Rock Cycle...... INFINITY AND BEYOND!
The rock cycle has been going on for millions and millions of years. it is a process... or CYCLE, that changes rocks from one kind to another. It is not a quick process, but happens over the course of long periods of time..... it can take thousands to millions of years! The rock cycle isn't always in a circle, like most cycles are. It can go any of the ways displayed on the picture above, and still has even more paths!
http://www.brainpop.com/science/earthsystem/rockcycle/
http://www.brainpop.com/science/earthsystem/rockcycle/