Report on Semeru (Indonesia) — 16 April-22 April 2003
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 16 April-22 April 2003
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2003. Report on Semeru (Indonesia). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 16 April-22 April 2003. Smithsonian Institution and US Geological Survey.
8.108°S, 112.922°E; summit elev. 3657 m
All times are local (unless otherwise noted)
During the week of 16-22 April, Semeru was continually active. A white-gray ash plume@ rose 400-500 m over the summit. Seismic signals interpreted as pyroclastic flows were recorded multiple times during the week. One pyroclastic flow on 18 April traveled into several local drainages, reaching lengths of ~2.5 and ~3.5 km.
Geologic Background. Semeru, the highest volcano on Java, and one of its most active, lies at the southern end of a volcanic massif extending north to the Tengger caldera. The steep-sided volcano, also referred to as Mahameru (Great Mountain), rises above coastal plains to the south. Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano.