Jamaica lies 90 miles (140 km) south of Cuba and 118 miles (190 km) west of Haiti. At its greatest extent, Jamaica is 146 mi long (235 km), and it varies between 21-and-52 mi wide (34-and-84 km). With an area of 10,911 km2 (4,213 sq mi), Jamaica is the largest island of the Commonwealth Caribbean and the third largest of the Greater Antilles, after Cuba and Hispaniola. Along the south coast of Jamaica, a number of small islands are located, such as the Port Royal Cays. Pedro Bank, an area of shallow seas, with a number of cays (low islands or reefs), extending generally east to west for over 160 km (99 mi), lies southwest of Jamaica. To the southeast lies Morant Bank, with the Morant Cays, 51 kilometres or 32 mi from Morant Point, the easternmost point of mainland Jamaica. Alice Shoal, 260 kilometres (160 mi) 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 that of 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 3 kilometers, the crest of the ridge exceeds 1,800 meters. The highest point is Blue Mountain Peak at 7,402 feet (2,256 m). The Blue Mntains rise to these elevations from the coastal plain in the space of about sixteen kilometers, 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 1,000 meters. 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.
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