Report on Merapi (Indonesia) — June 1991
Bulletin of the Global Volcanism Network, vol. 16, no. 6 (June 1991)
Managing Editor: Lindsay McClelland.
Merapi (Indonesia) Gas plumes and seismicity
Please cite this report as:
Global Volcanism Program, 1991. Report on Merapi (Indonesia) (McClelland, L., ed.). Bulletin of the Global Volcanism Network, 16:6. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199106-263250.
7.54°S, 110.446°E; summit elev. 2910 m
All times are local (unless otherwise noted)
Diffuse to dense gas plumes rose 475 m in June, with SO2 fluxes averaging 80 t/d. The weekly number of volcanic earthquakes fluctuated, briefly rising to 33 during the third week in June, of which 28 were recorded on the 22nd. Three volcanic earthquakes were recorded below the crater at 3.0-3.5 km depth. An average of two multiphase events and 10-12 tectonic earthquakes were recorded weekly.
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: W. Modjo, VSI.