Kinetic City has a great site called Shape it Up: An Earth Changing Erosion Activity. As a Science Teacher at heart, I love this site. It allows kids to play the game and match weathering and erosion and time for a desired outcome. It's a quick little game but very good in showing kids what happens and how long it takes for each process to actually occur.
The main site for Kinetic City is http://www.kineticcity.com/
Enjoy and Happy Friday!