The Cretaceous/Triassic (K/T) extinction

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The Cretaceous/Triassic (K/T) extinction

• 65 mya the dinosaurs vanished, along with 70 of
  all species.
• Our ancestors survived.

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The extinction at the end of the Cretaceous
totally wiped out these groups Dinosaurs
Pterosaurs Large marine reptiles
(ichthyosaurs, plesiosaurs mosasaurs) Rudists
and many other invertebrate taxa Ammonoids
(cephalopods) There were drastic
reductions of these groups, wiping out entire
families. Some of these groups had very few
survivors Coccolithophores (calcareous
phytoplankton) Planktonic foraminifera
Radiolarians Belemnoids (cephalopods)
Echinoids Bryozoans
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On land, only small (less than 50 lb) animals
survived. Of the reptiles, only turtles, snakes,
lizards, crocodiles, and the tuatara (a reptile
from New Zealand) survived the extinction.
More than three quarters of the marine
plankton species disappeared at the end of the
Cretaceous. Many groups died out gradually, and
others disappeared suddenly. The extinctions did
not all happen simultaneously.
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MASS EXTINCTION/IMPACT RESEARCH GROUP (LEFT TO
RIGHT) HELEN MICHEL, FRANK ASARO, WALTER ALVAREZ
AND LUIS ALVAREZ  (1969 PHOTO).
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The red dots on the map show locations where high
concentrations of iridium have been found in
sediment at the Cretaceous-Tertiary boundary.
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Dr. Dale Russell, paleontologist Proposed that an
exploding star might have caused extinction of
the dinosaurs
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• The Alvarezes calculated that such a meteorite
  would have to have been
• Over 6 miles across
• As though Mount Everest had been fired into the
  planet at the speed of a bullet

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Further clues.

• Bits of shocked quartz in the clay from the K/T
  boundary, that could only have formed under
  intense pressure
• Deposits in Texas from the K/T boundary, carried
  there by a tsunami from the south
• Globules of glass in Haiti from the K/T boundary,
  formed as molten rock quickly cooled. Too heavy
  to have traveled very far.

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The meteorite that made this crater

• Entered the atmosphere at about 140,000 mph
• Ignited a jet of flame in its path, creating a
  tail of fire that would have burned the trees for
  thousands of miles
• Created a tsunami as high as 1000 ft that roared
  across the oceans
• Created a riptide that dragged entire forests
  into the water
• Vaporized 100 cu km of rock
• Sprayed rock 60 miles into the sky
• Created an earthquake 1000 times more powerful
  than anything in our history
• Triggered massive undersea landslides
• Created a fireball that spread hundreds of miles

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Some Environmental Stresses Caused by Meteorite
Impact

• Stress
• Darkness
• Winds (500 km/h)
• Tsunamis
• Fires
• Pyrotoxins
• Acid Rain
• Destruction of Ozone Layer
• Mutagens

• Time Scale
• Months
• Hours
• Hours
• Months
• Years
• Years
• Decades
• Millennia

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