Notes from Janice’s Desk
The diagram shows two paperback books of equal size separated by a space. The space represent a break in the crust beneath the ocean called a rift valley. .
Did You Know?
While the seafloor is spreading at ridges, the total amount of crust on the Earth stays the same. This is because as new crust is being formed at the midocean ridge, old crust is sinking into deep ocean valleys where it melts and is absorbed into the mantle.
Seems like a lot of movement going on, and it is. All this spreading and sinking happens at the boundaries of Earth’s tectonic plates. OH! I forgot to say that the Earth’s crust rests on a broken foundation. I have the same problem with my house in that the foundation is cracking. As the cracks widen they cause parts of the house to pull apart. But unlike the Earth, we are adding material to cover the cracks, so I guess my house is growing–
For more information about the spreading of Earth’s crust, see DIVERGENT BOUNDARIES.