Exploratour - The Surface of the Earth

This drawing represents the ocean crust being subducted beneath the continental crust.
Click on image for full size

Types of Crust

The Earth has two kinds of crust. The ground that we stand on is called continental crust . It is raised above the waters and is very thick. Continental crust can be as thick as 30 km or so. There is also crust under the waters of the ocean, but it is thinner. This crust is called oceanic crust . This picture to the left shows both ocean crust and continental crust.

Continental crust descends deeper into the Earth than does oceanic crust. If you look again at the rotating globe at the start of this tour, you see that the continents are higher than the ocean floor. But under the surface of the Earth, the continents also go down deeper beneath the surface than does the oceanic crust. So for every mountain range reaching into the sky, there is an equally deep "root" with reaches down into the depths of the interior of the Earth. If you were to dig down through the Earth, you would start with oceanic crust, because it is thinner.

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA