From: David A Gabel, ENN
Published August 21, 2012 09:38 AM

Study Reveals Reason Behind the locations of the Caribbean Islands

Over the last 50 million years, tectonic shifts in the Earth's crust caused by forces deep within the mantle have caused the Caribbean island chain to be pushed Eastward. Staring at a map will reveal the bulging shape of the lesser Antilles way out into the Atlantic. A new study by researchers from the University of Southern California has found the reason for this movement to be the South American plate. The South America is far larger and more heavily rooted in its location. The Caribbean movement to the east is caused by the underlying mantle pushing against the southern continent.

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The study was conducted in order to better understand how the continents resist movement and how their land masses affect the reshaping of the Earth's surface. "Studying the deep earth interior provides insights into how the Earth has evolved into its present form," said Meghan S. Miller, assistant professor of earth sciences in the USC Dornsife College of Letters, Arts and Sciences, and lead author of the paper. "We're interested in plate tectonics, and the southeastern Caribbean is interesting because it's right near a complex plate boundary."

Miller, together with associate professor Thorsten W. Becker, looked at the margin between the Caribbean and South American plate. However, to build their tectonic model, they had to incorporate the entire globe because everything is connected.

They used earthquake data which provides insight into the Earth's deep interior. The seismic waves produced can be tracked all over the world. The waves can move slowly or quickly depending on the rock composition and underlying temperature. The speed of the waves is also determined by how the crystals align within the rocks after eons of being pushed around by the mantle convection.

Multiple models were created, reconstructing the Earth to a depth of almost 3,000 kilometers. They found that the South American Plate was a "cratonic keel", or a landmass that is roughly three times thicker than normal lithosphere and stronger than typical mantle. The keel deflects and channels mantle flow.

"Oceanic plates are relatively simple, but if we want to understand how the Earth works as a system — and how faults evolved and where the flow is going over millions of years — we also have to understand continental plates," Becker said.

The sturdy South American plate is going nowhere fast, so the Caribbean islands have nowhere to go but farther out to sea, away from the hulking landmasses that surround it. Who knows where they will be in another 50 million years.

This study has been published in the journal Nature Geoscience

Image credit: Wikimedia Commons

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