Plate Tectonics: 5 Things You Should Know

Question: South America’s east coast and Africa’s west coast fit together like puzzle pieces. Why do their shapes match so closely?

Answer: Earth’s continents were once joined in a supercontinent called Pangaea, which began breaking apart about 200 million years ago. The matching coastlines were one of the first clues that continents move.

Question: Earth’s continents ride on giant rocky plates that slowly shift a few centimeters each year. What causes the plates to move?

Answer: Earth’s outer shell is broken into about a dozen large plates resting on the hot, slowly flowing mantle. Heat escaping from the planet’s interior keeps that rock moving, so the plates never stop shifting.

Question: The Atlantic Ocean gets about 2.5 centimeters wider every year. What is happening along the ocean floor to widen the ocean?

Answer: Down the middle of the Atlantic runs the Mid-Atlantic Ridge, where molten rock wells up and forms new crust. As fresh seafloor is made, the plates on either side are pushed apart.

Question: Most of the world’s earthquakes and volcanoes cluster around the edges of the Pacific Ocean. Why are they so common there?

Answer: Around the Pacific, ocean plates dive under neighboring plates in a process called subduction, forming the “Ring of Fire.” The grinding sets off earthquakes, and melting rock rises to feed volcanoes.

Question: Fossils of ancient sea creatures have been found near the top of Mount Everest. How did ocean rock end up so high?

Answer: When two continental plates collide, neither sinks easily, so the crust crumples and stacks upward. India is still pushing north, and the Himalayas keep rising a few millimeters each year.