1. Determining Absolute Age
Chapter 8 - 2
Determining Absolute Age

2. Absolute Age Numeric age Observed geologic processes
Chemical composition of rocks

3. Rate of Erosion Measure rate at which streams erode a bed
Can estimate the age of the rock

4. Niagara Falls
Erodes at 1.3 m per year.
9,900 years

7. Rate of Deposition How long it takes for sediment to be deposited
Floods can deposit faster

8. Varve Count Rings on a tree
Varve - Sedimentary deposits in annual layers

9. Glacier lakes – Summer melt deposits in layers
Coarse – bottom
Fine - top

10. The Atom

11. Radiometric Dating Radioactive isotope – nuclei emit particles
Compare % of radioactive to stable isotopes

12. Half-Life Time it takes for ½ the mass of an element to decay
Parent to daughter

13. Radioactive Isotope Table 1 page 195
Different elements take different amounts of time to decay

14. Carbon Dating
Younger rocks
How much organic material is in the rock

15. Carbon-14 combines with oxygen to form CO2
Most CO2 has carbon-12
Pants and animals take in CO2
Die and become part of the rock

16. Organic material in rock – compare C-14 to C-12
Constant while alive
Ration changes when dead