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Nature

Geologic History

Central America, a particularly unstable region of the earth’s crust, is on the western edge of the Caribbean plate. Subduction of oceanic crust beneath this edge, beginning in the Miocene Epoch, about 25 million years ago, has lifted the land from the sea. In the earliest stage, a peninsula and archipelago formed. Later, about three million years ago, the scattered islands coalesced to form a true land bridge, or isthmus, linking North and South America.

Keeping pace with subduction and uplift have been volcanic eruptions—Central America has at least 14 active volcanoes—and frequent earthquakes. In this century alone, Managua, the capital of Nicaragua, has twice been destroyed by earthquakes. The most recent, in 1972, took 10,000 lives. In 1976 some 25,000 people were killed in an earthquake registering 7.5 on the Richter scale and centered in the Motagua depression in Guatemala. This quake left 25 percent of the country’s population homeless. Volcanic activity has produced a landscape dotted with majestic cones built from eruptions of ash and lava, and beautiful lakes formed in collapsed volcanic craters called calderas.

 
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