Types of Volcanoes

Volcanoes are classified into different types based on their shape, eruptive behavior, and magma composition. Here are some of the main types of volcanoes:

1. Shield Volcanoes:

• Shape: Broad, gently sloping sides forming a shield-like structure.
• Eruptive Behavior: Effusive eruptions with low-viscosity lava flows.
• Magma Composition: Basaltic, with low silica content.
• Examples: Mauna Loa and Kilauea in Hawaii.

2. Cinder Cones:

• Shape: Steep-sided, conical shape built from cinders (fragments of lava).
• Eruptive Behavior: Strombolian eruptions with moderate explosivity.
• Magma Composition: Basaltic to andesitic.
• Examples: Parícutin in Mexico and Sunset Crater in Arizona.

3. Composite Volcanoes (Stratovolcanoes):

• Shape: Steep-sided, symmetrical cone shape with alternating layers of lava and pyroclastic material.
• Eruptive Behavior: Both effusive and explosive eruptions.
• Magma Composition: Andesitic to dacitic.
• Examples: Mount Fuji in Japan and Mount St. Helens in the United States.

4. Caldera Volcanoes:

• Shape: Large, basin-shaped depressions formed by the collapse of a volcano’s summit.
• Eruptive Behavior: Can have both effusive and explosive eruptions.
• Magma Composition: Varies depending on the volcano.
• Examples: Yellowstone Caldera in the United States and Crater Lake in Oregon.

5. Lava Domes:

• Shape: Rounded, steep-sided mounds formed by viscous lava flows.
• Eruptive Behavior: Extrusive eruptions with slow-moving, viscous lava.
• Magma Composition: Rhyolitic, with high silica content.
• Examples: Mont Pelée in Martinique and Lassen Peak in California.

6. Pyroclastic Shield Volcanoes:

• Shape: Broad, shield-like structure with steep sides built from pyroclastic material.
• Eruptive Behavior: Highly explosive eruptions with pyroclastic flows and ash clouds.
• Magma Composition: Rhyolitic to dacitic.
• Examples: Aso Caldera in Japan and Santorini in Greece.

7. Submarine Volcanoes:

• Shape: Can vary, but often form seamounts or underwater ridges.
• Eruptive Behavior: Effusive or explosive eruptions, depending on magma composition.
• Magma Composition: Varies depending on the volcano.
• Examples: Loihi Seamount in Hawaii and the Mid-Atlantic Ridge.

It’s important to note that volcanoes can exhibit complex behavior and may have characteristics of multiple types. Volcanic activity can also change over time, and new types of volcanoes can form as a result of changes in magma composition and eruptive dynamics.

List Of Important Volcanoes As Per UPSC:

1. Barren Island Volcano, Andaman and Nicobar Islands

• The only active volcano in India.
• Located in the Andaman Sea, about 138 km northeast of Port Blair.
• Part of the Barren Island Wildlife Sanctuary.
• Last erupted in 2017.

2. Deccan Traps, Maharashtra

• A large igneous province (LIP) located on the Indian subcontinent.
• Formed by a series of volcanic eruptions that occurred between 66 and 60 million years ago.
• Covers an area of about 500,000 square kilometers.
• One of the largest volcanic eruptions in Earth’s history.

3. Lonar Crater, Maharashtra

• A meteorite impact crater located in Buldhana district, Maharashtra.
• Formed by the impact of a meteorite about 50,000 years ago.
• Has a diameter of about 1.2 kilometers and a depth of about 150 meters.
• Filled with a saline, alkaline lake.

Different Types of Volcanic Eruption:

Volcanic eruptions are classified based on various factors such as the characteristics of the magma, the style of eruption, and the resulting volcanic landforms. Here are some common types of volcanic eruptions:

1. Hawaiian Eruption:

• Characteristics:
• Low-viscosity basaltic magma.
• Effusive eruption with gentle lava flows.
• Forms shield volcanoes with broad, gently sloping sides.
• Examples: Kilauea Volcano in Hawaii, Mauna Loa Volcano in Hawaii.

2. Strombolian Eruption:

• Characteristics:
• Moderate-viscosity basaltic to andesitic magma.
• Explosive eruption with frequent bursts of lava fragments called scoria.
• Forms cinder cones with steep sides and a central vent.
• Examples: Stromboli Volcano in Italy, Paricutin Volcano in Mexico.

3. Vulcanian Eruption:

• Characteristics:
• High-viscosity andesitic to rhyolitic magma.
• Explosive eruption with violent ejection of viscous lava fragments called bombs.
• Forms steep-sided composite volcanoes with alternating layers of lava and pyroclastic material.
• Examples: Vulcano Volcano in Italy, Mount Pelée in Martinique.

