Active Volcano

An active volcano is a volcano that has had at least one eruption during the past 10,000 years. These geological structures are formed when magma from the Earth’s mantle rises through the crust and erupts onto the surface. India also has several active volcanoes, most of which are located in the Andaman and Nicobar Islands.

Types of Active Volcanoes

• Stratovolcano (Composite Volcano): These are tall, conical volcanos composed of many layers of hardened lava, pumice, and volcanic ash. Stratovolcanoes are known for their explosive eruptions due to the thick, viscous lava that often clogs the vents. Example: Barren Island Volcano, Andaman Islands.
• Shield Volcano: These volcanoes are built almost entirely of fluid lava flows, resulting in a gently sloping, shield-like appearance. They are formed by the eruption of low-viscosity lava that can flow a great distance from a vent. Example: Réunion Island, Indian Ocean.
• Caldera: A caldera is a large, circular depression formed when a volcano’s magma chamber is emptied, and the overlying rock and soil collapse into the void. Calderas can be as large as 100 kilometers in diameter and several kilometers deep. Example: Atal Crater, Barren Island.

Formation and Characteristics

Active volcanoes are formed in areas where the Earth’s tectonic plates are diverging or converging. In divergent plate boundaries, such as mid-ocean ridges, magma rises to fill the gaps created by the separating plates. In convergent boundaries, like subduction zones, magma is generated when one plate is forced beneath another, melting the rock above.

Active volcanoes are characterized by regular seismic activity, emission of gases, and occasional eruptions of lava, ash, and pyroclastic material. Scientists monitor these signs to predict impending eruptions and issue warnings to nearby populations.

Hazards and Risk Mitigation

Volcanic eruptions can pose significant risks to human life, property, and the environment. Some of the hazards associated with active volcanoes include:

• Lava flows: Streams of molten rock that can destroy everything in their path and ignite fires.
• Pyroclastic flows: High-speed avalanches of hot ash, rock fragments, and gases that can travel hundreds of kilometers.
• Volcanic ash: Fine particles of pulverized rock that can cause respiratory problems, damage machinery, and disrupt transportation.
• Volcanic gases: Emissions of carbon dioxide, sulfur dioxide, and other toxic gases that can cause acid rain and pose health risks.
• Lahars: Mudflows or debris flows composed of volcanic ash, rock, and water from melting snow or heavy rainfall.

To mitigate these risks, volcanologists use various monitoring techniques, including seismic sensors, GPS, and satellite imagery, to track volcanic activity and predict eruptions. Governments also establish evacuation plans and exclusion zones around active volcanoes to protect nearby communities.

Prominent Active Volcanoes in the Indian Subcontinent

• Barren Island Volcano: Located in the Andaman Sea, Barren Island is the only confirmed active volcano in South Asia. It has erupted several times since 1787, with the most recent eruption occurring in 2017.
• Narcondam Volcano: Narcondam Island, located in the Andaman Sea, is a dormant volcano that last erupted in the Holocene epoch (approximately 10,000 years ago). Although not currently active, it is considered a potentially active volcano.
• Deccan Traps: The Deccan Traps are a large igneous province located on the Deccan Plateau of west-central India. These are not active volcanoes but were formed by a series of massive volcanic eruptions around 66 million years ago. Some scientists suggest that the gases released during the formation of the Deccan Traps played a role in the Cretaceous-Paleogene extinction event.