Ijen Crater

Ijen Crater sits atop Ijen, a stratovolcano on the border of the Banyuwangi and Bondowoso regencies of East Java, Indonesia, part of the Sunda volcanic arc and rising to an elevation of 2,769 meters. The active crater, Kawah Ijen, measures about 722 meters across, up to 200 meters deep and covers roughly 0.41 square kilometers, sitting within a much larger surrounding caldera some 20 kilometers wide. It holds a turquoise, highly acidic lake, the largest of its kind in the world, with a pH measured as low as 0.3 to 0.5 near its edges because of dissolved sulfuric acid. Along the crater rim, sulfuric gas escapes through cracks at temperatures up to 600 degrees Celsius and ignites into blue flames reaching up to five meters high, a phenomenon known as blue fire, while an active vent nearby produces elemental sulfur that workers extract through ceramic pipes at a rate of roughly 14 tons a day. The volcano last erupted in 1999. This entity documents Ijen Crater specifically as a geological formation, an active volcanic crater holding the world's largest highly acidic lake.