Report on Merapi (Indonesia) — February 1981
Scientific Event Alert Network Bulletin, vol. 6, no. 2 (February 1981)
Managing Editor: Lindsay McClelland.
Merapi (Indonesia) Lava dome growth; hot avalanches
Please cite this report as:
Global Volcanism Program, 1981. Report on Merapi (Indonesia). In: McClelland, L. (ed.), Scientific Event Alert Network Bulletin, 6:2. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198102-263250.
7.54°S, 110.446°E; summit elev. 2910 m
All times are local (unless otherwise noted)
The lava dome that began to emerge at the summit in 1979 was still growing in February and had reached an altitude of 2947 m. Lava fragments from the E and central part of the cone had moved 2.0 km toward the Batang River, and 250-500 m farther in December. Personnel at the Ngepos Observatory have counted 34 larger and 468 smaller lava avalanches in recent months; the time interval was not reported. Nuées ardentes d'avalanche occurred in November and December but were confined to the summit area. Two Minakami A-type earthquakes, the first in several months, were recently recorded by the seismograph at the Babadan Observatory (4 km from the summit). No important lahars have occurred along the Putih, Bebeng, and Krasak Rivers since the beginning of this year's rainy season.
Further Reference. Tazieff, H., 1983, Monitoring and interpretation of activity on Mt. Merapi, Indonesia, 1977-80: a practical example, Civil Defense, in Tazieff, H. and Sabroux, J.C. (eds.): Forecasting Volcanic Events, Elsevier, Amsterdam, p. 485-494.
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: A. Sudradjat and L. Pardyanto, VSI.