Report on Merapi (Indonesia) — 18 April-24 April 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 18 April-24 April 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, 18 April-24 April 2001. Smithsonian Institution and US Geological Survey.
7.54°S, 110.446°E; summit elev. 2910 m
All times are local (unless otherwise noted)
VSI reported that during 9-15 April lava avalanches continued to fill the upstream areas of the Sat, Senowo, Lamat, and Bebeng rivers, with a maximum runout distance of 2 km in the Sat River. In addition, eleven pyroclastic flows entered the Sat and Lamat rivers, reaching as far as 3 km. Avalanche earthquakes continued to dominate the seismicity, but their amplitude and frequency decreased in comparison to the previous week. An observer reported that on 13 April a small amount of ash fell around the Babadan Post Observatory ~7 km W of the volcano. 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 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.