Title: Asteroid belt
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3Asteroid belt
4Kuiper Belt and Oort Cloud
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6IMPACT EVENTS
7Known impact craters
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9http//www.lpl.arizona.edu/SIC/impact_cratering/Ch
icxulub/Animation.gif
10Barringer Meteor Crater, AZ (49,000 yrs)
11Manicouagan Crater, Canada (212 Ma)
100 km
12Clearwater Lakes, Canada(290 Ma)
13Chesapeake Bay Crater (35 Ma)
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15Chicxulub Crater, Mexico(65 ma)
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17Map of Cenotes
18Global 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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21http//www.lpl.arizona.edu/SIC/news/chicxulub2.htm
l
22Mass Extinctions
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25Causes 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
26Causes (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
27Causes (continued)
- Extraterrestrial
- Impact events
- Excessive radiation (weakened magnetic field)
- Biological
- Random extinction
- Predation or disease
28Permo-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