4. Plinian Eruption:

• Characteristics:
• Highly explosive eruption with a towering eruption column.
• Produces large amounts of pumice and ash.
• Forms caldera volcanoes after the collapse of the magma chamber.
• Examples: Mount Vesuvius in Italy (79 AD eruption), Mount Pinatubo in the Philippines (1991 eruption).

5. Phreatomagmatic Eruption:

• Characteristics:
• Occurs when magma interacts with water, such as groundwater, lakes, or the ocean.
• Produces violent steam explosions and ash clouds.
• Forms tuff rings or maars, which are circular craters.
• Examples: Surtsey Volcano in Iceland, Taal Volcano in the Philippines.

6. Pyroclastic Flow:

• Characteristics:
• Rapidly moving mixture of hot gas, ash, and volcanic fragments.
• Flows downslope at high speeds, destroying everything in its path.
• Can reach temperatures of up to 1,000 degrees Celsius.
• Examples: Mount St. Helens in the United States (1980 eruption), Mount Unzen in Japan (1991 eruption).

7. Lahar:

• Characteristics:
• A destructive mudflow composed of volcanic debris and water.
• Occurs when volcanic material mixes with water from heavy rainfall, melted snow, or glacial ice.
• Can travel long distances and cause significant damage.
• Examples: Nevado del Ruiz Volcano in Colombia (1985 eruption), Mount Pinatubo in the Philippines (1991 eruption).

These are just a few examples of the diverse types of volcanic eruptions. Each eruption is unique and can vary in intensity, duration, and impact on the surrounding environment.

Negative Effects of Volcanoes

Volcanoes are powerful geological features that can have both positive and negative impacts on the environment and human populations. While they can provide fertile soil, geothermal energy, and awe-inspiring landscapes, they can also cause significant destruction and disruption. Here are some of the negative effects of volcanoes:

1. Volcanic Eruptions:

• Ashfall: Volcanic eruptions release enormous amounts of ash into the atmosphere, which can block sunlight, disrupt air travel, and cause respiratory problems in humans and animals.
• Lava Flows: Lava flows can destroy entire communities, infrastructure, and ecosystems in their path. They can also block roads, rivers, and other transportation routes.
• Pyroclastic Flows: These fast-moving clouds of hot ash, gas, and volcanic fragments can travel at speeds of up to 700 kilometers per hour (435 miles per hour), incinerating everything in their path.
• Lahars: Volcanic eruptions can trigger lahars, which are destructive mudflows or debris flows composed of volcanic ash, rock fragments, and water. They can travel at high speeds and cause significant damage to infrastructure and settlements.

2. Climate Impact:

• Global Cooling: Large volcanic eruptions can inject sulfur dioxide and other aerosols into the stratosphere, leading to a temporary cooling effect on the Earth’s climate. This can disrupt weather patterns and affect agriculture.
• Acid Rain: Volcanic emissions, such as sulfur dioxide and hydrogen sulfide, can react with water vapor in the atmosphere to form acid rain. Acid rain can damage forests, lakes, and aquatic ecosystems.

3. Health Hazards:

• Respiratory Problems: Volcanic ash and gases can cause respiratory problems, such as asthma, bronchitis, and other respiratory illnesses.
• Volcanic Gases: Toxic gases released during volcanic eruptions, such as sulfur dioxide, hydrogen sulfide, and carbon dioxide, can be harmful to human health and can cause respiratory distress, burns, and even death.

4. Economic Impact:

• Property Damage: Volcanic eruptions can cause extensive damage to property, infrastructure, and agricultural land, leading to significant economic losses.
• Tourism Disruption: Volcanic activity can disrupt tourism in affected areas, impacting local economies that rely on tourism revenue.
• Crop Damage: Ashfall and volcanic gases can damage crops, affecting food supplies and livelihoods.

5. Social Impact:

• Displacement: Volcanic eruptions can force people to evacuate their homes and communities, leading to displacement and social disruption.
• Loss of Life: Volcanic eruptions can result in loss of human life, both directly from the eruption itself and indirectly from the aftermath, such as ash-related respiratory problems or lahars.

Conclusion:

Volcanoes are powerful natural forces that can have devastating effects on human populations and ecosystems. While they can provide certain benefits, it is crucial to understand and mitigate the risks associated with volcanic activity to minimize their negative impacts.

