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Mount Kusatsu-Shirane, Kusatsu city, Agatsuma county, Gunma pref., Japan


Kusatsu Mine


Fumarole deposit

Sulphur melt drifing on the surface of the crator lake. This crator is the Shirane Pyroclastic Cone, one of the pyroclastic cones formed by the younger volcanic activity of Mount Kusatsu-Shirane since the Late Pleistocene (16 ka). The Shirane Pyroclastic Cone is composed of calc-alkaline andesite. The crator has produced sulphur melt since 1882. Mount Kusatsu-Shirane was active in the Middle Pleistocene (0.6-0.3 Ma) and has been active since the Late Pleistocene (16 ka).


A crater lake, Yugama, of the Shirane Pyroclastic Cone in Mount Kusatsu-Shirane. The yellow lines drifting on the surface of the blue-green crater lake are liquid sulphur. Acidity of this lake is approximately pH 1.0, and one of the world's most acidic lakes. Fragments of erupted lava and pumice forms the wall of this crater lake. The wall of this crater lake is composed of lava and pumice of the Shirane Pyroclastic Cone.

Reported Minerals

  • Sulphur


  • 1805: Erupted.
  • 1882: Erupted. Melted sulphur formed a mound in the middle of the crater lake. The lake water has been strong acidic since this eruption.
  • 1880's: Began to mine sulphur.
  • 1897: Erupted. 2 mine workers were injured.
  • 1900: Erupted. A mine worker was injured.
  • 1925: Erupted.
  • 1927: Erupted.
  • 1932: Erupted. 2 mine workers died, and 7 mine workers were injured.
  • 1937-1939: Erupted.
  • 1976: Erupted.
  • 1982-1983: Erupted.


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