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Image from: Rick Kohrs, Space Science and Engineering Center, University of Wisconsin, Madison
Surface of the Earth
Underneath the water that fills the oceans, and the dirt and plants that cover the land, the Earth’s surface layer is made of rock. Long ago, this rocky outer layer of Earth formed a hard crust when lava cooled.
The surface layer is broken into many large plates that move very slowly, much too slowly to see with your eyes. Mountain ranges are pushed up if two plates crash into each other. Other surface features are the result of the moving plates too, including the shape of the continents. About 250 million years ago, most of the land was connected together, and over time it has separated into seven continents as the plates move.
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