Report on Merapi (Indonesia) — 3 October-9 October 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 3 October-9 October 2001
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2001. Report on Merapi (Indonesia). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 3 October-9 October 2001. Smithsonian Institution and US Geological Survey.
7.54°S, 110.446°E; summit elev. 2910 m
All times are local (unless otherwise noted)
During 1-7 October 59 incandescent lava avalanches were observed travelling SW. The avalanches predominately traveled to the upstream portions of the Sat River, and to a lesser extent down the Lamat and Senowo rivers to a maximum run-out distance of 2.5 km. Seismicity was dominated by approximately the same number and intensity of avalanche earthquakes as the previous week. An average of 80 tons per day of SO2 was measured. The Alert Level remained at 2.
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.