Report on Merapi (Indonesia) — 17 November-23 November 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 17 November-23 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, 17 November-23 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 on 15 November no pyroclastic flows descended Merapi's flanks and few avalanches were detected compared to the previous day. During 16-18 November, the number of seismic signals and the number of avalanches both continued to decrease. Although fog often prevented observations, a gas-and-ash plume was observed rising 1.5 km above the crater and drifting SW. A steam plume rose 250 m above the crater and drifted W. On 18 November a pyroclastic flow occurred with low intensity. Lahar deposits were seen in multiple drainages. CVGHM noted areas that remained within a 10-20 km danger zone. On 21 November one pyroclastic flow was detected and five were recorded the next day. During 21-23 November avalanches continued to occur. Lahars traveling S on 23 November carried material up to 100 cm in diameter. According to news articles, the Yogyakarta airport resumed operations on 20 November. The death toll from the eruption reached 322 and more than 130,000 people continued to live in temporary shelters.
Based on analysis of satellite imagery, the Darwin VAAC reported that during 16-21 November ash plumes rose to altitudes of 4.6-6.1 km (15,000-20,000 ft) a.s.l. and drifted 55-165 km W and NW.
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.