| Back to Current Volcanic Activity |
|
Barren Island, Andaman Islands, Indian Ocean, India  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).
|
|
|