Report on Ijen (Indonesia) — 21 March-27 March 2012
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 21 March-27 March 2012
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2012. Report on Ijen (Indonesia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 21 March-27 March 2012. Smithsonian Institution and US Geological Survey.
8.058°S, 114.242°E; summit elev. 2769 m
All times are local (unless otherwise noted)
On 24 March, CVGHM reported that Ijen's lake water chemistry changed during 10 January-17 March, exhibiting a significant increase in carbon dioxide, especially after 5 February, and an increase in acidity. The lake surface temperature increased from 28.8 degrees Celsius on 3 March to 45.1 degrees Celsius on 17 March. The lake water temperature at a depth of 5 m also rose from 42.7 to 44.7 degrees Celsius on 3 and 17 March, respectively. Seismicity increased starting in March. The Alert Level remained at 2 (on a scale of 1-4). [Correction: the Alert Level remained at 3.]
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.