Sado Island is Japan’s sixth largest island. Located in the eastern region of the Sea of Japan, this island features a tripartite physical geography. This means that the island has three distinctive landform features: two mountain ranges that sandwich an alluvial plain.
Both mountain ranges on Sado Island were formed by volcanic activity about 20 million years ago.
Main physical geography of Sado Island
To the north is the Ōsado range. Found on this range is Mount Kinpoku, the highest point on Sado Island with a peak of 3,845 feet (1,172 meters).
South of the Osado range is the Kuninaka Plain. The Kunikaka Plain is a relatively flat, inland area on Sado Island. The 12-mile long Kokufugawa River flows through this plain before emptying into Mano Bay. Kokufugawa River is the longest river on Sado Island. Lake Kamo lies at the eastern end of Kuninaka Plain.
On the other side of the Kuninaka Plain is the Kosado range. This range is lower in altitude than the Ōsado range – the highest peak Mount Ōjiyama with an elevation of 2,119 feet (646 meters).
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Mines on Sado Island
Geologic processes from the volcanic formation of both mountain ranges on Sado Island also produced deposits of metals including gold and silver. The Aikawa-Tsurushi Gold and Silver Mine located in the Ōsado range dates from the 1500s. The Nishimikawa Placer Gold Mine located in the Kosado range was mined starting in the 1100s.
