Geologic Timescale

Introduction

• The Earth is approximately 4.6 billion years old.
• Geologists created the geologic timescale, an important tool for studying geology.

Conceptualizing Time

• Comparisons to human lifespan:
  • 4.6 billion years = 100 years (human lifespan).
  • One pixel for a human lifespan when zoomed out to 100,000 years.
  • To reach 1 billion years, we would add up to 1,000 human lifespans.

Eons of the Geologic Timescale

• The vast timeline is divided into eons, eras, periods, and epochs.

1. Hadean Eon

• Duration: ~0.5 billion years.
• Description: The Earth is a hot ball of rock; the moon is forming.

2. Archean Eon

• Duration: ~1.5 billion years.
• Description:
  • The Earth cools and continents form.
  • Life begins to form in the oceans; microorganisms start producing oxygen.

3. Proterozoic Eon

• Duration: ~2 billion years.
• Description:
  • Introduction of first complex cells and multicellular life.
  • Leads to the emergence of first plants and animals.

4. Phanerozoic Eon

• Duration: ~500 million years to present.
• Meaning: Visible life; characterized by an explosion of diverse life forms.

Eras of the Phanerozoic Eon

1. Paleozoic Era
   • Meaning: Old life (squiggly, weird, and creepy-crawly life).
2. Mesozoic Era
   • Meaning: Middle life (dinosaur life).
   • Ends with a giant asteroid impact.
3. Cenozoic Era
   • Meaning: New life (furry and flying creatures).
   • Diverse life forms including blooming plants.

Anthropocene

• Some propose that human activity has altered the Earth significantly, marking a new period called the Anthropocene.

Conclusion

• The geologic timescale is a crucial framework for understanding Earth's history and biological evolution.