Our previous report on Barren Island (BGVN 33:11) noted frequent thermal anomalies recorded by MODIS instruments and processed by the MODVOLC system through the last half of 2008. This report notes activity between 1 January and 15 September 2009.

Ash plumes from Barren Island were a frequent occurrence during January 2009, and intermittent from February through 15 September 2009 (table 3). MODVOLC thermal anomalies remained frequent, usually daily, during 1 January 2009 through 15 September 2009.

Table 3. Ash plumes from Barren Island, 4 January 2009-14 September 2009. Courtesy, Darwin Volcanic Ash Advisory Centre, based on satellite imagery, SIGMET notices, and pilot observations.

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: Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).