Arguments Against
However, although the theory has many strong and believable factors, some scientists do not believe that the asteroid impact theory is true. This is because the evidence that supports the theory cannot prove the theory is true; it can only back it up. For example, although we know an asteroid hit earth, scientists cannot prove that it was the same time the dinosaurs became extinct. This shows that there is some doubt in the theory, and that we cannot be certain that it is true.
Comparison
Both the arguments for and against the Asteroid Impact theory pose as good arguments. However, the arguments for state only that it is likely that the theory is true, and cannot prove that the theory is definitely true. Scientists who believe that the Asteroid Theory is true cannot state that they are certain the theory is correct. However, this is true of all theories, and therefore the argument for the case against shows a poor argument.
This picture shows how the asteroid impact would affect the whole planet, and wipe out any life forms. (Taken from www.daviddarling.info/images/asteroidimpact2.jpg)
The second theory that I am going to write about is the Volcanic Eruption theory. This is the theory that a massively large number of volcanoes took part in a chain reaction, and they all erupted together. Scientists calculate that the eruption would cause over ten times more impact on the change of climate than the asteroid theory. The theory states that the eruptions would have huge effects on the environment, for starters burying most of West-India in nearly 12,000 feet of rock. It is thought that the massive waves combined with the quick change in climate would have killed the dinosaurs.
Evidence
Some evidence found by scientists is linked with the volcanic eruption theory. The sediments of fossils have been found in the same layer of rock that supports the idea of lava flow. This shows that it is likely that the eruption and the dinosaur extinction happened very closely to each other, as it backs up the idea that the lava flow caused by eruption was the reason for the extinction of the dinosaurs. The scientific evidence supports the claim made and gives relevant information, however, although it backs up the claim made, it does not prove it.
There is also fossil evidence in Texas and Mexico, which supports the volcanic eruption theory. It suggests that the dinosaur extinction coincided with the final flow of lava from the eruption. The scientist Gerta Keller from the Princeton University suggests that there is more evidence for the volcanic eruption happening at the same time as the species extinction than the asteroid impact theory. However, little evidence of this is shown.
Arguments For
The Volcanic Eruption theory seems fairly likely, as although it is not the most widely believed theory, scientists do not dismiss it. There seems to be more evidence that backs up the volcanic eruption theory than the asteroid impact theory. The evidence that does back up the theory can be explained in little other ways. However, although there is evidence, it does not prove the volcanic eruption theory.
Arguments Against
However, the theory does seem fairly unreliable in some areas. For example, it is unlikely that a vast amount of volcanoes would all erupt at around the same time, and there is no scientific evidence to explain this. Also, after the extinction of the dinosaurs, there were still some small mammals and fish left alive. The volcanic eruption theory cannot explain why these animals were left while the dinosaurs were killed. The theory has been around for a long time, and although it has not been widely dismissed by scientists, it has not developed. Therefore, a lot of questions about this theory go unanswered.
Ice Ages have occurred throughout history, and the last one ended around 10,000 years ago. One theory that explains the extinction of dinosaurs is the ice age theory, which states that an ice age, which changed temperatures dramatically and froze waters, killed the dinosaurs, as they were not able to stay alive under these conditions. Many scientists link the ice age theory with the asteroid theory, saying that it was the asteroid impact, which triggered the ice age.
Evidence
There is one piece of major evidence, which supports this theory. A team of researchers, from Holland and Italy found cold-water plankton in an area in modern day Tunisia, which was previously thought to have been a warm sea. This suggests that the sea suddenly turned extremely cold around 65,000 years ago. "The fossils indicate that something suddenly made the water cold enough to support these tiny critters." This evidence links clearly with the claims made, but also supports the claim. There is little other explanation for the evidence.
"We theorise that the meteor strike produced huge quantities of sulphate particles, such as are often blown high into the atmosphere during a volcanic eruption, and these particles shielded the Earth's surface from sunlight. The decrease in solar energy ultimately caused a long cold spell, called an 'impact winter,' that persisted for years." Said Matthew Huber of Indiana's Purdue University. This claim is merely a theory, and is backed up with little evidence.
Other than this piece of evidence, none other has been found, which may be why many scientists discard this idea as unlikely.
Arguments For
The theory has been closely linked by scientists with the popular asteroid theory, which suggests that it may be likely, as the asteroid theory is one of the most respected and believed theories. The theory also makes scientific sense when explained with the asteroid theory. The evidence linked with this theory backs up the claims made, but does not prove it.
Arguments Against
Although the evidence does supports the theory, the evidence backing the theory up does not explain why an ice age would have occurred. It also does not explain why some animals were left alive after the dinosaurs became extinct. The evidence is also not solid, and can be explained in other ways. The unreliability is shown in the lack of support by scientists.
This graph (taken from ) shows how there is no record of temperatures falling during or near the time of the dinosaur extinction.
There are plenty of theories to why the dinosaurs became extinct. I have simply reviewed the three theories that I believed to be most likely, and are most respected by scientists. The three theories I have studied all have valid arguments, and without the other theories I would believe each one. Each of the theories has interesting ideas, and there is scientific evidence for each one.
