What’s spewing lava from India’s only active volcano? 2004 Andamans tsunami fault line holds the answer

Credit: @InsightGL (X)

India’s only active volcano, located on the uninhabited Barren Island in the Andaman Sea, erupted twice within a span of seven days on September 13 and 20. The rare spectacle lit up the sky and drew scientific attention across South Asia.

According to The Times of India, the second eruption on September 20 was triggered by a 4.2-magnitude earthquake that struck the region two days prior. While the eruptions posed no immediate threat to human settlements in the Indonesian archipelago, they are significant because Barren Island lies on a fault line that shifted during the devastating December 2004 tsunami.

What caused the volcanic eruption?

According to O P Mishra, Director of the National Centre for Seismology, the eruption was caused by the “shaking intensity” inside the volcano’s magma chamber. Barren Island, which is about 3.2 km in diameter and rises nearly 2 km above the sea floor, has an average height of 300 metres above sea level.

It sits on the West Andaman Fault, a zone where the Indian plate is continuously moving beneath the Sunda Plate, resulting in regular moderate to strong seismic events. These tremors disrupt the magma chamber, located 18-20 km below, and drive molten lava to the surface via fissures and openings

Link between earthquakes and volcanic disturbances

This is not the first time the Barren Island volcano has erupted in recent history. Similar episodic eruptions were observed in 1991, 2004, and 2005. Each event followed seismic activity, which suggests a direct link between earthquakes and volcanic disturbances in this region.

According to the scientists, the eruptions are usually short-lived but unpredictable, as the magma remains in motion underground. During seismic events, the accumulated heat and gases ascend rapidly, expelling lava and ash. Although the volcano has shown activity for years, it erupts only occasionally, influenced by seismic energy. Notably, another volcano close by, Narcondam, is currently inactive.

Although the recent eruption was relatively small, experts warn that these occurrences signal the delicate geological structure of the Andaman and Nicobar Islands. Due to their position in a highly seismic region, the islands continue to be susceptible to both earthquakes and volcanic events.