Definition of Tectonic Plates for Kids

By Lissa Delisle; Updated April 24, 2017
The Earth's rocky outer crust solidified billions of years ago.

The theory of plate tectonics is a part of geology, which is the study of the earth and how it changes. Developed in the 1960s and 1970s, this theory states that the earth’s outer crust is made up of plates of rock that shift all over the globe. Tectonics is the branch of geology that studies these rock formations and how they change and affect the planet.

Who Discovered Plates?

In 1915, a German geologist named Alfred Wegener first proposed the theory that the earth’s crust was not one solid piece of rock. Instead, he thought there were many large pieces that could drift around and bump into each other. His original theory was called “continental drift.” He believed that all the continents on the planet look like they could have fit together like a puzzle, and that they used to be one big land mass that got broken up into smaller pieces and drifted apart. He really didn’t have any explanation for why the continents split apart, so many other scientists didn’t believe him. Even though he couldn’t prove his theory, it gave scientists the foundation for the plate tectonics theory.

What Exactly Are Plates?

Plates are large pieces of rock in the earth’s outer shell. The earth is made of the inner core, the outer core, the mantle and the crust. The crust has large plates that also fit together like large pieces of a jig saw puzzle around the planet.

How Many Plates Are There?

The earth’s outer layer is broken into seven large pieces, or plates. They are called the African, North American, South American, Eurasian, Australian, Antarctic and Pacific plates. The mantle on which they are floating behaves like an ocean of rock, and just as they do in oceans of water, currents move through this ocean, driven by temperature differences, gravity and the rotation of the earth. They drive the plates in different directions and at different speeds. The plates move between 2 to 10 centimeters (about 1 to 4 inches) per year, on average, which is about the same speed that your fingernails grow.

What Happens if the Plates Shift too Much?

If the plates shift against each other too much, the force can cause vibrations that shake and rumble. This is what causes earthquakes. Sometimes the shifting of the plates can even cause the rock formation to push straight up into the sky, causing mountains.

About the Author

Lissa Delisle began writing in 1997. She has been published in advertisements for Dillards and "The Tennessean." Her areas of expertise lie in graphics and Web design, marketing, social media, beauty and fashion. She is also a makeup artist. Delisle holds a Bachelor of Arts in graphic design from the International Academy of Design and Technology and certification in creative writing from Denver University.