Sensuijima Promenade
Sensuijima Promenade runs from Tanoura Beach to Hikoura Beach, a total of 600 meters along the southern coastline. It passes rock formations, sea caves, and other sites significant to the island’s geological history.
The bedrock of Sensuijima is mostly rhyolitic tuff, formed from volcanic ash and debris ejected during large, explosive eruptions. The tuff was created about 90 million years ago during a period of intense volcanic activity, when the Japanese archipelago was still part of the Eurasian continent. Fault lines in the coastal bluffs are evidence of considerable seismic activity. Sedimentary rock, which formed underwater from ancient sand, silt, and mud, is visible in some outcrops.
There are approximately 200 sea caves on the island, some of which are visible from the promenade. Several are located above the current high tide line; evidence that the sea level was higher when they were formed. Near the end of the promenade is Goshiki-iwa (literally, colored rock), an outcrop of exposed rhyolitic tuff. Its color variations reflect the island’s diverse mineral composition and the varying oxidation levels of iron in the rock.