Hagi Geopark: Susa Area
Mt. Kōyama sits atop a peninsula that juts out into the Japan Sea 38 kilometers northeast of Hagi Castle Town. There are excellent natural harbors at Susa, to the west of Mt. Kōyama, and at Esaki, to its east. The area is famed for its seafood, particularly swordtip squid, known locally as mikoto-ika, which thrive in the craggy seabed created by the many lava flows that have occurred in the area over the past million years.
The geological feature for which this area is most famous is the Susa Hornfels, a beautifully banded cliff that rises 12 meters out of the ocean. Hornfels is a type of metamorphic rock that is found all over the world. The name comes from the German word meaning “horn stone,” after the rock’s layered appearance, and its toughness, which is reminiscent of animal horn.
The Susa Hornfels is made up of layers of mudstone and sandstone. The layers were slowly formed beginning roughly 15 million years ago, as sand and mud alternately accumulated on the seabed. The layers were then rapidly heated by magma, crystallizing them into the hornfels formation. The darker bands were formed from layers of mud, and the lighter bands were once sand. At some point after the hornfels’ formation, there was a great geologic shift, and the stone was lifted up, forming the cliff. Similarities can be found between this geological marvel on the Hagi coastline and the Flysch Formation in Zumaia Spain.
Access: 10 minutes by taxi from JR Susa station.
Admission free, open 24 hours.
Susa Hornfels Google Maps link: here