing approaches used by the VHP. The committee believes that VHP scientists should be in the forefront of such efforts, either by obtaining this equipment themselves or by actively collaborating with groups who are developing these tools.

Although less prominent in the public’s awareness than lava flows or pyroclastic phenomena, mixtures of volcanic debris and water are among the most deadly products of volcanoes. Detection of volcanic debris flows (lahars) close to their sources can provide timely warnings to people in downstream areas. Over the next five years, the VHP plans to improve and field-test remote eruption detection stations for possible deployment in the western Aleutians and the Cascades. The committee supports this goal because it is relevant to the VHP mission to mitigate volcano hazards. The VHP should also explore ways to better monitor groundwater flow and pore pressures within volcanic edifices. This type of information could help establish the potential for phreatic and phreatomagmatic activity, sector collapse, and internal pressure buildups capable of generating explosive blasts. Such hydrologic monitoring warrants greater attention by the VHP. The incorporation of glacier budget studies as part of VHP monitoring on ice-clad volcanoes would also contribute to this goal.

Another VHP goal that the committee fully supports is the continued development of near real-time remote sensing of volcanoes and their associated ash clouds in areas that are difficult to access. Most of the VHP’s remote sensing work is centered at AVO, where satellite data are used to identify thermal anomalies and track eruption plumes and where inclement weather makes traditional observations of volcanoes more difficult. Remote sensing data are becoming integrated only slowly into the monitoring strategies of the other VHP observatories.

A new generation of EOS instruments is now providing potentially useful information for volcano monitoring (e.g., data on thermal regimes, SO 2 gas emissions, deformation, and digital topography). The committee

believes strongly that the VHP should take advantage of this opportunity to the fullest extent possible. In addition, the committee urges the USGS to work with NASA to argue in support of an InSAR satellite specifically designed for natural hazards monitoring .

The committee also considered the potential value to volcano monitoring of two existing remote sensing programs based outside the VHP, the Hazard Support System and the Center for Integration of Natural Disaster Information. The classified nature of the data and the fact that military priorities control which observations are made mean that VHP personnel have limited access and must work through the DOD. This adds an extra bureaucratic layer of communication and interpretation, slowing responsiveness and potentially reducing the effectiveness of the monitoring effort. Second, these programs are very expensive. Thus, the CINDI and HSS initiatives run the risk of draining sparse resources away from the VHP for questionable returns. For these reasons, the committee cautions against greater involvement with CINDI and HSS unless and until better assurances can be obtained about data access and cost containment. A potentially less problematic alternative would be to establish closer ties with the nonclassified EOS program run by NASA.

Many volcanoes in the Cascades and several in Alaska lie within wilderness areas and other lands managed by the U.S. National Park Service and the U.S. Forest Service. This situation creates a conflict between the need for effective monitoring in order to serve public interests and the desire to minimize mechanized access to the areas in question. High-level administrators within the USGS and other organizations must actively campaign to gain recognition that monitoring efforts require special attention and priority.

CRISIS RESPONSE

The transition from monitored volcanic activity to a volcanic crisis has as much to do with potential societal impact as with the nature of the eruptive phenomena. Within the United States, the USGS is expressly and uniquely empowered by the Stafford Act (Public Law 93–288) to issue timely warning of potential volcanic disasters to affected communities and civil authorities. Although not an explicitly mandated part of

its mission, the VHP has also developed an international crisis response capability, the Volcano Disaster Assistance Program.

Often, the most valuable asset for a scientist responding to a crisis is relevant prior experience. Because its members are exposed to a wide variety of eruption styles and settings, VDAP offers the most effective way to prepare VHP staff for future domestic crises. The present system for selecting non-VDAP members of the VHP to join foreign deployments appears too haphazard. The VHP should implement a more formal mechanism for participation in VDAP to see that as many people as possible are exposed to this type of training.

Another missed opportunity for expanding the training potential of foreign volcanic crisis responses comes from the inability of VDAP members to archive their observations. The success of VDAP should be measured not only in terms of mitigation of eruption impact, but also in terms of how well information and knowledge are disseminated in anticipation of future crises. This change of strategy might ensure greater access to data that could be used to prepare future crisis teams.

A related programmatic issue is how staff members balance their responsibilities. Even if assistance were provided for archiving and distributing data from volcanic crises, individual scientists still have to incorporate their experiences into the published scientific literature. The stated VHP goal of carefully documenting actual volcanic crises and responses is extremely important if the maximum information is to be obtained from any given eruption and is strongly endorsed by the committee. This issue demands close monitoring, coordination, and allocation of staff time by the relevant scientists in charge to ensure that such information is forthcoming.

In addition to the valuable staff training opportunities provided by VDAP missions, foreign responses also allow new hardware and software to be evaluated under crisis conditions. The technical development of new instrumentation requires field tests for accurate calibration. A consequence of continuing tight VHP budgets has been the growing obsolescence of much of the equipment used in crisis response. One way in which the VHP can extend its equipment budget is to partner with manufacturers and other government agencies that design new instruments. The committee encourages the VHP and VDAP to work more closely with NASA, DOE, DOD, and NOAA, as well as with NSF-funded consortia such as UNAVCO and IRIS, in the development of new in -

strumentation and approaches suitable for detecting the conditions within erupting volcanoes.

The current level of VDAP funding allows a maximum of one deployment at a time, leading to occasional difficult decisions about priorities when multiple crises occur almost simultaneously. The committee unconditionally supports the stated VHP desire to expand the size of the VDAP.

PROGRAMMATIC AND INSTITUTIONAL ISSUES

Currently the VHP has a large number of capable scientists. However, the almost total failure of the program to hire more than a token number of new personnel over the past 15 years has created a crisis of continuity in which much of the VHP’s accumulated knowledge is in danger of being lost because of upcoming retirements. Overlap of new staff with existing staff is essential for orderly transition of duties and transfer of knowledge, not only of volcanology and associated hydrology, but also of procedures for communicating with users of information. With the loss of personnel and no replacements, the domestic response capability is likely to collapse and programs such as VDAP could disappear. The committee believes that if the VHP does not begin to hire new staff immediately, the program will not be able to maintain response readiness. The committee suggests that the VHP begin planning for rejuvenation of its work force. This exercise should build upon the program’s strategic plan and should take into account the new areas of expertise that will be needed in the future.

The importance of technicians to the VHP in many ways equals that of scientists. These individuals have highly eclectic backgrounds and in many cases have participated in several decades’ worth of crisis response, especially as VDAP has expanded. The lack of hiring in this area seriously threatens the well-being of the program. Even if the number of VHP employees increases over the next few years, it will probably be insufficient to keep up with new techniques and with the increased flow of scientific knowledge that threatens to overwhelm the already overworked VHP staff. The resulting shortage means that the program will have to either reduce the scope of its mission or increase the pool of workers who can help them accomplish their goals. Because of this situation, the committee concludes that the VHP can no longer

accomplish all of its goals through in-house activities. The committee recommends that to accomplish its goals, the VHP increase its coordination and collaboration with researchers from other parts of the USGS, other federal agencies, academic institutions, and industry. The committee concludes that there is insufficient integration and communication between the VHP and other government entities involved in volcano hazards. The VHP should take steps to ensure that USGS management realizes that the overall scientific goals of the program would be enhanced by such interactions. The committee recommends that the VHP improve outside communication and better integrate its programs with those of other relevant organizations and government agencies. One place where this coordination appears to be working well is in the separation between the assessment of volcanic hazards carried out by the VHP and the development of responses to those hazards conducted by local civil defense officials.

The VHP’s Five-Year Science Plan for 1999 to 2003 outlines a wide array of program activities, ranging from volcano monitoring and crisis response to scientific outreach and information dissemination. If the VHP continues to be faced with flat budgets and limited staff growth, it must prioritize more clearly among these activities and see that they are consistent with stated program goals. The committee urges the VHP to put in place a more formal mechanism for prioritizing its activities and seeing that they are consistent with stated program goals.

Because most staff members of the VHP report to one of the scientists in charge of the four volcano observatories, these four individuals have special responsibilities for setting, assessing, enforcing, and coordinating prioritization across the program. In the observatory environment, volcano monitoring, hazard assessment, and communication with civil authorities may be most important, but during periods of volcano unrest and newly evolving activity, volcano crisis response assumes special priority.

A major issue that underlies any discussion of VHP priority setting and accountability is the lack of a clear and consistent management structure. Depending on his or her location and their inclination, an individual VHP scientist or technician might report to one of the four observatory scientists in charge, to the head of the Western Region in Menlo Park, to the local branch chief in Flagstaff, to the VHP coordinator in Reston, or to one of various administrators within the

Water Resources Division. The main drawback of the current complex structure is that it creates an institutional barrier to the emergence of strong leaders. This lack, in turn, makes individual staff members unsure about who sets their priorities and makes the VHP as a whole less influential within the prioritization and budget-setting processes of the USGS and the Department of the Interior.

An important aspect of priority setting relates to the timeliness of scientific publication. Scientific publication is an important end product of VHP research, not only for the needs of civil authorities but also for other scientists (both USGS and non-USGS) who benefit from additions to the literature on volcanoes and volcano products. The problem is particularly acute when unpublished studies involve volcano hazard assessments that could have a direct bearing on the safety of people and property. The committee urges that high priority be given to the timeliness of scientific publication.

From the late 1960s until Mount St. Helens erupted in May 1980, the GD administrated the VHP and carried out all programmatic investigations. Soon after the Mount St. Helens event, the VHP funded a number of WRD projects, and the two divisions worked together as a single team. In the 1980s, disagreements between the two divisions prompted the USGS director to partition the VHP into two parts. This division in effect created two programs, each staffed and operated separately, based on different floors of the same building. It is questionable whether the scientific investigations and results throughout the program are integrated as effectively as they could be. The VHP is a USGS program and should be operated in ways that foster seamless relationships among staff within the GD, and WRD. The committee recommends that USGS management integrate the GD and WRD parts of the VHP.

Standardization of data management protocols and formats across observatories and VDAP deployments is essential to improve access for the scientific community and others. The committee believes that the potential benefits of public access outweigh the possible drawbacks of data misuse. The committee recommends that the VHP set standards for documentation, archiving, and access policies, including the length of the proprietary period.

The United States has more than 65 active or potentially active volcanoes, more than those of all other countries except Indonesia and Japan. During the twentieth century, volcanic eruptions in Alaska, California, Hawaii, and Washington devastated thousands of square kilometers of land, caused substantial economic and societal disruption and, in some instances, loss of life. More than 50 U.S. volcanoes have erupted one or more times in the past 200 years. Recently, there have been major advances in our understanding of how volcanoes work. This is partly because of detailed studies of eruptions and partly because of advances in global communications, remote sensing, and interdisciplinary cooperation.

The mission of the Volcano Hazards Program (VHP) is to "lessen the harmful impacts of volcanic activity by monitoring active and potentially active volcanoes, assessing their hazards, responding to volcanic crises, and conducting research on how volcanoes work." To provide a fresh perspective and guidance to the VHP about the future of the program, the Geologic and Water Resources Divisions of the United States Geological Survey (USGS) requested that the National Research Council conduct an independent and comprehensive review.

Review of the U. S. Geological Survey's Volcano Hazards Program is organized around the three components of hazards mitigation. Chapter 2 deals with research and hazard assessment. Chapter 3 covers monitoring and Chapter 4 discusses crisis response and other forms of outreach conducted by the VHP. Chapter 5 describes various cross-cutting programmatic issues such as staffing levels, data formats, and partnerships. Chapter 6 offers a vision for the future of the Volcano Hazards Program, and Chapter 7 summarizes the conclusions and recommendations of the preceding chapters. Throughout the report, major conclusions are printed in italics and recommendations in bold type.

The committee has written this report for several different audiences. The main audience is upper management within the USGS and the VHP. However, the committee believes that scientists within the VHP will also find the report valuable. The report is written in such a manner as to be useful to congressional staff as well.

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Essay on Volcanoes: Mount St. Helens Eruption — Before and After

Essay on volcanoes: introduction.

• Mount St Helens Before the Eruption

What Happened During the Eruption of Mount St Helens?

Effects of mt st helens eruption 1980, mount st helens eruption 1980: deaths, mount st helens eruption 1980: damage, essay about volcanoes: conclusion, works cited.

The life of human beings has for a long time witnessed occurrences and impacts of different types of disasters. Natural disasters constitute part of many disasters that are likely to occur in the world. In addition, natural disasters are ultimate effect of natural hazards such as flood, tornado, hurricane, volcanic eruption, earthquakes, and landslide (Hyndman and Hyndman, 1).

When natural disasters occur, they results into diverse negative economic, social, physical and psychological impacts to the people and societies affected either directly or indirectly. Volcano eruptions are categorized as part of natural disasters that are likely to affect human beings.

When they occur, volcanic eruptions are likely to results into widespread negative consequences such as rampant destructions of vegetations and infrastructures, displacement of people, death of people and other animal species, and many other negative consequences (Hyndman and Hyndman, 2).

Mt St. Helens is one of the remaining active stratovolcano mountains in the world, specifically found in United States of America (Meister 20). It is located between Washington and Oregon, in the Cascade Range, where it is part of Cascade Volcanic Arc, and the youngest mountain of Cascade Mountains (Geological Survey-USA 3).

Cascade Volcanic Arc constitutes part of 160 active volcanoes that make up ‘Pacific Ring of Fire’. Mt St. Helens has reclaimed place in the history as far as natural disasters resulting from volcanic eruptions are concerned. The interest of this paper is to look at the Mt St. Helens within the perspectives of natural disaster realms evaluating its history and widespread impacts, together with resilience strategies that have been adopted over time.

What Did Mount St Helens Look Like Before the Eruption?

In trying to understand the genesis of eruption of Mt St. Helens, it is important to locate and describe the historical geographical location of the mountain. Mt St. Helen is estimated to be 2950 meters in height, and as it was seen earlier, it is located in the sparsely populated Cascade Mountains in north-west USA (Meister 20).

Before the famous 1980 eruption of the mountain, it had been established that the mountain had been inactive for about 123 years, a situation that had convinced majority of people in the area that nothing like an eruption could occur in the area (Payne and Jennings 102).

The eruption itself that year was one of the worst eruptions in the country and around the world in a period of 60 years. Mt St. Helens is described as a subduction zone volcano, and this means that the mountain is located on a tectonic plate’s boundary and not necessarily on a hotspot.

Furthermore, description and reaction of tectonic plates shows that, tectonic plates normally move due to convection currents in the earth’s liquid layers (Gray and Schunn 455). In most instances, plates lying below the mountain normally push together or converge, a situation that leads to subduction (Gray and Schunn 455).

Moreover, when the process of subduction occurs, which involves one tectonic plate sliding over the other, solid mantle from the bottom plate are forced down to areas that have high temperatures. As a result, the mantle, which is totally solid in nature, is able to burn and melt in the high temperatures transforming the solid mantle into a viscous liquid magma (Meister 20).

The process of Mt St. Helen’s eruption is described below. Prior and subsequent eruptions history of the mountain has been investigated and narrated by many authors. Here, it has been found that, numerous eruptions took place on the mountain before the main eruption of 1980. Such eruptions have been found to occur when the Juan de Fuca, which is an oceanic crust, moves eastwards towards the North American Plate, which is a continental crust.

The process results in a situation where the continental crust is forced to submerge or move downwards. This process largely constitutes movement, whereby, friction is created that produces earthquake, and since the process is characterized by increase in temperature, the oceanic crust is automatically destroyed. The result of the process was the build-up of magma beneath the mountain, and as pressure increased, the magma forced its way into the earth’s surface.

The formed viscous magma builds up, and this situation is responsible for the increase in the pressure on the earth’s surface. However, since the pressure is not released immediately but waits until the magma shifts, an eruption takes place (Gray and Schunn 455). It has been found out that, volcanic eruption takes place only when the magma rises to the earth’s surface.

Mt St. Helens has been described by geologists as a composite volcano (stratovolcano), which is a term given to steep-sided and symmetrical cones, usually made of alternating layers of lava flows, ash, and related volcanic debris (MountStHelens.com Information Resource Center 1).

One thing that has been observed with the composite volcanoes is that, they normally erupt with great force, a situation that sometimes becomes violent. Due to this, composite volcanoes result into great negative and serious impacts on lives and properties around the mountains (Mt. St. Helens 1).

Before the 1980 eruption, Mt St. Helens had a snowcap and was symmetrical in shape, which led to many people around the mountain referring it as ‘Fujiyama of America’ (History – Mt. St. Helens 1). This nickname may have come about due to the fact that the mountain is part of active Cascade volcanoes, which form part of the circum-Pacific ‘Ring of Fire’, and this zone in the larger American and world history is known to be a dangerous zone characterized by frequent and destructive earthquake activities and volcano eruptions (Furgang 5).

