The mountainous islands of the Japanese Archipelago form a crescent off the eastern coast of Asia. They are separated from the mainland by the Sea of Japan, which historically served as a protective barrier. Japan's insular nature, together with the compactness of its main territory and the cultural homogeneity of its people, enabled the nation to remain free of outside domination until its defeat in World War II. The country consists of four principal islands: Hokkaido, Honshu, Shikoku, and Kyushu; more than 3,000 adjacent islands and islets, including Oshima in the Nampo chain; and more than 200 other smaller islands, including those of the Amami, Okinawa, and Sakishima chains of the Ryukyu Islands. The national territory also includes the small Bonin Islands (called Ogasawara by the Japanese), Iwo Jima, and the Volcano Islands (Kazan Retto), stretching some 1,100 kilometers from the main islands. A territorial dispute with the Soviet Union, dating from the end of World War II, over the two southernmost of the Kuril Islands, Etorofu and Kunashiri, and the smaller Shikotan and Habomai Islands northeast of Hokkaido remained a sensitive spot in Japanese-Russian relations as the mid-1990s approached. Excluding disputed territory, the archipelago covers about 377,000 square kilometers. No point in Japan is more than 150 kilometers from the sea.
The four major islands are separated by narrow straits and form a natural entity. The Ryukyu Islands curve 970 kilometers southward from Kyushu.
The distance between Japan and the Korean Peninsula, the nearest point on the Asian continent, is about 200 kilometers at the Korea Strait. Japan has always been linked with the continent through trade routes, stretching in the north toward Siberia, in the west through the Tsushima Islands to the Korean Peninsula, and in the south to the ports on the south China coast.
The Japanese islands are the summits of mountain ridges uplifted near the outer edge of the continental shelf. About 75 percent of Japan's area is mountainous, and scattered plains and intermontane basins (in which the population is concentrated) cover only about 25 percent. A long chain of mountains runs down the middle of the archipelago, dividing it into two halves, the "face," fronting on the Pacific Ocean, and the "back," toward the Sea of Japan. On the Pacific side are steep mountains 1,500 to 3,000 meters high, with deep valleys and gorges. Central Japan is marked by the convergence of the three mountain chains--the Hida, Kiso, and Akaishi mountains--that form the Japanese Alps (Nihon Arupusu), several of whose peaks are higher than 3,000 meters. The highest point in the Japanese Alps is Kitadake at 3,192 meters. The highest point in the country is Mount Fuji (Fujisan, also called Fujiyama in the West but not in Japan), a volcano dormant since 1707 that rises to 3,776 meters above sea level in Shizuoka Prefecture. On the Sea of Japan side are plateaus and low mountain districts, with altitudes of 500 to 1,500 meters.
None of the populated plains or mountain basins is extensive in area. The largest, the Kanto Plain, where Tokyo is situated, covers only 13,000 square kilometers. Other important plains are the Nobi Plain surrounding Nagoya, the Kinki Plain in the Osaka-Kyoto area, the Sendai Plain around the city of Sendai in northeastern Honshu, and the Ishikari Plain on Hokkaido. Many of these plains are along the coast, and their areas have been increased by reclamation throughout recorded history.
The small amount of habitable land prompted significant human modification of the terrain over many centuries. Land was reclaimed from the sea and from river deltas by building dikes and drainage, and rice paddies were built on terraces carved into mountainsides. The process continued in the modern period with extension of shorelines and building of artificial islands for industrial and port development, such as Port Island in Kobe and the new Kansai International Airport in Osaka Bay. Hills and even mountains have been razed to provide flat areas for housing.
Rivers are generally steep and swift, and few are suitable for navigation except in their lower reaches. Most rivers are fewer than 300 kilometers in length, but their rapid flow from the mountains provides a valuable, renewable resource: hydroelectric power generation. Japan's hydroelectric power potential has been exploited almost to capacity. Seasonal variations in flow have led to extensive development of flood control measures. Most of the rivers are very short. The longest, the Shinano, which winds through Nagano Prefecture to Niigata Prefecture and flows into the Sea of Japan, is only 367 kilometers long. The largest freshwater lake is Lake Biwa, northeast of Kyoto.
Extensive coastal shipping, especially around the Inland Sea (Seto Naikai), compensates for the lack of navigable rivers. The Pacific coastline south of Tokyo is characterized by long, narrow, gradually shallowing inlets produced by sedimentation, which has created many natural harbors. The Pacific coastline north of Tokyo, the coast of Hokkaido, and the Sea of Japan coast are generally unindented, with few natural harbors.
The country's forty-seven prefectures are grouped into eight regions frequently used as statistical units in government documents. The islands of Hokkaido, Shikoku, and Kyushu each form a region, and the main island of Honshu is divided into five regions.
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