Galunggung volcano (West Java, Indonesia): alert status raised due to changes in crater lake
Monday Feb 13, 2012 17:01 PM | BY: T
The alert status of Galunggung volcano in West Java, Indonesia, was raised today (Mon 13 Feb 2012) due to an increase of its water temperature and a change in color.
Discoloration of the crater lake had started to be noticed in September 2011, but the changes have increased recently. According to the local volcanologists monitoring the volcano, the whole lake is now of muddy khaki color. In addition to the color change which could be caused by an increase of lake fumarole activity, an steep sudden increase by 13°C of the lake water temperature was detected, based on measurements taken on and before 5 February when it was at normal 27°C, and on 8 Feb, when it was 40°C warm.
Most fish in the lake have died and occasionally dead birds are found at the shore.
No other signs of a possible volcanic awakening were detected at the moment. The ph level of the water is still at normal levels 7-8, and there is no sulfur smell. Also, no significant seismic activity has been detected.
Nevertheless, PVMBG has now placed the volcano at alert level 2 ("watch", on a scale of 1-4) and recommends to stay away at least 500 m from the lake shore.
The last eruptions of Galunggnug was a small phreatic explosion in 1984, and the major destructive eruption in 1982-83, which produced violent explosions with ash columns reaching 20 km height, pyroclastic flows and large lahars. The eruption destroyed an older lava lake, killed many people and displaced up to 35,000.
The eruption is infamous for the aircraft accident on 24 June 1982: a British Airways Boeing 747 with 262 people on board flew through the ash plume and had to make an emergency descent after the ash caused all 4 engines to fail; fortunately, the plane could land safely.
The present-day crater lake (Danau kawah Galunggung) has a diameter of 1000 m and is 11 m deep and contains a volume of about 8 million m3 of water.
In the middle of the lake, a small 250 x 165 m diameter scoria cone which was produced during the final staged of the 1982-83 eruption rises to 30 m elevation.
A main hazard of the volcano are phreatic and phreatomagmatic eruptions capable of draining the lake and producing mud flows.
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