Geography of El Salvador

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El Salvador, the smallest Spanish-speaking nation in the Western Hemisphere, is located on the western side of the Central American isthmus. With an area of 21,041 square kilometers, the country is only slightly larger than Massachusetts. It is roughly rectangular in shape with 515 kilometers of land boundaries and 307 kilometers of coastline on the Pacific Ocean. El Salvador is bounded by Guatemala to the west and Honduras to the north and east, and it is separated from Nicaragua on the southeast by the Golfo de Fonseca.

Geology

El Salvador, along with the rest of Middle America (a region comprising mainly Mexico and Central America), is one of the most seismologically active regions on earth, situated atop three of the large tectonic plates that constitute the earth's surface. The motion of these plates causes the area's earthquake and volcanic activity.

Most of Central America and the Caribbean Basin rests on the relatively motionless Caribbean Plate. The Pacific Ocean floor, however, is being carried northeast by the underlying motion of the Cocos Plate. Ocean floor material is relatively dense; when it strikes the lighter granite rocks of Central America, the ocean floor is forced down under the land mass, creating the deep Middle America Trench that lies off the coast of El Salvador. The subduction of the Cocos Plate accounts for the frequency of earthquakes near the coast. As the rocks constituting the ocean floor are forced down, they melt, and the molten material pours up through weaknesses in the surface rock, producing volcanoes and geysers.

North of El Salvador, Mexico and most of Guatemala are riding on the westward-moving North American Plate that butts against the northern edge of the stationary Caribbean Plate in southern Guatemala. The grinding action of these two plates creates a fault, similar to the San Andreas in California, that runs the length of the valley of the Rio Motagua in Guatemala. Motion along this fault is the source of earthquakes in northernmost El Salvador.

El Salvador has a long history of destructive earthquakes and volcanic eruptions. San Salvador was destroyed in 1756 and 1854, and it suffered heavy damage in the 1919, 1982, and 1986 tremors. The country has over twenty volcanoes, although only two, San Miguel and Izalco, have been active in recent years. Violent eruptions are rare. From the early nineteenth century to the mid1950s , Izalco erupted with a regularity that earned it the name "Lighthouse of the Pacific." Its brilliant flares were clearly visible for great distances at sea, and at night its glowing lava turned it into a brilliant luminous cone.

Physical Features

Two parallel mountain ranges cross El Salvador east to west with a central plateau between them and a narrow coastal plain hugging the Pacific. These physical features divide the country into two physiographic regions. The mountain ranges and central plateau covering 85 percent of the land comprise the interior highlands. The remaining coastal plains are referred to as the Pacific lowlands.

The northern range of mountains, the Sierra Madre, forms a continuous chain along the border with Honduras. Elevations in this region range from 1,600 to 2,200 meters. The area was once heavily forested, but overexploitation led to extensive erosion, and it has become semibarren. As a result, it is the country's most sparsely populated zone, with little farming or other development.

The southern range of mountains is actually a discontinuous chain of more than twenty volcanoes, clustered into five groups. The westernmost group, near the Guatemalan border, contains Izalco and Santa Ana, which at 2,365 meters is the highest point in El Salvador. Between the cones lie alluvial basins and rolling hills eroded from ash deposits. The volcanic soil is rich, and much of El Salvador's coffee is planted on these slopes.

The central plateau constitutes only 25 percent of the land area but contains the heaviest concentration of population and the country's largest cities. This plain is about 50 kilometers wide and has an average elevation of 600 meters. Terrain here is rolling, with occasional escarpments, lava fields, and geysers.

A narrow plain extends from the coastal volcanic range to the Pacific Ocean. This region has a width ranging from one to thirty-two kilometers with the widest section in the east, adjacent to the Golfo de Fonseca. Near La Libertad, however, the mountains pinch the lowlands out; the slopes of adjacent volcanoes come down directly to the sea. Surfaces in the Pacific lowlands are generally flat or gently rolling and result from alluvial deposits from nearby slopes.

El Salvador has over 300 rivers, the most important of which is the Rio Lempa. Originating in Guatemala, the Rio Lempa cuts across the northern range of mountains, flows along much of the central plateau, and finally cuts through the southern volcanic range to empty into the Pacific. It is El Salvador's only navigable river, and it and its tributaries drain about half the country. Other rivers are generally short and drain the Pacific lowlands or flow from the central plateau through gaps in the southern mountain range to the Pacific.

Numerous lakes of volcanic origin are found in the interior highlands; many of these lakes are surrounded by mountains and have high, steep banks. The largest lake, the Lago de Ilopango, lies just to the east of the capital. Other large lakes include the Lago de Coatepeque in the west and the Lago de Gija on the Guatemalan border. The Cerron Grande Dam on the Rio Lempa has created a large reservoir, the Embalse Cerron Grande, in northern El Salvador.

Climate

El Salvador has a tropical climate with pronounced wet and dry seasons. Temperatures vary primarily with elevation and show little seasonal change. The Pacific lowlands are uniformly hot; the central plateau and mountain areas are more moderate.

The rainy season, known locally as invierno, or winter, extends from May to October. Almost all the annual rainfall occurs during this time, and yearly totals, particularly on southern-facing mountain slopes, can be as high as 200 centimeters. Protected areas and the central plateau receive lesser, although still significant, amounts. Rainfall during this season generally comes from low pressure over the Pacific and usually falls in heavy afternoon thunderstorms. Although hurricanes occasionally form in the Pacific, they seldom affect El Salvador.

From November through April, the northeast trade winds control weather patterns. During these months, air flowing from the Caribbean has had most of the precipitation wrung out of it passing over the mountains in Honduras. By the time this air reaches El Salvador, it is dry, hot, and hazy. This season is known locally as verano, or summer.

Temperatures vary little with season; elevation is the primary determinant. The Pacific lowlands are the hottest region, with annual averages ranging from 25C to 29C. San Salvador is representative of the central plateau, with an annual average temperature of 23C and absolute high and low readings of 38C and 7C, respectively. Mountain areas are the coolest, with annual averages from 12C to 23C and minimum temperatures sometimes approaching freezing.

SOURCES: Library of Congress Country Studies/Area Handbook

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