Mt. Tadakariyama
The source of scoria
Mt. Tadakariyama, a gentle rise in the middle of the southernmost peninsula of Fukue Island, is made up almost entirely of scoria, a very light, porous basaltic rock. The holes in the rock are formed during an eruption, as gases are trapped within the magma as it cools and hardens into rock.
Although it is light in weight, scoria is strong and durable, so it is widely used in the area to construct rock walls, particularly on the perimeter of the island’s circular farming fields. It is also used for walls in buildings, set along drainage ditches, and as everything but the roofs and doors of the area’s distinctive storehouses.
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While scoria is very porous, it is not good at holding water in the soil. Instead of rice, therefore, satsuma imo sweet potatoes are the most common crop in the circular, rock-walled fields around Mt. Tadakariyama.