Hachiman-zaki Cape is a cliff protruding from the northern tip of Tobishima Island. It was formed by volcanic ash that accumulated from submarine volcanic activity.
Around the cape, you can find many dikes, which from their shapes have earned nicknames like “Godzilla’s tail” and “dragon’s back.” When traced, the dikes all meet in one place, which is thought to have been a volcanic crater.

Rocks called xenoliths can be found here. These rocks are precious because they teach us about the makeup of the Earth’s interior. From the presence of these rocks, the volcanic activity at Hachiman-zaki Cape is thought to have occurred around 15 million years ago, when Japan had separated from the continent and begun sinking into a shallow sea. However, the exact details are not yet known.