India's only active volcano in the Barren Island in the Andaman Sea is at least 1.8 million years old, a new study has said.
Scientists at the IIT-Bombay and Physical Research Laboratory (PRL), Ahmedabad used the Argon dating technique to find out the age of the two ash layers older than 42,000 years and generated by this volcano.
The Barren Island volcano, towering some 300 metres above the sea level, has erupted sporadically over the last 70,000 years but it was not known when it had formed and breached the sea surface.
The scientists found that the age of the minerals they studied was older than the age of deposition of the ash layer, which indicates that the minerals were derived from older rocks present in the plumbing system of the volcano.
They studied ash layers in a 400-centimetre-long sediment core raised from the Andaman Sea collected from 32 km southeast of the island.
Reliable Argon age of 1.8 million years plagioclase grains separated from the ash layer at a depth of 310 centimetres is surprisingly very much older than its conceivable depositional age of 61,000 years, Jyotiranjan S Ray of PRL reported in Current Science.
The volcano, located about 140 km from Port Blair, became active in 1991 after lying dormant for 159 years.
In the past two decades, it has remained active emitting spurts of ash and produced at least four major lava eruptions.
Being a stratovolcano, it may have massive eruptions in the future that could seriously affect life in the Andaman Sea, Andaman and Nicobar Islands and neighbouring Southeast Asian countries, the scientists said.
