Dinosaur Extinction

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Biology 103
2000 Second Web Report
On Serendip

Dinosaur Extinction

Julie Kwon

Massive creatures have once ruled the earth over 65 million years ago. Some dinosaurs were found to be tons in weight and over a hundred feet in height. How did these large creatures just disappear from the face of the earth and in such a short period of time? We have discovered that not only dinosaurs became extinct but also other organisms in the ocean and land were greatly affected. The structure of Earth has also changed where continents had moved, major ridge expansion took place, and land has sunken under sea or risen above water (1). Some evidences also show a "massive destabilization of the oceans and atmosphere" (1).A number of theories of what caused the extinction of the dinosaurs as well as other organisms developed, such as: giant meteor or comet impacts, volcanic eruptions, radiation from a nearby supernova, extreme changes in climate, diseases, and predation of dinosaur eggs by early mammals (4).The death of the dinosaurs is neither the most recent nor the most severe extinction; yet, it is a controversial debate where scientists are still trying to solve this great mystery.

Because dinosaurs were not the only organisms to become extinct the scientific theory of what caused this massive disappearance should have certain guidelines. "Clearly any successful extinction theory must explain not only why the dinosaurs became extinct; it must also explain what happened to the marine ecosystems, that so many lineages of plants and animals were wiped out. It must also explain why so many organisms were able to survive the catastrophe. It is estimated that somewhere in the range of 20% to 25% of all species extant at the beginning of the Late Cretaceous were extinct by its close" (4).

At the end of the Cretaceous Period over half the number of organisms disappeared leaving traces of evidences of what caused this extinction. Luis and Walter Alveraz were studying the K-T boundary in Gubbio, Italy where they found an unusual layer of clay at the boundary point which contained around thirty times the normal level of the rare element iridium (3),(5). The two most common source of iridium are from outer space in the form of cosmic dust, which is constantly showering the planets and the Earth's core when there are eruptions of certain types of volcano (3).This evidence alluded to two different theories, The Impact Theory and the Volcanic Theory.

The volcanic theory is somewhat similar to the impact theory and is also heavily supported by a number of scientists. As mentioned before the K/T boundary was discovered to have high contents of iridium. The basaltic lava eruptions of the Deccan Traps of western India was mentioned as a possible source of the iridium found in the K/T boundary "iridium spike" (1). "It has been proposed that the out gassing, combined with possible explosive episodes, could have been sufficient of itself to have caused the same kind of a "Nuclear Winter" scenario as proposed for the giant meteor impact" (1). Other areas in the Pacific Basin show a fairly high level of volcanic eruptions (1). This theory would further explain the possibility of how some organisms survived and the irregular distribution of iridium peaks in some areas.

The impact theory or the possibility that an asteroid or comet destroyed over half of the species on earth has been a strongly supported theory of why the dinosaurs became extinct. The impact of the asteroid or comet caused a chain of events beginning with the flying object becoming intensely hot and heading towards earth (1). This asteroid is believed to impact the ocean "ejecting massive amounts of dust and water into the atmosphere" (1). Everything within the radius of 500 kilometers would have been instantly destroyed (3).Many of the groups of organisms that were hit hardest by the K/T extinction lived in the ocean (4).Many enormous tidal waves would be started causing even more damage as well as start a chain reaction of earthquakes and volcanic activity (3).The dust particles will envelop the earth covering the earth into total darkness making vegetation to dematerialize away, leave little food for the animals, and create a cold environment (2).Temperatures may have fluctuated below freezing point to high temperatures and photosynthesis may have ceased (2).At the same time large fires would have been started by the intense shock wave later creating global fires that would release large amounts of carbon dioxide increasing temperatures and cause chemical reactions forming acid rain (3).The impact may also have released sulfur dioxide, which may help created acid rain with a low pH causing an environment where some organism may not have been able to survive (2).Evidence of acid rain was found in a number of rock samples (1).

