This article was originally featured on Knowable Magazine.
Over millions of years, the Earth’s upper layers have performed a dance that has created mountains, volcanoes, continents, ridges and ocean trenches.
Tectonic plates play a key role in this process. These huge, irregular slabs of the Earth’s crust—the solid rock surface where humans live—and the upper part of the underlying mantle “float” on a deeper, warmer layer of the mantle. When two plates meet, sometimes one gives way and ends up sinking little by little into the depths, in a process known as subduction.
If the phenomenon occurs along the entire length of the plate boundary, a line of volcanoes, known as a volcanic arc, forms. There are volcanic arcs in the Andes of South America, Tonga in the South Pacific Ocean, the Aleutian Islands of Alaska, the Philippine Islands and Central America, among others — all of them part of the Pacific Ring of Fire, where earthquakes and volcanoes are common.
The Central American arc is relatively small, just 1,100 kilometers long. But it contains an important variety of different types of magmas, some of which are unique on the planet. It is a “geological paradise” hiding secrets worthy of investigation, says Esteban Gazel, a geochemist at Cornell University in Ithaca, New York. “Central America has a rich combination of conditions that allow the comparison of different natural experiments in magma generation,” he and his two coauthors wrote in a review published in the 2021 Annual Review of Earth and Planetary Sciences.
Central America was born on what used to be an oceanic plate, as a consequence of the subduction of tectonic plates. About 150 million years ago, a slow process began that gradually allowed volcanic islands to grow between the continental masses of northern and southern America. About 3 million years ago, the area now comprising Costa Rica and Panama was finally joined to the north of…
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