Contrary to the common belief that India is geologically stable and lacks volcanic activity, the country does possess volcanoes in various states of activity. These features range from a currently erupting island to ancient, massive rock formations that cover a significant portion of the subcontinent.
The Active Volcano of Barren Island
India’s only confirmed active volcano is located on Barren Island, a small, uninhabited piece of land in the Andaman Sea. It lies approximately 138 kilometers northeast of Port Blair, the capital of the Andaman and Nicobar Islands. The volcano is classified as a stratovolcano, a steep, conical structure built up by alternating layers of hardened lava, ash, and other volcanic debris.
The volcanic edifice rises 354 meters above sea level, though its base extends about 2,250 meters below the ocean surface. Barren Island has a well-documented history of eruptions, with the first recorded outbreak occurring in 1787. Since then, the volcano has erupted more than ten times, including phases of activity seen in 2017 and 2022.
The eruptions are generally mild, often involving the emission of ash clouds visible during the day. Observers have reported seeing hot lava flowing down the slopes and red lava fountains spewing from the crater after sunset. Because the island is remote and uninhabited, this recurrent activity poses minimal immediate threat to human settlements or major maritime routes.
Narcondam Island and Other Dormant Systems
Just north of the active Barren Island is Narcondam Island, home to another significant volcanic system in the Andaman Sea. Narcondam is classified as a dormant volcano, meaning it has not erupted for a very long period but retains the potential to become active again. The last known eruption is often cited as occurring around 1680.
The distinction between a dormant and an extinct volcano is based on the geological time scale and the likelihood of future activity. A dormant volcano, like Narcondam, is merely sleeping, while an extinct one is not expected to erupt again. Narcondam is a stratovolcano formed from andesite rock and reaches a maximum elevation of 710 meters.
While historically inactive, an episode of minor activity was reported in 2005 when the volcano released smoke and mud. This event was possibly triggered by the immense seismic forces of the 2004 Indian Ocean earthquake, highlighting the complex geological forces acting beneath the surface. The island is also a designated wildlife sanctuary, protecting endemic species like the Narcondam hornbill.
Geological History: The Deccan Traps
The most massive evidence of volcanism in India is not a recent island peak but an ancient, vast formation known as the Deccan Traps. Located primarily across central and western India, this formation represents one of the largest volcanic provinces on Earth. The Traps are not volcanoes in the traditional sense but rather immense layers of solidified flood basalt.
These rock layers were formed by fissure eruptions, where highly fluid lava poured out of long cracks in the Earth’s crust instead of from a central vent. This process occurred approximately 66 million years ago, near the end of the Cretaceous period. The sheer volume was staggering, with the basalt flows reaching a composite thickness of over 2,000 meters in some areas.
The original extent of the Deccan Traps is estimated to have covered an area as large as 1.5 million square kilometers. Erosion and tectonic forces have since reduced the directly observable area to about 500,000 square kilometers, spanning states like Maharashtra, Gujarat, and Karnataka. The name “Trap” comes from the Swedish word for “stairs” (trapp), referring to the step-like hills and plateaus created by the layered lava flows.
Tectonic Setting and Volcanic Formation
The different volcanic features in India are the result of two distinct geological processes linked to the movement of the Indian Plate. The active and dormant volcanoes of Barren and Narcondam Islands are examples of volcanism at a plate boundary. The Indian Plate is slowly subducting beneath the Burma Plate along the Andaman Sea, creating a subduction zone.
As the oceanic crust is forced downward, the resulting heat and pressure cause the rock to melt, generating magma that rises to the surface. This process forms the volcanic arc that includes the Andaman Islands and is a common mechanism for creating steep, explosive stratovolcanoes. The Deccan Traps, however, formed through a different mechanism entirely, known as intraplate volcanism.
The massive flood basalts were generated when the Indian Plate passed over the Réunion hotspot, a deep-seated, stationary column of superheated rock rising from the mantle. This hotspot weakened the continental lithosphere, causing large amounts of basaltic magma to erupt through fissures. This event, which occurred as India moved north, is a classic example of a large igneous province associated with a mantle plume.