Report on Merapi (Indonesia) — 7 September-13 September 2011
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 7 September-13 September 2011
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2011. Report on Merapi (Indonesia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 7 September-13 September 2011. Smithsonian Institution and US Geological Survey.
7.54°S, 110.446°E; summit elev. 2910 m
All times are local (unless otherwise noted)
CVGHM reported that during 29 August-4 September white solfatara plumes rose at most 350 m above Merapi and drifted W. On 4 September small avalanches traveled 700 m SW. The Alert Level remained at 2 (on a scale of 1-4). Based on a pilot observation, the Darwin VAAC reported that on 8 September an ash plume rose to an altitude of 3.7 km (12,000 ft) a.s.l. and drifted almost 30 km N.
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.