Mt St. Helens got its name from George Vancouver In 1792, a British Royal Navy office and also an enthusiastic explorer. The name St. Helens was in honor of George’s countryman, known as Alleyne Fitzherbert, who was the holder of the title ‘St. Helens’ and at the time, was the British Ambassador to Spain. Separately, locals of the area referred to the mountain as ‘Louwala-Clough’ or ‘the smoking mountain’, probably due to frequent ‘smokes’ of volcanoes from the mountain (Furgang 5).

The eruption of Mt St. Helen did not take place for the first time in 1980, but some credible accounts reveal how the mountain had been experiencing small eruptions for ages. For instance, accounts are made of local inhabitants of the region who were Indians, together with early settlers who came and settled in the region, of how they witnessed less frequent violent outbursts of the mountain (History – Mt. St. Helens 1).

Moreover, other historical evidences advance the notion that, during the mid-19th century, Mt St. Helen was an active volcano mountain for about 26 years between the period 1831 and 1857. Subsequently, the mountain was still active during the three decades prior to the 1831 period, although the nature and extent of the eruption of the mountain was not severe, except for 1800 when there was a major eruption of the mountain (History – Mt. St. Helens 1).

Since 1898 when the mountain was characterized with some forms of eruptions, no thought ever crossed people’s minds that it could reach a time when the mountain could become so violent and so destructive – the way it did in 1980. There was actually no evidence, and even people in the area had settled peacefully in the adjacent lands.

In fact, before the volcano eruption of 1980, Mt St. Helen was regarded and considered one of the serene, quiet, peaceful, and beautiful mountains that had attracted a high number of wildlife, and many people had settled in the region. Moreover, the region was live for tourism activities, since the area had numerous recreational and leisure activities and sites.

Besides all these, at the base of Mt St. Helen, there was Spirit Lake, which had fresh waters, its shores had numerous, and beautiful woods, and this made the lake to become a popular tourism and recreational area for activities such as hiking, camping, fishing, swimming, and boating.

The following is an account of events that were witnessed prior to the occurrence of Mt St. Helen eruption in 1980. The signs for the eruption of the mountain became evident during the spring of 1980, which actually was in March (Kranz 8). Appropriate date that been accounted in books of history point to 20 March of 1980 as a day when minor earthquakes measuring about 4.1 on the Richter scale was realized (Waugh 266).

In the next few days, the region experienced a number of minor tremors, which continued to take place until 27 March of the year when for the first time, a small eruption of steam and ash was seen coming out of the mountain. These things continued for a number of days, a scenario that became strange to many people, and many tourists were attracted to the mountain.

From March to late April, people in the region were just subjected to instances of tremor and ash coming from the mountain. However, in early May, people found it perplexing when the north side of the mountain began bulging by about 1.5 meters a day, which was a direct indication of how there was build-up of magma and increase of pressure in the mountain.

In early hours of 18 May 1980, an earthquake, which measured about 5.0 on the Richter scale, was experienced in the region, and the earthquake led to the already formed bulge to move forward and downward. This rhythmic forward and downward movement resulted into release of materials, which later formed landslide of rock, glacier ice, and soil (Waugh 266). These materials found their way down to Spirit Lake, leading to displacement.

Due to displacement, materials from the mountain aided by waters from the lake moved in a faster speed to the northern fork of Toutle Valley. On the other hand, the mudflow, which was part of this material movement, moved and found its way to Baker Camp, while floodwater continued down the valley where sediment blocked the port of Portland on the Columba River (Waugh 266).

Almost 20 minutes after these events took place, at about 0833 hours on the same day (18 May), the already exposed magma exploded on its sideways, precipitating a huge blast of waves of volcanic gas, steam, and dust. These found way to the north side of the mountain about 25 kilometers, where all animals and vegetations within this range were totally and completely destroyed (Waugh 266).

In the subsequent hours of the morning after these blasts, there was a series of eruptions, ejecting gases together with ash and volcanic rocks from the mountain, creating magma vents. A thick ash, which formed an invisible cloud, went up about 20 kilometers and drifted to the east of the mountain, where it moved before settling in the Yakima region, which is located 120 kilometers away from the mountain.

This led to an immediate precaution on the people of the region being taken, and people advised to stay indoors and only come out of houses when in facemasks.

Furthermore, three days after the eruption, the volcanic cloud, which had formed in the sky and composed of fine ash, reached the east cost USA. In addition, after several days, it was established that the ash had moved across the world and almost the entire sky of the world was full of volcanic plumes. Estimates from the eruption activities of 18 May 1980 show that the volume of all materials ejected from the mountain was about 2.79 km cubic (Munsart 26).

Further, the eruption was responsible for the removal of the north side of the mountain, and this resulted into a reduction of the height of the mountain by about 400 meters. At the same time, it created a wide crater with an in-depth height of about 800 meters. There was also the opening of the north end, which resulted in creation of a huge breach. By the time the eruption was over, a lot of damage had been done in terms of destruction and loss of lives, as it will be discussed in subsequent paragraphs.

The eruption of Mt St. Helen resulted into many negative consequences that had not been witnessed for a long time in the regions near the mountain and even as far as parts of Alberta Canada. Death of people and animals occurred, together with destructions of vegetations, fish species, and destruction of infrastructures.

It has been noted by numerous authors that the events resulting from the 1980 eruption on St. Helens caused a succession of interacting biological, geological, hydrologic and anthropogenic changes in the surroundings and neighborhoods of Mt. St. Helens (Dale, Swanson and Crisafulli 27). The initial events of the eruption are responsible for the change of landforms, watershed hydrology, availability, and delivery of sediments and the disturbance caused on the vegetations and animals in regulating physical and biological processes (Dale, Swanson, and Crisafulli 27).

At the same time, it has been noted that hydrologic and geomorphic processes were responsible for the change in the paths and rates of ecological responses, which saw habitats change; here, some species were favored, while others were destroyed (Dale, Swanson, and Crisafulli 27).

The first effect of the eruption was on the mountain itself, whereby, geological estimates shows that St. Helens reduced by about 390 meters to its current height of 2560 meters (Waugh 267). Moreover, a huge and wide crater was formed on the mountain, and estimated figures show that the crater measures 3 kilometers long and 0.5 kilometers deep (Bao 186). The created crater is found on the north-facing slope of the mountain.

Moreover, it has been noted that, during the eruption, valleys that surround the mountain were glaciated, a situation that has continued in the region leading to fluvial activities and erosion related activities, which have largely led to erosion in the valleys, giving way to creation and exposure of new landforms. In addition, the next to be affected in the eruption was the drainage system of the region, which changed, and in subsequent years, became dangerous and destructive to the surrounding communities and people.

There are notable three primary rivers in the region covered by Mt St. Helen, which are Toutle River, the Kalama River, and Lewis River. The three Rivers create the Cowlitz River Basin, which was a great and celebrated recreational area before eruption. It should be noted that, the eruption of the mountain was responsible for the production and spread of huge debris and avalanche, and at same time, mudflows and lahars, storm flows, and tephra deposits became common characteristics of the eruption.

The debris avalanche resulted into greater deposition taking place in the Spirit Lake, and the deposition has been estimated to be about 45 to 180 meters deep. Due to this deposition, there was formation of new drainage system on top of avalanche, since major ponds and lakes in the region were breached. This changed the course of many tributaries and water flow patterns, a pattern that has persisted for a long time in the region.

Other features resulting from the change of drainage system of the area include the mudflows and lahars, which also became common features of the eruption. The mudflows developed specifically after the debris avalanche in the South Fork Toutle River and in the tributaries of Lewis River (Lee 75).

Mudflows at the same time caused destruction of the Toutle and Cowlitz Rivers due to high deposition, and this event led to closure of Columbian River for shipping purposes (Lee 77). This came about after the channel capacity of Cowlitz River reduced in size, and this was largely attributed to high levels of deposition.

On the other hand, deposition in the Lewis River and the Swift Reservoir resulted to the rise of water levels in the lake and river by about 0.85 meters. The adverse effect of this increase in water levels was experienced in increased floods in the area, since tributaries of the Lewis River such as Swift Creek, Pine Creek, and Muddy River were affected and they could not find the right course to the river.

Other activities that changed drainage pattern in the area included presence of storm flows due to absence of rivers and vegetations on the riverbanks of major rivers. What this meant was that, during the moments of precipitation and due to lack of friction, water moved fast on the surface of riverbanks, causing aggravated erosion and sedimentation of rivers.

The deposition of sediments in rivers meant that there was reduction in the depth of the river, a situation that became susceptible to increased chances of floods. Furthermore, tephra deposits affected Clearwater River Basin, although the effects of the deposits did not cause adverse effects like the other discussed deposits.

Apart from change in drainage system of the area, other effects of eruption included loss of human life and destruction of numerous settlements, communication, and transport systems. In addition, vegetation and forestry were not spared, while majority of wildlife died. Moreover, farming in the area was disrupted and provision of services was rendered difficult. With regard to loss of lives, it has been estimated that about 57 people perished in the disaster, many were injured, and thousands were left homeless (Lopes and Lopes 127).

It has been observed that, before the eruption took place, there had been promotion of awareness and warnings about the pending disaster, but some people ignored these calls. Some argued from the point that the relative peace and calmness that had been enjoyed in the region could not just end in one day of a disaster to the ‘harmless’ St. Helens mountain (Campbell 1980).

As a result, majority of people not evacuated died, as their homes were buried by the lava of eruption. In addition, people died from burns caused by overwhelming ash, and those who survived to narrate what happened describe the situation to have led to total darkness, high temperatures that resulted into unbearable heat, and suffocating due to lack of oxygen (Fisher, Heiken, and Hulen 8-10).

With regard to infrastructure, historical records indicate that about 123 buildings were destroyed and everything in the Toutle Valley that was upright before eruption was buried in a few hours the eruption took place. Some of the destroyed infrastructure in the valley included bridges, roads, human settlements, electricity supply, and everything that had been developed in the area (Campbell 1980).

Automobiles were affected, as ash from the eruption plugged engines of motors (Noji 190). Subsequently, due to high concentration of volcanic ash in the air, Airports and highways were closed as high volumes of ash fell on farms, towns, forestlands, and all open areas, largely in Washington, Idaho, Montana and the nearby areas (Bryant 247).

Forestry and related vegetations were also not spared, as more destruction took place. For example, when the eruption took place, it was established that every tree located in the 250 kilometer square and lying within the 25 kilometer blast zone, which is to the north of the volcano, was completed destroyed and everything in the name of tree or vegetation was brought to the ground.

Moreover, those trees that were carried away by water caused logjam over a long distance, and in subsequent years, many trees (about 10 millions) had to be re-planted in the region. Apart from vegetation, wildlife was also casualties to the eruption. It has been established that many species of animals, which had attracted tourists in the region and which fell within the blast zone, were completed eliminated.

This also includes fish species, which, majority died due to deposition, sedimentation, and increase in water temperatures and a few managed to hibernate or migrate. On overall, aquatic and marine life of species was destroyed, especially for salmon and trout fish species (Kramer 388).

Mt. St. Helens is one of the Volcano Mountains in the United States of America. Before the mountain erupted in 1980, it was regarded to be a ‘harmless’ mountain, and had become a perfect social, economic, cultural, and physical symbol to the natives of the area and tourist. However, events of May 1980 changed everything, as everybody was shocked by the magnitude of the impact the eruption of the mountain had caused.

The mountain is just one example of the many forms of natural disasters, which cause great effect to the people and other biodiversity. Natural disasters are known to cause death, injuries, and displacement of people, destruction of biodiversity, animal species, and destruction of infrastructures.

The effects become aggravating when the larger population and communities affected by the natural disasters are not fully resilient to such disasters. Therefore, it is important and necessary that mitigation strategies to deal with natural disasters should look into ways of increasing education and awareness among people about the disasters in order to increase their resilience capabilities (Ronan and Johnston 72).

Bao, Sandra. Washington, Oregon and the Pacific Northwest . New York, USA: Lonely Planet, 2008. Print.

Bryant, Edward. Natural Hazards . Cambridge, UK: Cambridge University Press, 2005. Print.

Campbell, Ballard C. Disasters, Accidents, and Crises in American History . New York, USA: InfoBase Publishing, 2008. Print.

Dale, Virginia, Frederick Swanson & Charles Crisafulli. Ecological Responses to the 1980 Eruption of Mount St. Helens . New York, USA: Springer. Print.

Fisher, Richard, Grant Heiken and Jeffrey Hulen. Volcanoes: Crucibles of Change . New Jersey, USA: Princeton University Press, 1998. Print.

Furgang, Kathy. Mount St. Helens: The Smoking Mountain . New York, USA: The Rosen Publishing Group, 2001. Print.

Geological Survey-USA. The 1980 eruptions of Mount St. Helens, Washington . Washington DC, USA: U.S. Department of the Interior, U.S. Geological Survey, 1981. Print.

Gray, Wayne & C. Schunn. Proceedings of the Twenty-Fourth Annual Conference of the Cognitive Science Society . New York, USA: Routledge, 2002. Print.

MountStHelens.com Information Resource Center . History – Mt. St. Helens. n.d.

Hyndman, Donald & D. Hyndman. Natural Hazards and Disasters . Ohio, USA: Cengage Learning, 2010. Print.

Kramer, William M. Disaster Planning and Control . New York, USA: Fire Engineering Books, 2009. Print.

Kranz, Rachel. Mount St. Helens . New York, USA: Benchmark Education Company, 2011. Print.

Lee, Douglas B. Effects of the Eruptions of Mount St. Helens on Physical, Chemical, and Biological Characteristics of Surface Water, Ground Water, and Precipitation in the Western United States . New York, USA: DIANE Publishing, 1998. Print.

Lopes, Rosaly M.C. and Rosaly Lopes. The Volcano Adventure Guide . Cambridge, UK: Cambridge University Press, 2005. Print.

Meister, Cari. Volcanoes . New York, USA: ABDO, 1999. Print.

Munsart, Craig A. American History through Earth Science . New York, USA: Libraries Unlimited, 1997. Print.

Noji, Eric K. The Public Health Consequences of Disasters . Oxford, UK: Oxford University Press, 1996. Print.

Payne, David and Sue Jennings. Issues and Environments: GCSE geography for AQA specification C . London, UK: Heinemann, 2002. Print.

Ronan, Kevin R. and David Moore Johnston. Promoting Community Resilience in Disasters: The Role for Schools, Youth, and Families . New York, USA: Springer, 2005. Print.

Waugh, David. The New Wider World . Cheltenham, UK: Nelson Thornes, 2003. Print.

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Your Article Library

Essay on volcanoes | geology.

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After reading this article you will learn about:- 1. Introduction to Volcanoes 2. Volcano Formation 3. Volcanic Landforms 4. Major Gases Emitted by Volcanoes 5. Lightning and Whirlwinds 6. Features Produced by the Escape of Gases from Volcanic Lavas 7. Volcanic Products 8. Source of the Explosive Energy 9. Classification of Pyroclastics 10. Lahars-Mudflows on Active and Inactive Cones and Other Details.

Essay Contents:

• Essay on the Volcanoes and Atmospheric Pollution

Essay # 1. Introduction to Volcanoes :

A volcano is a cone shaped hill or mountain which is built-up around an opening in the earth’s surface through which hot gases, rock fragments and lavas are ejected.

Due to the accumulation of the solid fragments around the conduit a conical mass is built which increases in size to become a large volcanic mountain. The conical mass so built-up is called a volcano. However the term volcano is taken to include not only the central vent in the earth but also the mountain or hill built around it.

Volcanoes are in varying sizes, varying from small conical hills to loftiest mountains on the earth’s surface. The volcanoes of the Hawaiian Islands are nearly 4300 metres above sea level since they are built over the floor of the Pacific ocean which at the site is 4300 to 5500 metres deep, the total height of the volcano may be about 9000 m or more.

The very high peaks in the Andes, in the Cascade Range of the Western United States, Mt. Baker, Mt. Adams, Mt. Hood etc. are all volcanoes which have now become extinct. Over 8000 independent eruptions have been identified from earth’s volcanoes. There are many inaccessible regions and ocean floors where volcanoes have occurred undocumented or unnoticed.

The eruption of a volcano is generally preceded by earthquakes and by loud rumblings like thunder which may continue on a very high scale during the eruption. The loud rumblings are due to explosive movement of gases and molten rock which are held under very high pressure. Before eruption of a volcano fissures are likely to be opened, nearby lakes likely to be drained and hot springs may appear at places.

The eruptive activity of volcanoes is mostly named after the well-known volcanoes, which are known for particular type of behaviour, like Strambolian, Vulcanian, Vesuvian, Hawaiian types of eruption. Volcanoes may erupt in one distinct way or may erupt in many ways, but, the reality is, these eruptions provide a magical view inside the earth’s molten interior.

The nature of a volcanic eruption is determined largely by the type of materials ejected from the vent of the volcano. Volcanic eruptions may be effusive (fluid lavas) or dangerous and explosive with blasts of rock, gas, ash and other pyroclasts.

