The Barren Island (12017’N: 93051’E) located 135km NE of Port Blair in the Andaman Sea forms a part of the inner volcanic arc of the Indonesian Island arc system. Having remained dormant for nearly a decade since the last eruption in 1994-95 this active volcano once again witnessed violent open vent eruption ( Fig.1 ) of ash and larger sizes fragments since 28th May, 2005. Dr. Sumit Kr. Mitra, Dr. P.C. Bandopadhyay, Mr Sanjeev Raghav and Dr. Tapan Pal of Geological Survey of India landed on Barren Island on 13th June, 2005 by Indian Navy ship for an on-the-spot study of the recent eruption.
Initially the eruption was spewing grey smoke of ash, charged with water vapour from the main crater and a subsidiary vent at the southwestern slope of existing crater. This was followed by violent type eruption. Around 13th June the intensity of the activity of subsidiary vent decreased considerably ( Fig.2 ) and lava debris formed a mound of loose hot debris on the south west slope ( Fig.3 ). Subsequently forceful ejection of huge pyroclasts comprising of bombs and lapilli continued from the main crater. The temperature of the accumulated pyroclasts at the depositional site varied from 900^oC to more than 2000^oC. A number of kinks and dents within the unconsolidated pyroclastic deposits still glow with red colour revealing presence of very hot material (fire eyes) ( Fig.4 ). The fumerolic activity associated with the main eruption shows emission of water vapour and sulphur fumes with a temperature of more than 1000^oC. Fragments of red hot lava were forcefully ejecting out from the main crater with loud explosion to a height of more than 100m. The eruption was pulsative at an interval of 15 to 30 seconds as fire fountain. The eruption column at its top form spectacular mushroom of smoke, blowing to the North direction (Fig.5). The nature of eruption is “Strombolian” type.
Hand specimen study enables identification of two distinct types of fragments of basaltic lava, one being jet black and the other is brownish black in colour. Both types show presence of large phenocrysts of plagioclase and pyroxene set in finer black groundmass revealing a typical porphyritic texture. The GSI team apprised the Chief secretary of Andaman & Nicobar administration about preliminary study of the new eruption on Barren Island. The team also handed over samples of pyroclasts to Indian navy for other scientific organizations interested to study the recent eruption.