However, because each of the theories has scientific evidence, if one theory was correct, the evidence for the other theories would be explained in some other way. None of the theories explain why some animals were left alive, and only dinosaurs became extinct, which shows that there is no certainty and that each theory is not quite perfected. This leaves me to ask, which of these theories is correct?
The evidence given supporting the ice-age theory certainly supports the claims made about the theory. However, different claims about this evidence could be made, and still supported.
The sediments of fossils found in the same layer as the rock certainly suggests that the volcanic eruption theory is likely. However, the unlikely-ness of this theory being 100% true and the fact that the theory has not been fully developed stop me from agreeing with this theory.
I do not think that any of the theories are 100% true, but I do believe that each theory has an amount of truth to it. However, I have decided that one theory stands out from the other two, and I agree with the scientists in saying that the asteroid theory is the most likely theory.
I believe this because the asteroid theory has the most evidence to back it up. We cannot be certain about how the dinosaurs became extinct, but the asteroid theory has the least problems and the most evidence.
“The great extinction that wiped out all of the dinosaurs, large and small, in all parts of the world, and at the same time brought to an end various lines of reptilian evolution, was one of the outstanding events in the history of life and in the history of the earth.... It was an event that has defied all attempts at a satisfactory explanation.”
EDWIN H. COLBERT, The Age of Reptiles
“If we measured success by longevity, then dinosaurs must rank as the number one success story in the history of land life.”
ROBERT T. BAKKER, The Dinosaur Heresies
Megalosaurus – The first dinosaur to be discovered.
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Each page has the references used at the bottom of the page.
Front page:
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Introduction:
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Background:
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Asteroid Impact Theory:
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Volcanic Eruption Theory:
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Ice Age Theory:
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Enchanted learning is a source for a lot of my information. In some ways it is a good source of information, for it provides a lot of information simply and it is easy to understand. However, the site is not professional, or famous, and I had never heard of it before. Although the site has been useful to me, I do not think that the information it has given me is entirely reliable.
Much like the site above, this website gave me a lot of information, but the information was not entirely reliable.
http://www.kidcyber.com.au/
This website gave a very useful timeline, and useful information about different eras. However, I am not sure that this website was entirely reliable, as it did not look professional, and I did not recognise the website address.
http://www.aerospaceguide.net/
This website was very helpful, but because of reasons previously mentioned, was not overly reliable. However, the information on this website was fairly basic, therefore is more trustworthy.
http://library.thinkquest.org/
Like other websites mentioned, this website was helpful but not entirely reliable.
http://www.wired.com/wiredscience/
This was the first website that I used that I found reliable. I recognized the name, and the website itself looked very professional.
National Geographic is a website that I have used very frequently when writing scientific or geographic reports. It is well known, professional and reliable.
Although television sites do not always supply reliable information, this particular program was very professional and reliable.
This website gave interesting information, but looked unprofessional, and I had not heard of it before. For these reasons, it is likely that the website was not very reliable.
I was not convinced that this website was entirely reliable, however it did act as a good source of information, and was quite professional looking.
I found this website to be fairly reliable. It gave a lot of useful information, and was professional and well heard of.
Introduction 3
Background Information 4
Asteroid Theory 5
Volcano Theory 6
Ice Theory 7
Conclusion 8
Bibliography 9
The dinosaurs were a species, which lasted an incredibly long time. Many scientists would argue that the dinosaurs were one of the most successful animals that have lived on Earth, as they survived for over one hundred million years. Dinosaurs were not the first animals to live on the Earth. There is evidence that some reptiles and sea mammals lived on the earth millions of years before the dinosaurs first began. However, the years when the dinosaurs are thought to be alive have since been separated into periods by archaeologists called the Mesozoic era. The era before the dinosaurs set foot on Earth was called the Palaeozoic era, and started over 570 million years ago. Scientists find out about dinosaurs and when they existed by looking at fossils, and can tell the form of the earth by looking at the layers of rock that match certain continents to each other.
245 million years ago, the Triassic period began. It was at the beginning of this period when the first dinosaurs and mammals are thought to have lived on Earth. It was not just the animals that fist set foot on the Earth at this time. Many coniferous trees (trees with needle shaped leaves) and ferns are thought to have appeared in the Triassic period. During the Triassic period, all the continents were joined together to make a giant block of land known as Pangea. The Earth’s climate was generally hot and dry at this time with the occasional rain shower.
The second period, starting 208 million years ago, was called the Jurassic period. This is when the first birds evolved. Dinosaurs were still alive and forming new species. As the huge continent Pangea began to form into smaller continents, the climate got cooler and rain was more frequent. This prompted more plant growth. There are thought to be forests of cycads, conifers and gingko, of which still exist now.
The third and final period was the Cretaceous period. This began 144 million years ago. The Cretaceous period ended when the dinosaurs became extinct, which was over 65 million years ago. When the dinosaurs died out, the first snakes and modern mammals were left. During this period of time, the major continents had formed, apart from Australia and Antarctica, which were still joined together. The first flowering plants and trees evolved during this period.