Some volcanoes erupt for just a few minutes while some volcanoes spew their products for a decade or more. Between these two main types viz. effusive and explosive eruptions, there are many subdivisions like, eruption of gases mixed with gritty pulverised rock forming tall dark ash clouds seen for many kilometres, flank fissure eruptions with lava oozing from long horizontal cracks on the side of a volcano.

There is also the ground hugging lethally hot avalanches of volcanic debris called pyroclastic flows. When magma rises, it may encounter groundwater causing enormous phreatic, i.e., steam eruptions. Eruptions may also release suffocating gases into the atmosphere. Eruptions may produce tsunamis and floods and may trigger earthquakes. They may unleash ravaging rockslides and mudflows.

Volcanoes which have had no eruptions during historic times, but may still show fairly fresh signs of activity and have been active in geologically recent times are said to be dormant. There are also volcanoes which were formerly active but are of declining activity a few of which may be emitting only steam and other gases.

Geysers are hot springs from which water is expelled vigorously at intervals and are characteristics of regions of declining volcanic activity. Geysers are situated in Iceland, the Yellowstone park in USA and in New Zealand.

In contrast to the explosive type of volcanoes, there exist eruptions of great lava flows quietly pouring out of fissures developed on the earth’s surface. These eruptions are not accompanied by explosive outbursts. These are fissure eruptions.

Ex: Deccan Trap formations in India. The lavas in these cases are mostly readily mobile and flow over low slopes. The individual flows are seldom over a few meters in thickness; the average thickness may be less than 15 meters. If the fissure eruptions have taken place in valleys however, the thickness may be much greater.

A noteworthy type of volcano is part of the world encircling mid-ocean ridge (MOR) visible in Iceland. The MOR is really a single, extremely long, active, linear volcano, connecting all spreading plate boundaries through all oceans. Along its length small, separate volcanoes occur. The MOR exudes low-silica, highly fluid basalt producing the entire ocean floor and constituting the largest single structure on the face of the earth.

Essay # 2. Location of Volcanoes:

Volcanoes are widely distributed over the earth, but they are more abundant in certain belts. One such belt encircles the Pacific ocean and includes many of the islands in it. Other volcanic areas are the island of West Indies, those of the West coast of Africa, the Mediterranean region and Iceland.

Most volcanoes occur around or near the margins of the continents and so these areas re regarded as weak zones of the earth’s crust where lavas can readily work their way upward. There are over 400 active volcanoes and many more inactive ones. Numerous submarine volcanoes also exist.

Since it is not possible to examine the magma reservoir which fees a volcano our information must be obtained by studying the material ejected by the volcano. This material consists of three kinds of products, viz. liquid lava, fragmented pyroclasts and gases. There may exist a special problem in studying the gases, both in collecting them under hazardous conditions or impossible conditions.

It may also be difficult to ascertain that the gases collected are true volcanic gases and are not contaminated with atmospheric gases. Investigation of the composition of extruded rock leads to a general, although not very detailed, correlation between composition and intensity of volcanic eruption.

In general, the quite eruptions are characteristic of those volcanoes which emit basic or basaltic lavas, whereas the violent eruptions are characteristic of volcanoes emitting more silicic rocks.

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Essay # 3 . formation of volcanoes :.

The term volcano is used to mean both the opening in the earth’s crust, i.e. the vent through which the eruption of magma occurs as well as the hill built- up by the erupted material. Volcanoes occur where the cracks in the earth’s crust lead to the magma chamber.

The liquid magma which is lighter than the surrounding rocks is under high pressure is pushed up towards the surface through these cracks. In this process the gases dissolved in the magma which expand are released providing an upward push to the magma.

As the magma gets closer to the surface, due to the reducing confining pressure to overcome, the magma and the gases flow faster. The magma, depending on its viscosity may quietly pour to the surface in the form of a flood of molten rock or it may explosively spurt out the molten rock to considerable heights as showers on the surrounding region with solid rock fragments and globs of molten rock. The liquid magma discharged to the surface is called lava.

Essay # 4 . Volcanic Landforms :

Many surface features of volcanic origin are created. These features range from towering peaks and huge lava sheets to small and low craters. The features created by a volcano vary depending on the type of eruption, the material erupted and the effects of erosion.

Four types of volcanic landforms are formed:

i. Ash and Cinder Cones or Explosion Cones:

These appear where explosive eruptions take place. When very hot solid fragments from a central crater (or a subsidiary crater) are ejected. A concave cone of height not exceeding 300 m is formed.

ii. Lava Cones:

These are formed from slowly upwelling lava.

These are of two types:

(a) Steep Sided Volcanoes:

These are formed from sticky acid lava which gets hardened quickly. The highly viscous lava which is squeezed out makes spines like tower.

(b) Shield Volcanoes:

These show gently sloping dome features. These are formed from runny lava which flows long distances, before getting hardened.

iii. Composite Cones or Strato-Volcanoes or Strato Cones:

These volcanoes have concave cone shaped sides of alternating ash and lava layers. These are common in most very high volcanoes. In some cases solid lava may plug the main pipe to the crater. Then pent up gases may blast the top off.

When the magma chamber empties, the summit of the volcano collapses. As a consequence, the feature produced is a vast shallow cavity called a Caldera. Strato volcanoes are the accumulated products of many volcanoes. Chemically most of these products are andesite. Some are dacite and a few are basalt and rhyolite. Due to this chemical mix and characteristic interlayering of lava flows, this volcano is called strato volcano.

iv. Shield Volcanoes:

When a volcano vent produces many successive basaltic lava flows stacked one on top of another in eruptive order, the resulting landform is called a shield volcano. A cinder cone and its associated lava flow can be thought of as the initial building blocks of a shield volcano.

A cinder cone is monogenetic because it forms from a single short-lived eruption (of a few years to a decade or two in duration). In contrast, a shield volcano that is an accumulation of the products of many eruptions over a period of say thousands to hundreds of thousands of years is polygenic.

On land these volcanoes have low angle cones. When they form under water they start with a steeper shape because the lava freezes much faster and does not travel far. The shape fattens to the shield form as the cone builds above the sea level.

v. Plateau Basalts or Lava Plains:

These form the bulk of many volcanic fields. These are features which occur where successive flows of basic lava leaks through fissures, over land surface and then cools and hardens forming a blanket-like feature.

The surface appearance of a flow provides information on the composition and temperature of the magma before it solidified. Very hot low viscosity basalt flows far and fast and produces smooth ropy surfaces. Cooler and less-fluid basalt flows form irregular, jagged surfaces littered with blocks.

The lava flows have blanketed to about 2000 m thickness covering 6,50,000 sq.km. in the Indian Deccan Plateau. Such lava flows have also created the U.S. Columbia River Plateau, the Abyssinian Plateau, the Panama Plateau of South America and the Antrim Plateau of Northern Ireland.

Magmas like dacite and rhyolite that have high silica contents are cooler and more viscous than basalt and hence they do not flow far resulting in the features, lobes, pancakes and domes. Domes often plug up the vent from which they issued, sometimes creating catastrophic explosions and may create a crater.

Eroded volcanoes have their importance. They give us a glimpse of the interior plumbing along which the magma rose to the surface. At the end of an eruption, magma solidifies in the conduits along which it had been rising. The rock so formed is more resistant than the shattered rock forming the walls and hence these lava filled conduits are often left behind when the rest of the volcano has been eroded away.

The filling of the central vertical vent is somewhat circular in section and forms a spire called a neck. The filling of cracks along which lava rose forms nearly vertical tabular bodies called dikes. Sometimes magma works its way along cracks that are nearly horizontal, often along bedding planes of sedimentary rocks. This results in the formation of table-like bodies called sills.

Essay # 5 . Major Gases Emitted by Volcanoes :

Volcanic gases present within the magma are released as they reach the earth’s surface, escaping at the major volcanic opening or from fissures and vents along the side of the volcano. The most prevalent gases emitted are steam, carbon dioxide and hydrogen sulphide. Carbon dioxide is an invisible, odourless poisonous gas. The table below shows the gases emitted from volcanoes.

Essay # 6 . Lightning and Whirlwinds :

Lightning flashes accompany most volcanic eruptions, especially those involving dust. The cause of this lightning is believed to be either contact of sea water with magma or generation of static electricity by friction between colliding particles carried in the erupting gases. Lightning is characteristic of vulcanian eruptions and is common during glowing avalanches.

Whirlwinds are seen during many volcanic eruptions. They are seen above hot lavas. Sometimes they form inverted cones extending a little below the eruption cloud. Energy for the whirlwinds might be from the hot gases and lava, high velocity gas jets in the eruption, heat released into the atmosphere during falls of hot tephra or where lava flows into the sea creating steam.

Essay # 7 . Features Produced by the Escape of Gases from Volcanic Lavas :

The gases of volcanic lavas produce several interesting features while they escape. They expand in the lava of the flow and thus cause the formation of Scoriaceous and Pumiceous rocks. By their explosion, they blow the hardened lava above them in the conduit, into bits and thus produce pyroclastic material.

They form clouds above volcanoes, the rain from which assists in the production of mud flows. When the volcano becomes inactive, they escape aiding in the formation of jumaroles, geysers and hot springs. Scoriaceous rocks are extremely porous. They are formed by the expansion of the steam and other gases beneath the hardened crust of a lava. The final escape of the gases from the hardening lava leaves large rounded holes in the rock.

Pumice is a rock also formed by the expansion and escape of gases. In pumice, many of the holes are in the form of long, minute, closed tubes which make the rock so light that it will float on water.

These tubes are formed by the expansive force of large amounts of gases in an extremely viscous lava that cools very rapidly, forming a glassy rock. Pumice is the rock that is usually formed from the lava ejected from explosive volcanoes. It can be blown to kilometres by explosions.

Essay # 8 . Volcanic Products :

Volcanoes give out products in all the states of matter – gases, liquids and solids.

Steam, hydrogen, sulphur and carbon dioxide are discharged as gases by a volcano. The steam let out by a volcano condenses in the air forming clouds which shed heavy rains. Various gases interact and intensify the heat of the erupting lavas. Explosive eruptions cause burning clouds of gas with scraps of glowing lava called nuees ardentes.

The main volcanic product is liquid lava. Sticky acid lava on cooling, solidifies and hardens before flowing long distances. Such lava can also block a vent resulting in pressure build-up which was relieved by an explosion. Basic fluid lava of lesser viscosity flows to great distances before hardening.

Some lava forms are produced by varying conditions as follows. Clinkery block shaped features are produced when gas spurted from sluggish molten rock capped by cooling crust. These are called Aa.

Pahoehoe is a feature which has a wrinkled skin appearance caused by molten lava flowing below it.

Pillow lava is a feature resembling pillows. This feature piles up when fast cooling lava erupts under water.

Products in explosive outbursts are called Pyroclasts. These consist of either fresh material or ejected scraps of old hard lava and other rock. Volcanic bombs include pancake-flat scoria shaped on impacting the ground and spindle bombs which are twisted at ends as they whizzle through the air. Acid lava full of gas formed cavities produces a light volcanic rock.

Pumice which is so light it can float on water. The product Ignimbrite shows welded glassy fragments. Lapilli are hurled out cinder fragments. Vast clouds of dust or very tiny lava particles are called volcanic ash. Volcanic ash mixed with heavy rain creates mudflows.

Sometimes mudflows can bury large areas of land. Powerful explosions can smoother land for many kilometres around with ash and can hurl huge amount of dust into the higher atmosphere. Violent explosions destroy farms and towns, but volcanic ash provides rich soil for crops.

i. Hot springs:

The underground hot rocks heat the spring waters creating hot springs. The hot springs shed minerals dissolved in them resulting in crusts of calcium carbonate and quartz (geyserite).

ii. Smoker:

This is a submarine hot spring at an oceanic spreading ridge. This submarine spring emits sulphides and builds smoky clouds.

iii. Geyser:

Periodically steam and hot water are forced up from a vent by super-heated water in pipe like passage deep down. Famous geysers are present in Iceland and Yellowstone National Park.

iv. Mud volcano:

This is a low mud cone deposited by mud-rich water gushing out of a vent.

v. Solfatara:

This is a volcanic vent which emits steam and sulphurous gas.

vi. Fumarole:

This is a vent which emits steam jets as at Mt. Etna, Sicily and Valley of Ten Thousand smokes in Alaska.

vii. Mofette:

This is a small vent which emits gases including carbon dioxide. These occur in France, Italy and Java.

Various terms used while describing volcanic features are given below:

i. Magma Chamber:

Magma is created below the surface of the earth (at depth of about 60 km) and is held in the magma chamber until sufficient pressure is built-up to push the magma towards the surface.

This is a pipe like passage through which the magma is pushed up from the magma chamber.

This is the outlet end of the pipe. Magma exits out of the vent. If a vent erupts only gases, it is called fumarole.

iv. Crater:

Generally the vent opens out to a depression called crater at the top of the volcano. This is caused due to the collapse of the surface materials.

v. Caldera:

This is a very big crater formed when the top of an entire volcanic hill collapses inward.

When the erupted materials cover the vent, a volcanic dome is created covering the vent. Later as the pressure of gas and magma rises, another eruption occurs shattering the dome.

A mountain-like structure created over thousands of years as the volcanic lava, ash, rock fragments are poured out onto the surface. This feature is called volcanic cone.

viii. Pyroclastic Flow :

A pyroclastic flow (also known as nuee ardentes (French word) is a ground hugging, turbulent avalanche of hot ash. pumice, rock fragments, crystals, glass shards and volcanic gas. These flows can rush down the steep slopes of a volcano at 80 to 160 km/li, burning everything in their path.

Temperatures of these flows can reach over 500°C. A deposit of this mixture is also often referred to as pyroclastic flow. An even more energetic and dilute mixture of searing volcanic gases and rock-fragments is called a pyroclastic surge which can easily ride up and over ridges.

ix. Seamounts :

A spectacular underwater volcanic feature is a huge localized volcano called a seamount. These isolated underwater volcanic mountains rise from 900 m to 3000 m above the ocean floor, but typically are not high enough to poke above the water surface.

Seamounts are present in all the oceans of the world, with the Pacific ocean having the highest concentration. More than 2000 seamounts have been identified in this ocean. The Gulf of Alaska also has many seamounts. The Axial Seamount is an active volcano off the north coast of Oregon (currently rises about 1400 m above the ocean floor, but its peak is still about 1200 m below the water surface.

Essay # 9 . Source of the Explosive Energy :

The energy for the explosive violence comes from the expansion of the volatile constituents present in the magma, the gas content of which determines the degree of commination of the materials and the explosive violence of the eruption.

This energy is expanded in two ways, firstly in the expulsion of the materials into the atmosphere and secondly, due to expansion within the magma leading to the development of vesicles. The most important gas is steam, which may form between 60 to 90 per cent of the total gas content in a lava. Carbon dioxide, nitrogen and sulphur dioxide occur commonly and hydrogen, carbon monoxide, sulphur and chlorine are also present.

Essay # 10 . Classification of Pyroclastics :

Pyroclastics refer to fragmental material erupted by a volcano. The larger fragments consisting of pieces of crystal layers beneath the volcano or of older lavas broken from the walls of the conduit or from the surface of the crater are called blocks.

Volcanic bombs are masses of new lava blown from the crater and solidified during flight, becoming round or spindle shaped as they are hurled through the air. They may range in size from small pellets up to huge masses weighing many kilonewtons.

Sometimes they are still plastic when they strike the surface and are flattened or distorted as they roll down the side of the cone. Another type called bread crust bomb resembles a loaf of bread with large gaping cracks in the crust.

This cracking of the crust results from the continued expansion of the internal gases. Many fragments of lava and scoria solidified in flight drop back into the crater and are intermixed with the fluid lava and are again erupted.

In contrast to bombs, smaller broken fragments are lapilli (from Italian meaning, little stones) about the size of walnuts; then in decreasing size, cinders, ash and dust. The cinders and ash are pulverized lava, broken up by the force of rapidly expanding gases in them or by the grinding together of the fragments in the crater, as they are repeatedly blown out and dropped back into the crater after each explosion.

Pumice is a type of pyroclastic produced by acidic lavas if the gas content is so great as to cause the magma to froth as it rises in the chimney of the volcano. When the expansion occurs the rock from the froth is expelled as pumice. Pumice is of size ranging from the size of a marble to 30 cm or more in diameter. Pumice will float in water due to many air spaces formed by the expanding gases.

Lava fountains in which steam jets blow the lava into the air produce a material known as Pele’s hair which is identical with rock wool which is manufactured by blowing a jet of steam into a stream of molten rock (Rock wool is used for many types of insulation).

