Here is a plate tectonic demonstration/lab idea for all grade levels. You can easily use this video when teaching about earthquakes and plate movements. All you will need is a hot plate, pan, some milk and chocolate powder. Place the pan on the hot plate, pour in some milk, pour a thick layer of chocolate powder on top of the milk until the milk is covered. Turn on the hot plate and then wait a few minutes up to about 5 and you should start to see the "crust" break apart and "magma" rise to the surface. Extension in your conversation can be:
Plate tectonics
Cracks in the crust
Earthquakes
The "magma" turns brown due to the "crust" so you can talk about how igneous rocks get some of their characteristics due to the surrounding rock.