Stopdisastergame.org is a great website for your students to learn about various natural disasters such as tsunamis, bush fires, earthquakes and more by managing a village or city through a disaster period. Anyone who has played SimCity will pick this up in a flash and discover the purpose of the game with ease. Quite simply you are given a budget and limited time to create natural and manmade infrastructure to both prevent a an imminent catastrophe and manage it once it occurs. Your kids will really enjoy this challenge and it has loads of replay value in it across a range of disasters. Check it out here.