Report on Marapi (Indonesia) — 20 July-26 July 2005
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 20 July-26 July 2005
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2005. Report on Marapi (Indonesia). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 20 July-26 July 2005. Smithsonian Institution and US Geological Survey.
0.38°S, 100.474°E; summit elev. 2885 m
All times are local (unless otherwise noted)
DVGHM raised the Alert Level at Marapi from 1 to 2 on 18 July after the number of earthquakes increased dramatically during 8-14 July. During this period, the volcano's seismic network recorded 112 deep volcanic earthquakes. Normally, an average of 7 deep volcanic earthquakes occur in 1 week. No significant activity changes were seen at the volcano; gas emissions rose ~50 m above the summit (9,650 ft a.s.l.) and fumarole temperatures were normal.
Geologic Background. Gunung Marapi, not to be confused with the better-known Merapi volcano on Java, is Sumatra's most active volcano. This massive complex stratovolcano rises 2,000 m above the Bukittinggi Plain in the Padang Highlands. A broad summit contains multiple partially overlapping summit craters constructed within the small 1.4-km-wide Bancah caldera. The summit craters are located along an ENE-WSW line, with volcanism migrating to the west. More than 50 eruptions, typically consisting of small-to-moderate explosive activity, have been recorded since the end of the 18th century; no lava flows outside the summit craters have been reported in historical time.