Geologic+Time+Slides

Age of the Earth

  • Estimated Age: 4.6 billion years old.

  • Formation: Represents the formation of Earth, Sun, and other planets.

  • Dating Methods:

    • Radioactive dating of meteorites, moon rocks, and oldest Earth rocks.

  • Humanity's Span: Very minuscule compared to Earth's age, referred to as "deep time" or "geologic time."

Key Evidence for Earth's Age

  • Zircon Crystals (Australia) - found to be 4.4 billion years.

  • Acasta Gneiss (Canada) - 4.03 billion years.

  • Isua (Greenland) - 3.7 - 3.8 billion years.

  • Meteorites:

    • Canyon Diablo (Arizona) - 4.54 billion years.

    • Allende (Mexico) - 4.567 billion years.

  • Moon Rocks:

    • Apollo 15 (Genesis) - 4.1 billion years.

Historical Perspectives on Earth's Age

  • James Hutton: Proposed Uniformitarianism, suggesting that processes observed today happened similarly in the past, indicating Earth's age is much older than previously thought.

  • Biblical Chronology: Bishop Ussher estimated Earth's age at 6000 years.

  • Scientific Estimates:

    • DeBufon (75,000 years); Kelvin (98 million years); Darwin (300 million years); Halley (100 million years); Lyell (240 million years).

Dating Methods

  • Relative Dating: Determining the sequence of events but not exact ages.

  • Absolute Dating: Establishing the actual age of events in years.

  • Steno’s Laws: Key principles for relative dating (e.g., Law of Superposition, Original Horizontality, Cross-Cutting Relationships).

Unconformities

  • Definition: Interruptions in the rock record indicating periods of erosion and missing deposition.

  • Types: Angular unconformity, Disconformity, Nonconformity.

Fossil Dating and Evolution

  • Fossils: Remains or traces of prehistoric life, crucial for understanding ancient climates and relative dating (Fossil Succession).

  • Darwin's Theory: Proposed that life forms evolve through natural selection, adapting to their environments over vast time periods.

  • DNA Evidence: Foundation for modern evolutionary theory, illustrating shared ancestry among living organisms.

Conclusion

  • The study of Earth's age incorporates scientific methods across geology and biology, linking fossil records, radiometric dating, and evolution to provide a comprehensive understanding of the planet's history.