Know Before You Go
Check daily tide charts, best viewed at low tide.
A bridge connects Oujima to Kumejima.
Kumejima-chō, Japan
Tatami-ishi (Tatami Rocks)
Unusual hexagonal rocks formed by cooling lava named for their resemblance to traditional Japanese tatami mats.
Tatami-ishi 畳石 (Tatami-Rocks) is a Nationally Designated Natural Monument located on the south coast of Oujima 奥武島 (Ou Island). These pentagonal and hexagonal shaped rocks, formed by andesite magma cooled under a geological process called columnar jointing, are called Tatami-Rocks because of the resemblance to the tatami mats of traditional Japanese home design. Water erosion has leveled and smoothed the tops of the rock structures.
