Report on Merapi (Indonesia) — 21 March-27 March 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 21 March-27 March 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, 21 March-27 March 2001. Smithsonian Institution and US Geological Survey.
7.54°S, 110.446°E; summit elev. 2910 m
All times are local (unless otherwise noted)
Visual and instrumental monitoring by VSI personnel through 18 March revealed that volcanic activity continued at Merapi. Hot lava avalanches continued to enter the Sat, Senowo, Bebeng, and Lamat rivers, with a maximum runout distance of 3 km in the Sat River. Pyroclastic flows traveled up to 1 km down the Sat, Senowo, and Bebeng rivers. Superficial earthquakes dominated the seismicity, though the number and amplitude decreased from the previous week. Observations during a summit visit on 17 March revealed that high-pressure fumaroles remained on most of the dome's surface. The volcano 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.