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The Ijen volcano complex is a group of stratovolcanoes in the Banyuwangi Regency of East Java, Indonesia. It is inside a larger caldera Ijen, which is about 20 kilometers wide. The Gunung Merapi stratovolcano is the highest point of that complex. The name "Gunung Merapi" means "mountain of fire" in the Indonesian language (api being "fire"); Mount Merapi in central Java and Marapi in Sumatra have the same etymology. West of Gunung Merapi is the Ijen volcano, which has a one-kilometer-wide turquoise-colored acidic crater lake. The lake is the site of a labor-intensive sulfur mining operation, in which sulfur-laden baskets are carried by hand from the crater floor. The work is paid well considering the cost of living in the area, but is very onerous.〔Megan Lane, "Sulphur mining in an active volcano," BBC News. February 2011. http://www.bbc.com/news/world-asiapacific-12301421〕 Workers earn around Rp 50,000 - 75,000 ($5.50-$8.30) per day and once out of the crater, still need to carry their loads of sulfur chunks about three kilometers to the nearby Paltuding Valley to get paid.〔Indra Harsaputra, (Kawah Ijen: Between potential and threat' ), ''The Jakarta Post'', 19 December 2011.〕 Many other post-caldera cones and craters are located within the caldera or along its rim. The largest concentration of post-caldera cones run east-west across the southern side of the caldera. The active crater at Kawah Ijen has a diameter of and a surface area of . It is deep and has a volume of . The lake is recognised as the largest highly acidic crater lake in the world. It is also a source for the river Banyupahit, resulting in highly acidic and metal-enriched river water which has a significant detrimental effect on the downstream river ecosystem.〔(【引用サイトリンク】title=University of Amsterdam, Faculty of Earth and Life Sciences, Natural Pollution Caused by the Extremely Acidic Crater Lake Kawah Ijen, East Java, Indonesia )〕 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.〔(Measuring the acidity of Kawah Ijen crater lake )〕 ==Blue Fire Crater== Since National Geographic mentioned the electric-blue flame of Ijen, tourist numbers increased. The phenomenon has occurred for a long time, but beforehand there was no midnight hiking. A two-hour hike is required to reach the rim of the crater, followed by a 45-minute hike down to the bank of the crater. The blue fire is ignited sulphuric gas, which emerges from cracks at temperatures up to 600 degrees Celsius (1,112 degrees Fahrenheit). The flames can be up to 5 meters (16 feet) high; some of the gas condenses to liquid and is still ignited.〔(【引用サイトリンク】title=Stunning Electric-Blue Flames Erupt From Volcanoes )〕〔(【引用サイトリンク】title=The Dark Secret of Indonesia’s Blue-Fire Volcano )〕 It is the largest blue flame area in the world and local people refer to it as 'Blue Fire'. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ijen」の詳細全文を読む スポンサード リンク
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