Report on Merapi (Indonesia) — 31 May-6 June 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 31 May-6 June 2006
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2006. Report on Merapi (Indonesia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 31 May-6 June 2006. Smithsonian Institution and US Geological Survey.
7.54°S, 110.446°E; summit elev. 2910 m
All times are local (unless otherwise noted)
The Alert Level at Merapi remained at 4, the highest level, during 31 May to 6 June. Sulfur-dioxide plumes were observed daily during this period and reached a height of 1.3 km above the summit (13,900 ft a.s.l.) on 1 June. According to the Darwin VAAC, low-level emissions were visible on satellite imagery on 1 and 6 June. Multiple pyroclastic flows reached a maximum distance of 4 km SE toward the Gendol River and 3.5 km SW toward the Krasak and Boyong Rivers. CVGHM reported on 31 May that lava avalanches moved towards the W for the first time during the recent eruption.
According to a volcanologist in Yogyakarta, lava-flow distances and lava-dome volume had both approximately doubled since the 27 May M 6.2 earthquake. The lava-dome volume was estimated at 4 million cubic meters. On 6 June, groups living near the base of the volcano began to move into temporary shelters. Activities remain restricted within a 7 km radius from the volcano's summit and within 300 m of the banks of Krasak/Bebeng, Bedog, and Boyong Rivers to the SW, and Gendol River to the SE.
Geologic Background. Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately north of the major city of Yogyakarta. It is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano. Growth of Old Merapi during the Pleistocene ended with major edifice collapse perhaps about 2,000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequent growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent activity, began SW of the earlier collapse scarp. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated lands on the western-to-southern flanks and caused many fatalities.