Report on Merapi (Indonesia) — June 1997
Bulletin of the Global Volcanism Network, vol. 22, no. 6 (June 1997)
Managing Editor: Richard Wunderman.
Merapi (Indonesia) Pyroclastic flows and vigorous plumes noted in first half of 1997
Please cite this report as:
Global Volcanism Program, 1997. Report on Merapi (Indonesia) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 22:6. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199706-263250.
7.54°S, 110.446°E; summit elev. 2910 m
All times are local (unless otherwise noted)
The Societe Volcanologique de Geneve (SVG) reported that on 11 January a member of the Volcanological Survey of Indonesia (VSI) noticed the emplacement of ~ 400,000 m3 of material on the dome. On 14 January, at 0930 the first of many pyroclastic flows was observed. During the following 10 hours 81 pyroclastic flows ran down the flanks, reaching as far as 4 km. Tremors and volcano-tectonic earthquakes were recorded. On 17 January a strong explosion threw a 4,000-m-high column above the crater and another pyroclastic flow raced down the slopes at 1040.
The National Coordinating Board for Disaster Management (BAKORNAS PB) of the Indonesian Government later announced that an eruption took place at 1035 on 17 January. Heavy rains on 17 and 18 January in surrounding areas could have caused mudflows. Reuters reported that about 5,000 people living near Merapi were evacuated from their villages after the volcano started spewing burning ash and hot lava. By 18 January the volcanic activity started decreasing. On 24 January the volcano began spewing hot clouds again; many of the evacuees returned home despite the warnings. According to local newspapers, six people were missing, several were injured, and many had been blinded by the heat clouds, but none were dead. Damage included hundreds of hectares of crops burned.
SVG also reported that a new crater had formed within the 1992 lavas and the early- 1997 lavas. A new dome was growing inside this crater; its volume was estimated to be 160,000 m3. On 22 March and 29 June 1997 Qantas flights over Merapi reported ash at ~ 6.1 and 10 km altitude, respectively. In both cases, however, satellite imagery failed to confirm the plumes because of high clouds.
From 12 to 15 April a field party from the European Volcanological Society (SVE) observed the volcano, from Kaliungarang village, ~6 km from the dome; later they moved to closer positions. They reported pyroclastic flows and rockfalls with frequencies of 5-10 events/hour; the longest runout distances were 2 km from the summit. Of these rockfalls, only a few were made of incandescent materials, indicating that the others involved remobilized older material. A plume was almost always present at the summit.
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: M. Vigny and P. Vetsch, Societe de Volcanologie Geneve (SVG), B.P. 298, CH-1225, Chenebourg, Switzerland; Reuters; Department of Humanitarian Affairs, United Nations, Palais de Nations 1211 Geneva, Switzerland; Henry Gaudru and Patrick Barons, European Volcanological Society (SVE), C.P. 1, 1211 Geneva 17, Switzerland; Bureau of Meteorology, Northern Territory Regional Office, P.O. Box 735, Darwin NT 0801, Australia.