[Free Registration/Login may be required to access all resource tools.] Looks at how stratigraphy can be used to determine the relative ages of rocks, how unconformities occur, ways to match rock layers in different areas, and how...

[Free Registration/Login may be required to access all resource tools.] Identifies and describes the two internal layers of Earth.

This one-page explanation of the rock cycle contains a very helpful diagram and useful explanatory notes. Site explains how rocks are made and broken down.