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Report on Merapi (Indonesia) — December 1986


Scientific Event Alert Network Bulletin, vol. 11, no. 12 (December 1986)
Managing Editor: Lindsay McClelland.

Merapi (Indonesia) Lava flow from October-November dome advances onto SW flank

Please cite this report as:

Global Volcanism Program, 1986. Report on Merapi (Indonesia) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 11:12. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198612-263250



7.54°S, 110.446°E; summit elev. 2910 m

All times are local (unless otherwise noted)

Aerial observations 6-7 January revealed no evidence of major new dome growth since Oct-Nov 1986. The volume of the summit crater lava dome was > 4 x 106 m3. From the SW base of the Oct-Nov dome, a lava flow extended through the breach in the crater wall onto the volcano's SW flank, where it continued to advance slowly. Incandescent rockfalls from the toe of the flow, and from the area where the flow emerged from the dome, were observed at night in early January. The number of earthquakes has declined since peaking in late October and early November.

Geological Summary. 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.

Information Contacts: VSI.