1. Geologic Time and Earth History

2. Two Conceptions of Earth History: Catastrophism Assumption: Great Effects Require Great Causes Earth History Dominated by Violent Events Uniformitarianism Assumption: We Can Use Cause And Effect to Determine Causes of Past Events Finding: Earth History Dominated by Small-scale Events Typical of the Present. Catastrophes Do Happen But Are Uncommon

3. Two Kinds of Ages Relative - Know Order of Events But Not Dates Civil War Happened Before W.W.II Bedrock in Wisconsin Formed Before The Glaciers Came Absolute - Know Dates Civil War 1861-1865 World War II 1939-1945 Glaciers Left Wisconsin About 11,000 Years Ago

4. Law of Superposition Youngest rock layers are on top.

5. Law of Superposition Superposition - Young Events Leave Traces Behind of Older Rocks Young Rocks Laid Down on Older Rocks Intrusions Are Younger Than The Rocks They Intrude Folds And Faults Are Younger Than The Rocks They Occur in

6. Rock layers in the grand canyon can be dated and matched with other regions.

7. The Geologic Time Scale