Report on Ijen (Indonesia) — 6 July-12 July 2011
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 6 July-12 July 2011
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2011. Report on Ijen (Indonesia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 6 July-12 July 2011. Smithsonian Institution and US Geological Survey.
8.058°S, 114.242°E; summit elev. 2769 m
All times are local (unless otherwise noted)
The Darwin VAAC reported that on 10 July a pilot observed an ash plume drifting W from Ijen at an altitude of 3.7 km (12,000 ft) a.s.l. [Correction: Later reports from observers indicated that the plume was likely from a nearby forest fire and not from Ijen. Scientists noted that the seismic activity was quiet and that there were no increases in degassing or boiling of the lake.]
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.