Tectonic plates

[psi20]

I'm not a big fan of geology, but I'm looking at a map that shows tectonic plates and which direction they move. I was wondering whether or not the direction of the plates will change or has changed in the past.

Secondly, I was wondering if a plate could be swallowed. I think I'm referring to an ocean trench. How does that work? Does one plate go over another plate? What if that plate is entirely engulfed?

[Cap'n Refsmmat]

All right, let's see here...

The plate directions can change. The predictions of where they will go is based on what they have done, but that's no guarantee.

Plates are "swallowed," it's called "subduction." In an ocean trench, one plate hits another, and is sucked under. In a mid-ocean ridge, the opposite occurs, and volcanic activity spreads the sea floor out with more material.