One of the greatest discoveries that show great support for the impact theory is a crater called the Chicxulub(1),(2), (3),(5). Alan Hildebrand found a ring structure 180 kilometers in diameter in the Yucatan Peninsula. The Chicxulub is also believed to be 65 million years old. Alan Hildebrand wrote further explaining that the K/T boundary had two layers (2).The upper layer, the Fireball layer, was about 3mm thick and represented 1500 cubic kilometers of debris deposited globally with not variation in thickness. The Lower layer, the ejecta layer, was about 2mm thick (2).The Fireball layer contains certain traces of elements in approximately the same proportion as some meteorites (2).Furthermore, Tektites and micro tektites, black glassy objects produced at the time of the impact, have been found in the ejecta layer of the K-T boundary (2).

Evidences that further support the impact theory is the presence of soot within the clay layer. The presence of soot usually implies that a large global fire occurred as a result of temperature changes from an impact (3),(5). Quartz crystals were also found physically altered within the clay layer (3),(5). "This alteration only occurs under conditions of extreme temperatures and pressure" (3).These evidences also show that a great climatic change has taken place.

Most of the evidence that was discovered points toward the impact theory. This theory explains most of the changes that occur towards the end of the Cretaceous period. Though the volcanic eruption explain some evidence that are not supported by the Impact theory, the Impact theory clearly explains the events that occurred during the period of dinosaur downfall and is more strongly supported by the evidence that was found. Temperature data shows that there was a temperature drop and later a temperature rise. The 65 million year old crater that exist on the Yucatan Peninsula shows that an asteroid did indeed collided onto Earth. Iridium, which is a common component of asteroids, was found in sediments of the Cretaceous layer. These evidences as well as other information strongly support the theory that an asteroid impacted the earth 65 million years ago and destroyed a large number of species including the massive sized dinosaurs.

 

WWW Sources

1),"Dinosaur Extinction: No Asteroid or Comet Impact Here"

2)"Dinosaurs: Death from Space"

3)"Dinosaur Extinction Page"

4) "Dinosaur Extinction"

5) "What Killed the Dinosaurs"



Comments made prior to 2007
Of the many theories of dinosaur extinction, there is one I'd like to propose. I would like feedback on the theory that dinosaurs became extinct because the change of temperature caused the female to produce either male or female of the species. I believe this similar to humans in that the sex of the fetus is partially regulated by temperature. If the dinosaurs produced only one sex of offspring, the race would eventually become extinct ... Don DeFrance, 27 February 2007

Comments

Charles Weber's picture

cause of Cretaceous savanna vertebrate dcline

The Cretaceous ocean predators were very large. I suspect that the productivity implied by this was caused by a flow of phosphorus toward the ocean from the savannas (seasonal rainfall areas) permitted by erosion of phosphorus rich runways of plant smothering termites in the Amitermitinae starting in late Jurassic in Australia where the first ocean phosphorite deposits occurred. Anoxic conditions in the oceans were also probably caused by this. This anoxic bottom condition probably helped reduce the ammonites also, in addition to competition from phosphorus enhanced vertebrates. The savanna herbivore dinosaurs declined in armor, teeth, and quite a bit in bony structure across the Cretaceous outside of South America, especially in southeast Asia. Many even lost teeth. I suggest it was due to this same phosphorus famine created by erosion of the soil of the runways of plant smothering termites. Pterosaurs and birds probably lost teeth primarily because of the young eating iron oxide and bauxite in the flying reproductive soil borne termites’ guts, which bound the phosphates. You may see this discussed in more detail starting in http://www.angelfire.com/nc/isoptera/termites.html and its links, which links explore the possible affect that ant evolution had upon them. You may see a journal article in http://gsjournal.net/Science-Journals/Essays-Paleontology/Download/4717 . By the time the Cretaceous ended the world ended up with tiny savanna vertebrates, most of them mammals, which were able to give their young phosphorus in milk at that critical stage. They were a far cry from the massive, well boned Stegosaurs, etc., which roamed around the Jurassic, and had diminished tooth structure at first. They were a long time starting to increase in size (several million years).
You may see the affects on soil discussed in more detail in http://www.angelfire.com/nc/isoptera/soil.html .
Sincerely, Charles Weber

PS It is conceivable that you would also find interesting a hypothesis of my son explaining the Decca (or Deccan) lava flows as disruption of the crust by the disruption of the crust at the antipode (opposite side of a sphere) by a huge meteorite impact. You may see my version in http://charles_w.tripod.com/antipode.html .
Sincerely, Charles Weber

