Week 15 - EXTINCTION

Mass Extinction

Extinction hypotheses must be testable and answer the following three questions (A, B, C).

  1. What is the geologic evidence for the mechanism?
  2. Does this mechanism account for other the organisms that went extinct (p. 22-24) and those that survived?
    1. the K-T extinction affected not only dinosaurs, but many planktonic foraminifera and coccoliths; all ammonites, rudists, inoceramids, pterosaurs, ichthyosaurs, plesiosaurs, and mososaurs; many marsupials and some multituberculates; and many plants.
  3. How long did it take for this mechanism to cause the extincions and what is the geologic evidence for the this?

The LATE TRIASSIC EXTINCTION

Timing

Species Affected

Causes previously given for the presumed Carnian extinction of terrestrial vertebrates.

  1. global cooling
  2. bolide impact
    1. Manicougan Crater in Quebec

Reading assignments


TERMINAL CRETACEOUS EVENT

EXTINCTION AND SURVIVAL IN THE OCEAN

Marine Species Affected

Marine Species not affected

EXTINCTION AND SURVIVAL ON THE CONTINENTS

Continental Species Significantly Affected by Extinction

Continental Species not Affected


EXTINCTION HYPOTHESES

Top Ten: Theories of Dinosaur Extinction  by Nikheel Dhekne from HMS Beagle (Posted April 16, 1999  Issue 52)

  1. Asteroid Collision
  2. Volcanic Eruption
  3. Galactic Dust
  4. Arctic Ocean Spillover
  5. Predatory Mammals
  6. Magnetic Reversals
  7. Orbital Tilt
  8. Cosmic Radiation from a Nearby Supernova
  9. Disease
  10. Suffocation


DINOSAUR EXTINCTION from Dinosaurs of Colorado

Introduction
The Magnitude of the K/T Extinction
Giant Meteor Impact
Other Theories
Volcanic Eruptions - The Deccan Traps
The 26 Million Year Death Star
Radiation from a Nearby Supernova
Galactic Dust
Changes in Climate
Epidemic Diseases
Egg Predation by Mammals. 
"Changing Paleoclimates and Mass Extinctions"


Extinction Hypotheses in Dingus and Rowe

  1. The Rise of the Angiosperms
    1. loss of fern oil and/or production of alkaloids
    2. pollen
  2. Epidemics
  3. Cataracts
  4. Climatic Warming
    1. Temperature dependant sex determination
  5. The Rise of the Mammals
    1. competition for resources
    2. egg eating mammals
  6. Cost of Large Size
  7. Thin Eggshells
  8. Magnetic Reversals
  9. Marine Regression (Dingus and Rowe: pp. 18, 19)
    1. effects of a more seasonal climate on "reptiles"
    2. loss of a temperature buffer causes hotter days and cooler nights, and warmer summers and cooler winters
  10. Volcanism
    1. locations of extensive late Cretaceous Flood Basalt Eruptions
      1. Rocky Mountains
      2. Deccan traps
    2. Products of volcanism
      1. volcanic ash
      2. toxic gases
      3. carbon dioxide, sulfur, and chlorine
      4. acid rain
  11. A Catastrophic Impact
    1. Iridium spike, shocked quartz, etc. at over 100 boundary sections
    2. apparent tsunami deposits and impact breccias around the Caribbean
    3. a 10 km wide bolide (asteroid or comet) impacts in the Gulf of Mexico
      1. Chicxulub (in the Yucatan)
      2. 80-100km wide, 20-40 km deep impact crater
      3. 21,000 km3 (5,000 cubic miles) of ash into the atmosphere
      4. initial heating of the atmosphere triggers global forest fires
      5. months of darkness and freezing
      6. 75-90 m high tsunami
      7. triggering of volcanic activity on opposite side of the earth?


Coincidence does not prove causality. Whether it was the chief agent of change or was just one causal factor among many remains to be determined.

Possible Catastrophic Results from volcanism or impact


 

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