Smithsonian Institution
Global Volcanism Network Bulletin v. 20, no. 6, June 1995

Barren Island (India)  Lava flow from W flank of cone; central
      vent explosions

Barren Island
Andaman Islands, India
12.29N, 93.88E; summit elev. 305 m

The Geological Survey of India (GSI) visited Barren Island again
on 11 May. At that time only the central conduit was vigorously
active, with continuing phreatomagmatic eruptions. The vents near
the S crater wall and S foot of the volcanic cone, sites of
strong activity on 8 March (Bulletin v. 20, no. 4), were
inactive. Seawater temperature at the only landing site ranged
widely from 38 to 70 deg C, and atmospheric temperatures were 70
and 55 deg C at distances of ~10 and 15 m, respectively, from the
advancing lava front.

Fire fountains from the central vent rose to a height of ~150 m.
Dark fumes sometimes attained a height of ~400 m. The eruption
column was ~100 m across and fed a mushroom-shaped cloud over the
crater region. Approximately 90% of the activity from the main
conduit was explosive, but eruptive pulses occurred without
rumbling sounds. Eruption column fall-out consisted of profuse
quantities of cinder, ash, and rock debris.

A new vent at the W foot of the cone, ~1.5 km ESE of the landing
site, exhibited continuous emission of very liquid lava and
bluish fumes, but no explosive activity. The lava erupted from
this vent formed a 15-m-high and 70-m-wide flow front that was
slowly advancing W towards the landing site, threatening to
engulf it. The lava flow was advancing at a rate of ~2 m/hour on
11 May.

The 1995 lava is a basalt (50.4-52.3% SiO2 and 2.5-3.1% Na2O +
K2O) with mega-xenocrysts of plagioclase, clinopyroxene, and
olivine in decreasing abundance. The groundmass is composed of
glass, plagioclase microlites, and Fe-Ti oxides showing
intersertal to very rare fluidal texture. The 1995 lava differs
from the lava erupted in 1991 in its the absence of wall-rock
xenoliths, its greater abundance of mega-xenocrysts, and its
groundmass texture. Major elements were determined for ten
samples of January 1995 lava. Compared to 1991 lavas (13
samples), the 1995 basalt is deficient in SiO2 and K2O (although
total alkali values are similar), but enriched in Al2O3, CaO, and

Information Contacts: Director General, Geological Survey of
India, 27 Jawaharlal Nehru Road, Calcutta 700 016, India; Deputy
Director General, Geological Survey of India, Ops. WSA Eastern
Region, 4 Chowringhee Lane, Calcutta 700 016, India.