Exploration of Nature or Human Exploitation
Ijen volcano in East Java contains the world's largest acidic volcanic crater lake, called Kawah Ijen, famous for its turquoise color. 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 stratovolcano, which forms the 2799 m high point of the Ijen complex. The largest concentration of post-caldera cones forms an E-W-trending zone across the southern side of the caldera. Coffee plantations cover much of the Ijen caldera floor, and tourists are drawn to its waterfalls, hot springs, and dramatic volcanic scenery. Immediately west of Gunung Merapi is the renowned historically active Kawah Ijen volcano, which contains a nearly 1-km-wide, turquoise-colored, acid crater 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.
Eruption History
Eruptions from Ijen are very hazardous because of the risk of the lake draining to form catastrophic lahars.The active crater measuring 950x600 m is known for its rich sulphur deposits which are being quarried. The volcano is one of several active stratovolcanoes constructed over the 20 km wide Ijen caldera, the largest caldera in Java.
Blessing of Sulfure
An active vent at the edge of the lake is a source of elemental sulfur, and supports a mining operation. The lake is recognised as the largest highly acidic crater lake in the world, and since it is also a source for the river Banyupahit, resulting in highly acidic and metal-polluted water, it has a significant detrimental effect on the downstream river ecosystem. In 2008, explorer George Kourounis took a small rubber boat out onto the acid lake to measure its acidity. The pH of the water in the crater was measured to be 0.5 due to sulfuric acid. Escaping volcanic gasses are channeled through a network of ceramic pipes, resulting in condensation of molten sulfur. The sulfur, which is deep red in color when molten, pours slowly from the ends of these pipes and pools on the ground, turning bright yellow as it cools. Most miners make this journey twice a day. A nearby sugar refinery pays the miners by the weight of sulfur transported; as of September 2012, the typical daily earnings were equivalent to approximately $ 8 US. The miners break the cooled material into large pieces and carry it away in baskets. Miners must carry loads, which range from 75 kilograms (170 lb) to 90 kilograms (200 lb), up 300 metres (980 ft) to the crater rim, with a gradient of 45 to 60 degrees and then 3 kilometers (1.86 miles) down the mountain for weighing. The miners often use insufficient protection while working around the volcano and complain of numerous respiratory afflictions. There are 200 miners, who extract 14 tons per day or only 20 percent of the continuous daily deposit.
