1. Dating Notes
Donald’s 101 to Dating

2. Earth Science Trivia
If you were contracted to construct a timeline of the Earth’s history
What are at least 2 things that you would have to study to create the time scale?
What type of scientist could you be?
Rock Layers and Fossils
Paleontologist (studies fossils) or Geologist (studies rocks)

3. Why is Geological Dating Important in Science?
To know when an organism existed and construct a history of prehistoric Earth!
Geological Time Scales are made by piecing together the fossil record

4. The Fossil Record Paleontologists group similar organisms together
Structure
Habitat
Location
They also arrange organisms in the order in which they lived, from earliest to latest

5. Geologic Time Scale
A CHRONOLOGICAL record of the life forms and geological events in Earth’s history
Developed from studying ROCK LAYERS and INDEX FOSSILS

6. But, How Do Scientists Know How Old Something is???
Through the use of 2 dating techniques
Relative Dating
Determining the order of events by examining the positions of rock layers
Absolute Dating
Determining the age, in years, of an event through the use of technological tools and tests

7. Relative Dating Relies on the Principle of Superposition!
Remember…oldest rocks are the bottom layer etc. etc. etc.
Used for giving the ORDER of events ONLY (this is older than this, this is younger than that)
Will NOT tell an exact age in years

8. Relative Dating UNCONFORMITIES ONE PROBLEM
Most rock layers are not pristine (they have been disturbed)
Uplift, rock layer tilting and EROSION angle and remove rock layers causing GAPS in the fossil record known as…
UNCONFORMITIES

9. Unconformity
Angular Unconformity - Result when horizontal layers lie on top of tilted layers

10. Unconformity
Disconformity /Nonconformity - Results when top rock layer is eroded away BEFORE a new layer is deposited = GAP in record

11. So what do we really use this for?
Correlation of rock layers
To identify gaps called…
UNCONFORMITIES
To help us understand early Earth and continental positioning
This means we have to study land ALL aver the world!

12. Absolute Dating Relies on atoms and their radioactive decay
Assigns a number in years to the event

13. Important Vocab
Radioactive Decay: When an atom releases energy as it changes to a new kind of atom
Isotope: An atom of the same element with a different number of neutrons
Parent Material: Original isotope (pre-decay)

14. Important Vocab
Daughter Material: What the parent becomes as it decays
Half Life: The time it takes for HALF of the radioactive atoms to decay
Page 347: Using Math
5 lives have past, 5 x 1600 = 8000 years

15. Absolute Dating Radiometric Dating
Age calculation from measuring the parent to daughter material ratio and applying the elements half life
Types
Carbon - 14
Potassium - Argon

16. Absolute Dating Carbon - 14 Dating: Carbon-14 decays to nitrogen-14
ALL plants and animals contain carbon
Scientists measure the amount of carbon-14 left in the remains
Carbon-14 half life is 5730 years

17. C - 14 Problems EXPENSIVE Difficult
Accuracy
Recent = 200 year span
Older = year span
EXPENSIVE
Difficult
Sample - Only useful for dating once living materials UP TO 50,000 years old

18. Sample Problems
Homework!

19. Summary Geologic Dating is important because… Two types of dating are…
Relative dating is…
Absolute Dating is…
They are different because…