Shop Windows to the Universe

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 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.

Shop Windows to the Universe Science Store!

Learn about Earth and space science, and have fun while doing it! The games section of our online store includes a climate change card game and the Traveling Nitrogen game!

Windows to the Universe Community



You might also be interested in:

Traveling Nitrogen Classroom Activity Kit

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more


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 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