Report on Tengger Caldera (Indonesia) — 2 December-8 December 2015
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 2 December-8 December 2015
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2015. Report on Tengger Caldera (Indonesia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 2 December-8 December 2015. Smithsonian Institution and US Geological Survey.
7.942°S, 112.95°E; summit elev. 2329 m
All times are local (unless otherwise noted)
PVMBG reported that during 15 November-4 December white plumes from Tengger Caldera's Bromo cone rose as high as 150 m above the crater, and an intense sulfur dioxide odor was noted at the Bromo observation post. On 15, 23, and 27 November dense ash plumes rose 150 m above the crater rim. RSAM values increased at the beginning of November, and then sharply increased in the beginning of December. Based on seismic analysis, visual observations, and hazard potential, the Alert Level was raised to 3 (on a scale of 1-4) on 4 December. Residents and visitors were warned not to approach the crater within a radius of 2.5 km.
Based on information from PVMBG and satellite images, the Darwin VAAC reported that during 5 and 7-8 December ash plumes rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted 55-185 km W, SW, S, and SE.
Geologic Background. The 16-km-wide Tengger caldera is located at the northern end of a volcanic massif extending from Semeru volcano. The massive volcanic complex dates back to about 820,000 years ago and consists of five overlapping stratovolcanoes, each truncated by a caldera. Lava domes, pyroclastic cones, and a maar occupy the flanks of the massif. The Ngadisari caldera at the NE end of the complex formed about 150,000 years ago and is now drained through the Sapikerep valley. The most recent of the calderas is the 9 x 10 km wide Sandsea caldera at the SW end of the complex, which formed incrementally during the late Pleistocene and early Holocene. An overlapping cluster of post-caldera cones was constructed on the floor of the Sandsea caldera within the past several thousand years. The youngest of these is Bromo, one of Java's most active and most frequently visited volcanoes.