Volcanology and eruptive styles of Barren Island: an active mafic stratovolcano in the Andaman Sea,NE Indian Ocean |
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| Authors: | Hetu C Sheth Jyotiranjan S Ray Rajneesh Bhutani Alok Kumar R S Smitha |
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| Institution: | (1) Department of Earth Sciences, Indian Institute of Technology Bombay (IITB), Powai, Mumbai, 400076, India;(2) Planetary and Geosciences Division, Physical Research Laboratory (PRL), Navrangpura, Ahmedabad, 380009, India;(3) Department of Earth Sciences, Pondicherry University, Puducherry, 605014, India |
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| Abstract: | Barren Island (India) is a relatively little studied, little known active volcano in the Andaman Sea, and the northernmost
active volcano of the great Indonesian arc. The volcano is built of prehistoric (possibly late Pleistocene) lava flows (dominantly
basalt and basaltic andesite, with minor andesite) intercalated with volcaniclastic deposits (tuff breccias, and ash beds
deposited by pyroclastic falls and surges), which are exposed along a roughly circular caldera wall. There are indications
of a complete phreatomagmatic tephra ring around the exposed base of the volcano. A polygenetic cinder cone has existed at
the centre of the caldera and produced basalt-basaltic andesite aa and blocky aa lava flows, as well as tephra, during historic
eruptions (1787–1832) and three recent eruptions (1991, 1994–95, 2005–06). The recent aa flows include a toothpaste aa flow,
with tilted and overturned crustal slabs carried atop an aa core, as well as locally developed tumuli-like elliptical uplifts
having corrugated crusts. Based on various evidence we infer that it belongs to either the 1991 or the 1994–95 eruptions.
The volcano has recently (2008) begun yet another eruption, so far only of tephra. We make significantly different interpretations
of several features of the volcano than previous workers. This study of the volcanology and eruptive styles of the Barren
Island volcano lays the ground for detailed geochemical-isotopic and petrogenetic work, and provides clues to what the volcano
can be expected to do in the future. |
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