CHUGOKU RANGE

Japanese Chugoku-sammyaku, mountain range, in Chugoku ("China") chiho (region), western Honshu, Japan. It forms the major mountain system of Yamaguchi, Hiroshima, Shimane, Okayama, and Tottori ken (prefectures) and extends to the fault scarp of the Hira Range along Lake Biwa. The mountains to the east of the Kako and Yura river valleys in Hyogo prefecture and Kyoto fu (urban prefecture) of Kinki region, however, are generally considered a separate formation, the Tamba Plateau. The Chugoku Range consists of three landforms-the Backbone Range, the Kibi Plateau, and the Iwami Plateau. The Backbone Range constitutes a sharp divide between the Sea of Japan and the Inland Sea, broken only by the gorge of the Gono River in the west. The Gono River has been bordered by an important highway since ancient times. The Kammuri Mountains to the west of the gorge are sometimes considered to be an independent unit. Only a few peaks of the Chugoku Range exceed 3,300 feet (1,000 m); the Kammuri block, however, rises to 4,393 feet (1,339 m). To the south, the Backbone Range descends abruptly in a steep escarpment to the Kibi Plateau. The plateau, at an elevation between 660 and 1,970 feet (200 and 600 m), is composed of eroded hilly land surfaces, separated by steep, younger gorges. Between the Kibi Plateau and the range, a row of intermontane basins is followed by the east-west inland rail lines. Major basins are those of Tsuyama, Niimi, and Miyoshi. The Iwami Plateau, lying to the north of the Backbone Range, is narrower and more dissected than the Kibi Plateau, except in the Akiyoshi Plateau area in the west, where karst topography occurs in some places. Numerous semicircular depressions have been buried by lava-dome volcanoes, including Mount Dai, which rises to 5,673 feet (1,729 m) in Tottori prefecture.