Extinctions, Anomaly, and a Crater

K/Pg (Cretaceous/Paleogene) Extinction

• the dinosaur killer
• at least 50% of all species were lost
  • classified as an intermediate mass extinction
• nothing over 55 pounds on land survives
• this didn’t just happen to land species
• marine animals suffered too
  • example: ammonites, marine reptiles
  • 80-90% of marine species were lost

Iridium Anomaly

• chemical element that’s much more abundant in meteoroids than on Earth
• last clay layer formed during the Cretaceous is strongly enriched in iridium
• it was noticed first in Gubbio, Italy, but it was a global phenomenon

The Smoking Gun: Chicxulub Crater

• years before a crater was discovered, “odd”, melted rocks were found
• melted rocks weren’t explored further until…
• gravity survey revealed a 93 mile diameter crater
  • shallow entry (20-30 degrees)
  • 6.8-50.3 mile diameter impactor

Meteorite Effects

• initial effects:
  • vaporizes everything close by
  • causes wildfires
  • generates tsunamis
• longer term effects:
  • sunlight shut off
  • photosynthesis effectively stops on land and in oceans for up to several months
• even longer-term effects:
  • up to 18 degree Fahrenheit global warming
  • water vapor remains in the atmosphere after the dust clears
  • CO2 produced from vaporization of certain rocks during the impact
  • acid rain
  • NOx (oxides of nitrogen) formed due to impact combined with the water in the atmosphere →nitric acid
    • oceans and soils acidified

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