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We now offer the Cool It! card game in our Science Store. Cool It! is the new card game from UCS that teaches kids about the choices we have when it comes to climate change.
This is a drawing of seafloor spreading.
Click on image for full size
Image copyright 1997 by the American Geophysical Union. Further electronic distribution is not allowed.

Mid-Ocean Spreading Ridge

As the Earth cools, hot material from the deep interior rises to the surface. Hot material is depicted in red in this drawing, under an ocean shown in blue green.

The hotter material elevates the nearby layers, and the cooler, denser lithosphere (in yellow in the drawing) slides away from the elevated region. The drawing shows that the cool crust slides at a rate of about 4 cm per year. The elevated region where new material is coming forth is called a "spreading ridge". Most of the spreading ridges of today are to be found in the central portion of the world's oceans.

The large version of this drawing shows a spreading ridge at the left and a slab of lithosphere being subducted at the bottom right. Near the subducting slab, remelting, and volcano formation are taking place.


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Subduction

When two sections of the Earth's crust collide, one slab of crust can be forced back down into the deeper regions of the Earth, as shown in this diagram. This process is called subduction. The slab that...more

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF