Latest Issue

2023 Vol.132 No.1

Investigating a Sea Arch (Megane Cave) Formed at Mado-Shima Island, San’in Coast

Wave erosion produces a variety of marine cavernous forms along rocky coasts. The San’in Coast is a ria coast composed of extensive rocky cliffs that include more than one hundred marine caves. The cover image shows a sea arch formed at an island composed of rhyolite rocks, which was taken using a camera mounted on an UAV. A small boat (lower-right corner) was used for investigating marine caves at inaccessible sea cliffs or offshore islands. We measured the strength and structure of bedrock from the bow of the boat and launched an UAV from the boat to take aerial images from various directions. These aerial images were combined to produce 3-D models of cavernous forms, from which topography and rock structure were analyzed.

(Photograph: Takuro OGURA, Photographed on September 26, 2022; Explanation: Norikazu MATSUOKA)