A great way to explain plate tectonics and simple plate movements is by using Oreos. This is based on a lecture by Dr Bob Lillie of the Department of Geosciences at Oregon State University. I found the PPT online at the Oregon State University website but frankly, the internet is quite full of “Geo-reo activities”
Here is the PPT: 
Oreos Plate Tectonics. I have changed the PPT a little (mainly to get rid of Comic Sans, I get a bit twitchy whenever I see that font).
The kids responded really well to this activity. There is nothing better than some hands-on activities to make information stick. The students were like little Pavlovian dogs; salivating while moving the “plates” around on the “magma”. After 15 minutes of playing with Oreos they gobbled it up in 1 second flat. Added lesson: delayed gratification!