Mount Kusatsu-Shirane, Active stratovolcano in Kusatsu, Gunma Prefecture, Japan
Mount Kusatsu-Shirane rises to 2,171 meters (7,123 feet) and consists of andesitic rock formed through millennia of volcanic activity. The surface shows three crater lakes, with Yu-gama being the largest and containing green acidic water.
Records document volcanic eruptions across several centuries, with the peak repeatedly ejecting material from overlapping pyroclastic cones. An eruption in January 2018 caused an avalanche on the slopes and led to temporary closure of hiking trails.
The name comes from nearby Kusatsu hot springs, while the andesitic rock gives the peak its characteristic gray coloring. Hikers follow marked trails through a landscape of volcanic deposits and crater lakes.
Buses run from late April through early November between Kusatsu terminal and Shirane Resthouse near the summit area. Hikers should follow weather forecasts and bring warm clothing, as temperatures remain cool at high elevation even in summer.
Sulfur deposits float on the surface of Yu-gama, creating a yellow pattern amid the emerald color of the water. The overlapping arrangement of multiple pyroclastic cones creates an unusual topography at the summit, different from most other Japanese volcanoes.
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