1. Geochronology Methods for Determining the Relative and Absolute Age of Rocks THE LANGUAGE OF THE EARTH – PART VII

2. Relative Age Dating - Superposition

3. Principles of Faunal Succession and Faunal Assemblage Index Fossils - Widespread distribution - Restricted, known time of existence - Common to many environments

4. Principle of Cross-cutting Relationships

5. Global Time Markers Global Time Markers Volcanic Ash Eruptions

6. Global Time Markers Global Time Markers Magnetic Reversals

7. Global Time Markers Global Time Markers Meteor Impacts K-T impact site K-T Boundary coal mudstone-impact layer

8. Global Time Markers Global Time Markers Climate Change

9. Gaps in the Geological Record Gaps in the Geological Record Unconformities

10. Creating Unconformities

11. Gaps in the Minnesota Timescale

12. Regional Correlation of Units Regional Correlation of Units Piecing the Rock Record Together

13. Absolute Age Determinations Absolute Age Determinations Radiometric Dating

14. Radioactive Isotopes

15. Radioactive Decay

16. Radioactive Decay Half-life Zircon ZrSiO 4 U substitutes for Zr, but Pb does not.

17. 87 Rb  87 Sr; 86 Sr is stable Rb – chemically substitutes for K Sr – chemically substitutes for Ca 87 Rb/ 86 Sr 87 Sr/ 86 Sr Ca-plagioclase Granite whole rock K-feldspar Biotite (K-rich) t=0 87 Sr/ 86 Sr° t=1 Metamorphism at t=1 t=2 Isochron 87 Sr/ 86 Sr°(m) Rb-Sr Dating of a Granite

18. GEOPUZZLE 1

19. GEOPUZZLE 2

20. GEOPUZZLE 3