A slight increase in activity of Semeru volcano's activity has been observed by the Indonesian Geological Survey in recent weeks and its alert level was raised to 3 (out of 4, "watch") on 3 February 2012, after it had been on level 2 since 16 July 2009.
Only small to moderate eruptions had been occurring over most of the past year. Between 29 December and 15 January, 8 explosions were counted which produced ash clouds up to 600 m high. One explosion threw incandescent bombs to a distance of 300 m from the Jonggring Seloko crater. During 15-29 January, only weak explosions were recorded and a small steam and ash plume rising 25-50 m was observed.
Between 30 and 31 January, 5 explosions were recorded. They produced incandescent fallout in up to 400 m distance. On 2 February at 07:47 local time, a stronger explosion produced incandescent bombs that reached 750 m distance and caused a small avalanche of blocks rolling down a distance of up to 2.5 km (note: no pyroclastic flows). The heightened activity triggered the raise in alert level the following day.
At its present status level of 3, PVMBG recommends to stay away at least 4 km from the summit on the SE side of the volcano and climbers are advised not to approach the Jonggring Seloko crater less than 1 km.
As of 6 February, no significant changes to its activity have been reported by our correspondent on location.
Volcano Discovery
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