Stratum

The Yokoyu-river flowing in the Jigokudani has its source in the Onuma-ike of the Shiga-kogen. It runs down to the Japan Sea with joining several mountain streams and with changing the name from Yamase-river to Chikuma-river and to Shinano-river.

The eye-catching scenery in the Jigokudani is steep cliffs and piled sharp angular rocks.

The geological layer is comprised of quarts diorite. There are some rifts made by crustal movement or by magma which has firmed up after long-term cool down.

The rocks crumble and become angular by disintegration. The onsen of Jigokudani springs out from the layers of quartz diorite.

Onsen

Shibu no Jigokudani Geyser are officially designated as a natural monument by the Japanese government. According to a 1783 written record, the hot spring water outflow stopped temporarily on one occasion following a large explosion at Mount Asama, but the springs have otherwise churned out water around 100°C (212°F) water continuously. The phenomenon of hot spring water outflow along with sulfuric gases is known among geoscientists as the Jigoku Gensho, or “Hell Phenomenon.” This is likely where the area’s name, Jigokudani (“Hell Valley”), originates.

The hot spring facilities in Jigokudani utilize natural hot spring water outflows from the bed of the Yokoyugawa River for their baths. Shibu Hot Springs and Kanbayashi Hot Springs are supplied using these using sources, which provide clear water of the weak salt spring type. The buildings in the photograph were opened in 1864 as a medicinal spa facility, and are still in use today, operated by the Jigokudani Onsen Korakukan inn and spa.

Diverse organisms

Jigokudani is surrounded by precipitous cliffs, difficult to access. It has been known as a place of rich nature. Today, here is designated and preserved as part of the Joshinetsu-kogen national park and a game reserve.

In additions to creations introduced below, here is the habitat of various kinds of creations such as insects, fungi and algae.