Nukkakushi Crater (a.k.a. Ansei Crater) is a ravine surrounded by three mountains, Mt.Sandanyama, Mt.Kamihorokamettokuyama, and Mt.Kamifuranodake, as well as is located at the headwater of the Nukkakushi-Furanogawa River.
It is also called Ansei Crater. “Ansei”means one of the period between 1854-1860 in Japan, though there is no any proof that the crater was made by volcanic eruptions between Ansei period.

Phreatic explosions occurred at least three times during the last 3,000 years at Nukkakushi Crater. Most of eruptions were small, and ejecta only reached Tokachidake Hot Spring.

The fact that water of Nukkakushi-Furanogawa River became muddy in 1961 indicates that there was a small volcanic activity. As fumarole emission is still active, this crater is under monitoring.

Temperature and components of Tokachidake Hot Springs have been changed by volcanic activities of Nukkakushi Crater, because it is thought that thermal activities at Nukkakushi Crater are main heat sources for the Hot Springs.

Nukkakushi Crater is within 1-hour walking distance from Tokachidake Hot Springs, and provides experiences of fumarole activities to visitors. Therefore, it plays an important role for us to ponder and to learn volcanic activities in Mt.Tokachidake.
In addition, you can utilize hot spring discharge, such as Ryounkaku (Hot spring hotel), and Okina Hot Spring. Those volcanic activities might give you a blessing of a volcano.