Report on Ijen (Indonesia) — 11 April-17 April 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
11 April-17 April 2001
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2001. Report on Ijen (Indonesia). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 11 April-17 April 2001. Smithsonian Institution and US Geological Survey.
8.058°S, 114.242°E; summit elev. 2769 m
All times are local (unless otherwise noted)
Seismic activity at Ijen was high during 2-9 April. Five episodes of tremor were reported. The number of shallow volcanic earthquakes decreased in comparison to the previous week. Overall, seismographs recorded 13 shallow volcanic earthquakes, two tectonic earthquakes, and one small explosion event. The volcano is at Alert Level 2 (on a scale of 1-4).
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.