Relative and Absolute Dating

Introduction

• Conducting a discussion on Relative and Absolute Dating.
• Question: How do geologists determine the age of stratified rocks?

Relative Age vs Absolute Age

• Relative Age:

  • Refers to the sequence of events.
  • Does not provide an exact year or number.
  • Describes what came first and what followed.

• Absolute Age:

  • Provides a number indicating when an event occurred.
  • Uses field observations to determine relative ages.

Principles of Relative Dating

1. Original Horizontality:

   • Sediments are deposited in flat layers.

2. Superposition:

   • The layer underneath is older than the layer above.

3. Cross-Cutting Relationships:

   • Magma intrusion or fault becomes a younger layer.

4. Fossil Succession:

   • Fossils in rocks give information about the era when the layer was formed.

5. Lateral Continuity:

   • Layers may continue even if there are returns and cuts.

Absolute Dating

• Radiometric Dating:
  • Uses information from radioactive decay.
  • Radioactive decay occurs when unstable isotopes decompose.
  • Isotopes:
    • Atoms of the same element but with a different number of neutrons.
    • Example: Protium, Deuterium, Tritium for hydrogen.

Half-Life

• Half-Life:
  • The time needed for radioactive particles to become half of the original amount.
  • Examples of radioactive isotopes:
    • Carbon-14 (5,700 years),
    • Potassium-40 (1.3 billion years),
    • Uranium-238 (4.5 billion years).

How Half-Life is Used

• Measure the amount of radioactive isotopes in a rock and compare it to the stable element (daughter material).
• Example: Carbon-14 becomes Nitrogen-14 over time.
• As time passes, the parent material decreases, and the daughter material increases.

Importance of Analysis

• Knowledge of absolute and relative dating is important to understand the history of our planet.
• Recognizing our past can help with our future.

Conclusion

• Thank you very much for listening. Have a good day!