The cliff where Tobishima Minami Lighthouse stands is 20 m high, and is composed of alternating strata (layers) containing either round, green stones (about 5–10 cm in diameter) or volcanic ash. These strata were formed underwater by repeated volcanic activity on the sea floor between 16.5 and 9 million years ago. The deposits that formed the strata were eroded by the power of waves to create a sea cliff.

The flat, rocky surface surrounding Tobishima Island that appears only at low tide is called an “”abrasion platform.””
It is thought that this abrasion platform will eventually rise and become Tobishima Island’s fifth terrace.
Gotoro-hama Coast, the area where Minami Lighthouse is located, is a place where you can feel how dynamic the Earth’s processes are.