According to researchers, the Caribbean plate is being pushed eastward due to a thick section of the South American plate called a "cratonic keel."

A new study published in the journal Nature Geoscience indicates that the movement of Earth's viscous mantle against South America has pushed the Caribbean islands east over the last 50 million years.

In announcing the study, the University of Southern California (USC) said the findings upend previous hypotheses of the seismic activity beneath the Caribbean Sea and provide an important new look at the unique tectonic interactions that are causing the Caribbean plate to tear away from South America.

According to researchers, the Caribbean plate is being pushed eastward due to a thick section of the South American plate called a "cratonic keel." This section of crust is three times thicker than its surroundings.

Part of the South American plate is meanwhile being pushed beneath the Caribbean plate, a process called subduction. Intense heat and pressure gradually force water-containing magma to rise into the Earth's mantle and fuel the many active volcanoes in the region.

All of this pushing and pulling formed the distinctive arc shape of the Caribbean islands and has created a very complex system of faults between the two plates, in northern South America, according to the USC statement.

The study mapped several of these strike-slip faults, which are similar to California's notorious San Andreas Fault.

Recent earthquakes in the area helped researchers develop an image of the Earth's deep interior. The earthquake waves move slower or faster depending on the temperature and composition of the rock.

"Studying the deep Earth interior provides insights into how the Earth has evolved into its present form," researcher Meghan S Miller said in the statement.

The researchers used earthquake data to develop 176 computer models for their study, according to the USC.

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