• D1: Ana-iwa in Fuyushima

Hidaka Yabakei Area

Geological Site


Ana-iwa in Fuyushima

Ana-iwa in Fuyushima

The hole running through Ana-iwa (meaning "rock with a hole") is said to have formed naturally. The rock is located inside Fuyushima Fishing Port, and used to have a hole as high as 9 meters before the area was reclaimed. The place name Fuyushima also derives from the Ainu terms puy (hole), o (there) and shuma (stone).

The hole is a sea cave formed as a result of wave erosion. The rock itself is made of hornfels, which metamorphosed from sedimentary rock (e.g., sandstone, mudstone) due to heat from contact with magma.

This striking rock, which stands guard over the challenging local terrain, appears in the records of Japanese explorer Takeshiro Matsuura and a variety of other travelers who passed by during the Edo period (1603 - 1868).

The area is home to marine terraces, which are flat areas that were eroded by waves and became land as a result of ground uplift and sea-level lowering. To the east of Ana-iwa is a roadside marine terrace about 40 meters above sea level. Flat terrain like this is used for drying the local specialty of Hidaka Kombu kelp among other purposes.