This page will tell you how to use the Geo-Time-Machine, a learning tool developed at Iowa State University. This tool (called GTM from now on), will help beginning geology students to understand several important concepts connected to the concept of relative geologic time.
What is relative geologic time?
When the surface of the earth is shaped by geologic processes, such as erosion, sedimentation, faulting and rock intrusions from below, we could think of a puzzle being created over time: each process changes in some way what came before it - the result is a the accumulation of effects. We as geologists are faced with unraveling this puzzle with regard to what process happened when, similar to the "crime" shown in this cartoon. Try it: what happened first (at time step 1), what happened then (time step 2) and what happened last (time step 3)?