Report on Merapi (Indonesia) — 3 May-9 May 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 3 May-9 May 2006
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2006. Report on Merapi (Indonesia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 3 May-9 May 2006. Smithsonian Institution and US Geological Survey.
7.54°S, 110.446°E; summit elev. 2910 m
All times are local (unless otherwise noted)
CVGHM reported that on 6 May, gas plumes rose to 800 m above Merapi (or 12,300 ft a.s.l.) and 18 incandescent avalanches of volcanic material were observed. On 7 May, 26 incandescent avalanches that extended about 100 m were seen during the morning. Incandescence was seen at the summit ten times. On 6 and 7 May, the lava dome continued to grow and seismicity was dominated by multi-phase earthquakes. Shallow volcanic earthquakes and signals from landslides and rockfalls were also recorded. On 8 May, the Darwin VAAC reported that CVGHM warned of a plume rising to ~3.7 km (12,000 ft) a.s.l. No ash was visible on satellite imagery. Merapi remained at Alert Level 3 (on a scale of 1-4), as it has since 12 April.
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.