Volcanism

What is Volcanism?

• Volcanism refers to the process of magma (molten rock) rising from deep within the Earth and erupting onto the surface as lava, ash, and gases.

• It is a natural phenomenon that shapes the Earth's surface and is closely related to plate tectonics.

Causes of Volcanism

• Heat and Pressure Inside Earth: The Earth's interior is extremely hot, and this heat causes rocks to melt, forming magma.

• Plate Tectonics: Most volcanoes occur at tectonic plate boundaries:

  • Divergent Boundaries: Plates move apart, allowing magma to rise (e.g., Mid-Atlantic Ridge).

  • Convergent Boundaries: Plates collide, and one plate is forced beneath another, melting to form magma (e.g., Ring of Fire).

  • Hotspots: Areas where magma rises from deep within the mantle, unrelated to plate boundaries (e.g., Hawaiian Islands).

Types of Volcanoes

• Based on Activity:

  • Active: Erupting or likely to erupt (e.g., Mount Etna, Italy).

  • Dormant: Not currently active but may erupt in the future.

  • Extinct: No longer capable of erupting.

• Based on Shape:

  • Shield Volcanoes: Broad, gently sloping (e.g., Mauna Loa, Hawaii).

  • Composite Volcanoes: Steep, conical (e.g., Mount Fuji, Japan).

  • Cinder Cone Volcanoes: Small, steep-sided (e.g., Paricutin, Mexico).

Volcanic Eruptions

• Explosive Eruptions: Violent eruptions with ash, gases, and pyroclastic flows (e.g., Mount St. Helens).

• Effusive Eruptions: Gentle lava flows (e.g., Hawaiian volcanoes).

• Materials Ejected:

  • Lava: Molten rock on the surface.

  • Ash: Fine particles of rock and glass.

  • Gases: Water vapor, carbon dioxide, sulfur dioxide.

Volcanic Landforms

• Craters: Bowl-shaped depressions at the top of a volcano.

• Calderas: Large, basin-like depressions formed after a massive eruption.

• Lava Plateaus: Flat, elevated landforms created by successive lava flows (e.g., Deccan Traps, India).

• Volcanic Mountains: Formed by the accumulation of erupted materials.

Global Distribution of Volcanoes

• Ring of Fire: A major area in the Pacific Ocean with frequent volcanic activity (e.g., Japan, Indonesia, Philippines).

• Mid-Atlantic Ridge: Underwater volcanic activity where plates diverge.

• Hotspots: Isolated volcanic regions (e.g., Hawaii, Yellowstone).

Impact of Volcanism

• Positive Effects:

  • Fertile soil for agriculture (e.g., Java, Indonesia).

  • Geothermal energy production (e.g., Iceland).

  • Formation of new land (e.g., Hawaiian Islands).

• Negative Effects:

  • Destruction of life and property.

  • Climate change due to ash and gases blocking sunlight.

  • Air travel disruptions (e.g., 2010 Eyjafjallajökull eruption in Iceland).

Volcanism in India

• Deccan Traps: One of the largest volcanic features in the world, formed by massive lava flows 65 million years ago.

• Barren Island: India's only active volcano, located in the Andaman and Nicobar Islands.

Details about Types of Volcano

1.Shield Volcanoes

• Description:

  • Broad, gently sloping volcanoes formed by the eruption of low-viscosity (runny) basaltic lava.

  • The lava flows easily and spreads over large areas, creating a shield-like shape.

• Landforms:

  • Wide, flat domes with shallow slopes.

  • Often have a central crater or multiple vents.

• Examples:

  • Mauna Loa, Hawaii: The largest active shield volcano on Earth.

  • Kilauea, Hawaii: Known for its frequent and gentle eruptions.

2. Composite Volcanoes (Stratovolcanoes)

• Description:

  • Tall, steep, conical volcanoes formed by alternating layers of lava, ash, and volcanic debris.

  • Eruptions are explosive due to high-viscosity (thick) magma, which traps gases.

• Landforms:

  • Symmetrical cones with steep slopes.

