This electronic board will allow students to share their ideas with students around the country and people around the world. To learn how the surface of Earth grows and changes, specifically how oceanic crust forms and ages. You can download the text of these Web pages if computer access is an issue. The plates spread apart at ridges, causing cracking of the oceanic crust. Magma from Earth's mantle below rises into these cracks and cools.
Older crust is moved away from the ridges as new crust is created.
It gets deeper farther from the ridges. It's subducted, which means it sinks below the continent into Earth's mantle. Scientists don't know precisely what happens after that. Some think that the oceanic crust sinks all the way down and piles up at the mantle-core boundary. Others think that the oceanic crust breaks up and is stirred back into the mantle.