Mount Sempu is a volcano in the northern arm of Sulawesi, Indonesia, which contains a 3 km wide caldera. A maar, called Kawah Masem, was formed in the south-west of the caldera and contains a crater lake. Sulfur deposits have been extracted from the maar since 1938. Historical records, however, are unknown from the volcano. See also List of volcanoes in Indonesia References Active volcanoes of Indonesia Mountains of Sulawesi Volcanoes of Sulawesi Maars of Indonesia Volcanic crater lakes Calderas of Indonesia Landforms of North Sulawesi