Report on Merapi (Indonesia) — 19 April-25 April 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 19 April-25 April 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, 19 April-25 April 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 21-25 April seismicity at Merapi remained at high levels, with several seismic signals recorded that were associated with rockfalls. The sulfur-dioxide flux from the volcano was 175 metric tons on 22 April. On 22 and 23 April, fumarolic emissions reached a maximum height of 400 m above the volcano (or 11,000 ft a.s.l.). On the 25th, two rockslides from lava-flow fronts were heard from nearby observatories. According to news reports, about 600 of the approximately 14,000 people living near the volcano had been evacuated by the 24th. Merapi remained at Alert Level 3 (on a scale of 1-4).
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.