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What killed the dinosaurs - Coggle Diagram
What killed the dinosaurs
1) Introduction and background
The “great dying” and other mass extinctions
the great dying: is an example of a mass extinction
the largest extinction --> "permotriassic" extinction
%90 of species dead
k-t extinction
%60 of species extinguished
non-dinosaurs and mammals lived
2) Complications for scientists
The fossil record:
it is not perfect
hard to find and they are only formed under certain conditions
The nature of extinction:
if the species are constantly dying off and
Time resolution:
carbon dating cannot use
Reconstruction:
Falsifiability:
many hypothesis about dinasours extinction and might even corrrect.
3) Invalid hypotheses
Mammals outcompeted the Ds
Better theory
But not provable
Mammals were not found in the oceans
Ds. got so big that they crushed themselves
Proved that false
None became so large that they couldn't move
Disease killed the Ds
Travelling dinosaurs spread diseases(Unprovable)
We have no evidence
Mammals ate all of the Ds.’ eggs
Unprovable hypothesis
They cannot eat all the eggs
Cosmic rays killed the Ds
There was not extraterrestrial events which occured dangerous radiation
The Ds. just faded away into extinction
This is reasonable
Problem: Time resulation
and the inadequacy of the fossil record
4) Current arguments
The ‘intrinsic gradualists’
Volcansim
(End of Cretaceous) increased volcanic activity
could have created enough
dust and soot
to block out
sunlight
Climatic change
Example
In India during the late Cretaceous huge volcanic eruptions were spewing ( can be seen today at K/T boundary)
Plate Tectonics
Major changes in the organization of the continental plates
especially North America seaway
happened in earth it self
The ‘extrinsic catastrophists’:
The Alvarez Hypothesis Blame an astreoid impact
Large extraterrestrial object hit to earth (crater found in Mexico/ Yucatan Peninsula)
happened outside earth
what is K/T boundry
There was a fast
global climactic change
Mesozoic (Warm) / Cenozoic (Cold)
many organisms ( marine and terrestrial, vertebrate and invertebrate)
went extinct
Also there was less lasting changes (end of Cretaceous period)
may result of a massive terrestrial disturbance
threw up
soot
into the air
short term
= acid rain, emission of poisonous gases and cooling (like nuclear winter)
long term
= global greenhouse effect
At or near the K/T boundary there are thin layer of clay with unusually
high iridium
(normally rare in earth surface)
5) Conclusions
Why it is important to understand the K-T extinction:
understanding the k-t extinction would help usto understand mass extingtions in general and might provide a glimpse into the fleeting, transitory nature of our own mortality
The main problem with both the ‘intrinsic’ and ‘extrinsic’ hypotheses:
Selectivity of the mass extinction
we just do not know yet for sure
Terrestrial record strongly suggests a more gradual decline
marine fossil record support a slightly rapid decline
there is no way to test or prove(test)