Report on Merapi (Indonesia) — July 1990
Bulletin of the Global Volcanism Network, vol. 15, no. 7 (July 1990)
Managing Editor: Lindsay McClelland.
Merapi (Indonesia) Slight increase in seismicity; lava dome volume stable
Please cite this report as:
Global Volcanism Program, 1990. Report on Merapi (Indonesia). In: McClelland, L. (ed.), Bulletin of the Global Volcanism Network, 15:7. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199007-263250.
7.54°S, 110.446°E; summit elev. 2910 m
All times are local (unless otherwise noted)
The number of volcanic earthquakes at Merapi increased slightly during July, with six recorded events/week, compared to 4-5/week in June. During the first week of August, five earthquakes were recorded. Earthquakes associated with collapse episodes on the lava dome were recorded an average of 32 times/week. More than 36 volcanic events were recorded during a swarm in the 24 hours beginning 4 August at 0000. The volume of the lava dome was stable at 6.8 x 106 m3, up from 6.6 x 106 m3 in late 1989. Fumarole temperatures on the dome were measured at 555 and 820°C.
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.
Information Contacts: VSI.