Report on Ijen (Indonesia) — 2 May-8 May 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 2 May-8 May 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, 2 May-8 May 2001. Smithsonian Institution and US Geological Survey.
8.058°S, 114.242°E; summit elev. 2769 m
All times are local (unless otherwise noted)
During 23-29 April seismic activity was higher than normal at Ijen, with a high number of shallow volcanic earthquakes (nine). In addition, one small explosion event and seven tectonic earthquakes were recorded. Visual observations were not possible. The volcano remained at Alert Level 2 (on a scale of 1-4).
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.