A reappraisal of the eruptive history and recent (1991-2009) volcanic eruptions of the Barren Island, Andaman Sea

Abstract

The Barren Island volcano in the Western Sunda Arc has displayed explosive Strombolian eruptions for more than two decades. This recent explosive event, together with the historic and prehistoric volcanic landforms, present reliable information about explosive Strombolian eruptions and the volcanological evolution of the Barren Island volcano. This study is a re-evaluation of existing knowledge and incorporates new information and interpretations of the recent and past volcanic activity on Barren Island. Direct observations of explosive eruptions since 1991 showed discrete events of bursting and ballistic transport of blocks and formation of sustained ash plumes, indicating Strombolian and violent Strombolian eruptions. Active lava flows were not seen during the observations which, instead, reveal intact preservation of the historic lava flows. A prehistoric mafic stratocone with a central depression (caldera), a central scoria cone with summit crater and abundant basaltic lava flows of historic eruptions and the scoria cones of the recent activity are the major volcanic landforms. They bear evidence of alternating effusive and explosive activity during prehistoric times accompanied by caldera forming activity; scoria cone Strombolian activity switches over to effusive events during the historic period and exclusively Strombolian activity during recent times. The results of this study differ from previous studies that interpreted several episodes of active lava flows and Hawaiian, Plinian and Vulcanian styles of the recent eruptions. It also provides new insights into the volcanological evolution of the Barren Island volcano which is crucial in understanding the future behaviour of the volcano and risk assessment.