1. CRETACEOUS-TERTIARY
EXTINCTION
GLY 5020 EARTH HISTORY – DR. FARLEY
UNIVERSITY OF NORTH CAROLINA
PEMBROKE
FALL 2009
SARAH SEALEY

2. • Occurs when the last representative of a
taxon dies.
• For Earth History, extinction is the last, or
most recent, occurrence of an identifiable
fossil.

3. MASS EXTINCTION
• Greater than 50% of all species die at similar
time
• Geologically short intervals of intense
species extinction

4. Mass Extinction Events of Greatest Severity
60% Terrestrial 90%
Marine

6. Patterns during Mass Extinction
Occurs in both terrestrial and marine
environments
On land, animals suffer yet plants seem highly
resistant
Disappearance of tropical life forms
Tendency of certain animal groups to experience
and survive (trilobites and ammonoids)
Periodicity in geological time (occurring about
every 26 million years)

7. Extinction Agents
• Catastrophic
• Extraterrestrial impacts such as meteorites
or comet showers
• Geologic
• Volcanism, glaciation, sea levelvariations,
global climactic changes, oxygen/salinity
level changes in ocean

8. K/T Extinction 65 MYA

9. Victims
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Many species of coccolithophorid: never recover diversity
Many species of foram
All ammonoids
All belemnoids
All rudists
All plesiosaurs
All mosasaurs
All pterosaurs
All non-flying dinosaurs
Several clades of birds
Many mammal groups (only monotreme prototheres, multituberculate allotheres, the ancestors
and closest relatives of the marsupials among the metatheres, and the ancestors and closest
relatives of the placentals among the eutheres)

10. Proposed Causes: The Maastrichtian
Regression
Draining of epeiric seas would alter terrestrial
climate

11. Increased Maastrichtian volcanism,
especially the Deccan Traps
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Decrease insolation (incoming sunlight) by presence
of fine particles in high atmosphere
Also change Earth's albedo, although not as
dramatically
Would operate on the scale of a few tens of
thousands to hundreds of thousands of years

12. The Chicxulub Impact
• 1980 – Walter Alvarez
• Hypothesized: an asteroid impacted Earth at
the K/T boundary
• Evidence:
• Iridium
• Shocked Quartz
• Tektites

14. Chicxulub Crater
10-15 km diameter
(size of Manhattan)

15. Iridium
Platinum-like metal,
common in metallic
asteroids but very rare in
Earth's crust.

16. Shocked Quartz

17. Tektites

18. Tektites

19. Probable Effects
Short term:
• Release lots of energy near impact, form
huge crater: 1.8 x 108 megatons!!
• Burst of light would vaporize material for
kilometers around, just like thermonuclear
weapons
• Blast wave would devastate nearby region; it
would be felt around the world, but decrease
with distance
• Shockwaves from impact would generate
huge tsunamis ("tidal" waves)

20. Longer term:
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Material vaporized by impact kicked high up in
atmosphere: reduced amount of incoming sunlight
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Observations on Mars showed big temperature
drops due to high-level particles
In human history, eruption of Tambora in
Indonesia in 1815 produced chilling effects
worldwide for more than a year later
Dust and ash would block out sunlight, reducing
photosynthesis and killing off plants on land and
surface algae in water; herbivores feeding on these
would die; carnivores feeding on these would starve
(after a brief feast)
Collapse of foodwebs would require long term to

21. Tsunami

22. Crater Animation
BOOM!