Report on Merapi (Indonesia) — December 1994
Bulletin of the Global Volcanism Network, vol. 19, no. 12 (December 1994)
Managing Editor: Richard Wunderman.
Merapi (Indonesia) Pyroclastic flows continue through 7 December
Please cite this report as:
Global Volcanism Program, 1994. Report on Merapi (Indonesia). In: Wunderman, R. (ed.), Bulletin of the Global Volcanism Network, 19:12. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199412-263250.
7.54°S, 110.446°E; summit elev. 2910 m
All times are local (unless otherwise noted)
Collapse of the active summit dome on 22 November sent pyroclastic flows down the SW flank (19:10), overrunning several villages. Although no eruption column was described by VSI observers, aviation warnings on the 22nd stated that ash rose to 10 km; satellite analysis the next day indicated that the plume was a low-level feature well below 6 km. As of 7 December, the UNDHA had confirmed 58 deaths; an Antara news report on 19 December placed the number at 60. Indonesian and Japanese medical teams conducted life-saving plastic surgery on 22 critically injured burn victims.
Continuing small eruptions through 7 December sent pyroclastic flows up to 1.5 km down the Boyong River. An estimated 1 x 106 m3 of pyroclastic sediment has been deposited along the Boyong River, while another 12 x 106 m3 remains on the slopes near the crater. Geochemical analysis in late November indicated increased SO2 emissions of up to 44 t/d.
Most of the >6,000 evacuees were allowed to return home in early December. However, local authorities decided that 2,700 evacuees from five villages within 5 km of the summit in Sleman District (Turgo, Kinahredjo, Kaliadem, Tritis, and Ngandong) would be resettled locally. Although pyroclastic flows had damaged the spring-water source that supplies clean water to the Kaliurang Hill Resort, part of it was reopened on 19 December; the W part was not reopened because it was still considered dangerous.
Residents along the Code River (15,000 people in 11 villages) in Yogyakarta were alerted to the possibility of evacuation, because heavy rainfall in the Boyong River drainage could trigger cold lahars. Existing lahar control works and sabo dams have been constructed on the W side of the volcano in the Magelang District. The Boyong River has only two sabo dams with a capacity of 400,000 m3. The Indonesian government plans to construct three sabo dams of 350,000 m3 capacity each, downstream from the Boyong River.
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: UNDHA; Reuters; ANS; BOM Darwin, Australia.