Date: Mon, 28 Nov 1994 08:51:00 MST From: Global Volcanism NetworkSubject: Merapi VSI report, 28 Nov 1994 The following report was received from the Volcanological Survey of Indonesia by GVN on 28 November 1994. Merapi central Java, Indonesia (7.54 S, 110.44 E) All times are local (= GMT + 7 hours) Pyroclastic block-and-ash flows and glowing surges on 22 November resulted from the collapse of the active dome at the summit (figure 1). As of 28 November, 41 people had died and another 43 were injured and in serious condition at hospitals. All of the victims lived in areas near the bank of the Boyong River, which flows S from the summit of Merapi to the middle of Yogyakarta. The threat to areas on the S flank was noted in February 1994. The Boyong and other rivers on the SW flank where previous nuee ardentes have caused destruction had been mentioned in Berita Merapi (Merapi News), sent to local governments including Sleman Regency, every month since March. Rockfalls from the dome recently traveled down these rivers for distances of 500-1,500 m. Prior to February 1994, no rockfalls were observed or reported along the Boyong River. Activity increased with the appearance of low-frequency earthquakes on 20 October (figure 2). Multiphase events and rockfalls continued to be recorded at normal levels, with occasional low-frequency events and one tremor episode on 3 November. On 4 November the marked increase of activity was reported to the Chief of Regencies around Merapi. During 21-22 November, a team from the Merapi Volcano Observatory (MVO) climbed to the summit to observe dome development and install an extensometer station to measure cracks. The first nuee ardente was recorded instrumentally at 1014 on 22 November at MVO, and was observed visually from the Plawangan, Ngepos, Babadan, and Jrakah observation posts. The team at the summit saw a vertical plume that originated from a location somewhere on the S part of the dome. A glowing cloud was clearly seen from the direction of Plawangan to the S. The intensity of the nuee increased at 1020, prompting the observer at Plawangan to send a warning to the forestry officer posted at Kaliurang, a well-known tourist resort. The officer then yelled a warning to the local people. Five minutes later (1025) MVO instructed all observation posts and radio stations of the Regional Task Force that the Alert Status had been raised to Level 4, and that preparations for evacuation should begin. At 1045 the observer at Plawangan sent a message to the Chief of Pakem District, but he was already in the field, probably because he had heard the previous warning. An evacuation warning was radioed to regional task forces at 1100. By 1215 the first victim had been discovered. The Plawangan observation post was abandoned at 1508 and the personnel temporarily moved to Kaliurang. The nuees had diminished by 1720 that evening. Information Contact: Sukhyar, Volcanological Survey of Indonesia. Global Volcanism Network | Phone: 202-357-1511 Museum of Natural History, MRC 129 | Fax: 202-357-2476 Smithsonian Institution | Washington, DC 20560 USA | Internet: mnhms017@SIVM.SI.EDU