Mt. Tadakariyama

Mt. Tadakariyama on Nagasaki's Goto Islands is composed almost entirely of scoria, the lightweight porous basaltic rock formed when gas bubbles are trapped in cooling lava during an eruption. Despite its porous, airy texture, scoria is strong and durable, and local builders have long used it for farm field walls, building perimeters, drainage ditches, and storehouses. Because scoria drains water quickly and does not hold moisture, the surrounding soil is poorly suited to rice. Satsuma imo sweet potatoes are the dominant crop here instead. The mountain's scoria fields and circular walled farm plots make for a landscape that looks quite unlike anywhere else in Japan.