Class 10 : The KT impact The Alvarez Theory

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Class 10 The K-T impact (The Alvarez Theory)

• Geological anomalies at K-T boundary
• The K-T crater
• Timeline for devastation

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I Geological anomalies at the K-T boundary
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• Detailed investigation finds the following in the
  K-T transition layers
• Iridium
• In the K-T boundary everywhere in world!
• Higher levels of Iridium in North America
• Large impact or volcanism (Deccan Plateau)
• Shocked quartz
• Find very strongly shocked quartz
• Such quartz only thought to be found in impact
  sites
• Find more weakly shocked quartz in obvious
  volcanic sites
• Soot and lots of it!

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• Feldspar spherules
• Found spread throughout the KT boundary
• Formed as vaporized minerals started to
  recondense
• No known volcano can spread such spherules across
  the whole globe

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II The K-T crater
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• Alvarez theory given huge boost by discovery of
  the Chicxulub impact crater
• Circular crater revealed through pattern of
  cenotes (small sinkholes)
• Crater confirmed by detection of gravitational
  anomalies
• Crater is 170km diameter
• Exactly the kind of crater predicted by the
  Alvarezes
• Crater dated at 65Myrs

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III Timeline for devastation
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• Initial impact of a 10km asteroid or comet
• Atmosphere has almost no effect on incoming
  object strikes surface at full speed.
• Explosion yield of approximately 100 million
  megaton TNT equivalent
• Impacting asteroid and approx 100km3 of Earth
  rock are vaporized and thrown 100km into the
  atmosphere
• Intense fireball and blast wave flattens and
  ignites everything for 1000s km across
• Molten debris rains down across planet, seeding
  massive wildfires 90 of all plant life burns.
• Huge earthquakes cause massive Tsunamis
  devastate coastlines around the globe.

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• Next 10-1000 years
• Atmospheric debris and smoke completely blocks
  the Sun from reaching the surface
• Temperature plummets (like nuclear winter).
• Photosynthesis stops and most plants die
• Food chain collapses
• Eventually, debris settles out of atmosphere and
  the Sun starts to shine again
• But then theres dramatic global warming
• Carbon dioxide from fires causes a greenhouse
  effect temperature rises and planet becomes too
  hot!
• This lasts for an unknown length of time
• Few species survive this ordeal