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.
Steam rises from fumaroles on the SE crater wall of the highly acidic Kawah Ijen crater lake, which lies within one of the post-caldera cones of the massive 20-km-wide Ijen caldera. The renowned 1-km-wide turquoise-colored crater lake, located on the flank of Gunung Merapi stratovolcano near the eastern rim of Ijen caldera, has been the site of phreatic eruptions in historical time and is noted for its deposits of elemental sulfur. The acidic sulfate-chloride type crater lake has very low pH values of about 0.2.
Photo by Tom Casadevall, 1987 (U.S. Geological Survey).
Last updated 2019-10-31 16:00:03