Report on Merapi (Indonesia) — 7 June-13 June 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 7 June-13 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, 7 June-13 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)
On 8 June, according to a CVGHM report, the lava-dome growth rate at Merapi was an estimated 100 thousand cubic meters per day and the estimated volume was approximately 4 million cubic meters. An estimated volume loss of 400 thousand cubic meters on 4 June was due to a partial dome collapse of the S part of the Geger Buaya crater wall (constructed from 1910 lava flows).
Gas plumes were observed almost daily during 7-13 June and reached a maximum height of 1.2 km above the summit (13,600 ft a.s.l.) on 10 June. During 8-10 June, the Darwin VAAC reported that small ash plumes were visible on satellite imagery and minor ashfall was reported to the S at the Merapi Volcano Observatory and in Yogyakarta, about 32 km (19.9 miles) away. On 8 June a pyroclastic flow, lasting 12 minutes, reached a maximum distance of 5 km SE toward the Gendol River, the predominate travel direction since the 27 May earthquake (M 6.2). According to a news report, the 8 June event prompted approximately 15,500 people to evacuate from the Sleman district to the S and the Magelang district to the W. On 13 June, the Alert Level was lowered from 4 to 3 but renewed pyroclastic-flow activity the next day again prompted a return to Alert Level 4, the highest level.
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 2000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequently growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent eruptive 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 during historical time.