Coarse angular fragments become cemented to form a rock called volcanic breccia. The finer material like cinders and ash forms thick deposits which get consolidated through the percolation of ground water and is called tuff. Tuff is a building stone used in the volcanic regions. It is soft and easily quarried and can be shaped and has enough strength to be set into walls with mortar.

i. Agglomerate:

The debris in and around the vent contains the largest ejected masses of lava bombs which are embedded in dust and ash. A deposit of this kind is known as agglomerate. The layers of ash and dust which are formed for some distance around the volcano and which builds its cone, become hardened into rocks which are called tuffs.

Ash includes all materials with size less than 4 mm. It is pulverized lava, in which the fragments are often sharply angular and formed of volcanic glass; these angular and often curved fragments are called shards.

Since the gas content of ash on expulsion is high it has considerable mobility on reaching the surface; it is also hot and plastic, the result of these conditions being that the fragments often become welded together. The finest of ash is so light that wind can transport it for great distances.

The table below sets out a general classification of pyroclastic rocks based on the particle size of the fragments forming the rocks.

The chart in Fig. 15.3 summarizes the names of the common magmas and their associated ranges in silica. A very important property of magma that determines the eruption style and the eventual shape of the volcano it builds, is its resistance to flow, namely its viscosity.

Magma viscosity increases as its silica content increases. Eruptions of highly viscous magmas are violent. The highly viscous rhyolite magma piles up its ticky masses right over its eruptive vent to farm tall steep sided volcanoes.

On the contrary the basaltic magma flows great distances from its eruptive vent to from low, broad volcanic features. Magma in the intermediate viscosity spectrum say the andesite magma tends to form volcanoes of profile shapes between these two extremes.

An additional important ingredient of magma is water. Magmas also contain carbon dioxide and various sulphur-containing gases in solution. These substances are considered volatile since they tend to occur as gases at temperatures and pressures at the surface of the earth.

As basaltic magma changes composition toward rhyolite the volatiles become concentrated in the silica-rich magma. Presence of these volatiles (mainly water) in high concentration produces highly explosive volcanoes. It should be noted that these volatiles are held in magma by confining pressure. Within the earth, the confining pressure is provided by the load of the overlying rocks.

As the magma rises from the mantle to depths about 1.5 km or somewhat less, the rock load is reduced to that extent that the volatiles (mainly water) start to boil. Bubbles rising through highly viscous rhyolitic magma have such difficulty to escape their way, that many carry blobs of magma and fine bits of rock with them and they finally break free and jet violently upward resulting in a violent buoyant eruption column that can rise to kilometres above the earth.

The fine volcanic debris in such a powerful eruption gets dispersed within the upper atmosphere, hide the sunlight affecting the weather. The greater the original gas concentration in a magma and the greater the volume rate of magma leaving the vent, the taller is the eruption column produced.

The gases escaping from magma during eruption mix with the atmosphere and become part of the air humans, animals and plants breath and assimilate. However as magma cools and solidifies to rock during eruption, some of the gas remains trapped in bubbles creating vesicles. Generally all volcanic rocks contain some gas bubbles. A variety of vesicular rhyolite is pumice. Pumice is vesicular to such an extent, it floats in water.

Essay # 15. Classification of Volcanic Activity:

A classification of volcanic activity based on the type of product is shown in Fig. 15.4. The basic subdivision is based on the proportions of the gas, liquid and solid components, which can be represented on a triangular diagram. The four basic triangles represent the domain of four basic kinds of volcanic activity.

Essay # 16. Cone Topped and Flat Topped Volcanoes:

Generally rhyolite volcanoes are flat-topped because rhyolite magma which is extremely viscous, oozes out of the ground, piles up around the vent and then oozes away a bit to form a pancake shape. In contrast basalt volcanoes generally feed lava flows that flow far from the vent, building a cone.

Basaltic tephra (large particles of different size) is a spongy-looking black, rough material of pebble or cobble. Commercially this tephra is known as cinder and is used for gardening and rail-road beds. In some situations basaltic volcanoes develop flat top profile.

Flat topped volcanoes of basalt can form when there is an eruption under a glacier. Instead of getting ejected as tephra to form a cone, it forms a cauldron of lava surrounded by ice and water and eventually solidifying. When the ice melts, a steep-sided, table-shaped mountain known as a tuya remains. Volcanoes of this type are common in Iceland and British Columbia, where volcanoes have repeatedly erupted under glaciers.

Surprisingly, the Pacific ocean is a home to many flat-topped undersea basaltic mountains. These are called seamounts. How these seamounts were formed was a mystery for a long time. Surveying and dredging operations revealed that most seamounts were formerly conical volcanoes projecting above the water.

Geologists found that the conical volcanoes got lowered due to subsidence and the tops of the volcanoes came near the sea water level and the powerful waves mowed them flat. Continued subsidence caused them to drop below the water surface.

Essay # 17. Types of Volcanoes :

There are many types of volcanoes depending on the composition of magma especially on the relative proportion of water and silica contents. If the magma contains little of either of these, it is more liquid and it flows freely forming a shallow rounded hill.

Large water content with little silica permits the vapour to rapidly rise through the molten rock, throwing fountains of fire high into the air. More silica and less water in the magma make the magma more viscous. Such magma flows slowly and builds-up a high dome.

High content of both water and silica create another condition. In such a case the dense silica prevents the water from vaporizing until it is close to the surface and results in a highly explosive way. Such an eruption is called a Vulcan eruption.

Other types of eruption are named after people or regions associated with them. Vesuvian eruption named after Vesuvius is a highly explosive type occurring after a long period of dormancy. This type ejects a huge column of ash and rock to great heights upto 50 km.

A peleean eruption named after the eruption of Mt. Pelee in Martin que in 1902 is a highly violent eruption ejecting a hot cloud of ash mixed with considerable quantity of gas which flows down the sides of the volcano like a liquid. The cloud is termed nuee ardente meaning glowing cloud. Pyroclastic or ash flow refers to a flow of ash, solid rock pieces and gas. Hawaiian eruptions eject fire fountains.

Essay # 18. Violence of Volcanic Eruptions :

Volcanic activity may be classified by its violence, which in turn is generally related to rock type, the course of eruptive activity and the resulting landforms. We may in general distinguish between lava eruptions associated with basic and intermediate magmas and pumice eruptions associated with acid magmas.

The percentage of the fragmentary material in the total volcanic material produced can be used as a measure of explosiveness and if calculated for a volcanic region can be adopted as an Explosion Index (E), useful for comparing one volcanic region with others. Explosion Index for selected volcanic regions by Rittmann (1962) are shown in the table below.

Newhall and Self (1982) proposed a Volcanic Explosivity Index (VEI) which helps to summarize many aspects of eruption and is shown in the table below.

Essay # 19. Famous Volcanoes around the World :

Many volcanoes are present around the world. Some of the largest and well known volcanoes are listed in the table below.

Essay # 20. Volcanic Hazards :

Volcanic eruptions have caused destruction to life and property. In most cases volcanic hazards cannot be controlled, but their impacts can be mitigated by effective prediction methods.

Flows of lava, pyroclastic activity, emissions of gas and volcanic seismicity are major hazards. These are accompanied with movement of magma and eruptive products of the volcano. There are also other secondary effects of the eruptions which may have long term effects.

In most cases volcanoes let out lava which causes property damage rather than injuries or deaths. For instance, in Hawaii lava flows erupted from Kilauea for over a decade and as a consequence, homes, roads, forests, cars and other vehicles were buried in lavas and in some cases were burned by the resulting fires but no lives were lost. Sometimes it has become possible to control or divert the lava flow by constructing retaining walls or by some provision to chill the front of the lava flow with water.

Lava flows move slowly. But the pyroclastic flows move rapidly and these with lateral blasts may kill lives before they can run away. In 1902, on the island of Martinique the most destructive pyroclastic flow of the century occurred resulting in very large number of deaths.

A glowing avalanche rushed out of the flanks of Mount Pelee, running at a speed of over 160 km/h and killed about 29000 people. In A.D. 79 a large number of people of Pompeii and Herculaneum were buried under the hot pyroclastic material erupted by Mount Vesuvius.

The poisonous gas killed many of the victims and their bodies got later buried by pyroclastic material. In 1986, the eruption of the volcano at Lake Nyos, Cameroon killed over 1700 people and over 3000 cattle.

When magma moves towards the surface of the earth rocks may get fractured and this may result in swarms of earthquakes. The turbulent bubbling and boiling of magma below the earth can produce high frequency seismicity called volcanic tremor.

There are also secondary and tertiary hazards connected with volcanic eruptions. A powerful eruption in a coastal setting can cause a displacement of the seafloor leading to a tsunami. Hazardous effects are caused by pyroclastic material after a volcanic eruption has ceased.

Either melt water from snow or rain at the summit of the volcano can mix with the volcanic ash and start a deadly mud flow (called as lahar). Sometimes a volcanic debris avalanche in which various materials like pyroclastic matter, mud, shattered trees etc. is set out causing damage.

Volcanic eruptions produce other effects too. They can permanently change a landscape. They can block river channels causing flooding and diversion of water flow. Mountain terrains can be severely changed.

Volcanic eruptions can change the chemistry of the atmosphere. The effects of eruption on the atmosphere are precipitation of salty toxic or acidic matter. Spectacular sun set, extended period of darkness and stratospheric ozone depletion are all other effects of eruptions. Blockage of solar radiation by fine pyroclastic material can cause global cooling.

Apart from the above negative effects of volcanisms there are a few positive effects too. Periodic volcanic eruptions replenish the mineral contents of soils making it fertile. Geothermal energy is provided by volcanism. Volcanism is also linked with some type of mineral deposits. Magnificent scenery is provided by some volcanoes.

The study of volcanoes has great scientific as well as social interest. Widespread tephra layers inter-bedded with natural and artificial deposits have been used for deciphering and dating glacial and volcanic sequences, geomorphic features and archeological sites.

For example, ash from Mt. St. Helens Volcano in Washington travelled at least 900 km into Alberta. North American Indians fashioned tools and weapons out of volcanic glass, the origin of which is used to trace migratory and trading routes.

Volcanoes are windows through which the scientists look into the interiors of the earth. From volcanoes we learn the composition of the earth at great depths below the surface. We learn about the history of shifting layers of the earth’s crust. We learn about the processes which transform molten material into solid rock.

From the geological historical view point, volcanic activity was crucial in providing to the earth a unique habitat for life. The degassing of molten materials provided water for the oceans and gases for the atmosphere – indeed, the very ingredients for life and its sustenance.

Essay # 21. Volcanoes and Atmospheric Pollution :

During eruptions volcanoes inject solid particles and gases into the atmosphere. Particles may remain in the atmosphere for months to years and rain back on to the earth. Volcanoes also release chlorine and carbon dioxide.

The main products injected into the atmosphere from volcanic eruptions however are volcanic ash particles and small drops of sulphuric acid in the form of a fine spray known as aerosol. Most chlorine released from volcanoes is in the form of hydrochloric acid which is washed out in the troposphere. Volcanoes also emit carbon dioxide.

During the times of giant volcanic eruptions in the past the amount of carbon dioxide released may have been enough to affect the climate. In general global temperatures are cooler for a year or two after a major eruption.

A large magnitude pyroclastic eruption such as a caldera-forming event can be expected to eject huge volumes of fine ash high into the atmosphere where it may remain for several years, carried around the globe by strong air currents in the upper atmosphere.

The presence of this ash will increase the opacity of the atmosphere, that is, it will reduce the amount of sunlight reaching the earth’s surface. Accordingly, the earth’s surface and climate will become cooler. Various other atmospheric effects may be observed. Particularly noticeable is an increase in the intensity of sunsets.

i. Global Warming :

Besides blocking the rays of the sun, the vast clouds of dust and ash that result from a volcanic eruption can also trap ultraviolet radiation within the atmosphere causing global warming.

Volcanic eruptions usually include emissions of gases such as carbon dioxide which can further enhance this warming. Even if it lasted only for a relatively short time, a sudden increase in temperature could in turn have contributed to extinctions by creating an environment unsuitable for many animals.

ii. Geothermal Energy :

Geothermal energy is the heat energy trapped below the surface of the earth. In all volcanic regions, even thousands of years after activity has ceased the magma continues to cool at a slow rate. The temperature increases with depth below the surface of the earth. The average temperature gradient in the outer crust is about 0.56° C per 30 m of depth.

There are regions however, where the temperature gradient may be as much as 100 times the normal. This high heat flow is often sufficient to affect shallow strata containing water. When the water is so heated such surface manifestations like hot springs, fumaroles, geysers and related phenomena often occur.

It may be noted that over 10 per cent of the earth’s surface manifests very high heat flow and the hot springs and related features which are present in such areas have been used throughout the ages, for bathing, laundry and cooking.

In some places elaborate health spas and recreation areas have been developed around the hot-spring areas. The cooling of magma, even though it is relatively close to the surface is such a slow process that probably in terms of human history, it may be considered to supply a source of heat indefinitely.

Temperatures in the earth rise with increasing depth at about 0.56°C per 30 m depth. Thus if a well is drilled at a place where the average surface temperature is say 15.6°C a temperature of 100°C would be expected at about 4500 m depth. Many wells are drilled in excess of 6000 m and temperatures far above the boiling point of water are encountered.

Thermal energy is stored both in the solid rocks and in water and steam filling the pore spaces and fractures. The water and steam serve to transmit the heat from the rocks to a well and then to the surface.

In a geothermal system water also serves as the medium by which heat is transmitted from a deep igneous source to a geothermal reservoir at a depth shallow enough to be tapped by drilling. Geothermal reservoirs are located in the upward flowing part of a water – convective system. Rainwater percolates underground and reaches a depth where it is heated as it comes into contact with the hot rocks.

On getting heated, the water expands and moves upward in a convective system. If this upward movement is unrestricted the water will be dissipated at the surface as hot springs; but if such upward movement is prevented, trapped by an impervious layer the geothermal energy accumulates, and becomes a geothermal reservoir.

Until recently it was believed that the water in a geothermal system was derived mainly from water given off by the cooling of magma below the surface. Later studies have revealed that most of the water is from surface precipitation, with not more than 5 per cent from the cooling magma.

Production of electric power is the most important application of geothermal energy. A geothermal plant can provide a cheap and reliable supply of electrical energy. Geothermal power is nearly pollution free and there is little resource depletion.

Geothermal power is a significant source of electricity in New Zealand and has been furnishing electricity to parts of Italy. Geothermal installations at the Geysers in northern California have a capacity of 550 megawatts, enough to supply the power needs of the city of San Francisco.

Geothermal energy is versatile. It is being used for domestic heating in Italy, New Zealand and Iceland. Over 70 per cent of Iceland’s population live in houses heated by geothermal energy. Geothermal energy is being used for forced raising of vegetables and flowers in green houses in Iceland where the climate is too harsh to support normal growth. It is used for animal husbandry in Hungary and feeding in Iceland.

Geothermal energy can be used for simple heating processes, drying or distillation in every conceivable fashion, refrigeration, tempering in various mining and metal handling operations, sugar processing, production of boric acid, recovery of salts from seawater, pulp and paper production and wood processing.

Geothermal desalinization of sea water holds promise for abundant supply of fresh water. In some areas it is a real alternative to fossil fuels and hydroelectricity and in future may help meet the crisis of our insatiable appetite for energy.

iii. Phenomena Associated with Volcanism :

In some regions of current or past volcanic activity some phenomena related to volcanism are found. Fumaroles, hot springs and geysers are the widely known belonging to this group. During the process of consolidation of molten magma either at the surface or at some depths beneath the surface gaseous emanations may be given off.

These gas vents constitute the fumaroles. The Valley of Ten Thousand Smokes in Alaska is a well-known fumarole and is maintained as a national monument. This group of fumaroles was formed by the eruption of Mount Katmai in 1912. This valley of area of about 130 square kilometres contains thousands of vents discharging steam and gases.

These gases are of varied temperatures and the temperatures vary from that of ordinary steam to superheated steam coming out as dry gas. Many of the gases escaping from the vents may be poisonous, such as hydrogen sulphide and carbon monoxide which are suffocating and may settle at low places in the topography. For example, the fumaroles at the Poison Valley, Java discharge deadly poisonous gases.

Solfataras are fumaroles emitting sulphur gases. At some places, the hydrogen sulphide gases undergo oxidation on exposure to air to form sulphur. The sulphur accumulates in large amount so that the rocks close to the solfataras may contain commercial quantities of sulphur.

Hot springs are also phenomena associated with volcanic activity. Waters from the surface which penetrate into the ground can get heated either by contact with the rocks which are still hot or by gaseous emanations from the volcanic rocks. The water so heated may re-emerge at the surface giving rise to hot springs. In some situations the hot springs may be intermittently eruptive. Such intermittently hot springs are called geysers.

Related Articles:

• Lava: Types and Eruptions | Volcanoes
• Submarine and Sub Glacial Eruptions | Volcanoes

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Essay On The Volcano – 10 Lines, Short & Long Essay For Kids

Key Points To Remember When Writing An Essay On The Volcano For Lower Primary Classes

10 lines on the volcano for kids, a paragraph on the volcano for children, short essay on volcano in 200 words for kids, long essay on volcano for children, interesting facts about volcanoes for children, what will your child learn from this essay.

