Report on Tambora (Indonesia) — 12 October-18 October 2011
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 12 October-18 October 2011
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2011. Report on Tambora (Indonesia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 12 October-18 October 2011. Smithsonian Institution and US Geological Survey.
8.25°S, 118°E; summit elev. 2850 m
All times are local (unless otherwise noted)
CVGHM reported that during 22 September-9 October plumes did not rise from Tambora; seismicity fluctuated, but declined overall. Based on visual observations, deformation data, and seismicity, the Alert Level was lowered to 2 (on a scale of 1-4) on 9 October.
Geologic Background. The massive Tambora stratovolcano forms the entire 60-km-wide Sanggar Peninsula on northern Sumbawa Island. The largely trachybasaltic-to-trachyandesitic volcano grew to about 4,000 m elevation before forming a caldera more than 43,000 years ago. Late-Pleistocene lava flows largely filled the early caldera, after which activity changed to dominantly explosive eruptions during the early Holocene. Tambora was the source of history's largest explosive eruption, in April 1815. Pyroclastic flows reached the sea on all sides of the peninsula, and heavy tephra fall devastated croplands, causing an estimated 60,000 fatalities. The eruption of an estimated more than 150 km3 of tephra formed a 6-km-wide, 1250-m-deep caldera and produced global climatic effects. Minor lava domes and flows have been extruded on the caldera floor at Tambora during the 19th and 20th centuries.