Report on Tengger Caldera (Indonesia) — 22 December-28 December 2010

Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 22 December-28 December 2010
Managing Editor: Sally Kuhn Sennert

Please cite this report as:

Global Volcanism Program, 2010. Report on Tengger Caldera (Indonesia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 22 December-28 December 2010. Smithsonian Institution and US Geological Survey.

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Tengger Caldera

Indonesia

7.942°S, 112.95°E; summit elev. 2329 m

All times are local (unless otherwise noted)


CVGHM reported that during 8-19 December gray-to-brown plumes from Tengger Caldera's Bromo cone rose 400-800 m above the crater and drifted E, NE, and N. On 19 December explosions produced an ash plume that rose 2 km above the crater rim. Ashfall was heavy around the crater and was reported in areas as far away as the Juanda Airport (70 km NNW) in Surabaya. The ash damaged agricultural land, impacted trees and river valleys, and disrupted transportation infrastructure. The Alert Level remained at 3 (on a scale of 1-4). Residents and tourists were not permitted within a 2-km-radius of the active crater.

During 20-25 December gray-to-brown plumes rose 800-1,200 m above the crater and drifted N and NE. Ejected material fell back around the crater. On 25 December, ash and occasionally lapilli fell at the Bromo observation post, about 2 km away. The ashfall was about 20 cm thick.

Based on analysis of satellite imagery and information from CVGHM, the Darwin VAAC reported that during 26-27 December an ash plume rose to an altitude of 5.5 km (18,000 ft) a.s.l. and drifted 150 km NE.

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.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM), Darwin Volcanic Ash Advisory Centre (VAAC)