Report on Ijen (Indonesia) — December 2001
Bulletin of the Global Volcanism Network, vol. 26, no. 12 (December 2001)
Managing Editor: Richard Wunderman.
Ijen (Indonesia) Higher-than-normal seismic activity from October 2001 through at least 6 January 2002
Please cite this report as:
Global Volcanism Program, 2001. Report on Ijen (Indonesia) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 26:12. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200112-263350.
8.058°S, 114.242°E; summit elev. 2769 m
All times are local (unless otherwise noted)
During 1 October 2001 through at least 6 January 2002, activity at Ijen was higher than normal, though low visibility often restricted visual observation of the summit. Activity included heightened continuous tremor, shallow volcanic (B-type) earthquakes, and one small explosion earthquake (table 2). No deep volcanic (A-type) earthquakes were reported.
|Date||Shallow volcanic earthquakes (B-type)||Small explosion earthquakes||Tectonic earthquakes||Continuous tremor (max. amp.)|
|01 Oct-07 Oct 2001||10||--||1||0.5-6 mm|
|15 Oct-21 Oct 2001||4||--||2||0.5-3 mm|
|22 Oct-28 Oct 2001||5||--||7||0.5-5 mm|
|29 Oct-04 Nov 2001||6||--||--||0.5-6 mm|
|05 Nov-11 Nov 2001||2||--||2||0.5-2 mm|
|12 Nov-18 Nov 2001||1||1||1||0.5-4 mm|
|19 Nov-25 Nov 2001||4||--||--||0.5-5 mm|
|26 Nov-02 Dec 2001||3||--||--||0.5-6 mm|
|03 Dec-09 Dec 2001||3||--||--||0.5-3 mm|
|17 Dec-30 Dec 2001||5||--||3||0.5-4 mm|
|31 Dec-06 Jan 2002||3||--||1||0.5-4 mm|
During 1-7 October a thin, white, low-pressure plume was observed reaching ~50-100 m above the summit. Ijen volcano remained at Alert Level 2 (on a scale of 1-4) through at least 6 January 2002.
Geologic Background. The Ijen volcano complex at the eastern end of Java consists of a group of small stratovolcanoes constructed within the large 20-km-wide Ijen (Kendeng) caldera. The north caldera wall forms a prominent arcuate ridge, but elsewhere the caldera rim is buried by post-caldera volcanoes, including Gunung Merapi, which forms the high point of the complex. Immediately west of the Gunung Merapi stratovolcano is the historically active Kawah Ijen crater, which contains a nearly 1-km-wide, turquoise-colored, acid lake. Picturesque Kawah Ijen is the world's largest highly acidic lake and is the site of a labor-intensive sulfur mining operation in which sulfur-laden baskets are hand-carried from the crater floor. Many other post-caldera cones and craters are located within the caldera or along its rim. The largest concentration of cones forms an E-W zone across the southern side of the caldera. Coffee plantations cover much of the caldera floor, and tourists are drawn to its waterfalls, hot springs, and volcanic scenery.
Information Contacts: Dali Ahmad, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).