Our last couple weeks were focused on plates. You see, we're floating on a bunch of plates of rock. There are three types of movement: sliding by, crashing into, and moving away.

Plates that are moving away makes new land (called divergent boundaries). Plates crashing together (they call 'em convergent plates) recycles old plate 'cause one plate will go under another into the mantle (called subduction). That's how deep ocean trenches are formed. Plus really DEEP earthquakes: not big earthqauakes, deep ones from the mantle.

Now, the cool part about WA is that it's the only boundary where two plates slide by. Isn't that great? Only one. Plus there's a mini-plate called the Juan de Fuca that's subducting under the North American Plate.

The one plate that's really weird is Africa. It seems to be shrinking in on itself. How is that happening? Any ideas? Because I don't.