Numanotaira Crater
Numanotaira Crater is a volcanic crater northwest of Mt. Adatara’s peak. The crater is around 1.2 kilometers across and 150 meters deep. Descending into the crater itself is prohibited due to the risk of volcanic activity and poisonous fumes. It was formed by repeated eruptions over thousands of years. In the most recent eruption, in 1900, a sulfur refinery was destroyed and 72 miners working on the mountain died.
From the peak of Mt. Adatara, the closest point with a view of the crater is a 15-minute walk north along a broad ridge called the “Ox’s Back” (Ushi no se). The interior of the crater gradually comes into view along the way—a gouge in the mountainside almost completely devoid of vegetation.
A trail leads around the entire crater, but the full 7.4-kilometer circuit takes three or four hours to complete. Most visitors simply retrace their steps, with an optional detour to the peak of Mt. Tetsu and back. The Mt. Tetsu detour is an additional 30-minute walk north along the “Horse’s Back” (Uma no se), a ridge following the crater’s eastern edge that is slightly narrower than the “Ox’s Back” to the south.
