Situated at the meeting point of three tectonic plates, it is highly seismologically active and the location of numerous earthquakes and volcanic eruptions.

[1] Ocean floor material is largely composed of basalt, which is relatively dense; when it collides with 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.

[1] Two parallel mountain ranges cross El Salvador to the west with a central plateau between them and a narrow coastal plain hugging the Pacific.

[1] The mountain ranges and central plateau, covering 85 percent of the land, comprise the interior highlands.

[1] The northern range of mountains, the Sierra Madre, form a continuous chain along the border with Honduras.

[1] The westernmost group, near the Guatemalan border, contains Izalco and Santa Ana, which at 2,365 meters is the highest volcano in El Salvador.

[1] The central plateau constitutes only 25 percent of the land area but contains the heaviest concentration of population and the country's largest cities.

[1] 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.

[1] Near La Libertad, however, the mass of the mountains push the lowlands out; the slopes of adjacent volcanoes come down directly to the ocean.

[1] Surfaces in the Pacific lowlands are generally flat or gently rolling and result from the alluvial deposits of nearby slopes.

[1] The Pacific lowlands are uniformly hot and humid; the central plateau and mountain areas are more moderate.

[1] Almost all the annual rainfall during this time, and yearly rain totals, particularly on southern-facing mountain slopes, can be as high as 2,000 millimeters (78.7 in).

[1] Rainfall during this season generally comes from low pressure over the Pacific and usually falls in heavy afternoon thunderstorms.

[1] San Salvador is representative of the central plateau, with an annual average temperature of 23 °C (73 °F) and absolute high and low readings of 38 and 6 °C (100.4 and 42.8 °F), respectively.