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.