Asteroid belt

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Asteroid belt
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Kuiper Belt and Oort Cloud
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IMPACT EVENTS
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Known impact craters
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http//www.lpl.arizona.edu/SIC/impact_cratering/Ch
icxulub/Animation.gif
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Barringer Meteor Crater, AZ (49,000 yrs)
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Manicouagan Crater, Canada (212 Ma)
100 km
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Clearwater Lakes, Canada(290 Ma)
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Chesapeake Bay Crater (35 Ma)
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Chicxulub Crater, Mexico(65 ma)
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Map of Cenotes
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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)

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http//www.lpl.arizona.edu/SIC/news/chicxulub2.htm
l
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Mass Extinctions
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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

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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

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Causes (continued)

• Extraterrestrial
• Impact events
• Excessive radiation (weakened magnetic field)
• Biological
• Random extinction
• Predation or disease

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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