Geohistory - Terrain
Yui Maenosu is a shallow rocky surface that extends about 170 m from the shore to the sea. For most of the year it is hidden beneath the surface of the sea, but during low tide in winter, the water gets low enough to reveal the vast wave-cut platform, an approximately 20-million-year-old formation of conglomerate rock. The west-facing coast of Dōgo has been particularly prone to the effects of erosion, and Yui Maenosu is believed to have been formed by continuous erosion thousands of years ago, when the sea level was higher than it is today.
Of the numerous wave-cut platforms in the Oki Islands, the one in Yui is one of the largest and widest. It is valued by the local people as a source of high-quality iwa-nori rock seaweed. Yui Maenosu changes its appearance depending on season and time of day, and is a popular photo spot especially at sunset, when the surface of the sea can sometimes be seen shining like a mirror.
