Geography of Jamaica

Jamaica

Native name: Xaymaica Nickname: Land of Wood and Water
Map of Jamaica
Geography
Location	Caribbean Sea
Coordinates
Archipelago	Greater Antilles
Area
Area rank	71st
Length	248 km (154.1 mi)
Width	84 km (52.2 mi)
Coastline	1,022 km (635 mi)
Highest elevation	2,256 m (7,402 ft)
Highest point	Blue Mountain Peak
Country
Jamaica
Largest settlement	Kingston (pop. 651,880)
Demographics
Population	2,804,332 (as of 2008)
Density	252 /km2 (653 /sq mi)
Ethnic groups	90.0% Black, 1.5% East Indian, 0.4% White, 7.3% Multiracial

Jamaica's parishes, main rivers and main centres

Jamaica lies 140 km (90 mi) south of Cuba and 190 km (118 mi) west of Haiti. At its greatest extent, Jamaica is 235 km (146 mi) long, and its width varies between 34 and 84 km (21 and 52 mi). 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. 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 160 km (99 mi). To the southeast lies Morant Bank, with the Morant Cays, 51 km (32 mi) from Morant Point, the easternmost point of mainland Jamaica. Alice Shoal, 260 km (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 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 kilometres (1.9 mi), the crest of the ridge exceeds 1,800 metres (5,900 ft). The highest point is Blue Mountain Peak at 2,256 metres (7,402 ft). The Blue Mountains rise to these elevations from the coastal plain in the space of about 16 kilometres (9.9 mi), 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 metres (3,300 ft). 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 120 metres (390 ft) 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, 80 km (50 mi) long and 32 km (20 mi) wide. Queen of Spains Valley, Nassau Valley, and Cave Valley were formed by the same process.

Coasts

The coastline of Jamaica is one of many contrasts. The northeast shore is severely eroded by the ocean. There are many small inlets in the rugged coastline, but no coastal plain of any extent. A narrow strip of plains along the northern coast offers calm seas and white sand beaches. Behind the beaches is a flat raised plain of uplifted coral reef.

The southern coast has small stretches of plains lined by black sand beaches. These are backed by cliffs of limestone where the plateaus end. In many stretches with no coastal plain, the cliffs drop 300 metres (980 ft) straight to the sea. In the southwest, broad plains stretch inland for a number of kilometres. The Black River courses 70 kilometres (43 mi) through the largest of these plains. The swamplands of the Great Morass and the Upper Morass fill much of the plains. The western coastline contains the island's finest beaches.

Climate

Kingston
Climate chart (explanation)
J F M A M J J A S O N D     19     30 21     19     30 21     20     30 22     30     31 23     100     32 24     74     32 24     42     33 24     98     33 24     114     32 24     177     32 23     65     31 23     47     31 22 Average max. and min. temperatures in °C Precipitation totals in mm Source: Meteorological Service, Jamaica
Imperial conversion J F M A M J J A S O N D     0.7     86 70     0.7     86 70     0.8     86 72     1.2     88 73     3.9     90 75     2.9     90 75     1.7     91 75     3.9     91 75     4.5     90 75     7     90 73     2.6     88 73     1.9     88 72 Average max. and min. temperatures in °F Precipitation totals in inches

Two types of climate are found in Jamaica. An upland tropical climate prevails on the windward side of the mountains, whereas a semiarid climate predominates on the leeward side. Warm trade winds from the east and northeast bring rainfall throughout the year. The rainfall is heaviest from May to October, with peaks in those two months. The average rainfall is 1,960 millimetres (77.2 in) per year. Rainfall is much greater in the mountain areas facing the north and east, however. Where the higher elevations of the John Crow Mountains and the Blue Mountains catch the rain from the moisture-laden winds, rainfall exceeds 5,080 millimetres (200 in) per year. Since the southwestern half of the island lies in the rain shadow of the mountains, it has a semiarid climate and receives fewer than 760 millimetres (29.9 in) of rainfall annually.

Temperatures in Jamaica are fairly constant throughout the year, averaging 25 to 30 °C (77 to 86 °F) in the lowlands and 15 to 22 °C (59.0 to 71.6 °F) at higher elevations. Temperatures may dip to below 10 °C (50 °F) at the peaks of the Blue Mountains. The island receives, in addition to the northeast trade winds, refreshing onshore breezes during the day and cooling offshore breezes at night. These are known on Jamaica as the "Doctor Breeze" and the "Undertaker's Breeze," respectively.

Jamaica lies in the Atlantic hurricane belt; as a result, the island sometimes experiences significant storm damage. Powerful hurricanes which have hit the island directly causing death and destruction include Hurricane Charlie in 1951 and Hurricane Gilbert in 1988. Several other powerful hurricanes have passed near to the island with damaging effects. In 1980, for example, Hurricane Allen destroyed nearly all Jamaica's banana crop. Hurricane Ivan (2004) swept past the island causing heavy damage and a number of deaths; in 2005, Hurricanes Dennis and Emily brought heavy rains to the island. A Category 4 hurricane, Hurricane Dean, caused some deaths and heavy damage to Jamaica in August 2007.

The first recorded hurricane to hit Jamaica was in 1519. The island has been struck by tropical cyclones regularly. During two of the coldest periods in the last 250 years (1780s and 1810s), the frequency of hurricanes in the Jamaica region was unusually high. Another peak of activity occurred in the 1910s, the coldest decade of the 20th century. On the other hand, hurricane formation was greatly diminished from 1968 to 1994, which for some reason coincides with the great Sahel drought.

Vegetation and wildlife

Although most of Jamaica's native vegetation has been stripped in order to make room for cultivation, some areas have been left virtually undisturbed since the time of Columbus. Indigenous vegetation can be found along the northern coast from Rio Bueno to Discovery Bay, in the highest parts of the Blue Mountains, and in the heart of the Cockpit Country.

As in the case of vegetation, considerable loss of wildlife has occurred beginning with the settlement of native peoples in the region millennia ago. For example, the only pinniped ever known to the Caribbean, the Caribbean monk seal once occurred in Jamaican waters and has now been driven to extinction.

See also

• Jamaica
• List of cities and towns in Jamaica

References

•  This article incorporates public domain material from websites or documents of the Library of Congress Country Studies.
•  This article incorporates public domain material from websites or documents of the CIA World Factbook.