The water is highly acidic, with a pH level often measuring around 2.0.
The distinct turquoise color of the pond is caused by the high concentration of sulfur and iron deposits.
Vegetation directly around the pond is sparse due to the high toxicity and heat of the volcanic gases.
The pond is part of a larger geothermal zone that provides water to the nearby famous Sukayu Onsen.
Jigoku-numa Pond is a volcanic crater lake located in the Hakkoda Mountains of Aomori Prefecture, Japan. The name translates to 'Hell Swamp,' referencing the active volcanic gasses that bubble through the acidic, mineral-rich water. The pond maintains a temperature of approximately 40 to 50 degrees Celsius due to geothermal activity. It was formed by the eruption of the Hakkoda volcanic group. The surrounding landscape features a stark contrast between barren, sulfur-stained earth and dense, lush vegetation. It is a prominent stop along the Hakkoda Gold Line scenic driving route.
The designated wooden observation deck provides the safest and most comprehensive view of the entire pond against the backdrop of the Hakkoda peaks.
Wear sturdy, closed-toe walking shoes as the terrain around the pond can be uneven and rocky.
Bring a face mask if you are sensitive to strong sulfur smells, which can be intense on windy days.
Stick strictly to marked trails, as the ground in some sections can be unstable or dangerously hot.
Avoid walking off-trail, as the geothermal vents can create hidden soft spots or release concentrated volcanic gases.
Access is typically closed during the winter months due to heavy snow accumulation on the mountain roads.
Do not attempt to touch or bathe in the pond water, as it is highly acidic and hazardous to skin.
