Report on Merapi (Indonesia) — 3 July-9 July 2002
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 3 July-9 July 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, 3 July-9 July 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 24-30 June, observers noted 68 incandescent lava avalanches flowing predominately down Merapi's SW flank into the upstream portions of the Sat, Lamat, and Senowo rivers. The avalanches reached a maximum run-out distance of ~2.5 km. Seismicity appeared to decrease in comparison to the previous week and no low-frequency earthquakes were recorded. 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.