Report on Merapi (Indonesia) — 20 February-26 February 2002
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 20 February-26 February 2002
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2002. Report on Merapi (Indonesia). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 20 February-26 February 2002. Smithsonian Institution and US Geological Survey.
7.54°S, 110.446°E; summit elev. 2910 m
All times are local (unless otherwise noted)
During 18-24 February there were 67 incandescent lava avalanches observed traveling down Merapi's flanks, predominately WSW to the upstream portions of the Lamat and Senowo rivers and partly SW toward the Sat and Bebeng rivers. The maximum run-out distance was ~2.2 km. One minor pyroclastic flow was observed; it traveled 2.2 km down the Senowo River. Seismicity was dominated by avalanche earthquakes (607), which slightly increased in comparison to the previous week (600). Merapi remained at Alert Level 2 (on a scale of 1-4).
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 2,000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequent growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent 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.