Date: Thu, 9 Mar 1995 17:32:06 MST
From: Global Volcanism Network
Subject: Barren Island eruption, December 1994-March 1995
Barren Island
Andaman Islands, Indian Ocean, India
12.29 N, 93.88 E; summit elev. 305 m
A new eruption at Barren Island was first noticed by the Indian
Navy on 20 December 1994. A team composed of scientists from the
Geological and Zoological surveys of India arrived at the island
early on 24 January, and an aerial survey over the volcano was made
on the 31st. As of 22 February, this Strombolian eruption was
still "in its initial stage, gradually gaining momentum."
Vegetation in the path of the advancing lava flow has been
destroyed.
During January and February, a thick column consisting of pale
brownish gas, dark ash particles, and white steam was rising ~200
m from the crater area at intervals of 30 seconds, accompanied by
continuous rumbling and intermittent "cracking" sounds. Two new
vents were active, the first within the main crater near the SW
corner, and the second ~50 m from the summit down the SW flank.
The eruption is believed to have started from the flank vent,
around which a new 100-m-diameter subsidiary crater had formed.
Liquid lava emission was volumetrically minor; most of the eruptive
products consisted of cinder and volcanic bombs. Incandescent
material rising to heights of 20 m could be seen from 4 km
offshore. Particles ranged in size from a few cubic centimeters to
~1 m3, with the average size being slightly less than 10 cm3.
Ejecta filled the pre-existing valley, located S of the western-
most 1991 lava bed, from which lava flows travelled ~1.5 km from
the active vents into the sea, producing profuse steaming at the
ocean entry. The moving lava front was ~50 m wide and 6 m thick by
22 February. Megascopically the lava was basaltic andesite,
similar to that erupted during September 1991, with a high
percentage of large plagioclase phenocrysts and frequent olivine in
a dark-gray glassy groundmass.
On 9 March at around 0530 GMT astronauts on the Space Shuttle
noticed a small plume rising from Barren Island. A short video
recording (~15 seconds) showed a "V" shaped plume that extended for
~3 km before dispersing. Visible imagery from the NOAA-14 (at 0730
GMT) and GMS (0430-0830 GMT) satellites failed to reveal a volcanic
plume.
Located ~135 km NE of Port Blair (South Andaman Island), Barren
Island contains a 1.6-km-wide somma open to the W with a central
pyroclastic cone that has been the source of historical eruptions
reported in 1787, 1789, 1795, 1803, possibly 1852, and 1991. The
1803 eruption produced lava flows that reached the coast. The 1991
eruption began in late April with hot gases and strong ash
emissions and ended in late October (Bulletin v. 16, nos. 5, 8, 10,
12, and v. 17, nos. 1 & 5). Basaltic andesite lava flows covered
an area of about 1,600 m2 to an average thickness of 5-6 m and
reached the NW coast. Initial activity was from a vent on the
upper NE flank of the central cone, but expanded to include the
main crater. Gas emissions were observed from lava flows near the
NW coast in April 1993 (Bulletin v. 18, no. 9).
Information Contacts: Director General, Geological Survey of India,
27 Jawaharlal Nehru Road, Calcutta - 700016, India; Cindy Evans,
Space Shuttle Earth Observations Office, Mail Code C102, Lockheed
Engineering & Sciences, P.O. Box 58561, Houston, TX 77258 USA
(Email: evans@sn.dnet.nasa.gov); Jim Lynch, NOAA/NESDIS Synoptic
Analysis Branch, Room 401, 5200 Auth Road, Camp Springs, MD 20746
USA.
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