Sado Island is Japan’s sixth largest island. Located in the Sea of Japan off the coast of Niigata Prefecture, the island is known for its tripartite physical geography: two mountain ranges separated by a central alluvial plain.
The island’s landscape was shaped by volcanic activity that began about 20 million years ago, forming the two mountain ranges that define Sado’s topography today.
Main physical geography of Sado Island
The Ōsado Range occupies the northern part of the island and contains Mount Kinpoku, Sado Island’s highest peak at 3,845 feet (1,172 meters).
Between the island’s two mountain ranges lies the Kuninaka Plain, a relatively flat lowland that serves as the agricultural and population center of Sado Island. Formed by sediments carried from the surrounding mountains, the plain contains some of the island’s most productive farmland and largest settlements. The 12-mile-long Kokufugawa River, the island’s longest river, flows through the plain before emptying into Mano Bay. Lake Kamo is located at the eastern end of the plain.
The Kosado Range occupies the southern portion of the island. Lower in elevation than the Ōsado Range, its highest point is Mount Ōjiyama, which rises to 2,119 feet (646 meters).
Sado Island’s defining landform pattern consists of two mountain ranges separated by a central plain. Image: Landsat 8, April 22, 2024, NASA.
Mines on Sado Island
The same geologic processes that formed Sado Island’s mountain ranges also created deposits of gold and silver, making mining an important part of the island’s history.
The Aikawa-Tsurushi Gold and Silver Mine, located in the Ōsado Range, dates to the 1500s. The Nishimikawa Placer Gold Mine in the Kosado Range has an even longer history, with mining activity beginning in the 1100s.
