May 28

digital tectonic activity map of the earth Image Credit: NASA/Goddard Space Flight Center

Science Fact

Cocos Plate

The Cocos Plate, running along the ocean floor off the Pacific coast of Central America, moves 75 mm or 3 inches a year -- almost 25 feet per century. That's roughly twice the average velocity of the earth's plates.

The Cocos Plate is one of the pieces of rock that make up the topmost levels of the earth's surface (or lithosphere). These plates all move slowly over the earth, shifted by the convective heating at the earth's core.

The earth is divided into seven major plates, eight minor plates (of which the Cocos is one), and dozens of small tertiary plates. Where plates meet, called plate boundaries, they interact in one of three ways: they transform, or grind alongside each other; they diverge, or slide apart from one another; or they converge, crashing into one another and forcing the denser plate below the less dense one in a process called subduction. (The Cocos Plate is a subducting plate where it converges with the Caribbean Plate.) These interactions are what are responsible for earthquakes, oceanic trenches, mountains, and volcanoes.

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