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The Geography of Oklahoma encompasses terrain and ecosystems ranging from arid plains to subtropical forests and mountains. Oklahoma contains 10 distinct ecological regions, more per square mile than in any other state by a wide margin. One of six states on the Frontier Strip, it is situated in the Great Plains and U.S. Interior Highlands region near the geographical center of the 48 contiguous states. Usually considered part of the South Central United States, Oklahoma is bounded on the east by Arkansas and Missouri, on the north by Kansas, on the northwest by Colorado, on the far west by New Mexico, and on the south and near-west by Texas. The state has four primary mountain ranges: the Arbuckle Mountains, the Wichita Mountains, the Ozark Mountains and the Ouachita Mountains.〔 Part of the U.S. Interior Highlands region, the Ozarks and Ouachitas form the only major highland region between the Rocky Mountains and the Appalachians. A portion of the Flint Hills stretches into north-central Oklahoma, and in the state's southeastern corner, Cavanal Hill is officially regarded as the world's tallest hill; at 1,999 feet (609 m), it fails the definition of a mountain by one foot. More than 500 named creeks and rivers make up Oklahoma's waterways, and with 200 lakes created by dams, it holds the highest number of reservoirs in the nation.〔 Oklahoma covers an area of , with of land and of water, making it the 20th-largest state in the United States. Generally, it is divided into seven geographical regions: Green Country, or Northeast Oklahoma, Southeastern Oklahoma, Central Oklahoma, South Central Oklahoma, Southwest Oklahoma, Northwest Oklahoma, and the Oklahoma Panhandle. ==Topography== Situated between the Great Plains and the Ozark Plateau in the Gulf of Mexico watershed, Oklahoma tends to slope gradually downward from its western to eastern boundaries. Its highest and lowest points follow this trend, with its highest peak, Black Mesa, at 4368 feet (1,516 m) above sea level, situated near the far northwest corner of the Oklahoma Panhandle. The state's lowest point is on the Little River near its far southeastern boundary, which dips to 289 feet (88 m) above sea level. Most of the state lies in two primary drainage basins belonging to the Red and Arkansas rivers, though the Lee and Little rivers also contain significant drainage basins.〔 In the state’s northwestern corner, semi-arid high plains harbor few natural forests and rolling to flat landscape with intermittent canyons and mesa ranges like the Glass Mountains. Partial plains interrupted by small mountain ranges like the Antelope Hills and the Wichita Mountains dot southwestern Oklahoma, and transitional prairie and woodlands cover the central portion of the state. The Ozark and Ouachita Mountains rise from west to east over the state's eastern third, gradually increasing in elevation in an eastward direction.〔〔 Oklahoma had few natural lakes. Those that did exist were either oxbow or playa lakes. Oklahoma has sixty-two oxbow lakes above in size. The largest, near the Red River in McCurtain County is . The prolonged drought that started in 1930 and created the condition called the "Dust Bowl", led to the construction of a great many reservoirs throughout the state. Now, Oklahoma has the largest number of lakes created by dams of any state in the United States, with more than 200. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Geography of Oklahoma」の詳細全文を読む スポンサード リンク
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