Follow the path that leads downhill toward the ocean and climb to the top of the observation tower. You will see Mt. Onidake behind you and long stretches of dark black rock in both directions along the coast.
Blackened rocky coastlines are nothing unusual in the Goto Islands, but the Abunze Lava Coast has a special history. Some 18,000 years ago, Onidake erupted, and some of that lava flowed down to this area.
This lava, known as a’a, is rough in texture. When it cools, it creates large, uneven, black rocks, many pockmarked with holes where gas escaped from the solidifying ooze. This a’a lava also produces sharp, black fragments called clinkers, which are visible here among the larger rocks. Over the millennia, these all suffered erosion from the pounding ocean and were broken down further, creating volcanic rocks of all sizes and shapes.
The eruptions of Onidake and other nearby volcanoes produced this 7-kilometer-long jagged coastline which, thanks to the Tsushima Current, is the warmest place on the island. There are even subtropical plants growing here.
The name Abunze is quite unusual, meaning “stirrup shallows.” An old story says that a local lord tried to escape an uprising against his rule in 1507, fleeing on horseback along the coast, but at this point one of his stirrups broke, and he was forced to escape in a fishing boat to a nearby island. He ultimately killed himself rather than be captured. Thus was born the legend of the “stirrup shallows.”