1. Absolute Age Dating

2. Absolute Age/Dating the numeric age of an object or event
Stated in years
Variety of methods can be used

3. Methods of Absolute Age Dating
Rates of Erosion
Rates of Deposition
Varve Count
Radiometric Dating
Carbon Dating

4. Method 1: Rates of Erosion
Uses the rates at which geological features erode
Only practical for geological features that formed within the past 10,000-20,000 years.
Example: scientists can measure the rate at which a stream erodes in its bed to estimate the age of the stream.

5. Method 2: Rates of Deposition
Scientists use the rate at which sediment is deposited for common sedimentary rocks such as limestone, shale, and sandstone.
Generally, about 30cm of sedimentary rock are deposited over a period of 1,000 years.
Not always accurate—floods and erosion can affect the average rate.

6. Method 3: Varve Count
Varve-banded layer of sand & silt that is deposited annually in a lake
One varve represents one year of deposition
By counting the varves scientists can estimate the age of sediment

8. Method 4: Radiometric dating
Method of comparing the relative percentages of a radioactive (parent) isotope and a stable (daughter) isotope.
Radioactive isotopes have nuclei that emit particles & energy at a constant rate regardless of surrounding conditions.

9. Method 5: Carbon Dating C14 dating/radiocarbon dating
Used to date younger rock layers by dating organic material found within the rock.
The ages of wood, bones, shells & other organic remains that are included in the layers & are less than 70,000 years old can be determined.