Volcanism and volcanicity UPSC

Volcanism and volcanicity

Volcanism

Definition: Volcanism refers to all the processes related to the movement and eruption of molten rock (magma) from the interior of the Earth to its surface. This encompasses both the formation of volcanic features and the associated phenomena such as lava flows, pyroclastic flows, and volcanic gases.

Types of Volcanism:

1. Intrusive Volcanism:
   • Plutonic Activity: When magma solidifies below the Earth’s surface, forming various igneous rock structures.
   • Features:
     • Batholiths: Large masses of igneous rock formed deep within the Earth.
     • Laccoliths: Dome-shaped masses of igneous rock intruded between sedimentary layers.
     • Dikes: Vertical or steeply inclined sheets of igneous rock that cut through pre-existing rocks.
     • Sills: Horizontal or gently inclined sheets of igneous rock intruded between sedimentary layers.
2. Extrusive Volcanism:
   • Volcanic Activity: When magma reaches the Earth’s surface as lava, leading to the formation of various volcanic landforms.
   • Features:
     • Volcanoes: Mountains formed by the accumulation of lava, ash, and other volcanic materials.
       • Types of Volcanoes:
         • Shield Volcanoes: Broad, gently sloping volcanoes formed by low-viscosity basaltic lava (e.g., Mauna Loa in Hawaii).
         • Composite Volcanoes (Stratovolcanoes): Steep-sided volcanoes composed of alternating layers of lava and pyroclastic material (e.g., Mount Fuji in Japan).
         • Cinder Cone Volcanoes: Small, steep-sided volcanoes built from tephra (e.g., Parícutin in Mexico).
     • Lava Plateaus: Extensive, flat regions formed by the outpouring of low-viscosity lava over a large area (e.g., Deccan Traps in India).
     • Volcanic Domes: Mounds formed by viscous lava that piles up near the vent (e.g., Mount St. Helens’ Lava Dome).
     • Calderas: Large, bowl-shaped depressions formed by the collapse of a volcano into itself after a major eruption (e.g., Crater Lake in Oregon).

Volcanicity

Definition: Volcanicity refers to all processes related to the formation, activity, and types of volcanic phenomena, including both intrusive and extrusive activities.

Volcanic Materials:

1. Lava: Molten rock that reaches the Earth’s surface.
   • Types of Lava:
     • Basaltic Lava: Low viscosity, flows easily, forms shield volcanoes.
     • Andesitic Lava: Intermediate viscosity, forms composite volcanoes.
     • Rhyolitic Lava: High viscosity, flows slowly, forms lava domes and composite volcanoes.
2. Pyroclastic Material: Fragmented volcanic rock ejected during eruptions.
   • Types:
     • Ash: Fine particles of volcanic rock.
     • Lapilli: Small, pebble-sized fragments.
     • Volcanic Bombs: Large, rounded or elliptical fragments.
     • Tephra: General term for all pyroclastic material.
3. Volcanic Gases: Gases emitted during volcanic eruptions, including water vapor, carbon dioxide, sulfur dioxide, and other trace gases.

Volcanic Eruptions:

1. Effusive Eruptions: Eruptions that produce low-viscosity lava flows (e.g., Hawaiian eruptions).
2. Explosive Eruptions: Eruptions that produce high-viscosity lava, pyroclastic material, and significant gas emissions (e.g., Plinian eruptions).

Volcanic Hazards:

1. Lava Flows: Can destroy property and landscapes but typically move slowly enough for people to evacuate.
2. Pyroclastic Flows: Fast-moving, hot avalanches of ash, rock, and gas that can be deadly.
3. Ash Fall: Can cause respiratory issues, damage infrastructure, and disrupt air travel.
4. Lahars: Volcanic mudflows that can bury communities and infrastructure.
5. Volcanic Gases: Can be toxic and cause environmental and health issues.

Practice Questions

1. Define volcanism and explain the difference between intrusive and extrusive volcanism. Provide examples of landforms created by each.
2. Describe the different types of volcanoes and the characteristics of the lava that forms them. Provide examples for each type.
3. What are pyroclastic materials, and how do they contribute to the formation of volcanic landforms?
4. Explain the formation and characteristics of calderas. Provide examples of well-known calderas.
5. Discuss the hazards associated with volcanic eruptions and the measures that can be taken to mitigate their impacts.
6. Compare and contrast effusive and explosive volcanic eruptions. What factors determine the type of eruption?
7. Describe the role of volcanic gases in volcanic eruptions and their impact on the environment and human health.
8. Explain the formation of lava plateaus and provide examples of significant lava plateaus around the world.

Also Read-

• Endogenetic and Exogenetic Forces
• Earthquake Waves and Shadow Zones
• continental drift, sea-floor spreading, and plate tectonics.
• Interior of the Earth UPSC
• Internal Structure of Earth: Crust, Mantle & Core, Discontinuities