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Report on Ijen (Indonesia) — September 2001


Ijen

Bulletin of the Global Volcanism Network, vol. 26, no. 9 (September 2001)
Managing Editor: Richard Wunderman.

Ijen (Indonesia) Heightened seismicity through at least September 2001, white-gray plume to ~100 m

Please cite this report as:

Global Volcanism Program, 2001. Report on Ijen (Indonesia) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 26:9. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200109-263350



Ijen

Indonesia

8.058°S, 114.242°E; summit elev. 2769 m

All times are local (unless otherwise noted)


As summarized in table 1, beginning in February and lasting through at least September 2001, Ijen displayed heightened seismicity including tremor, shallow volcanic (B-type) earthquakes, and explosion earthquakes. Deep volcanic (A-type) earthquakes also occurred on a few occasions. The Alert Level remained at 2 (on a scale of 1-4) during most of the report period. Our last report (BGVN 25:10) covered activity through October 2000.

Table 1. Summary of seismicity at Ijen, 30 January-30 September 2001. Measurements in millimeters (mm) indicate amplitudes. Courtesy of the Volcanological Survey of Indonesia (VSI).

Date Deep volcanic (A-type) Shallow volcanic (B-type) Small explosion Tectonic Tremor
30 Jan-05 Feb 2001 -- 75 2 6 2 (4 mm)
06 Feb-11 Feb 2001 -- 36 2 6 --
13 Feb-19 Feb 2001 1 30 3 4 --
20 Feb-26 Feb 2001 -- 42 -- 5 --
27 Feb-05 Mar 2001 42 (4 mm) -- -- 5 --
06 Mar-12 Mar 2001 -- 17 -- -- --
12 Mar-18 Mar 2001 -- 27 3 1 --
19 Mar-23 Mar 2001 -- 12 4 -- --
27 Mar-01 Apr 2001 -- 47 1 7 --
02 Apr-08 Apr 2001 -- 13 1 -- 2
09 Apr-15 Apr 2001 -- 9 -- 10 --
16 Apr-23 Apr 2001 1 10 -- 2 --
23 Apr-29 Apr 2001 -- 9 1 7 --
30 Apr-06 May 2001 -- 4 -- 6 --
07 May-13 May 2001 -- 11 -- 3 --
14 May-20 May 2001 -- 3 -- -- --
28 May-03 Jun 2001 -- 9 2 9 discontinuous (0.5-3 mm)
02 Jul-08 Jul 2001 -- 9 2 9 discontinuous (0.5-3 mm)
09 Jul-15 Jul 2001 1 31 2 7 discontinuous (0.5-3 mm)
13 Aug-26 Aug 2001 -- 42 1 6 continuous
27 Aug-02 Sep 2001 -- 16 1 1 continuous
03 Sep-09 Sep 2001 -- 1 5 5 discontinuous
10 Sep-16 Sep 2001 -- 14 -- 4 continuous
17 Sep-23 Sep 2001 -- 13 -- 1 continuous (0.5-3 mm)
24 Sep-30 Sep 2001 -- 14 -- 4 continuous (0.5-3 mm)

During May, a thin-white plume reached to ~50 m above the summit. The Darwin VAAC reported that at 0120 on 15 July sulfur fumes entered the cabin of an aircraft flying from Singapore to Denpasar. At the time, the aircraft was flying at an altitude of ~2.4 km about 15 km SE of Ijen, the suspected source of the sulfur gas. During mid-August, the crater began to produce a white-grey plume. By the end of September, the plume reached up to ~100 m above the summit.

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/).