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Dinosaur Extinction
Dinosaurs inhabited the earth for over 165 million years,
during the
Mesozoic Era.
Most dinosaur species lived and died out during this period, but
at the end of the Cretaceous period
(65 million years ago),
all remaining
types of dinosaurs
(with the exception of birds which
had already evolved, and are widely believed to be descended from dinosaurs)
died out.
At the same time many other creatures
(for example
Ammonites,
and Belemnites,
as well as
Pterosaurs,
and many large marine reptiles such as
Mosasaurs.
Plesiosaurs and
Pliosaurs)
also became extinct.
In fact,
all animals
weighing more than 55 pounds (25 kilograms) seem to have died out!
While are not sure what happened, we do know that something happened at about
65 million years ago. This
event shows up as clear boundary in the rocks, known as the "K-T boundary",
the extinction event usually being referrred to as the
"Cretaceous-Tertiary mass extinction".
Scientists have proposed many different possible explanations
for what may have happened, and
why this mass extinction might have happened:
(Note: Sometimes these suggested explanations are informally called "theories", however in this case
"hypotheses" is the correct term, since in science a theory
means a well-substantiated explanation of some natural phenomenon or observation,
whereas as "hypothesis" means a suggested explanation which needs
to be tested against experimental evidence).
- Asteriod Impact Hypothesis
- Hypothesis: An asteriod hit the earth.
- Effect: Apart from the immediate impact of fires and flooding (if it hit the sea), this would have
caused catastrophic changes in the environment because of the dust thrown up in to the air blocking out sunlight.
- Our Evaluation: This is currently the most popular hypothesis with scientists, because,
as
Luis and Walter Alvarez
pointed out,
iridium (which comes from asteroids) has been found all over the world
in rocks at the K-T boundary (which were laid down at
the time of the mass extinction).
There is also a large
crater at Chixulub in southern Mexico,
which appears to be of the right age,
and could have been made as a result of an asteroid hitting the earth.
- Volcanism Hypothesis
- Hypothesis: Volcanoes (there is known to have been very active volcanic around this time, especially in
India in a region that is today known as the Deccan Traps) could have caused catastrophic changes in the environment.
- Effect: The dust from volcanoes would have affected the climate, sulphur from
volcanoes could have caused immensely strong acid rain, and poisonous
substances such as selenium could have been released into the atmosphere.
- Our Evaluation: After the Asteroid Impact Hypothesis,
this is probably the second most popular explanation among scientists - partly, because we know that
volcanoes were active at about this time.
- Supernova Hypothesis
- Hypothesis: A nearby star exploded as a supernova.
- Effect: A nearby supernova would have bathed the earth in deadly radiation.
- Our Evaluation: If this hypothesis is true, rocks at the K-T boundary should contain 244Pu (a long-lived isotope of Plutonium). However, this does not seem to be the case.
- Climatic Change Hypothesis
- Hypothesis: Changes in the Earth's climate caused the mass extinction.
This could have been caused by gradual changes in the positions of continents
effecting ocean currents and winds, or by changes in the Earth's orbit around
the sun, or even by a relatively sudden greenhouse effects.
- Effect: Depends on the particular climate change theory in question.
- Our Evaluation: This hypothesis can not be discounted, and even if climate change was not
the main cause of the extinction, it could have played a part -
there is some evidence that the Earth cooled at the end of the
Cretaceous period.
- Flowers Drugged the Dinosaurs Hypothesis
- Hypothesis: The first flowering plants appeared during the
Cretaceous period,
and if dinosaurs ate them they could have been drugged by them.
- Effect: Could perhaps have wiped out some dinosaurs.
- Our Evaluation: This hypothesis does not explain the extinction of many other species, especially
marine species. It also struggles with the fact that dinosaurs and flowering
plants were contempories for many millions of years, and only suddenly, at
65 million years ago, the dinosaurs died out.
- Mammals Ate the Dinosaurs' Eggs Hypothesis
- Hypothesis: Mammals ate the dinosaurs' eggs.
- Effect: Could perhaps have wiped out some dinosaurs.
- Our Evaluation: This used to be a popular hypothesis -
but does not explain the extinction of many other species, especially
marine species. It also does not explain why dinosaurs were very successful
for millions and millions of years, during most of which time, mammals were also around.
