Report on Merapi (Indonesia) — 10 November-16 November 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 10 November-16 November 2010
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2010. Report on Merapi (Indonesia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 10 November-16 November 2010. 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 10-11 November seismicity from Merapi along with the number of avalanches and pyroclastic flows decreased compared to the previous two days. Lahar deposits were seen in multiple drainages around Merapi at a maximum distance of 16.5 km from the summit.
On 10 November, plumes generally rose 800 m above the crater, but at about 2200 a brownish plume rose to a height of 1.5 km. Heavy ashfall was reported in areas to the WSW and WNW. A 3.5-km-long pyroclastic flow and a 200-m-long avalanche both traveled S in the Gendol drainage. Incandescence from the crater was observed through a closed-circuit television (CCTV) system installed at the Merapi museum. On 11 November, roaring was followed by light ashfall at the Ketep observation post. Plumes, brownish-black at times, rose 800 m above the crater and drifted W and NW. Avalanches again traveled S in the Gendol drainage. One pyroclastic flow was observed through the CCTV traveling 3 km S. A brownish plume rose 1.5 km above the crater. The Alert Level remained at 4 (on a scale of 1-4).
Based on analysis of satellite imagery, the Darwin VAAC reported that during 12-14 November ash plumes drifted 185-280 km SW at an altitude of 7.6 km (25,000 ft) a.s.l. High-altitude sulfur dioxide clouds detected over the Indian Ocean possibly contained ash. In the latter part of 14 November and during 15-16 November, ash plumes rose to altitude of 6.1-7.6 km (20,000-25,000 ft) a.s.l. and drifted 110-130 km S, SW, and W. The sulfur dioxide concentration in the high-level clouds had decreased; the clouds were not thought to contain ash.
During 14-15 November, news articles stated that the death toll from the eruption was over 250, and the Yogyakarta airport had remained closed. About 390,000 residents also began to return home after the "danger zones" were reduced in some areas due to decreased activity during the previous few days.
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.