Download The surface of Earth is made of several pieces, called plates, that

Space Place Newspaper Column
November 2008
Sliding on Your Own Home Plate
Like cars in a demolition derby, pieces of Earth’s surface are skidding around, sideswiping each other, smashing into each other, or ripping apart from each other. All this
movement takes place in slow motion most of the time, so you will not notice it—unless
there’s an earthquake!
This exciting feature of our planet is called plate tectonics [tek-TAWN-iks]. Earth is the
only planet in the solar system that has it.
Plate tectonics causes not only earthquakes, but also volcanoes and tidal waves. It also
causes much of the beautiful landscape on Earth, such as mountains.
Plate tectonics occurs because Earth’s outer layer, called the crust, is broken into pieces,
called plates. The plates move. Under the crust is a layer of hot, squishy rock. The plates
float around on this less solid layer. Where the plates meet, several kinds of things can
happen.
First, volcanoes occur where hot, liquid rock pushes up through cracks and weak points
between the plates. Earthquakes occur when the plates move suddenly, either slipping
past each other or diving one under the other. The plates may move only a few inches or
feet at a time, but the movement creates a shockwave in the ground that can cause terrible
damage and injury to people if their buildings are too flimsy to stand the shaking.
Mountain ranges form when one plate slides under another pushing it upward, or when
two plates push against each other and they both lift up. Plates also pull apart in some
places, allowing the soft or liquid rock beneath to rise and form a ridge.
The boundary between two major plates runs right through California. It is called the San
Andreas Fault. Los Angeles is on the Pacific Plate, moving toward the northwest. San
Francisco is on the North American Plate, moving toward the southeast. In about 20
million years, the two cities, now about 450 miles apart, will slide right past each other!
Learn other fascinating facts about Earth at spaceplace.nasa.gov/en/kids/cs_earth.shtml.
This article was written by Diane K. Fisher. It was provided by the Jet Propulsion
Laboratory, California Institute of Technology, under a contract with the National
Aeronautics and Space Administration.
Space Place Newspaper Column
November 2008
Caption:
This map of Earth shows its major tectonic plates. Notice the major boundary between
the Pacific Plate and the North American Plate running right through California.
Notice to editors:
This image may be downloaded from
http://spaceplace.nasa.gov/news_images/earth_plates.jpg.