Puerto Rico lies
at the eastern end of the major island chain of the
Caribbean, the Greater Antilles. The other islands
in the chain, Cuba, Jamaica, and Hispaniola (Haiti
and the Dominican Republic) are larger and geographically
more diverse. Puerto Rico's total area, including
the neighboring islands it administers, is about
3,515 square miles (9,104 square kilometers). The
two largest island dependencies, Vieques and Culebra
lie east of Puerto Rico proper. In the west are three
smaller island dependencies; Mona, Monito, and Desecheo.
The relatively smooth coastline is fringed by many
small islands and cays, especially in the south and
east. The island is roughly rectangular in shape
and stretches for 110 miles (180 kilometers) from
east to west between Punta Jiguero and Punta Puerca,
with a width from north to south averaging 35 miles
(56 kilometers).
Deep oceanic waters fringe Puerto Rico. The Mona Passage, which
separates the island from Hispaniola to the west, is about 75
miles (120 kilometers) wide and more than 3,300 feet (1,000 meters)
deep. Off the northern coast is the 28,000 foot (8,500 meter)
deep Puerto Rico Trench, and to the south the sea bottom descends
to the 16,400 foot (5,000 meter) deep Venezuelan Basin of the
Caribbean. Only to the east is there a broad continental shelf
where the islands of Vieques and Culebra are structural continuations
of the nearby Virgin Islands.
Puerto Rico is topographically rugged; its surface consists largely
of hills, slopes, and mountains. The mountainous core is formed
by the Cordillera Central and the Sierra de Luquillo, continuations
of the Cordillera Central on neighboring Hispaniola. Both mountain
ranges represent uplifted old surfaces strongly dissected by
river erosion. Hill regions of equal irregularity and unevenness
extend north and south of these mountains. Only 30 percent of
the island can be classified as level or undulating, mostly in
the form of an encircling narrow coastal plain.
The topographical structure affects Puerto Rico's climate and
soils. The soil lacks depth and plant nutrients, with less than
a third that of the coastal plain having average to good qualities
for agriculture. Overuse of low-quality and inadequate soil,
especially in the hilly regions and mountainous interior, has
contributed to damaging erosion of hillsides and gullies. Intensive
conservation practices are encouraged in order to limit land
use to pasture or forest development and to conserve water resources.
The island is situated firmly within the zone of the trade winds,
which blow from the east and northeast most of the year, and
it has equitable temperature ranges differentiated only by altitude:
tierra caliente (hot, tropical) on the plains and low hills and
tierra templada (moderate, subtropical) in the mountains. Extreme
temperatures are rare, the average minimum and maximum being
63° F (17° C) in February and 88° F (31° C) in
August. Great variability in precipitation, however, is the norm.
Easterly waves, las ondas alisias, move westward within the trade-wind
zone and cause frequent intense rains that at times last two
to three days without interruption. Hurricanes every so often
strike Puerto Rico and every year some pass near enough to affect
the island's climate particularly causing heavy precipitation
during early fall, August to October. Cold fronts during the
winter months occasionally bring relatively cold north winds,
the "nortes", which drop the island's north coast temperatures
to about 60° F (16° C).
North of the mountainous
interior it is wet with between 80 and 120 inches
(200 and 300 centimeters) of rain annually. At the
northeastern end of the island lies the El Yunque
(The anvil) rain forest where the sounds of the coqui
frog can be heard in all its splendor at night. In
the south of the mountain backbone it is relatively
dry with between 40 and 50 inches (100 and 125 centimeters).
The high temperatures throughout the year result
in high evaporation rates of surface moisture so
that a section of Puerto Rico has semiarid conditions.
The natural vegetation of the island before it became inhabited
was forest. It ranged from low scrubby woodland, cactus scrub,
and mangrove in tidal lagoons along windswept coasts to luxuriant
tropical evergreen forests of the cordillera and sierras. Most
has disappeared, as virtually all of the island's lands have
been cultivated innumerable times. Only in those areas not amenable
to agricultural exploitation of any kind was natural vegetation
allowed to stand. Sites like the forest reserves of the Sierra
de Luquillo in the northeast and some swamps on private lands
are the sole remains of the once dense forest cover. Evergreen
tropical rain forest and mountain forest at higher altitudes
still survive at Luquillo. Tropical palm trees and tree ferns
still grow densely right up to the mountain crests. Elsewhere
semievergreen seasonal forests are found in the southern hills,
and dry woodland scrub and cactus savannas remain in coastal
areas of the south.
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