A volcano is a mountain formed through an opening on the Earth’s surface and pushes out lava and rock fragments through that. It is a conical mass that grows large and is found in different sizes. Volcanoes in Hawaiian islands are more than 4000 meters above sea level, and sometimes the total height of a volcano may exceed 9000 meters, depending on the region it is found. Here you will know and learn how to write an essay on a volcano for classes 1, 2 & 3 kids. We will cover writing tips for your essay on a volcano in English and some fun facts about volcanoes in general.

Volcanoes are formed as a result of natural phenomena on the Earth’s surface. There are several types of volcanoes, and each may emit multiple gases. Below are some key points to remember when writing an essay on a volcano:

• Start with an introduction about how volcanoes are formed. How they impact the Earth, what they produce, and things to watch out for.
• Discuss the different types of volcanoes and talk about the differences between them.
• Cover the consequences when volcanoes erupt and the extent of the damage on Earth.
• Write a conclusion paragraph for your essay and summarise it. 

When writing a few lines on a volcano, it’s crucial to state interesting facts that children will remember. Below are 10 lines on volcanoes for an essay for classes 1 & 2 kids.

• Some volcanoes erupt in explosions, and then some release magma quietly.
• Lava is hot and molten red in colour and cools down to become black in colour. 
• Hot gases trapped inside the Earth are released when a volcano erupts.
• A circle of volcanoes is referred to as the ‘Ring of Fire.’
• Volcano formations are known as seismic activities.
• Active volcanoes are spread all across the earth. 
• Volcanoes can remain inactive for thousands of years and suddenly erupt.
• Most volcanic eruptions occur underwater and result from plates diverging from the margins.
• Volcanic hazards happen in the form of ashes, lava flows, ballistics, etc.
• Volcanic regions have turned into tourist attractions such as the ones in Hawaii.

Volcanoes can be spotted at the meeting points of tectonic plates. Like this, there are tons of interesting facts your kids can learn about volcanoes. Here is a short paragraph on a volcano for children:

A volcano can be defined as an opening in a planet through which lava, gases, and molten rock come out. Earthquake activity around a volcano can give plenty of insight into when it will erupt. The liquid inside a volcano is called magma (lava), which can harden. The Roman word for the volcano is ‘vulcan,’ which means God of Fire. Earth is not the only planet in the solar system with volcanoes; there is one on Mars called the Olympus Mons. There are mainly three types of volcanoes: active, dormant, and extinct. Some eruptions are explosive, and some happen as slow-flowing lava.

Small changes occur in volcanoes, determining if the magma is rising or not flowing enough. One of the common ways to forecast eruptions is by analysing the summit and slopes of these formations. Below is a short essay for classes 1, 2, & 3:

As a student, I have always been curious about volcanoes, and I recently studied a lot about them. Do you know? Krakatoa is a volcano that made an enormous sound when it exploded. Maleo birds seek refuge in the soil found near volcanoes, and they also bury their eggs in these lands as it keeps the eggs warm. Lava salt is a popular condiment used for cooking and extracted from volcanic rocks. And it is famous for its health benefits and is considered superior to other forms of rock or sea salts. Changes in natural gas composition in volcanoes can predict how explosive an eruption can be. A volcano is labelled active if it constantly generates seismic activity and releases magma, and it is considered dormant if it has not exploded for a long time. Gas bubbles can form inside volcanoes and blow up to 1000 times their original size!

Volcanic eruptions can happen through small cracks on the Earth’s surface, fissures, and new landforms. Poisonous gases and debris get mixed with the lava released during these explosions. Here is a long essay for class 3 kids on volcanoes:

Lava can come in different forms, and this is what makes volcanoes unique. Volcanic eruptions can be dangerous and may lead to loss of life, damaging the environment. Lava ejected from a volcano can be fluid, viscous, and may take up different shapes. 

When pressure builds up below the Earth’s crust due to natural gases accumulating, that’s when a volcanic explosion happens. Lava and rocks are shot out from the surface to make room on the seafloor. Volcanic eruptions can lead to landslides, ash formations, and lava flows, called natural disasters. Active volcanoes frequently erupt, while the dormant ones are unpredictable. Thousands of years can pass until dormant volcanoes erupt, making their eruption unpredictable. Extinct volcanoes are those that have never erupted in history.

The Earth is not the only planet in the solar system with volcanoes. Many volcanoes exist on several other planets, such as Mars, Venus, etc. Venus is the one planet with the most volcanoes in our solar system. Extremely high temperatures and pressure cause rocks in the volcano to melt and become liquid. This is referred to as magma, and when magma reaches the Earth’s surface, it gets called lava. On Earth, seafloors and common mountains were born from volcanic eruptions in the past.

What Is A Volcano And How Is It Formed?

A volcano is an opening on the Earth’s crust from where molten lava, rocks, and natural gases come out. It is formed when tectonic plates shift or when the ocean plate sinks. Volcano shapes are formed when molten rock, ash, and lava are released from the Earth’s surface and solidify.

Types Of Volcanoes

Given below various types of volcanoes –

1. Shield Volcano

It has gentle sliding slopes and ejects basaltic lava. These are created by the low-viscosity lava eruption that can reach a great distance from a vent.

2. Composite Volcano (Strato)

A composite volcano can stand thousands of meters tall and feature mudflow and pyroclastic deposits.

3. Caldera Volcano

When a volcano explodes and collapses, a large depression is formed, which is called the Caldera.

4. Cinder Cone Volcano

It’s a steep conical hill formed from hardened lava, tephra, and ash deposits.

Causes Of Volcano Eruptions

Following are the most common causes of volcano eruptions:

1. Shifting Of Tectonic Plates

When tectonic plates slide below one another, water is trapped, and pressure builds up by squeezing the plates. This produces enough heat, and gases rise in the chambers, leading to an explosion from underwater to the surface.

2. Environmental Conditions

Sometimes drastic changes in natural environments can lead to volcanoes becoming active again.

3. Natural Phenomena

We all understand that the Earth’s mantle is very hot. So, the rock present in it melts due to high temperature. This thin lava travels to the crust as it can float easily. As the area’s density is compromised, the magma gets to the surface and explodes.

How Does Volcano Affect Human Life?

Active volcanoes threaten human life since they often erupt and affect the environment. It forces people to migrate far away as the amount of heat and poisonous gases it emits cannot be tolerated by humans.

Here are some interesting facts:

• The lava is extremely hot!
• The liquid inside a volcano is known as magma. The liquid outside is called it is lava.
• The largest volcano in the solar system is found on Mars.
• Mauna Loa in Hawaii is the largest volcano on Earth.
• Volcanoes are found where tectonic plates meet and move.

Your child will learn a lot about how Earth works and why volcanoes are classified as natural disasters, what are their types and how they are formed.

Now that you know enough about volcanoes, you can start writing the essay. For more information on volcanoes, be sure to read and explore more.

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Essay on volcanoes: top 7 essays on volcanoes| disasters | geography.

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Here is a compilation of essays on ‘Volcanoes’ for class 7, 8, 9, 10. Find paragraphs, long and short essays on ‘Volcanoes’ especially written for school students.

Essay on Volcanoes

Essay Contents:

• Essay on the World Distribution of Volcanoes

Essay # 1. Concept of Vulcanicity :

The terms volcanoes, mechanism of volcanoes and vulcanicity are more or less synonymous to com­mon man but these have different connotations in geology and geography. ‘A volcano is a vent, or opening, usually circular or nearly circular in form, through which heated materials consisting of gases, water, liquid lava and fragments of rocks are ejected from the highly heated interior to the surface of the earth’.

According to A. Holmes and D.L. Holmes (1978) a volcano is essentially a fissure or vent, communicating with the interior, from which flows of lava, fountains of incandescent spray or explosive bursts of gases and volcanic ashes are erupted at the surface.

On the other hand, ‘the term vulcanicity covers all those processes in which molten rock mate­rial or magma rises into the crust or is poured out on its surface, there to solidify as a crystalline or semicrystaline rock’.

Some scientists have also used the term of vulcanism as synonym to the term of vulcanicity. For example, P.G. Worcester (1948) has maintained that ‘vulcanism includes all phenomena connected with the movement of heated material from the interior to or towards the surface of the earth.’

It is apparent from the above definitions of volcano and vulcanicity (vulcanism) that the later (vulcanicity) is a broader mechanism which is related to both the environments, endogenetic and exogenetic. In other words, vulcanicity includes all those processes and mechanisms which are related to the origin of magmas, gases and vapour, their ascent and appear­ance on the earth’s surface in various forms.

It is evident that the vulcanicity has two components which operate below the crustal surface and above the crust. The endogenetic mechanism of vulcanicity includes the creation of hot and liquid magmas and gases in the mantle and the crust, their expansion and upward ascent, their intrusion, cooling and solidification in various forms below the crustal surface (e.g., batholiths, laccoliths, sills, dykes, lopoliths, phacoliths etc.) while the exogenous mechanism includes the process of appearance of lava, volcanic dusts and ashes, fragmen­tal material, mud smoke etc. in different forms e.g., fissure flow or lava flood (fissure or quiet type of volcanic eruption), violent explosion (central type of volcanic eruption), hot springs, geysers, fumaroles, solfatara, mud volcanoes etc. It may be, thus, con­cluded that the vulcanicity is a broader mechanism which includes several events and processes which work below the crust as well as above the crust whereas volcano is a part of vulcanicity (vulcanism).

Essay # 2. Components of Volcanoes :

Volcanoes of explosive type or central eruption type are associated with the accumulated volcanic materials in the form of cones which are called as volcanic cones or simply volcanic mountains. There is a vent or opening, of circular or nearly circular shape, almost in the centre of the summital part of the cone.

This vent is called as volcanic vent or volcanic mouth which is connected with the interior part of the earth by a narrow pipe, which is called as volcanic pipe. Vol­canic materials of various sorts are ejected through this pipe and the vent situated at the top of the pipe. The enlarged form of the volcanic vent is known as volcanic crater and caldera. Volcanic materials include lavas, volcanic dusts and ashes, fragmental materials etc. (fig. 9.1).

Essay # 3. Types of Volcanoes:

There is a wide range of variations in the mode of volcanic eruptions and their periodicity.

Thus, vocanoes are classified on the basis of:

(i) The mode of eruption, and

(ii) The period of eruption and the nature of their activities.

(i) Classification on the Basis of the Nature of Volcanic Eruptions :

Volcanic eruptions occur mostly in two ways viz.:

(i) Violent and explosive type of eruption of lavas, volcanic dusts, volcanic ashes and fragmental materi­als through a narrow pipe and small opening under the impact of violent gases, and

(ii) Quiet type or fissure eruption along a long fracture or fissure or fault due to weak gases and huge volume of lavas.

Thus, on the basis of the nature and intensity of eruptions volcanoes are divided into two types e.g.:

(1) Central eruption type or explosive eruption type, and

(2) Fissure eruption type or quiet eruption type.

(1) Volcanoes of central eruption type:

Central eruption type or explosive eruption type of volcanoes occurs through a central pipe and small opening by breaking and blowing off crustal surface due to violent and explosive gases accumulated deep within the earth. The eruption is so rapid and violent that huge quantity of volcanic materials consisting of lavas, volcanic dusts and ashes, fragmental materials etc., are ejected upto thousands of metres in the sky.

These materials after falling down accumulate around the volcanic vent and form volcanic cones of various sorts. Such volcanoes are very destructive and are disastrous natural hazards.

Explosive volcances are further divided into 5 sub-types on the basis of difference in the intensity of eruption, variations in the ejected volcanic material and the period of the action of volcanic events as given below:

(i) Hawaiin type of volcanoes:

Such volcanoes erupt quietly due to less viscous lavas and non-violent nature of gases. Rounded blisters of hot and glowing mass/boll of lavas (blebs of molten lava) when caught by a strong wind glide in the air like red and glowing hairs. The Hawaiin people consider these long glassy threads of red molten lava as Pele’s hair (Pele is the Hawaiin goddess of fire).

Such volcanoes have been named as Hawaiin type because of the fact that such eruptions are of very common occurrence on Hawaii island. The eruption of Kilavea volcano of the southern Hawaii island in 1959-60 continued for seven days (from November 14 to 20, 1959) when about 30 mil­lion cubic metres of lavas poured out.

The intermittent eruptions continued upto December 21, 1959, when the volcano became dormant. It again erupted on January 13, 1960 and about 100 million cubic metres of lavas were poured out of one kilometre long fissure.

(ii) Strombolian type of volcanoes:

Such volca-noes, named after Stromboli volcano of Lipari island in the Mediterranean Sea, erupt with moderate inten­sity. Besides lava, other volcanic materials like pum­ice, scoria, bombs etc. are also ejected upto greater height in the sky. These materials again fall down in the volcanic craters. The eruptions are almost rhythemic or nearly continuous in nature but sometimes they are interrupted by long intervals.

(iii) Vulcanian type of volcanoes:

These are named after Vulcano of Lipari island in the Mediterranean Sea. Such volcanoes erupt with great force and inten­sity. The lavas are so viscous and pasty that these are quickly solidified and hardened between two eruptions and thus they crust over (plug) the volcanic vents.

These lava crusts obstruct the escape of violent gases during next eruption. Consequently, the violent gases break and shatter the lava crusts into angular fragments and appear in the sky as ash-laden volcanic clouds of dark and often black colour assuming a convoluted or cauli­flower shape (fig. 9.2c).

(iv) Peleean type of volcanoes:

These are named after the Pelee volcano of Martinique Island in the Caribbean Sea. These are the most violent and most explosive type of volcanoes. The ejected lavas are most viscous and pasty. Obstructive domes of lava are formed above the conduits of the volcanoes. Thus, every successive eruption has to blow off these lava domes. Consequently, each successive eruption oc­curs with greater force and intensity making roaring noise.

The most disastrous volcanic eruption of Mount Pelee on May 8,1902 destroyed the whole of the town of St. Pierre killing all the 28,000 inhabitants leaving behind only two survivors to mourn the sad demise of their brethren. Such type of disastrous violent erup­tions are named as nuee ardente meaning thereby ‘glowing cloud’ of hot gases, lavas etc., coming out of a vocanic eruption.

The nuee ardente spread laterally out of the mountain (Mount Pelee) with great speed which caused disastrous avalanches on the hillslopes which plunged down the slope at a speed of about 100 kilometres per hour. The annihilating explosive erup­tion of Krakatoa volcano in 1883 in Krakatoa Island located in Sunda Strait between Java and Sumatra is another example of violent volcanic eruption of this type.

(v) Visuvious type of volcanoes:

These are more or less similar to Vulcanian and Strombolian type of volcanoes, the difference lies only in the intensity of expulsion of lavas and gases. There is extremely vio­lent expulsion of magma due to enormous volume of explosive gases.

Volcanic materials are thrown up to greater height in the sky. The ejected enormous vol­ume of gases and ashes forms thick clouds of ‘cauli­flower form.’ The most destructive type of eruption is called as Plinian type because of the fact that such type of eruption was first observed by Plini in 79 A.D.

(2) Fissure eruption type of volcanoes:

Such vol­canoes occur along a long fracture, fault and fissure and there is slow upwelling of magma from below and the resultant lavas spread over the ground surface. The speed of lava movement depends on the nature of magma, volume of magma, slope of ground surface and temperature conditions. The Laki fissure eruption of 1783 in Iceland was so quick and enormous that huge volume of lavas measuring about 15 cubic kilometers was poured out from a 28-km long fissure. The lava flow was so enormous that it travelled a distance of 350 kilometres.

(ii) Classification on the Basis of Periodicity of Erup­tions :

Volcanoes are divided into 3 types on the basis of period of eruption and interval period between two eruptions of a volcano e.g.:

(i) Active volcanoes,

(ii) Dormant volcanoes, and

(iii) Extinct volcanoes.

(i) Active Volcanoes:

Active volcanoes are those which constantly eject volcanic lavas, gases, ashes and fragmental ma­terials. It is estimated that there are about more than 500 volcanoes in the world. Etna and Stromboli of the Mediterranean Sea are the most significant examples of this category. Stromboli Volcano is known as Light House of the Mediterranean because of continuous emission of burning and luminous incandescent gases.

Most of the active volcanoes are found along the mid- oceanic ridges representing divergent plate margins (constructive plate margins) and convergent plate margins (destructive plate margins represented by eastern and western margins of the Pacific Ocean). The latest eruption took place from Pinatubo volcano in June 1991 in Philippines. Mayon of Philippines re-erupted in Feb. 2000.

(ii) Dormant Volcanoes:

Dormant volcanoes are those which become quiet after their eruptions for some time and there are no indications for future eruptions but suddenly they erupt very violently and cause enormous damage to human health and wealth.

