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Asteroid belt. Kuiper Belt and Oort Cloud. IMPACT EVENTS. Known impact craters. http://www.lpl.arizona.edu/SIC/impact_cratering/Chicxulub/Animation.gif. Barringer Meteor Crater, AZ (49,000 yrs). Manicouagan Crater, Canada (~212 Ma). 100 km. Clearwater Lakes, Canada (~290 Ma).
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http://www.lpl.arizona.edu/SIC/impact_cratering/Chicxulub/Animation.gifhttp://www.lpl.arizona.edu/SIC/impact_cratering/Chicxulub/Animation.gif
Global Effects • Dust in the atmosphere • Too dark to see for 1-6 months • No photosynthesis for 2 months to year • Drop in land surface temperatures • Carbonates and evaporites vaporized into sulfur gases and CO2 (with resulting acid rain • Massive forest fires (evidenced by charcoal and soot deposits)
Causes of Mass Extinction • Changes in seafloor spreading rates • Causes flooding of land • 110-85 Ma, sea level was over 200 m higher than today • Shallow seas doubled, land mass reduced, warmer climate • Sea level changes from glaciation
Causes (continued) • Number and sizes of continents • More continents can generate new species • Less continents can cause competition for space and niches • Continental position (near or away from poles) • Volcanism • Lava can displace ocean water • Expels atmospheric gases • Ocean composition • Circulation changes can cause anoxic bottom water • Salinity changes from glacial meltwater runoff or excessive evaporation
Causes (continued) • Extraterrestrial • Impact events • Excessive radiation (weakened magnetic field) • Biological • Random extinction • Predation or disease
Permo-Triassic Extinction(~250 Ma) • Formation of Pangaea (reducing area of tropical seas) • Sea level fall from slower seafloor spreading (less overall sea area) • Climate change (drier interior of continents) • Cold ocean water disappeared and no sinking for circulation • Siberian Traps flood basalts (700,000 cubic miles