  • Often have a crater at the summit and secondary vents on the sides.

• Examples:

  • Mount Fuji, Japan: A classic example of a composite volcano.

  • Mount St. Helens, USA: Known for its catastrophic 1980 eruption.

3. Cinder Cone Volcanoes

• Description:

  • Small, steep-sided volcanoes formed by the accumulation of volcanic cinders (small fragments of lava) ejected during explosive eruptions.

  • Usually short-lived and form quickly.

• Landforms:

  • Cone-shaped hills with a bowl-shaped crater at the top.

  • Often found on the flanks of larger volcanoes.

• Examples:

  • Paricutin, Mexico: A famous cinder cone that suddenly formed in a farmer's field in 1943.

  • Sunset Crater, USA: Located in Arizona, it is a well-preserved cinder cone.

4. Calderas

• Description:

  • Large, basin-shaped depressions formed when a volcano collapses into its magma chamber after a massive eruption.

  • Often associated with explosive eruptions that empty the magma chamber.

• Landforms:

  • Circular or oval-shaped depressions, sometimes filled with water to form lakes.

  • Can be several kilometers wide.

• Examples:

  • Yellowstone Caldera, USA: A supervolcano with a massive caldera.

  • Crater Lake, USA: Formed by the collapse of Mount Mazama.

5. Lava Plateaus

• Description:

  • Extensive, flat landforms created by successive eruptions of highly fluid lava that spreads over large areas.

  • The lava cools and solidifies to form thick, horizontal layers.

• Landforms:

  • Flat or gently rolling terrain.

  • Often dissected by rivers and erosion over time.

• Examples:

  • Deccan Traps, India: One of the largest volcanic features in the world, formed by massive lava flows 65 million years ago.

  • Columbia River Plateau, USA: Formed by ancient lava flows.

6. Fissure Volcanoes

• Description:

  • Volcanoes that erupt from long cracks or fissures in the Earth's crust, rather than a central vent.

  • Typically produce large volumes of lava that spread over wide areas.

• Landforms:

  • Flat, extensive lava plains.

  • Lack a prominent central cone.

• Examples:

  • Laki Fissure, Iceland: Erupted in 1783, producing one of the largest lava flows in history.

  • Deccan Traps, India: Also formed by fissure eruptions.

7. Submarine Volcanoes

• Description:

  • Volcanoes located underwater, often along mid-ocean ridges or hotspots.

  • Eruptions can create new islands or seamounts.

• Landforms:

  • Seamounts (underwater mountains) and volcanic islands.

  • Pillow lava formations (rounded lava shapes formed underwater).

• Examples:

  • Loihi Seamount, Hawaii: An active submarine volcano that may become an island in the future.

  • Surtsey, Iceland: An island formed by a submarine eruption in 1963.

8. Hotspot Volcanoes

• Description:

  • Volcanoes formed by plumes of hot magma rising from deep within the mantle, independent of plate boundaries.

  • As the tectonic plate moves over the hotspot, a chain of volcanoes forms.

• Landforms:

  • Volcanic islands or mountain chains.

  • Often have shield volcano characteristics.

• Examples:

  • Hawaiian Islands: Formed by the Pacific Plate moving over a hotspot.

  • Yellowstone, USA: A hotspot beneath the North American Plate.

Interesting Trivia about Volcano

The Pacific Ring of Fire

Location: Surrounds the Pacific Ocean, covering countries like the U.S. (Alaska, California),

Japan, Indonesia, Philippines, Chile, etc.

Length: Approximately 40,000 km (largest tectonic activity zone).

Volcanoes: Home to 75% of the world’s active volcanoes (~450 volcanoes)

Major Volcanoes in the Ring of Fire

Mount St. Helens (USA) – 1980 eruption was one of the most powerful in recent history.

Mount Fuji (Japan) – An iconic stratovolcano.

Krakatoa (Indonesia) – 1883 eruption caused global climatic effects.

Mount Pinatubo (Philippines) – 1991 eruption caused significant global cooling.

Mauna Loa & Kilauea (Hawaii, USA) – Active shield volcanoes.