Bio Chapter 7 Extinction Events

Volcanic Eruptions

Krakatau: 1883

Mt. St. Helens: 1980

Asteroid Impacts

Barringer Crater: 30,000 YA

Southwestern Egypt: 5-10,000 YA

Evidence of Cosmic Collisions

Chicxulub: 66MYA, 110KM crater

Vredefort: 2.2BYA, 170KM crater

Sudbury: 1.89 BYA, 40 KM crater

Barringer: 50,000 YA, 29 KM crater

Patterns of Extinction evetns

10-100 MYA massive events

65 MYA most recent

Major Extinction Events

• 66 MYA: End-Cretaceous Extinction event (K-T boundary)

• 206 MYA: End-Triassic Extinction event

• 255 MYA: End-Permian Extinction event

• 363 MYA: End-Devonian Extinction event

• 455 MYA: End-Ordovician Extinction event

Fossil

Any evidence of Pre-historic life

Fossil Preservation Types

• Compression

• Molds & Casts

• Impressions (Trace Fossils)

• Permineralizations

• Unaltered Material

Importance of Fossils

• changes in anatomy and diversity over time

• Reconstruct prehistoric:

  • Ecosystems

  • Physiologies

  • Anatomies

  • Climates & Document changes

  • Plant-animal interactions

• Studying biogeography

• Studying biostratigraphy with index fossils

Inferring Ages of Fossils and rocks

Absolute Dating (Radiometric Dating)

Relative Dating:

• Law of Superposition: Younger stuff toward surface

• Law of Strata Identified by Index Fossils: Rocks of known age used to compare fossils

Half-Life

Time it takes for half an amount of parent isotope to decay into daughter isotope

Carbon Dating

Carbon degrades into Nitrogen 14

Half-life of Carbon-14 = 5730 Yrs

Isotope System

Parent/Daughter/Half-Life/Dating Range/Datable Materials

Uranium-238/ Lead-206/ 4,500 million / 10-4,600 million/ Zircon

Potassium-40/ Argon-40/ 1,300 million / 0.05-4,600 million / Muscovite

Rubidium-87/ Strontium-87 / 47,000 million / 10- 4,600 million muscovite

Lutetium-176/ Hafnium-176 / 37,100 million / 10-3,600 million / Garnet

Carbon-14/ Nitrogen-14 / 5,730 years / 100-70,000 years/ wood, charcoal, peat, bone