Relative Dating

• Principle of Original Horizontality
• Principle of Superposition
• Principles of Cross-cutting and Inclusion
• Unconformities

Absolute Age

• Radioactive parent to radiogenic daughter
• Principle of half-lives
• Age of the Earth

Geologic Time Scale

• Cenozoic: 66 million years
  • Mammals and flowering plants
• Mesozoic: 245 million years
  • Dinosaurs
• Paleozoic: 570 million years
  • Invertebrates and land plants
• Precambrian: 4600 million years

Dino Death - What happened 66 million years ago?

• Gubbio outcrop
  • limestone with clay at extinction bed
• Iridium
• Spherules
• Shocked quartz
• Soot

Interpretation

• 10 km meteorite
• Creates 100 km crater (10000x all nuclear weapons)
• Killing mechanisms
  • Darkness
  • Cold
  • Greenhouse
  • Acid Rain
  • Fires