Age of the Earth

Age of the Earth

• Geologic Time: A timeline used by geologists and paleontologists to describe the timing and relationships of events in Earth's history.

Placing Events in Sequence

• Relative Dating: A method of dating geological events based on their position in the geologic record without assigning a specific numerical age.

• Two methods to relate time in geology:

  • Relative Dating: Sequencing events based on their positions in rock layers.

  • Chronologic Dating: Assigning specific numbers of years to an event or rock.

Geologic Time Scale

• A combination of relative and chronologic age determinations:

  • A relative sequence of lithologic units established using logical principles.

  • Measured against a framework of chronologic dates.

Development of the Geologic Column

• Developed through logical rules to establish relative sequences of events:

  • Principles used: Original Horizontality, Superposition, Lateral Continuity, Fossil correlation, Cross-cutting Relationships.

• Numerical dates attached to strata utilizing radiometric techniques.

• Continually refined as new information becomes available.

Relative Dating Methods

• Methods: Determines the relative sequence of events:

  • Principle of Original Horizontality: Sediments are deposited in horizontal layers.

  • Lateral Continuity: Sediment layers extend laterally until they thin out.

• Six Relative Age Principles:

  • 1. Superposition: In undisturbed strata, lower layers are older.

  • 2. Original Horizontality: Layers are originally horizontal.

  • 3. Lateral Continuity: Layers continually spread until they thin.

  • 4. Cross-cutting Relationships: Features that cut through rocks are younger.

  • 5. Inclusions: Rock fragments included in a rock layer are older than the rock itself.

  • 6. Fossil Succession: Fossil assemblages succeed one another through time.

Historical Geology Development

• Niels Stensen (Nicolaus Steno)

  • Introduced fundamental principles of relative time.

The Law of Superposition

• In undisturbed strata, the lowest layer is the oldest, and layers above are progressively younger.

Original Horizontality

• Sediments are generally deposited in horizontal layers.

• Lateral continuity describes how layers extend laterally until they thin out.

Cross-cutting Relationships

• The geological feature that cuts through another is younger than the feature it cuts through.

Principle of Inclusions

• Inclusions (pieces of one rock type within another) are older than the surrounding rock.

Faunal and Floral Succession

• Faunal Succession: Fossil assemblages succeed one another through time, allowing for relative dating.

• Correlation: Relates rocks from one location to another using stratigraphic principles.

• Unconformities: Surfaces representing gaps in the geologic record: Angular, Nonconformity, and Disconformity.

Biological Evolution and Major Events

• Demonstrates major geological and biological events across Earth’s history.

• Example Events:

  • Formation of Pangaea, extinction events, and emergence of key species.

Radioactive Dating Techniques

• Absolute Dating: Using radioactive decay to assign numerical ages to rocks.

  • Involves using isotopes with known decay rates to date materials.

Carbon and Radiocarbon Dating

• Carbon-14 Dating: Used for dating organic remains up to 70,000 years old based on C-14 to C-12 ratios.

• Effective for archaeological and geological samples.

The Importance of Life Characteristics

• Life is characterized by:

  • Acquisition and use of energy

  • Reproduction

  • Growth and development

  • Response to stimuli

  • Adaptation to environment

  • Homeostasis

Evolution of Life on Earth

• Discusses complex interactions within biological systems and adaptation over time.

• Early life likely arose in harsh conditions with minimal competition.