Visuvious volcano is the best example of dormant volcano which erupted first in 79 A.D., then it kept quiet upto 1631 A.D., when it suddenly exploded with great force. The subsequent eruptions occurred in 1803, 1872, 1906, 1927, 1928, and 1929.

(iii) Extinct volcanoes:

The volcanoes are con­sidered extinct when there are no indications of future eruption. The crater is filled up with water and lakes are formed. It may be pointed out that no volcano can be declared permanently dead as no one knows, what is happening below the ground surface.

Essay # 4. Mechanisms and Causes of Vulcanism:

As stated earlier the volcanic eruptions are asso­ciated with weaker zones of the earth surfaces repre­sented by mountain building at the destructive or convergent plate margins and fracture zones repre­sented by constructive or divergent plate boundaries at the splitting zones of mid-oceanic ridges and the zones of transform faults represented by conservative plate boundaries.

The mechanism of vulcanicity (vulcanism) and volcanic eruptions is closely associated with sev­eral interconnected processes such as:

(i) Gradual in­crease of temperature with increasing depth at the rate of 1°C per 32 m due to heat generated from the disintegration of radioactive elements deep within the earth.

(ii) Origin of magma because of lowering of melting point caused by reduction in the pressure of overlying superincumbent load due to fracture caused by splitting of plates and their movement in opposite direction.

(iii) Origin of gases and vapour due to heat­ing of water which reaches underground through per­colation of rainwater and melt-water (water derived through the melting of ice and snow).

(iv) The ascent of magma forced by enormous volume of gases and vapour, and

(v) Finally the occurrence of volcanic eruptions of either violent explosive central type or quiet fissure type depending upon the intensity of gases and vapour and the nature of crustal surface.

Theory of plate tectonics now very well explains the mechanism of vulcanism and volcanic eruptions. In fact, volcanic eruptions are very closely associated with the plate boundaries. It may be pointed out that the types of plate movements and plate boundaries also determine the nature and intensity of volcanic erup­tion. Most of the active fissure volcanoes are found along the mid-oceanic ridges which represent splitting zones of divergent plate boundaries (fig. 9.5).

Two plates move in opposite directions from the mid-oceanic ridges due to thermal convective currents which are originated in the mantle below the crust (plates). This splitting and lateral spreading of plates creates fractures and faults (transform faults) which cause pressure release and lowering of melting point and thus materials of upper mantle lying below the mid-oceanic ridges are melted and move upward as magmas under the impact of enormous volume of accumulated gases and vapour.

This rise of magmas along the mid-oceanic ridges (constructive or divergent plate bounda­ries) causes fissure eruptions of volcanoes and there is constant upwelling of lavas. These lavas are cooled and solidified and are added to the trailing ends of divergent plate boundaries and thus there is constant creation of new basaltic crust.

The volcanic eruptions of Iceland and the islands located along the mid- Atlantic ridge are caused because of sea-floor spread­ing and divergence of plates. It is obvious that diver­gent or constructive plate boundaries are always asso­ciated with quiet type of fissure flows of lavas because the pressure release of superincumbent load due to divergence of plates and formation of fissures and faults is a slow and gradual process.

It is apparent from the above discussion that the mid-oceanic ridges, representing splitting zones, are associated with active volcanoes wherein the supply of lava comes from the upper mantle just below the ridge because of differential melting of the rocks into tholeiitic basalts.

Since there is constant supply of basaltic lavas from below the mid-oceanic ridges and hence the volcanoes are active near the ridges but the supply of lavas decreases with increasing distance from the mid- oceanic ridges and therefore the volcanoes become inactive, dormant and extinct depending on their dis­tances from the source of lava supply, e.g., mid-oceanic ridges.

This fact has been validated on the basis of the study of the basaltic floor of the Atlantic Ocean and the lavas of several islands. It has been found that the islands nearer to the mid-Atlantic Ridge have younger lavas whereas the islands away from the ridge have older lavas. For example, the lavas of Azores islands Situated on either side of the mid-Atlantic Ridge are 4- million years old whereas the lavas of Cape Verde Island, located far away from the said ridge, are 120- million years old.

Destructive or convergent plate boundaries are associated with explosive type of volcanic eruptions. When two convergent plates collide along Benioff zone (subduction zone), comparatively heavier plate margin (boundary) is subducted beneath comparatively lighter plate boundary. The subducted plate margin, after reaching a depth of 100 km or more in the upper mantle, is melted and thus magma is formed.

This magma is forced to ascend by the enormous volume of accumulated explosive gases and thus magma appears as violent volcanic eruption on the earth’s surface. Such type of volcanic eruption is very common along the destructive or convergent plate boundaries which represent the volcanoes of the Circum-Pacific Belt and the Mid-Continental Belt.

The volcanoes of the island arcs and festoons (off the east coast of Asia) are caused due to subduction of oceanic crust (plate) say Pacific e below the continental plate, say Asiatic plate near Japan Trench.

Essay # 5. Hazardous Effects of Volcanic Eruptions :

Volcanic eruptions cause heavy damage to human lives and property through advancing hot lavas and fallout of volcanic materials; destruction to human structures such as buildings, factories, roads, rails, airports, dams and reservoirs through hot lavas and fires caused by hot lavas; floods in the rivers and climatic changes.

A few of the severe damages wrought by volcanic eruptions may be summarized as given below:

(1) Huge volumes of hot and liquid lavas mov­ing at considerably fast speed (recorded speed is 48 km per hour) bury human structures, kill people and ani­mals, destroy agricultural farms and pastures, plug rivers and lakes, burn and destroy forest etc. The great eruption of Mt. Loa on Hawaii poured out such a huge volume of lavas that these covered a distance of 53 km down the slope.

Enormous Laki Lava flow of 1783 A.D. travelled a distance of 350 km engulfing two churches, 15 agricultural farms and killing 24 per cent of the total population of Iceland. The cases of Mt. Pelee eruption of 1902 in Martinique Island (in Carib­bean Sea) (total death 28,000) and St. Helens eruption of 1980 (Washington, USA) are representative exam­ples of damages done by lava movement. The thick covers of green and dense forests on the flanks of Mt. St. Helens were completely destroyed due to severe forest fires kindled by hot lavas.

(2) Fallout of immense quantity of volcanic materials including fragmental materials (pyroclastic materials), dusts and ashes, smokes etc. covers large ground surface and thus destroys crops, vegetation and buildings, disrupts and diverts natural drainage sys­tems, creates health hazards due to poisonous gases emitted during the eruption, and causes killer acid rains.

(3) All types of volcanic eruptions, if not pre­dicted well in advance, causes tremendous losses to precious human lives. Sudden eruption of violent and explosive type through central pipe does not give any time to human beings to evacuate themselves and thus to save themselves from the clutches of death looming large over them. Sudden eruption of Mt. Pelee on the Island of Martinique, West Indies in the Caribbean Sea, on May 8, 1902 destroyed the whole of St. Pierre town and killed all the 28,000 inhabitants leaving behind only two survivors to mourn the sad demise of their brethren.

The heavy rainfall, associated with volcanic eruptions, mixing with falling volcanic dusts and ashes causes enormous mudflow or ‘lahar’ on the steep slopes of volcanic cones which causes sudden deaths of human beings. For example, great mud flow created on the steep slopes of Kelut volcano in Japan in the year 1919 killed 5,500 people.

(4) Earthquakes caused before and after the volcanic eruptions generate destructive tsunamis seis­mic waves which create most destructive and disas­trous sea waves causing innumerable deaths of human beings in the affected coastal areas. Only the example of Krakatoa in 1883 would be sufficient enough to demonstrate the disastrous impact of tsunamis which generated enormous sea waves of 30 to 40 m height which killed 36,000 people in the coastal areas of Java and Sumatra.

(5) Volcanic eruptions also change the radiation balance of the earth and the atmosphere and thus help in causing climatic changes. Greater concentration of volcanic dusts and ashes in the sky reduces the amount of insolation reaching the earth’s surface as they scat­ter and reflect some amount of incoming shortwave solar radiation. Dust veils, on the other hand, do not hinder in the loss of heat of the earth’s surface through outgoing long-wave terrestrial radiation.

The ejection of nearly 20 cubic kilometres of fragmental materials, dusts and ashes upto the height of 23 km in the sky during the violent eruption of Krakatoa volcano on August 27, 1883 formed a thick dust veil in the strato­sphere which caused a global decrease of solar radia­tion received at the earth’s surface by 10 to 20 per cent.

(6) A group of scientists believes that volcanic eruptions and fallout of dusts and ashes cause mass extinction of a few species of animals. Based on this hypothesis the mass extinction of dinosaurs about 60 million years ago has been related to increased world­wide volcanic activity. Acid rains accompanied by volcanic eruptions cause large-scale destruction of plants and animals.

Essay # 6. Volcanic Materials :

Volcanic materials discharged during eruptions include gases and vapour, lavas, fragmental materials and ashes.

(i) Vapour and Gases:

Steam and vapour consti­tute 60 to 90 per cent of the total gases discharged during a volcanic eruption.

Steam and vapour include:

(i) Phreatic vapour, and

(ii) Magmatic vapour whereas volcanic gases include carbon dioxide, nitrogen ox­ides, sulphur dioxide, hydrogen, carbon monoxide, etc.

Besides, certain compounds are also ejected with the volcanic gases e.g., sulphurated hydrogen, hydrochlo­ric acid, volatile chlorides of iron, potassium and other metallic matter.

(ii) Magma and Lava:

Generally, molten rock materials are called magmas below the earth’s surface while they are called lavas when they come at the earth’s surface.

Lavas and magmas are divided on the basis of silica percentage into two groups e.g.:

(i) Acidic magma (higher percentage of silica, and

(ii) Basic lava (low percentage of silica).

Lavas and magmas are also classified on the basis of light and dark coloured minerals into:

(i) Felsic lava, and

(ii) Mafic lava.

Basaltic or mafic lava is characterized by maxi­mum fluidity. Basaltic lava spreads on the ground surface with maximum flow speed (from a few kilome­tres to 100 kilometres per hour, average How speed being 45 to 65 km per hour) due to high fluidity and low viscosity. Basaltic lava is the hottest lava (1,000° to 1,200 C).

Lava flow is divided into two types on the basis of Hawaiin language e.g.:

(i) Pahoehoe, and

(ii) Aa Aa lava flow or block lava flow.

Pahoehoe lava has high fluidity and spreads like thin sheets. This is also known as ropy lava. On the other hand aa aa lava is more viscous. Pahoehoe lava, when solidified in the form of sacks or pillow, is called pillow lava.

(iii) Fragmental or Pyroclastic Materials:

Fragmental or pyroclastic materials thrown during explosive type of eruption are grouped into three categories:

(i) Essential materials include con­solidated forms of live lavas. These are also known as tephra which means ash. Essential materials are unconsolidated and their size is upto 1 mm.

(ii) Acces­sory materials include dead lavas,

(iii) Accidental materials include fragmental materials of crustal rocks.

On the basis of size pyroclastic materials are grouped into:

(i) Volcanic dust (finest particles),

(ii) Volcanic ash (2 mm in size),

(iii) Lapilli (of the size of peas) and

(iv) Volcanic bombs (6 cm or more in size), which are of different shapes viz. ellipsoidal, discoidal, cuboidal, and irregularly rounded.

The dimension of average volcanic bombs ranges from the size of a base-ball or basket-ball to giant size. Sometimes the volcanic bombs weigh 100 tonnes in weight and are thrown upto a distance of 10 km.

Essay # 7. World Distribution of Volcanoes :

Like earthquakes, the spatial distribution of volcanoes over the globe is well marked and well understood because volcanoes are found in a well-defined belt or zone (fig. 9.3). Thus, the distributional pattern of volcanoes is zonal in character.

If we look at the world distribution of volcanoes it appears that the volcanoes are associated with the weaker zones of the earth’s crust and these are closely associated with seismic events say earthquakes. The weaker zones of the earth are represented by folded mountains (western cordillera of North America, Andes, mountains of East Asia and East Indies) with the exceptions of the Alps and the Himalayas, and fault zones.

Volcanoes are also associated with the meeting zones of the continents and oceans. Occurrences of more volcanic eruptions along coastal margins and during wet season denote the fact that there is close relationship between water and volcanic eruption. Similarly, volcanic eruptions are closely associated with the activities of mountain building and fracturing.

Based on plate tectonics, there is close rela­tionship between plate margins and vulcanicity as most of the world’s active volcanoes are associated with the plate boundaries. About 15 per cent of the worlds’ active volcanoes are found along the construc­tive plate margins or divergent plate margins (along the mid-oceanic ridges where two plates move in opposite directions) whereas 80 per cent volcanoes are associ­ated with the destructive or convergent plate boundaries (where two plates collide). Besides, some volcanoes are also found in intraplate regions e.g., volcanoes of the Hawaii Island, fault zones of East Africa etc.

Like earthquakes, there are also three major belts or zones of volcanoes in the world viz.:

(i) Circum-Pacific belt,

(ii) Mid-continental belt, and

(iii) Mid-oceanic ridge belt (fig. 9.3).

(i) Circum-Pacific belt:

The circum-Pacific belt, also known as the ‘volcanic zones of the convergent oceanic plate margins’, includes the volcanoes of the eastern and western coastal areas of the Pacific Ocean (or the western coastal margins of North and South Americas and the eastern coastal margins of Asia), of island arcs and festoons off the east coast of Asia and of the volcanic islands scattered over the Pacific Ocean.

This volcanic belt is also called as the fire girdle of the Pacific or the fire ring of the Pacific. This belt begins from Erebus Mountain of Antarctica and runs north­ward through Andes and Rockies mountains of South and North Americas to reach Alaska from where this belt turns towards eastern Asiatic coast to include the volcanoes of island arcs and festoons (e.g., Sakhalin, Kamchatka, Japan, Philippines etc.).

The belt ulti­mately merges with the mid-continental belt in the East Indies. Most of high volcanic cones and volcanic mountains are found in this belt. Most of the volcanoes are found in chains e.g., the volcanoes of the Aleutian Island, Hawaii Island, Japan etc.

About 22 volcanic mountains are found in group in Ecuador wherein the height of 15 volcanic mountains is more than 4560 m AMSL. Cotopaxi is the highest volcanic mountain of the world (height being 19,613 feet). The other signifi­cant volcanoes are Fuziyama (Japan), Shasta, Rainier and Hood (western cordillera of North America), a valley of ten thousand smokes (Alaska), Mt St. Helens (Washington, USA), Kilavea (Hawaiiland), Mt. Taal, Pinatubo and Mayon (re-eruption in Feb. 2000) of Philippines etc.

Here volcanic eruptions are primarily caused due to collision of American and Pacific plates and due to subduction of Pacific plate below the Asiatic plate.

(ii) Mid-continental Belt:

Mid-continental belt is also known as ‘the vol­canic zones of convergent continental plate mergins’. This belt includes the volcanoes of Alpine mountain chains and the Mediterranean Sea and the volcanoes of fault zone of eastern Africa. Here, the volcanic erup­tions are caused due to convergence and collision of Eurasian plates and African and Indian plates.

The famous volcanoes of the Mediterranean Sea such as Stromboli, Visuvious, Etna etc. and the volcanoes of Aegean Sea are included in this belt. It may be pointed out that this belt does not have the continuity of volcanic eruptions as several gaps (volcanic-free zones) are found along the Alps and the Himalayas because of Compact and thick crust formed due to intense folding activity. The important volcanoes of the fault zone of eastern Africa are Kilimanjaro, Meru, Elgon, Birunga, Rung we etc.

(iii) Mid-Atlantic Belt:

Mid-Atlantic belt includes the volcanoes mainly along the mid-Atlantic ridge which represents the splitting zone of plates. In other words, two plates diverge in opposite directions from the mid-oceanic ridge. Thus, volcanoes mainly of fissure eruption type occur along the constructive or divergent plate mar­gins (boundaries).

The most active volcanic area is Iceland which is located on the mid-Atlantic ridge. This belt begins from Hekla volcanic mountain of Iceland where several fissure eruption type of volca­noes are found. It may be pointed out that since Iceland is located on the mid-Atlantic ridge representing the splitting zone of American plate moving westward and Eurasian plate moving eastward, and hence here is constant upwelling of magmas along the mid-oceanic ridge and wherever the crust becomes thin and weak, fissure flow of lava occurs because of fracture created due to divergence of plates.

The Laki fissure eruption of 1783 A.D. was so quick and enormous that huge volume of lavas measuring about 15 cubic kilometres was poured out from 28-km long fissure. Recently, Hekla and Helgafell volcanoes erupted in the year 1974 and 1973 respectively. Other more active volcanic areas are Lesser Antilles, Southern Antilles, Azores, St. Helena etc.

The dreadful and disastrous eruption of Mount Pelee occurred on May 8,1902 in the town of St. Pierre on the Martinique Island of West Indies in the Caribbean Sea. All the 28,000 inhabitants, except two persons, were killed by the killer volcanic eruption.

