Kusatsu-Shirane (草津白根山) 草津白根山
The Yugama crater is 300 m in diameter with a pH close to 1: among the most acidic lakes in the world.
An active volcano on the border between Gunma and Nagano, kept under priority monitoring by the Japan Meteorological Agency. For years access to the Yugama has been prohibited or heavily restricted depending on the alert level.
Gunma
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