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Jamaica lies south of Cuba and west of Haiti. At its greatest extent, Jamaica is long, and its width varies between . With an area of , Jamaica is the largest island of the Commonwealth Caribbean and the third largest of the Greater Antilles, after Cuba and Hispaniola. Many small islands are located along the south coast of Jamaica, such as the Port Royal Cays. Southwest of mainland Jamaica lies Pedro Bank, an area of shallow seas, with a number of cays (low islands or reefs), extending generally east to west for over . To the southeast lies Morant Bank, with the Morant Cays, from Morant Point, the easternmost point of mainland Jamaica. Alice Shoal, southwest of the main island of Jamaica, falls within the Jamaica–Colombia Joint Regime. ==Geology and landforms== Jamaica and the other islands of the Antilles evolved from an arc of ancient volcanoes that rose from the sea millions of years ago. During periods of submersion, thick layers of limestone were laid down over the old igneous and metamorphic rock. In many places, the limestone is thousands of feet thick. The country can be divided into three landform regions: the eastern mountains, the central valleys and plateaus, and the coastal plains. The highest area is the Blue Mountains. These eastern mountains are formed by a central ridge of metamorphic rock running northwest to southeast from which many long spurs jut to the north and south. For a distance of over , the crest of the ridge exceeds . The highest point is Blue Mountain Peak at . The Blue Mountains rise to these elevations from the coastal plain in the space of about , thus producing one of the steepest general gradients in the world. In this part of the country, the old metamorphic rock reveals itself through the surrounding limestone. To the north of the Blue Mountains lies the strongly tilted limestone plateau forming the John Crow Mountains. This range rises to elevations of over . To the west, in the central part of the country, are two high rolling plateaus: the Dry Harbour Mountains to the north and the Manchester Plateau to the south. Between the two, the land is rugged and here, also, the limestone layers are broken by the older rocks. Streams that rise in the region flow outward and sink soon after reaching the limestone layers. The limestone plateau covers two-thirds of the country, so that karst formations dominate the island. Karst is formed by the erosion of the limestone in solution. Sinkholes, caves and caverns, disappearing streams, hummocky hills, and terra rosa (residual red) soils in the valleys are distinguishing features of a karst landscape; all these are present in Jamaica. To the west of the mountains is the rugged terrain of the Cockpit Country, one of the world's most dramatic examples of karst topography. The Cockpit Country is pockmarked with steep-sided hollows, as much as deep in places, which are separated by conical hills and ridges. On the north, the main defining feature is the fault-based "Escarpment", a long ridge that extends from Flagstaff in the west, through Windsor in the centre, to Campbells and the start of the Barbecue Bottom Road (B10). The Barbecue Bottom Road, which runs north-south, high along the side of a deep, fault-based valley in the east, is the only drivable route across the Cockpit Country. However, there are two old, historical trails that cross further west, the Troy Trail, and the Quick Step Trail, both of which are seldom used as of 2006 and difficult to find. In the southwest, near Quick Step, is the district known as the "Land of Look Behind," so named because Spanish horsemen venturing into this region of hostile runaway slaves were said to have ridden two to a mount, one rider facing to the rear to keep a precautionary watch. Where the ridges between sinkholes in the plateau area have dissolved, flat-bottomed basins or valleys have been formed that are filled with terra rosa soils, some of the most productive on the island. The largest basin is the Vale of Clarendon, long and wide. Queen of Spains Valley, Nassau Valley, and Cave Valley were formed by the same process. 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 Jamaica」の詳細全文を読む スポンサード リンク
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