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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