- Caterpillars Ate All the Plants Hypothesis
- Hypothesis: Caterpillars ate all the plants and there was not enough food for
herbivores, and eventually not enough meat for carnivores.
- Effect: Could perhaps have wiped out some dinosaurs.
- Our Evaluation: This hypothesis
does not explain the extinction of marine species, and some may wonder whether
caterpillars could really affect every continent on the Earth at the same time
to this extent.
- Disease Epidemic Hypothesis
- Hypothesis: The dinosaurs could have been wiped out by a disease epidemic.
- Effect: Could perhaps have wiped out some dinosaurs.
- Our Evaluation: The
problem with this hypothesis, is could it effect dinosaurs to the extent of
wiping them all out, and how could it explain the simultaneous extinction of marine animals?
Although many scientists now favor the asteroid impact hypothesis,
it is not yet
actually certain that this is the reason why the
dinosaurs died out. It is possible that
one of the other theories might be the correct one. It is also possible, that
there could have been several events which happened together, and between
them, killed all the dinosaurs.
Related Information & Resources
See Also
Books about Dinosaur Extinction
Here are some books from Amazon.com:
Disclosure: Products details and descriptions provided by Amazon.com. Our company may receive a payment if you purchase products from them after following a link from this website.
By Christian Patrick Studs
Independently published
Released: June 21st, 2023
Paperback (40 pages)
 | Lowest New Price: $9.99*
In Stock*
*(As of 09:20 Pacific 20 Mar 2025 More Info)
Click Here | Description:
Zorian The Historian: Dinosaur Extinction- Manufacturer: Independently published
- EAN: 9798399268934
Details:- Paperback
- Number of Pages: 40
- Author: Christian Patrick Studs
- Publication Date: June 21st, 2023
- Release Date: June 21st, 2023
Physical Description:- Size: 9.0 inches by 6.0 inches by 0.1 inches
- Weight: 0.19 pounds
Click here for more information |
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By Ame Dyckman
Little, Brown Books for Young Readers
Released: April 18th, 2023
Hardcover (40 pages)
 | List Price: $18.99*
Lowest New Price: $12.54*
In Stock*
*(As of 09:20 Pacific 20 Mar 2025 More Info)
Click Here | Description:
How Dinosaurs Went Extinct: A Safety Guide- Manufacturer: Little, Brown Books for Young Readers
- ISBN: 031659329X
- EAN: 9780316593298
Details:- Hardcover
- Format: Picture Book
- Number of Pages: 40
- Author: Ame Dyckman
- Publication Date: April 18th, 2023
- Release Date: April 18th, 2023
Physical Description:- Size: 10.4 inches by 10.3 inches by 0.55 inches
- Weight: 2.314853751 pounds
Click here for more information |
|
By Riley Black
Griffin
Released: October 24th, 2023
Paperback (304 pages)
 | List Price: $19.00*
Lowest New Price: $10.79*
In Stock*
*(As of 09:20 Pacific 20 Mar 2025 More Info)
Click Here | Description:
Last Days of the Dinosaurs- Manufacturer: Griffin
- ISBN: 1250894867
- EAN: 9781250894861
- PartNumber: 9781250894861
Details:- Paperback
- Number of Pages: 304
- Author: Riley Black
- Publication Date: October 24th, 2023
- Release Date: October 24th, 2023
Physical Description:- Size: 8.1999836 inches by 5.3999892 inches by 0.7999984 inches
- Weight: 0.54895103238 pounds
Click here for more information |
|
By Steve Brusatte
Large Print Press
Released: October 16th, 2019
Paperback (533 pages)
 | Lowest New Price: $19.99*
In Stock*
*(As of 09:20 Pacific 20 Mar 2025 More Info)
Click Here | Description:
The Rise and Fall of the Dinosaurs: A New History of a Lost World- Manufacturer: Large Print Press
- Brand: Large Print Press
- ISBN: 1432869108
- EAN: 9781432869106
Details:- Paperback
