Report on Merapi (Indonesia) — 12 July-18 July 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 12 July-18 July 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, 12 July-18 July 2006. Smithsonian Institution and US Geological Survey.
7.54°S, 110.446°E; summit elev. 2910 m
All times are local (unless otherwise noted)
During 12-18 July, lava flows at Merapi were observed and reached a maximum distance of 2 km SE along the Gendol River. Gas plumes were also observed daily and reached heights of 1 km above the crater (12,800 ft a.s.l.). On 17 July, CVGHM reported that the Alert Level was lowered one level to 3 (on a scale of 1-4) in all remaining areas previously at Alert Level 4 (S slopes). Pyroclastic flows were not observed during the reporting period.
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.