Mt. Chōkai is made up of layers of lava from repeated volcanic activity since about 600 thousand years ago. Kamaiso Beach is also made up of lava that flowed into the sea from Mt. Chōkai.

Due to how the lava flowed and cooled, the uppermost and lowermost parts of the volcanic rock are filled throughout with small gaps. This allows the rock to hold a lot of water like a sponge; that water flows out from many natural springs, including Kamaiso’s sandy beach and rocky crevices. Spring water has even been found on the seafloor about 5 km offshore from Kamaiso Beach.

This spring water originates from rain and snow that fell on Mt. Chōkai about 20 years ago and slowly flowed through the volcanic rock.

In winter, the strong winds that blow from the Asian continent collect a lot of water vapor as they cross the Sea of Japan. As these winds then hit Mt. Chōkai, they cause large amounts of snow to fall. Mt. Chōkai and the Tōhoku region’s Sea of Japan coast have among the highest rates of snowfall in the world. This allows Mt. Chōkai to supply its land and residents with a rich abundance of water.