- Format: Large Print
- Edition: Large type / Large print
- Number of Pages: 533
- Author: Steve Brusatte
- Publication Date: October 16th, 2019
- Release Date: October 16th, 2019
Physical Description:- Size: 8.5 inches by 5.5 inches by 1.25 inches
- Weight: 1.3999353637 pounds
Click here for more information |
|
By Charlotte Lewis Brown
HarperCollins
Released: June 12th, 2007
Paperback (48 pages)
 | List Price: $4.99*
Lowest New Price: $3.99*
In Stock*
*(As of 09:20 Pacific 20 Mar 2025 More Info)
Click Here | Description:
The Day the Dinosaurs Died (I Can Read Level 2)- Manufacturer: HarperCollins
- Brand: HarperCollins
- ISBNs: 0060005300, 9780060005306
- EAN: 9780060005306
- PartNumber: FBA-|296035
Details:- Paperback
- Edition: Reprint
- Number of Pages: 48
- Author: Charlotte Lewis Brown
- Publication Date: June 12th, 2007
- Release Date: June 12th, 2007
Physical Description:- Size: 6.0 inches by 0.14 inches by 8.96 inches
- Weight: 0.20062065842 Pounds
Click here for more information |
|
By David E. Fastovsky
Cambridge University Press
Released: February 7th, 2005
Hardcover (485 pages)
 | Lowest New Price: $99.97*
In Stock*
*(As of 09:20 Pacific 20 Mar 2025 More Info)
Click Here | Description:
The Evolution and Extinction of the Dinosaurs- Manufacturer: Cambridge University Press
- Brand: Cambridge University Press
- ISBNs: 9780521811729, 0521811724
- EAN: 9780521811729
- PartNumber: 25 Halftones, unspecified; 225 Line draw
Details:- Hardcover
- Edition: 2nd
- Number of Pages: 485
- Authors: David E. Fastovsky, David B. Weishampel
- Publication Date: February 7th, 2005
- Release Date: February 7th, 2005
Physical Description:- Size: 10.25 inches by 8.25 inches by 0.75 inches
- Weight: 3.04899308346 pounds
Click here for more information |
|
By Williams Smith God'swill
Independently published
Released: March 14th, 2025
Paperback (92 pages)
 | Lowest New Price: $10.00*
In Stock*
*(As of 09:20 Pacific 20 Mar 2025 More Info)
Click Here | Description:
The mystery of dinosaurs: The extinction event- Manufacturer: Independently published
- EAN: 9798314112748
Details:- Paperback
- Format: Large Print
- Number of Pages: 92
- Author: Williams Smith God'swill
- Publication Date: March 14th, 2025
- Release Date: March 14th, 2025
Physical Description:- Size: 9.0 inches by 6.0 inches by 0.21 inches
Click here for more information |
|
By Charles Frankel
University of Chicago Press
Released: May 29th, 2024
Hardcover (288 pages)
 | List Price: $26.00*
Lowest New Price: $22.43*
In Stock*
*(As of 09:20 Pacific 20 Mar 2025 More Info)
Click Here | Description:
Extinctions: From Dinosaurs to You- Manufacturer: University of Chicago Press
- ISBN: 022674101X
- EAN: 9780226741017
Details:- Hardcover
- Number of Pages: 288
- Author: Charles Frankel
- Publication Date: May 29th, 2024
- Release Date: May 29th, 2024
Physical Description:- Size: 9.0 inches by 6.0 inches by 1.1 inches
- Weight: 1.19931470528 pounds
Click here for more information |
|
By Marco Signore
Abbeville Press
Released: October 26th, 2010
Hardcover (64 pages)
 | List Price: $15.95*
Lowest Used Price: $6.18*
In Stock*
*(As of 09:20 Pacific 20 Mar 2025 More Info)
Click Here | Description:
T. Rex and the Great Extinction (Dinosaurs)- Manufacturer: Abbeville Kids
- Brand: Abbeville Press
- ISBN: 0789210142
- EAN: 9780789210142
Details:- Hardcover
- Edition: Illustrated
- Number of Pages: 64
- Author: Marco Signore
- Publication Date: October 26th, 2010
- Release Date: October 26th, 2010
Physical Description:- Size: 11.5 inches by 8.0 inches by 0.5 inches
- Weight: 1.10231131 pounds
Features:- Used Book in Good Condition
Click here for more information |
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