The fastest way to get your students' attention is to break out the candy!
You'll want to use candy bars that have a pliable inside and are coated in chocolate - think Snickers, Milky Way, 3 Musketeers. The chocolate represents the Earth's crust and the filling represents the asthenosphere.
Use your fingernails to break up the chocolate crust - creating the fault.
To demonstrate shearing (strike-slip faults), push the two sides of the candy bar back together. Then slide one half forward while pushing the other one back.
Finally, to demonstrate compression forces, push the two ends of the candy bar together. You'll see the pieces of chocolate crust colliding and maybe even sliding over each other, creating mountains.