(iv) Intra-Plate Volcanoes:

Besides the aforesaid well defined three zones of volcanoes, scattered volca­noes are also found in the inner parts of the continents. Such distributional patterns of volcanoes are called as intraplate volcanoes, the mechanism of their eruption is not yet precisely known. Fig. 9.4 depicts the location of volcanoes of Pacific plate where one branch of volcanoes runs from Hawaii to Kamchatka.

Vulcanicity also becomes active in the inner parts of continental plates. Massive fissure eruption occurred in the north­western parts of North America during Miocene period when 1,00,000 cubic kilometres of basaltic lavas were spread over an area of 1,30,000 km 2 to form Columbian plateau. Similarly, great fissure flows of lavas covered more than 5,00,000 km 2 areas of Peninsular India. Parana of Barazil and Paraguay were formed due to spread of lavas over an area of 7,50,090 km 2 .

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Good Essay About Volcanic Eruption

Type of paper: Essay

Topic: Education , Disaster , Sea , Model , Rainfall , Volcano , Climate , Atmosphere

Words: 1000

Published: 05/31/2021

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There is a relationship between volcanic eruption and the climate of a place. After the eruption, the poisonous sulphur dioxide which is emitted out as a volcanic product, reacts and get oxidized to form sulphate aerosols in the stratosphere, hence affecting the climate adversely (Forster 2007). Volcanic ashes and particles having diameter larger than 2 um also affects the atmosphere. According to Ramaswamy (1996), ozone depletion results when the volcanic aerosols react with the balanced chemistry in the stratosphere. Mid and high latitudes volcanic eruptions create drastic climatic changes. The aerosols here retain over the hemisphere and cause climate to change. For example, the eruption of Laki volcano in Iceland in June was followed by ‘an exceptionally cold’ winter in 1783-84 (Thordason & Self 2003). The Millennium experiment has been used to study the climatic effects after volcanic eruptions in the mid and high latitudinal regions of the northern hemisphere with the coagulation of earth system model (Jungclaus et al, 2010). Jungclaus (2010) mentioned the use of COSMOS network which consisted of four models. The atmospheric general circulation model known as ECHAM5, the general circulation model known as MPI-OM, the ocean biogeochemistry model known as HAMMOC and lastly the land use and vegetation model JSBACH.

External natural forcing of the volcano, are based on observations, data and other references. The solar forcing depends on the tree ring and the ice core proxy reconstructions and also on the orbital forcing. Volcanic forcing is represented by varying the AOD at 0.55 um and the effective radius with a 10 days’ time resolution particularly for four latitudes: 30-90 degree north and south and 0-30 degree north and south latitudes. The volcanic AODs are based on a reconstruction. They used the data from 13 Greenland and Antarctic ice cores as the main source of data and spot data from the other sources. The effective radius growth and decay depends on the observations after the eruption happens. The temporal variation of the short wave radiation anomalies are based on changes in AOD, the solar zenith angle, the top surface of the atmosphere insolation and the surface albedo. Firstly, the aerosol radiative forcing becomes stronger with increasing AOD and secondly, the radiative forcing gets reduced in winter because the northern hemisphere receives less insolation than in summer. The AOD between 30 and 90 degree is horizontally uniform but in high latitudes, it is not uniform but peaks in summer. The temperature anomalies are similar to that of short wave radiation anomalies. The effects on the hemispheric scale are comparable with the internal variability of the model’s climate.

After evaluating the internal climate variability from a 1201 year simulation with the same model without external forcing, the result was that the standard deviation of northern hemisphere annual mean temperature was 0.24 K and the corresponding standard deviation for 2 years being 0.19 K. Anomalies are statistically significant at 90% level of large parts of continental and Arctic areas. Due to large heat capacity, the changes of the sea are small. After July, the largest anomalies start during autumn. The spatial distribution is similar to that in summer after January eruptions with anomalies smaller than 0.8 K. The distribution after the July eruption shows cooling over the Arctic sea. This is due to increased amount of sea ice during the autumn brought about by the cooling. September eruption caused the largest local anomalies in northeast Siberia, larger than 1.2 K and again above the continents and the Arctic Sea. In short, the volcanic eruptions in the Northern hemisphere in mid and high latitudes cause cooling over the continents and the northern ice sea as large as to 1 K. Internal and eruption induced climate variability sometimes causes slight warming in some regions.

The precipitation is also altered after a volcanic eruption. The precipitation anomalies tend to be negative after eruptions but a lot of variability exists. For example, after the January eruptions, the largest anomalies occur in September, December followed by next January and May. As earlier mentioned after an eruption, precipitation anomalies tend to be usually negative but only few of the mean monthly anomalies are statistically significant. A t-test was conducted considering the 21 months following the eruptions of January, July and September, the mean precipitation anomaly is 90% statistically significant. Hence, negative precipitation anomaly is significant. The result of the t-test shows larger variability in precipitation due to internal climate variability and other external factors.

The atmospheric carbon dioxide concentration anomalies are small after the eruptions around -0.0018 and 0.0043 kg per square meter compared to the mean burden of 4.3 kg per square meter. After the eruptions, anomalies are typically negative. In January and July eruptions, there are small positive anomalies during the summer and then larger positive anomalies in the following summer while for the September eruptions, no such increase is observed. The soil respiration and net primary production anomalies contributes to negative carbon dioxide burden while a slight reduction in the net primary production creates positive anomalies for January and July.

Summarising the paper, we have studied the change in climate in the mid and the high latitudes and also the anomalies associated with each climatic factor: temperature, precipitation, solar radiation, carbon dioxide burden etc and how the volcanic eruption affects these factors. The effects of eruption on temperature showed an average maximum temperature was -0.19 K and the average anomaly in the 21 months was -0.095 K following the eruptions. The average maximum anomaly in the hemisphere meant clear sky shortwave radiation was small. The effects of eruption on atmospheric carbon dioxide concentration were small. Precipitation anomalies also tend to be on a negative scale after the eruption.

Meronen, H. et al. ‘Climate Effects Of Northern Hemisphere Volcanic Eruptions In An Earth System Model’. Atmospheric Research 114-115 (2012): 107-118. Web.

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How To Make A Volcano

A volcano is one of the most unique natural occurrences of the planet earth. Further, the entire phenomenon is a dangerously beautiful sight that has been one of the most researched topics for climatologists and scientists worldwide. Moreover, some of the most iconic mountain peaks strewn all over the world are home to volcanoes that caused incidences of great historical and geographical importance since Planet Earth came into existence. Thus, we will learn how to make a volcano in this article.

Introduction to How to Make a Volcano

To understand the chemistry behind a Volcanic eruption, one needs to first understand how the eruption occurs. Thus, to make the process of Volcanic eruption easy to understand, one can conduct a very easy experiment using simple products readily available at home.

What Do you Need for the Experiment?

The experiment consists of two components:

• The apparatus for the experiment
• The compounds for the Volcanic eruption

Apparatus required –

• 1-litre plastic bottle
• Strips of newspapers
• Mixing Bowl to mix glue and paper mache for the conical peak

Volcanic compounds –

• Bicarbonate Soda
• Food colour (orange and yellow)

Experimental Procedure of How to Make a Volcano

The apparatus.

The plastic bottle is precisely cut along the middle and shaped into a conical form like a volcanic peak. Secure the cone in place with the cello tape firmly. For a better and more homogeneous look, glue the paper strips to the bottle design. Finally, it gets a proper conical shape like a mountain peak.

It is double ensured that the base of the conical-shaped bottle is well secured. Seal it by using tapes for extra protection. Now, wait for the glued papers are dry and the bottle to be stable enough to not wobble on a flat surface when you place it. Finally, it is time to create lava.

To add a bit of a more realistic appeal to the experiment, one can give a nice rough shape and appearance to the conical peak. Thus, take paper mache and glue mix and also colour the peak well. Black and brown are the perfect colour backdrop for a lava flow to look prominent.

The Lava compound

Approximately 4 to 5 tablespoons of Bicarbonate soda is ideal for the experiment. First, mix the food colour with vinegar and keep it aside.

The Process

Using a funnel drop the bicarbonate soda evenly at the bottom of the container. Once they are evenly distributed it’s time for the most crucial segment. The main catalyst of the volcanic reaction i.e the Vinegar.

Using the same funnel quickly pour the dyed vinegar into the bottle and remove the funnel as soon as possible.

The Observation

Within a few seconds of interaction between the bicarbonate powder and the vinegar solution, there is a massive effervescence that causes the excessive coloured foam to erupt out and flow alongside the conical body of the mountain lookalike bottle.

The Conclusion of the Experiment on How to Make a Volcano

Even though the experiment doe not reenacts the exact volcanic reaction that occurs naturally. However, it gives a basic idea about what Lava looks like when it erupts.

Facts about Volcanoes

Volcanic eruptions can occur both on land and water. Moreover, the pacific ring of fire is a famous geological hotspot. It consists of volcanic locations both on the surface as well as underwater.

Magma is the actual compound that is present deep inside the earth’s surface which on eruption is called Lava.

There are over 1500 volcanoes all around the world. While some are dormant, there are many that are active and are in a constant state of eruption.

Magma reaches the surface and erupts into hot liquid lava through the lava tubes that run from the Earth’s magma to the surface.

Causes of Volcanic Eruption

A volcanic eruption can occur due to many reasons. Some of the primary reasons for volcanic eruptions include

• Tectonic plate shift
• Increased liquefied gaseous remnants in the magma
• Excessive rise in the temperature melts the rocks causing overflowing into the lava tubes.

FAQ on How to Make a Volcano

Question 1: What are the effects of Volcanic Eruption?

Answer 1: In addition to excessive spewing of poisonous gases and substances on the surface, Volcanic eruption can cause massive destruction in form of lives as well as infrastructure.

Question 2: Is volcanic eruption harmful?

Answer 2: Volcanic eruption brings numerous harmful gaseous compounds to the surface along with hot bubbling chemicals. Moreover, the lava has a drastically high melting temperature that can cause severe damage. In addition, the lighter solid particles can flow for hundreds of miles and cause breathing and skin problems in humans and wildlife alike.

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Essay on Volcanic Eruption | Geography

In this essay we will discuss about: 1. Introduction to Volcanic Eruption 2. Effects of Volcanic Eruption 3. Types.

Essay on Volcanic Eruption

1. essay on the introduction to volcanic eruption:.

Explosive eruptions can inject large quantities of dust and gaseous material (such as sulphur dioxide) into the upper atmosphere, where sulphur dioxide is rapidly converted into sulphuric acid aerosols. Whereas volcanic pollution of the lower atmosphere is removed within days by the effects of rainfall and gravity, stratospheric pollution may remain there for several years, gradually spreading to cover much of the globe.

The volcanic pollution results in a substantial reduction in the direct solar beam, largely through scattering by the highly reflective sulphuric acid aerosols. This can amount to tens of per cent. The reduction, is however, compensated for by an increase in diffuse radiation and by the absorption of outgoing terrestrial radiation (the greenhouse effect). Overall, there is a net reduction of 5 to 10% in energy received at the Earth’s surface.

Clearly, this volcanic pollution affects the energy balance of the atmosphere whilst the dust and aerosols remain in the stratosphere. Observational and modelling studies of the likely effect of recent volcanic eruptions suggest that an individual eruption may cause a global cooling of up to 0.3°C, with the effects lasting 1 to 2 years. Such a cooling event has been observed in the global temperature record in the aftermath of the eruption of Mount Pinatubo in June 1991.

The climate forcing associated with individual eruptions is, however, relatively short-lived compared to the time needed to influence the heat storage of the oceans. The temperature anomaly due to a single volcanic event is thus unlikely to persist or lead, through feedback effects, to significant long-term climatic changes.

Major eruptions have been relatively infrequent this century, so the long-term influence has been slight. The possibility that large eruptions might, during historical and pre-historical times, have occurred with greater frequency, generating long-term cooling, cannot, however, be dismissed. In order to investigate this possibility, long, complete and well-dated records of past volcanic activity are needed. One of the earliest and most comprehensive series is the Dust Veil Index (DVI) of Lamb (1970), which includes eruptions from 1500 to 1900.

When combined with series of acidity measurements in ice cores (due to the presence of sulphuric acid aerosols), they can provide valuable indicators of past eruptions. Using these indicators, a statistical association between volcanic activity and global temperatures during the past millennia has been found. Episodes of relatively high volcanic activity (1250 to 1500 and 1550 to 1700) occur within the period known as the Little Ice Age, whilst the Medieval Warm Period (1100 to 1250) can be linked with a period of lower activity.

Bryson (1989) has suggested a link between longer time scale volcanic variations and the climate fluctuations of the Holocene (last 10,000 years). However, whilst empirical information about temperature changes and volcanic eruptions remains limited, this, and other suggested associations discussed above , must again remain speculative.

Volcanic activity has the ability to affect global climate on still longer time scales. Over periods of millions or even tens of millions of years, increased volcanic activity can emit enormous volumes of greenhouse gases, with the potential of substantial global warming. However, the global cooling effects of sulphur dioxide emissions will act to counter the greenhouse warming, and the resultant climate changes remain uncertain. Much will depend upon the nature of volcanic activity. Basaltic outpourings release far less sulphur dioxide and ash, proportionally, than do the more explosive (silicic) eruptions.

2. Essay on the Effects of Volcanic Eruption:

There are many different types of volcanic eruptions and associated activity – phreatic eruptions (steam-generated eruptions), explosive eruption of high-silica lava (e.g., rhyolite), effusive eruption of low-silica lava (e.g., basalt), pyroclastic flows, lahars (debris flow) and carbon dioxide emission. All of these activities can pose a hazard to humans. Earthquakes, hot springs, fumaroles, mud pots and geysers often accompany volcanic activity.

The concentrations of different volcanic gases can vary considerably from one volcano to the next. Water vapour is typically the most abundant volcanic gas, followed by carbon dioxide and sulphur dioxide. Other principal volcanic gases include hydrogen sulfide, hydrogen chloride, and hydrogen fluoride. A large number of minor and trace gases are also found in volcanic emissions, for example hydrogen, carbon monoxide, halocarbons, organic compounds, and volatile metal chlorides.

Large, explosive volcanic eruptions inject water vapour (H 2 O), carbon dioxide (CO 2 ), sulphur dioxide (SO 2 ), hydrogen chloride (HCl), hydrogen fluoride (HF) and ash (pulverized rock and pumice) into the stratosphere to heights of 16-32 kilometres (10-20 mi) above the Earth’s surface. The most significant impacts from these injections come from the conversion of sulphur dioxide to sulphuric acid (H 2 SO 4 ), which condenses rapidly in the stratosphere to form fine sulfate aerosols.

The aerosols increase the Earth’s albedo—its reflection of radiation from the Sun back into space – and thus cool the Earth’s lower atmosphere or troposphere; however, they also absorb heat radiated up from the Earth, thereby warming the stratosphere. Several eruptions during the past century have caused a decline in the average temperature at the Earth’s surface of up to half a degree (Fahrenheit scale) for periods of one to three years — sulphur dioxide from the eruption of Huaynaputina probably caused the Russian famine of 1601 – 1603.

One proposed volcanic winter happened c. 70,000 years ago following the super-eruption of Lake Toba on Sumatra Island in Indonesia. According to the Toba catastrophe theory to which some anthropologists and archeologists subscribe, it had global consequences, killing most humans then alive and creating a population bottleneck that affected the genetic inheritance of all humans today.

The 1815 eruption of Mount Tambora created global climate anomalies that became known as the “Year without a summer” because of the effect on North American and European weather. Agricultural crops failed and livestock died in much of the Northern Hemisphere, resulting in one of the worst famines of the 19th century. The freezing winter of 1740-41, which led to widespread famine in northern Europe, may also owe its origins to a volcanic eruption.

It has been suggested that volcanic activity caused or contributed to the End-Ordovician, Permian-Triassic, Late Devonian mass extinctions, and possibly others. The massive eruptive event which formed the Siberian Traps, one of the largest known volcanic events of the last 500 million years of Earth’s geological history, continued for a million years and is considered to be the likely cause of the “Great Dying” about 250 million years ago, which is estimated to have killed 90% of species existing at the time.

The sulfate aerosols also promote complex chemical reactions on their surfaces that alter chlorine and nitrogen chemical species in the stratosphere. This effect, together with increased stratospheric chlorine levels from chlorofluorocarbon pollution, generates chlorine monoxide (CIO), which destroys ozone (O 3 ). As the aerosols grow and coagulate, they settle down into the upper troposphere where they serve as nuclei for cirrus clouds and further modify the Earth’s radiation balance.

Most of the hydrogen chloride (HCl) and hydrogen fluoride (HF) are dissolved in water droplets in the eruption cloud and quickly fall to the ground as acid rain. The injected ash also falls rapidly from the stratosphere; most of it is removed within several days to a few weeks. Finally, explosive volcanic eruptions release the greenhouse gas carbon dioxide and thus provide a deep source of carbon for biogeochemical cycles.

