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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.



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.

Table 2. Summary of seismicity at Ijen during 1 October 2001- 6 January 2002. The left-hand column shows time intervals; the other columns indicate the number of earthquakes or maximum tremor amplitudes seen during the time intervals. Courtesy of the Volcanological Survey of Indonesia (VSI).

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.

Geological Summary. 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/).