Report on Egon (Indonesia) — 1 September-7 September 2004
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 1 September-7 September 2004
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2004. Report on Egon (Indonesia). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 1 September-7 September 2004. Smithsonian Institution and US Geological Survey.
8.676°S, 122.455°E; summit elev. 1661 m
All times are local (unless otherwise noted)
Strong volcanic activity at Egon beginning on 3 September led DVGHM to raise the Alert Level from 3 to 4 (on a scale of 1-4) on 4 September. The increase in volcanic activity began on 27 August when plumes rose to ~300 m above the volcano and explosion earthquakes were recorded. This activity prompted DVGHM to raise the Alert Level from 2 to 3. On 3 September an ash plume rose ~1 km above the summit and on 4 September an ash plume rose to ~3 km. As a consequence, all those living in the villages of Baokrengit, Welimwatu, and Natakoli were evacuated. On 6 September, an explosion produced a plume as high as 2.5 km above the volcano that drifted SW. According to a report released by the United Nations Office for the Coordination of Humanitarian Affairs (OCHA), as of 6 September activity at Egon led to the evacuation of 2,100 people. A total of 4,300 were expected to be evacuated.
Geologic Background. Gunung Egon, also known as Namang, sits astride the narrow waist of eastern Flores Island. The barren, sparsely vegetated summit region has a 350-m-wide, 200-m-deep crater that sometimes contains a lake. Other small crater lakes occur on the flanks. A lava dome forms the southern summit. Solfataric activity occurs on the crater wall and rim and on the upper S flank. Reports of historical eruptive activity prior to explosive eruptions beginning in 2004 were inconclusive. A column of "smoke" was often observed above the summit during 1888-1891 and in 1892. Strong "smoke" emission in 1907 reported by Sapper (1917) was considered by the Catalog of Active Volcanoes of the World (Neumann van Padang, 1951) to be an historical eruption, but Kemmerling (1929) noted that this was likely confused with an eruption on the same date and time from Lewotobi Lakilaki.