S P O T ／ SPOT-333

Yakama Potholes

八釜の甌穴群やかまのおうけつぐん

Deep in a V-shaped gorge near the center of Shikoku, the Kuro River has spent uncounted centuries doing something that looks deliberate but isn't: drilling 35 near-perfect round cavities into solid rock. These are potholes — formed when pebbles caught in a hollow are spun endlessly by the river's vortex, grinding the bedrock into a smooth basin — and at Yakama they cluster together at a density that is genuinely rare in Japan. Because the parent stone is hard flinty chert, the shapes stay crisp rather than crumbling, and the largest of them yawn 9 to 12 meters across. Eight especially huge "kettles" — the Tunnel Kettle, the Lion Kettle, the Spectacles Kettle, and more — give the site its name, Yakama, literally "eight kettles." The Japanese government recognized the formation as a National Natural Monument in 1934 and upgraded it to the highest tier, Special Natural Monument, in 1952. It is essentially an open-air earth-science lesson: the raw erosive power of water, frozen mid-sentence in stone. Reaching it means a 1.2-kilometer hike down into the gorge, where emerald pools sit cupped in bone-white rock beneath cliffs on both sides.