Serendip VisitorCharles Weber's picture

cause of the decline of Cretaceous savanna dinosaurs

The Cretaceous ocean predators were very large. I suspect that the productivity implied by this was caused by a flow of phosphorus toward the ocean from the savannas (seasonal rainfall areas) permitted by erosion of phosphorus rich runways of plant smothering termites in the Amitermitinae starting in late Jurassic in Australia where the first ocean phosphorite deposits occurred. Anoxic conditions in the oceans were also probably caused by this. This anoxic bottom condition probably helped reduce the ammonites also, in addition to competition from phosphorus enhanced vertebrates. The savanna herbivore dinosaurs declined in armor, teeth, and quite a bit in bony structure across the Cretaceous outside of South America, especially in southeast Asia. Many even lost teeth. I suggest it was due to this same phosphorus famine created by erosion of the soil of the runways of plant smothering termites. Pterosaurs and birds probably lost teeth primarily because of the young eating iron oxide and bauxite in the flying reproductive soil borne termites’ guts, which bound the phosphates. You may see this discussed in more detail starting in http://www.angelfire.com/nc/isoptera/termites.html and its links, which links explore the possible affect that ant evolution had upon them. By the time the Cretaceous ended the world ended up with tiny savanna vertebrates, most of them mammals, which were able to give their young phosphorus in milk at that critical stage. They were a far cry from the massive, well boned Stegosaurs, etc., which roamed around the Jurassic, and had diminished tooth structure at first. They were a long time starting to increase in size (several million years).
You may see the affects on soil discussed in more detail in http://www.angelfire.com/nc/isoptera/soil.html .
Sincerely, Charles Weber

PS It is conceivable that you would also find interesting a hypothesis of my son explaining the Decca (or Deccan) lava flows as disruption of the crust by the disruption of the crust at the antipode (opposite side of a sphere) by a huge meteorite impact. You may see my version in http://charles_w.tripod.com/antipode.html .
Sincerely, Charles Weber

poo's picture

why?

why?

Serendip Visitor's picture

Quite good

I'm quite impressed by this. The only thing that possibly slightly disappointed me is the fact that you have nothing describing any of the species that were still alive at the time...or maybe I missed that. Regardless quite well written.

Samantha's picture

Mistakes

There is a large slew of gramitical mistakes and spelling errors in this report. Therefore, this person is not credible. The presence of so many errors leads one to believe that the author is unintelligent. I was about to use this as one of my sources for my ten-paged thesis for Honors English. If the mistakes are corrected, maybe this would be a credible source.

Serendip Visitor's picture

reply

the spelling of grammatical is not "gramitical"for your information.just because the writer committed spelling errors he is not credible.Then are you?

Serendip Visitor's picture

Well spelling and grammar are

Well spelling and grammar are two completely different things. You cannot call my spelling mistake a GRAMMATICAL mistake. Then you asked if I was credible. Well, I was not providing any scientific information that was intended to inform readers. So, therefore, no. I am not credible.

Serendip Visitor's picture

?

Is all of this stuff true?

shamshan 's picture

wow,mind blowing Rticle but

wow,mind blowing Rticle but not containing wat i want so its useless for me
:)

Serendip Visitor's picture

Thanks

Hi Julie.
Absolutely fantastic piece of work which is detailed and explains many relevant points.
It helped me a lot with my scientific controversy and now i really do believe it was Volcanoes, not a meteor/asteroid!

Serendip Visitor's picture

Thanx Julie

Thanx Julie you have seriously helped with my science assignment

Serendip Visitor's picture

saved

thanks julie, i think you just about saved my grade for science this term with this!

Anonymous's picture

i think that a comet set off

i think that a comet set off volcanic eruptions and thats how they died

Daniel Ualesi's picture

Thanks, Julie ur a real

Thanks, Julie ur a real llifesaver i have 2 do an essay on dinosaurs and their extinction

Anonymous's picture

Thanks, im working on a

Thanks, im working on a science essay on dinosaur extinction theorys

Anonymous's picture

so let me get it straight.

so let me get it straight. the evidence of a KT impact. is; 1. the Chicxulub crater 2. acid rain found in rocks 3. soot 4. a layer of rare iridium 5. Tektites and micro tektites- meteor elements, that were found. & 6. Altered quartz .......thnx, I needed to know this.

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