Report on Merapi (Indonesia) — 27 October-2 November 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 27 October-2 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, 27 October-2 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)
According to the Darwin VAAC, ground-based reports indicated an eruption from Merapi on 28 October. Cloud cover prevented satellite observations. CVGHM reported that two pyroclastic flows occurred on 30 October. According to a news article, ash fell in Yogyakarta, 30 km SSW, causing low visibility. CVGHM noted four pyroclastic flows the next day.
On 1 November an eruption began mid-morning with a low-frequency earthquake and avalanches. About seven pyroclastic flows occurred during the next few hours, traveling SSE a maximum distance of 4 km. A gas-and-ash plume rose 1.5 km above the crater and drifted E and N. CVGHM recommended that evacuees from several communities within a 10-km radius should continue to stay in shelters or safe areas. The Darwin VAAC reported that a possible eruption on 1 November produced an ash plume that rose to an altitude of 6.1 km (20,000 ft) a.s.l., according to ground-based reports, analyses of satellite imagery, and web camera views. On 2 November an ash plume was seen in satellite imagery drifting 75 km N at an altitude of 6.1 km (20,000 ft) a.s.l. News outlets noted diversions and cancellations of flights in and out of the Solo (40 km E) and Yogyakarta airports. The Alert Level remained at 4 (on a scale of 1-4).
CVGHM reported 26 pyroclastic flows on 2 November. A mid-day report on 3 November stated that 38 pyroclastic flows occurred during the first 12 hours of the day. An observer from the Kaliurang post saw 19 of those 38 flows travel 4 km S. Plumes from the pyroclastic flows rose 1.2 km, although dense fog made visual observations difficult. Ashfall was noted in some nearby areas.
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.