Kuroshima Island
Evidence of volcanic ash
This circular island, about four kilometers off Fukue Island, had a population of one as of this writing. It is made up of basaltic lava and volcanic ash, and a large, open face at the harbor shows two distinct layers of ash: black below and dark brown above. The lower layer is possibly the result of a pyroclastic flow that occurred after an eruption, while the upper was likely formed from falling ash. A sea arch can be seen almost directly to the east across a small bay. Wave action is the most common cause of sea arches, but it is possible that this one is the remains of a lava tube. A number of houses still stand just beyond the harbor, a reminder of a very different time not that long ago when the island had a much larger population.