A scientific team from the GSI and the Zoological Survey of India visited Barren Island on 8-9 April 1993 to assess the impact of the 1991 eruption on the distribution, habit, and abundance of fauna. Gas emissions were seen coming from small openings in the lava flows near the NW coast, but were not observed from the central crater, which had exhibited fumarolic activity at least as late as May 1992. Water temperatures around the island were normal, except for near the landing area on the NW coast where a temperature of 45°C was recorded. Atmospheric temperature was generally 40-50°C, higher near the NE crater rim.

The eruption reduced the number of bird species and the total bird population; many species that migrated during the eruption have not yet returned. Out of 16 previously reported species, only six were observed during this visit, of which the Pied Emperial Pigeon (Ducula bicolor) was the most abundant. A night survey encountered only one rat species (Rattus rattus) and 51 species of insects from eight orders. Bones of rats, birds, and charred remains of land crabs were commonly seen. No live land crabs or butterflies were observed, though crabs were plentiful during fieldwork by other scientists in May 1992. Feral goats (Capra hircus) were the most noticeable wildlife on the island. The goats have survived well since being brought to the island in 1891, and their population remained almost intact after the eruption, possibly because they took shelter on the S slope of the island.

Geological Summary. Barren Island, a possession of India in the Andaman Sea about 135 km NE of Port Blair in the Andaman Islands, is the only historically active volcano along the N-S volcanic arc extending between Sumatra and Burma (Myanmar). It is the emergent summit of a volcano that rises from a depth of about 2250 m. The small, uninhabited 3-km-wide island contains a roughly 2-km-wide caldera with walls 250-350 m high. The caldera, which is open to the sea on the west, was created during a major explosive eruption in the late Pleistocene that produced pyroclastic-flow and -surge deposits. Historical eruptions have changed the morphology of the pyroclastic cone in the center of the caldera, and lava flows that fill much of the caldera floor have reached the sea along the western coast.

Information Contacts: K. Chandra, Zoological Survey of India.