Positive Effects of Volcanoes:

Volcanoes are often associated with destruction and danger, but they can also have many positive effects on the environment and human societies. Here are some of the benefits of volcanoes:

1. Soil Fertility

• Volcanic eruptions release ash and other minerals into the atmosphere, which can help to fertilize the soil.
• The ash contains essential nutrients, such as nitrogen, phosphorus, and potassium, which are necessary for plant growth.
• Volcanic soils are often very fertile and can support a wide variety of plant life.

2. Geothermal Energy

• Volcanoes can be used to generate geothermal energy, which is a clean and renewable source of power.
• Geothermal power plants use the heat from the Earth’s interior to generate steam, which is then used to drive turbines and produce electricity.
• Geothermal energy is a sustainable source of energy that does not produce greenhouse gases.

3. Tourism

• Volcanoes can be a major tourist attraction, drawing visitors from all over the world.
• Tourists come to see the natural beauty of volcanoes, as well as to learn about their history and geology.
• Volcano tourism can provide a significant source of revenue for local communities.

4. Mineral Deposits

• Volcanoes can create valuable mineral deposits, such as gold, silver, copper, and zinc.
• These minerals are often found in the rocks that surround volcanoes, and they can be mined and used for a variety of purposes.
• Mining can provide jobs and economic opportunities for local communities.

5. Biodiversity

• Volcanoes can create new habitats for plants and animals, which can lead to increased biodiversity.
• The lava and ash from volcanic eruptions can create new land, which can be colonized by a variety of species.
• Volcanic activity can also create new ecosystems, such as hot springs and lava fields, which support unique communities of plants and animals.

6. Climate Regulation

• Volcanoes can play a role in regulating the Earth’s climate.
• Volcanic eruptions can release aerosols into the atmosphere, which can reflect sunlight and cool the planet.
• Volcanic eruptions can also release carbon dioxide, which can contribute to global warming.
• However, the overall effect of volcanoes on climate is complex and not fully understood.

Conclusion

Volcanoes are powerful and destructive forces of nature, but they can also have many positive effects on the environment and human societies. By understanding the benefits of volcanoes, we can better appreciate their role in the natural world and take steps to mitigate their risks.

Volcanoes NCERT Notes FAQs

What is a volcano?

• A volcano is a vent in the Earth’s crust through which molten rock, ash, and gases erupt.
• Volcanoes are formed when magma, or molten rock, rises to the surface of the Earth.
• Magma can rise to the surface through cracks in the Earth’s crust, or it can erupt through a volcano.
• When magma erupts, it can flow out of the volcano as lava, or it can explode into the air as ash and pumice.

What are the different types of volcanoes?

• There are three main types of volcanoes:

  • Shield volcanoes are broad, gently sloping volcanoes that are formed by the eruption of low-viscosity lava.
  • Composite volcanoes, also known as stratovolcanoes, are steep-sided volcanoes that are formed by the eruption of both lava and ash.
  • Cinder cone volcanoes are small, steep-sided volcanoes that are formed by the eruption of cinders, which are fragments of lava that have been ejected into the air.

What causes volcanoes to erupt?

• Volcanoes erupt when magma rises to the surface of the Earth and escapes through a vent.
• The pressure of the magma inside the volcano can cause it to erupt explosively, or it can flow out of the volcano more gently.
• The type of eruption that occurs depends on the composition of the magma and the amount of gas it contains.

What are the dangers of volcanoes?

• Volcanoes can pose a number of dangers, including:

  • Lava flows can destroy buildings and infrastructure, and they can also cause wildfires.
  • Ash clouds can block out the sun, causing cooling and darkness.
  • Volcanic gases can be toxic, and they can cause respiratory problems and even death.
  • Lahars, which are mudflows made of volcanic ash and water, can destroy everything in their path.

How can we predict volcanic eruptions?

• Scientists can use a variety of methods to predict volcanic eruptions, including:

  • Monitoring seismic activity: Earthquakes can be a sign that magma is moving beneath the surface of the Earth.
  • Measuring ground deformation: The ground around a volcano can bulge or sink as magma moves beneath the surface.
  • Monitoring gas emissions: Changes in the composition of gases emitted by a volcano can indicate that an eruption is imminent.

What can we do to mitigate the effects of volcanic eruptions?

• There are a number of things that can be done to mitigate the effects of volcanic eruptions, including:

  • Monitoring volcanoes: Scientists can monitor volcanoes to identify those that are at risk of erupting.
  • Educating the public: People who live near volcanoes should be educated about the risks of volcanic eruptions and how to prepare for them.
  • Developing emergency plans: Communities near volcanoes should develop emergency plans that include evacuation routes and procedures.
  • Building infrastructure that is resistant to volcanic hazards: Buildings and infrastructure near volcanoes should be built to withstand the effects of lava flows, ash clouds, and lahars.