The green tuff here turns an even deeper green when wet. Like the nearby Tsubaki no Shiraiwa Rocks, it is a type of volcanic rock called lapilli tuff formed by volcanic activity about 21 million years ago, but it turned green due to influences such as warm water. The term “green tuff” is said to have originated here at Cape Tateyamazaki. At the time, volcanic matter was often greenish, and it spread throughout the coastal regions of Japan. You can also see the nearby Rousoku (Candle) Rocks (designated as One hundred strange stones from Japan and once called Kannon Rocks due to its shape), Oni no Ashiato (Ogre’s Footprint) Rocks, and Bego Rocks.