Report on Rinjani (Indonesia) — 6 October-12 October 2004
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 6 October-12 October 2004
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2004. Report on Rinjani (Indonesia). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 6 October-12 October 2004. Smithsonian Institution and US Geological Survey.
8.42°S, 116.47°E; summit elev. 3726 m
All times are local (unless otherwise noted)
An eruption occurred at Rinjani on 1 October at 1730 following an increase in seismicity that began on 5 September (0-7 earthquakes occurred per day). DVGHM raised the Alert Level to 3 (on a scale of 1-4) or Orange. During 2-4 October, explosions produced thick gray ash plumes to heights of ~300-800 m above the post-caldera cone, Barujari. The explosions occurred on the NE slope of Barujari cone every 5 to 160 minutes. Seismicity was dominated by explosion earthquakes.
Geologic Background. Rinjani volcano on the island of Lombok rises to 3726 m, second in height among Indonesian volcanoes only to Sumatra's Kerinci volcano. Rinjani has a steep-sided conical profile when viewed from the east, but the west side of the compound volcano is truncated by the 6 x 8.5 km, oval-shaped Segara Anak (Samalas) caldera. The caldera formed during one of the largest Holocene eruptions globally in 1257 CE, which truncated Samalas stratovolcano. The western half of the caldera contains a 230-m-deep lake whose crescentic form results from growth of the post-caldera cone Barujari at the east end of the caldera. Historical eruptions dating back to 1847 have been restricted to Barujari cone and consist of moderate explosive activity and occasional lava flows that have entered Segara Anak lake.