Gas emissions from volcanoes are a natural contributor to acid rain. Volcanic activity releases about 130 to 230 teragrams (145 million to 255 million short tons) of carbon dioxide each year. Volcanic eruptions may inject aerosols into the Earth’s atmosphere. Large injections may cause visual effects such as unusually colourful sunsets and affect global climate mainly by cooling it.

Volcanic eruptions also provide the benefit of adding nutrients to soil through the weathering process of volcanic rocks. These fertile soils assist the growth of plants and various crops. Volcanic eruptions can also create new islands, as the magma cools and solidifies upon contact with the water.

Ash thrown into the air by eruptions can present a hazard to aircraft, especially jet aircraft where the particles can be melted by the high operating temperature. Dangerous encounters in 1982 after the eruption of Galunggung in Indonesia, and 1989 after the eruption of Mount Redoubt in Alaska raised awareness of this phenomenon. Nine Volcanic Ash Advisory Centers were established by the International Civil Aviation Organization to monitor ash clouds and advise pilots accordingly. The 2010 eruption of Eyjafjallajokull caused major disruptions to air travel in Europe.

3. Essay on the Types of Volcanic Eruption:

During a volcanic eruption, lava, tephra (ash, lapilli, solid chunks of rock), and various gases, are expelled from a volcanic vent or fissure.

Several types of volcanic eruptions have been distinguished by volcanologists. These are often named after famous volcanoes where that type of behaviour has been observed. Some volcanoes may exhibit only one characteristic type of eruption during a period of activity, while others may display an entire sequence of types.

1. Magmatic Eruptions:

Magmatic eruptions produce juvenile clasts during explosive decompression from gas release. They range in size from the relatively small fire fountains on Hawaii to > 30 km Ultra Plinian eruption columns, bigger than the eruption that buried Pompeii.

2. Strombolian Eruptions:

Strombolian eruptions are relatively low-level volcanic eruptions, named after the Italian volcano Stromboli, where such eruptions consist of ejection of incandescent cinder, lapilli and lava bombs to altitudes of tens to hundreds of meters. They are small to medium in volume, with sporadic violence.

They are defined as “…Mildly explosive at discrete but fairly regular intervals of seconds to minutes…”

The tephra typically glows red when leaving the vent, but its surface cools and assumes a dark to black colour and may significantly solidify before impact. The tephra accumulates in the vicinity of the vent, forming a cinder cone. Cinder is the most common product, the amount of volcanic ash is typically rather minor. The lava flows are more viscous and therefore shorter and thicker, than the corresponding Hawaiian eruptions; it may or may not be accompanied by production of pyroclastic rock.

Instead the gas coalesces into bubbles, called slugs, that grow large enough to rise through the magma column, bursting near the top due to the decrease in pressure and throwing magma into the air. Each episode thus releases volcanic gases, sometimes as frequently as a few minutes apart. Gas slugs can form as deep as 3 kilometers, making them difficult to predict.

Strombolian eruptive activity can be very long-lasting because the conduit system is not strongly affected by the eruptive activity, so that the eruptive system can repeatedly reset itself. For example, the Paricutin volcano erupted continuously between 1943-1952, Mount Erebus, Antarctica has produced Strombolian eruptions for at least many decades, and Stromboli itself has been producing Strombolian eruptions for several thousand years.

3. Vulcanian Eruption:

Vulcanian eruptions are a type of volcanic eruption characterised by a dense cloud of ash-laden gas exploding from the crater and rising high above the peak. They usually commence with phreatomagmatic eruptions which can be extremely noisy due the rising magma heating water in the ground. This is usually followed by the explosive clearing of the vent and the eruption column is dirty grey to black as old weathered rocks are blasted out of the vent. As the vent clears, further ash clouds become grey-white and creamy in colour, with convolution of the ash similar to those of plinian eruptions.

The tephra is dispersed over a wider area than that from Strombolian eruptions. The pyroclastic rock and the base surge deposits form an ash volcanic cone, while the ash covers a large surrounding area. The eruption ends with a flow of viscous lava. Vulcanian eruptions may throw large metre-size blocks several hundred metres, occasionally up to several kilometres.

The term Vulcanian was first used by Giuseppe Mercalli, witnessing the 1888-1890 eruptions on the island of Vulcano. His description of the eruption style is now used all over the world. Mercalli described vulcanian eruptions as “…Explosions like cannon fire at irregular intervals…”

Their explosive nature is due to increased silica content of the magma. Almost all types of magma can be involved, but magma with about 55% or more silica (basalt-andesite) is most common. Increasing silica levels increase the viscosity of the magma which means increased explosiveness.

Vulcanian eruptions are dangerous to persons within several hundred metres of the vent. One feature of this type of eruption is the “Volcanic bomb.” These can be blocks often 2 to 3 m in dimensions. At Galeras a vulcanian eruption ejected bombs which impacted with several volcanologists who were in the crater and many died or suffered terrible.

4. Pel é an Eruption:

Peléan eruptions are a type of volcanic eruption. They can occur when viscous magma, typically of rhyolitic or andesitic type, is involved, and share some similarities with Vulcanian eruptions. The most important characteristics of a Peléan eruption are the presence of a glowing avalanche of hot volcanic ash, a pyroclastic flow. Formation of lava domes is another characteristical feature. Short flows of ash or creation of pumice cones may be observed as well.

The initial phases of eruption are characterised by pyroclastic flows. The tephra deposits have lower volume and range than the corresponding Plinian and Vulcanian eruptions. The viscous magma then forms a steep-sided dome or volcanic spine in the volcano’s vent.

The dome may later collapse, resulting in flows of ash and hot blocks. The eruption cycle is usually completed in few years, but in some cases may continue for decades, like in the case of Santiaguito. The 1902 explosion of Mount Pelée is the first described case of a Peléan eruption, and gave it its name.

Some other examples include the following:

i. The 1948-1951 eruption of Hibok-Hibok;

ii. The 1951 eruption of Mount Lamington, which remains the most detailed observation of this kind;

iii. The 1956 eruption of Bezymianny;

iv. The 1968 eruption of Mayon Volcano;

v. And the 1980 eruption of Mount St. Helens.

5. Hawaiian Eruption:

A Hawaiian eruption is a type of volcanic eruption where lava flows from the vent in a relative gentle, low level eruption, so called because it is characteristic of Hawaiian volcanoes. Typically they are effusive eruptions, with basaltic magmas of low viscosity, low content of gases, and high temperature at the vent. Very little amount of volcanic ash is produced. This type of eruption occurs most often on hotspot volcanoes such as Kilauea, though it can occur near subduction zones (e.g. Medicine Lake Volcano in California, United States.) Another example of Hawaiian eruptions occurred on Surtsey from 1964 to 1967, when molten lava flowed from the crater to the sea.

Hawaiian eruptions may occur along fissure vents, such as during the eruption of Mauna Loa Volcano in 1950, or at a central vent, such as during the 1959 eruption in Kilauea Iki Crater, which created a lava fountain 580 meters (1,900 ft) high and formed a 38 meter cone named Pu’u Pua’i. In fissure-type eruptions, lava spurts from a fissure on the volcano’s rift zone and feeds lava streams that flow downslope. In central-vent eruptions, a fountain of lava can spurt to a height of 300 meters or more (heights of 1600 meters were reported for the 1986 eruption of Mount Mihara on Izu Ôshima, Japan).

Hawaiian eruptions usually start by formation of a crack in the ground from which a curtain of incandescent magma or several closely spaced magma fountains appear. The lava can overflow the fissure and form pahoehoe style of flows. Eruptions from a central cone can form small lightly sloped shield volcanoes, for example the Mauna Loa.

6. Surtseyan Eruption:

A Surtseyan eruption is a type of volcanic eruption that takes place in shallow seas or lakes. It is named after the island of Surtsey off the southern coast of Iceland.

These eruptions are commonly phreatomagmatic eruptions, representing violent explosions caused by rising basaltic or andesitic magma coming into contact with abundant, shallow groundwater or surface water. Tuff rings, pyroclastic cones of primarily ash, are built by explosive disruption of rapidly cooled magma. Other examples of these volcanoes-Capelinhos, Faial Island, Azores; and Taal Volcano, Batangas, Philippines.

Several Specific Characteristics:

i. Physical nature of magma – viscous; basaltic.

ii. Character of explosive activity – violent ejection of solid, warm fragments of new magma; continuous or rhythmic explosions; base surges.

iii. Nature of effusive activity – short, locally pillowed, lava flows; lavas may be rare.

iv. Nature of dominant ejecta – lithic, blocks and ash; often accretionary lapilli; spatter, fusiform bombs and lapilli absent.

v. Structures built around vent – tuff rings

7. Plinian Eruption:

Plinian eruptions, also known as ‘Vesuvian eruptions’, are volcanic eruptions marked by their similarity to the eruption of Mount Vesuvius in AD 79, which killed Pliny the Elder.

Plinian eruptions are marked by columns of gas and volcanic ash extending high into the stratosphere, a high layer of the atmosphere. The key characteristics are ejection of large amount of pumice and very powerful continuous gas blast eruptions. Key characteristics are ejection of large amount of pumice and very powerful continuous gas blast eruptions.

Short eruptions can end in less than a day, but longer events can take several days to months. The longer eruptions begin with production of clouds of volcanic ash, sometimes with pyroclastic flows. The amount of magma erupted can be so large that the top of the volcano may collapse, resulting in a caldera. Fine ash can deposit over large areas. Plinian eruptions are often accompanied by loud noises, such as those generated by Krakatoa.

The lava is usually rhyolitic and rich in silicates. Basaltic lavas are unusual for Plinian eruptions; the most recent example is the 1886 eruption of Mount Tarawera.

8. Phreatomagmatic Eruptions :

Phreatomagmatic eruptions are the result of thermal contraction from chilling on contact with water. The products of phreatomagmatic eruptions are believed to have more regular shard shapes and be finer grained than the products of magmatic eruptions because of the different eruptive mechanism.

There is debate about the exact nature of the eruptive style. Fuel-coolant reactions may be more critical to the explosive nature than thermal contraction. Fuel coolant reactions fragment the material in contact with a coolant by propagating stress waves widening cracks and increasing surface area leading to rapid cooling rates and explosive thermal contraction.

9. Submarine Eruption:

A submarine eruption is a type of volcanic eruption where lava erupts under an ocean. Most of the Earth’s volcanic eruptions are submarine eruptions, but few have been documented because of the difficulty in monitoring submarine volcanoes. Most submarine eruptions occur at mid-ocean ridges and near hotspots.

10. Sub-Glacial Eruption:

A sub-glacial eruption is a volcanic eruption that has occurred under ice, or under a glacier. Sub-glacial eruptions can cause dangerous floods, lahars and create hyaloclastite and pillow lava. Only five of these types of eruptions have been recorded in recent history. Sub-glacial eruptions sometimes form a sub-glacial volcano called a tuya. Tuyas in Iceland are called Table Mountains because of their flat tops. Tuya Butte, in northern British Columbia is an example of a tuya.

A tuya may be recognized by its stratigraphy, which typically consists of a basal layer of pillow basalts overlain by hyaloclastite breccia, tuff, and capped off by a lava flow. The pillow lavas formed first as a result of subaqueous eruptions in glacial melt-water. Once the vent reaches shallower water, eruptions become phreatomagmatic, depositing the hyaloclastite breccia. Once the volcano emerges through the ice, it erupt lava, forming the flat capping layer of a tuya.

The thermodynamics of sub-glacial eruptions are very poorly understood. Rare published studies indicate that plenty of heat is contained in the erupted lava, with 1 unit-volume of magma sufficient to melt about 10 units of ice. However, the rapidity by which ice is melted is unexplained, and in real eruptions the rate is at least an order of magnitude faster than existing predictions.

Antarctica eruption-On January, 2008, the British Antarctic Survey that scientists led by Hugh Corr and David Vaughan, reported (in the journal Nature Geoscience) that 2,200 years ago, a volcano erupted under Antarctica ice sheet (based on airborne survey with radar images).

The biggest eruption in the last 10,000 years, the volcanic ash was found deposited on the ice surface under the Hudson Mountains, close to Pine Island Glacier. The ash covered an area the size of New Hampshire and was probably deposited from a 12 km high ash plume. Researchers have detected a mountainous peak some 100 meters beneath the surface believed to be the top of the tuya associated with this eruption.

11. Phreatic Eruption :

A phreatic eruption, also called a phreatic explosion or ultra-vulcanian eruption occurs when rising magma makes contact with ground or surface water. The extreme temperature of the magma [anywhere from 600 to 1,170°C (1,112 to 2,138°F)] causes near-instantaneous evaporation to steam resulting in an explosion of steam, water, ash, rock, and volcanic bombs. At Mount St. Helens hundreds of steam explosions preceded a 1980 plinian eruption of the volcano. A less intense geothermal event may result in a mud volcano. In 1949, Thomas Jaggar described this type of activity as a steam-blast eruption.

Phreatic eruptions typically include steam and rock fragments; the inclusion of lava is unusual. The temperature of the fragments can range from cold to incandescent. If molten material is included, the term phreatomagmatic may be used. These eruptions occasionally create broad, low-relief craters called maars. Phreatic explosions can be accompanied by carbon dioxide or hydrogen sulfide gas emissions. The former can asphyxiate at sufficient concentration; the latter is a broad spectrum poison. A 1979 phreatic eruption on the island of Java killed 149 people, most of whom were overcome by poisonous gases.

It is believed the 1883 eruption of Krakatoa, which obliterated most of the volcanic island and created the loudest sound in recorded history, was a phreatic event. Kilauea, in Hawaii, has a long record of phreatic explosions; a 1924 phreatic eruption hurled rocks estimated at eight tons up to a distance of one kilometer. Additional examples are the 1963-65 eruption of Surtsey, the 1965 eruption of Taal Volcano, and the 1982 Mount Tarumae eruption.

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70 Volcano Essay Topic Ideas & Examples

🏆 best volcano topic ideas & essay examples, 📌 most interesting volcano topics to write about, 👍 good research topics about volcano, ❓ essay questions about volcanoes.

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Mount Ruang Erupts in Indonesia, Spewing Lava Thousands of Feet Into the Sky

Hundreds of earthquakes were detected in the weeks preceding the eruption of the volcano in North Sulawesi province. Hundreds of people were evacuated.

By Christine Hauser

Mount Ruang, a volcano in Indonesia, erupted on Tuesday, spewing fiery lava and ash thousands of feet into the night sky and forcing the evacuation of hundreds of people in the North Sulawesi province, according to the authorities and local news reports.

The volcano erupted at about 7:19 p.m. local time, Antara, the national news agency, reported. The country’s National Disaster Mitigation Agency said on Wednesday that more than 800 people in nearby villages were displaced by the eruption, many using ferries and taking shelter in churches and community centers.

The authorities said supplies such as mats, blankets, cleaning materials, and tents were needed, and that more shelters might be opening for people fleeing the volcano.

Indonesia is the world’s largest archipelago nation. It is spread across what is known as the Ring of Fire, where tectonic plates clash under the surface of the Pacific Ocean and spawn earthquakes and eruptions from volcanoes.

Mount Ruang is a stratovolcano , or a steep, conical volcano that has built up over years in layers from explosive eruptions of lava, rock fragments, ash and other properties.

“It is in a part of the world where there are a lot of active volcanoes,” said Dr. Tracy K.P. Gregg , who chairs the geology department at the University at Buffalo.

Its last major eruption was in 2002, when the column of lava and ash that it spewed reached up to 17 miles, Dr. Gregg said.

She said the volcano in 2002 measured 4, a “large” volcano on the Volcanic Explosivity Index, a scale used to measure the strength of an eruption by looking at several factors, such as duration, ash volume and plume height. Mount Pinatubo in the Philippines in 1991 measured 6 on the index. Mount St. Helens in the United States in 1980 measured 5.

“So it is a little bit smaller than that,” she said of Mount Ruang. Right now, it is not as violent as the previous eruption, she added, but the volcano cannot be fully assessed while it is in progress.

More than 300 volcanic earthquakes were detected over a period of at least two weeks preceding the eruption of Mount Ruang.

It is not immediately clear why the volcano erupted when it did. “Every volcano has its own personality,” she said.

In the past few years, several volcanoes in Indonesia have erupted. In December, 2023, the bodies of 11 hikers were found on the slopes of Mount Marapi on the island of Sumatra, after an eruption that spewed an ash column of nearly 3,000 meters — about 10,000 feet high.

In December 2022, more than 1,900 people were evacuated from the area surrounding Mount Semeru as it erupted. In an eruption there the previous December , more than 50 people were killed and hundreds more were injured.

Christine Hauser is a reporter, covering national and foreign news. Her previous jobs in the newsroom include stints in Business covering financial markets and on the Metro desk in the police bureau. More about Christine Hauser