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The Winter 2010 issue of The Earth Scientist includes a variety of educational resources, ranging from astronomy to glaciers. Check out the other publications and classroom materials in our online store.
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 red in this drawing, under an ocean shown in blue green.

The hotter material raises the nearby layers, and the cooler, harder crust (in yellow in this drawing) slides away from the higher regions. The drawing shows that the cool crust slides at a rate of about 3 inches 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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Traveling Nitrogen Classroom Activity Kit

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Subduction

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

Volcano Formation

Volcanoes form when hot material from below rises and leaks into the crust. The hot material, called magma, rising from lower ground, gathers in a reservoir called the magma chamber. Eventually, but not...more

Basalt Rocks

Basalt is volcanic rock. It is the most common type of rock in the Earth's crust and it makes up most of the ocean floor. It forms when lava reaches the Earth's surface at a volcano or mid ocean ridge....more

Earthquakes Under Pacific Ocean Floor Reveal Surprising Flow of Water

A group of scientists have been studying an area of the ocean floor called the East Pacific Rise, which is about 565 miles southwest of Acapulco, Mexico. The East Pacific Rise is a ridge along the ocean...more

Volcanic Ash

Ash is formed as a volcano erupts when rocks made by the volcano blow apart into millions of tiny pieces. The rocks are still very hot, because they just formed from lava. If the hot rocks come into contact...more

Cinder Cones

Cinder cones are simple volcanoes which have a cone shape and are not very big. Compare the size of this volcano to the strato-volcano in this image. They are usually made of piles of lava, not ash. During...more

Flowing Lava

Lava can move in two ways, wide flat lava flows, or through channels which squeeze the lava into a small area. The fastest lava flows move at about 6 mi/hr, an easy jog, but they average between 2/3 and...more

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