Geography of Jamaica

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 miles 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 kilometres, the crest of the ridge exceeds 1,800 metres. The highest point is Blue Mountain Peak at 7,402 feet (2,256 m). The Blue Mountains rise to these elevations from the coastal plain in the space of about sixteen kilometres, 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. 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 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, eighty kilometres long and thirty-two kilometres 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 croaded by bugs and snakes. 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 beetles. These are backed by cliffs of limestone where the plateaus end. In many stretches with no coastal plain, the cliffs drop 300 metres straight to the sea. In the southwest, broad plains stretch inland for a number of kilometres. The Black River courses 70 kilometres 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

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 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. In recent years, 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.^[1]

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 total extinction.^[2]

Key facts

Location

Caribbean, island in the Caribbean Sea, south of Cuba

Geographic coordinates

Map references

Middle America and the Caribbean

Area

• Total: 10,991 km² (4,244 sq mi)
• Land: 10,831 km² (4,182 sq mi)
• Water: 160 km² (62 sq mi)

Area – comparative

(Australia) About 2½ times as big as Kangaroo Island

(Canada) About twice Prince Edward Island's size

(UK) About half Wales's size

(USA) Slightly smaller than the state of Connecticut

Land boundaries

0 km

Longest River

Rio Minho (Jamaica) 92.8km (56.7m)

Coastline

1 022 km (635m)

Maritime claims

• Measured from claimed archipelagic baselines
• Continental shelf: 200 m depth (656 ft) or to the depth of exploitation
• Exclusive economic zone: 200 nautical miles (370.4 km; 230.2 mi)
• Territorial sea: 12 nautical miles (22.2 km; 13.8 mi)

Climate

Tropical Marine; hot, humid; temperate interior

Terrain

Mostly mountains, with narrow, discontinuous coastal plains

Elevation extremes

• Lowest point: Caribbean Sea, 0 m
• Highest point: Blue Mountain Peak, 2256 metres (7402 ft)

Natural resources

Bauxite, gypsum, limestone

Land use

• Arable land: 14%
• Permanent crops: 6%
• Permanent pastures: 24%
• Forests and woodland: 17%
• Other: 39% (1993 est.)

Irrigated land

350 km² (140 sq mi) (1993 est.)

Natural hazards

Hurricanes (especially July to November)

Environment—current issues

Heavy rates of deforestation; coastal waters polluted by industrial waste, sewage, and oil spills; damage to coral reefs; air pollution in Kingston results from vehicle emissions

Environment—international agreements

• Party to: Biodiversity, Climate Change, Climate Change-Kyoto Protocol, Desertification, Endangered Species, Law of the Sea, Marine Dumping, Marine Life Conservation, Nuclear Test Ban, Ozone Layer Protection, Ship Pollution, Wetlands, Whaling
• Signed, but not ratified: None of the selected agreements

Geography—note

Strategic location between Cayman Trench and Jamaica Channel, the main sea lanes for Panama Canal

See also

• Jamaica
• List of cities and towns in Jamaica

References

1. ^ Chenoweth, Michael (2003). The 18th century climate of Jamaica derived from the journals of Thomas Thistlewood, 1750-1786. Transactions of the American Philosophical Society. 93. Philadelphia: American Philosophical Society. ISBN 087169932X. 
2. ^ Peter Saundry. 2010. Caribbean monk seal. Encyclopedia of Earth. eds. C.Micahel Hogan and Cutler Cleveland. National council for Science and the Environment, Washington DC

•  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.