Lake Matano

Lake Matano (Indonesian: Danau Matano), also known as Matana, is a tropical lake in East Luwu Regency, South Sulawesi province, Indonesia, that is noteworthy for the unique environment in its deeper layers. With a depth of 590 m (1,940 ft), it is the deepest lake in Indonesia (ranked by maximum depth), the 11th deepest lake in the world and the deepest lake on an island by maximum depth. The surface elevation from mean sea level is only 382 m (1,253 ft), which means that the deepest portion of the lake is below sea level (cryptodepression). It is one of the two major lakes (the other being Lake Towuti) in the Malili Lake system. Lake Matano is considered an ancient lake, and it formed in a tectonic graben around 1 to 2 million years ago. Lake Matano and its catchment area have a large amount of endemic flora and fauna. The catchment area's soils and rocks make it have a relatively high amount of iron. Because the temperature on Sulawesi Island does not change much during the year, the epilimnion never gets cold enough to mix with the hypolimnion. The environment in the hypolimnion is noteworthy for its possible similarity to oceans in the Archean and Paleoproterozoic Eons, before the Great Oxidation Event (GOE). The biogeochemical activity in the hypolimnion has been studied as a model for these oceans.