The Extinction of the Dinosaurs

The proof of the dinosaur's existence originally comes back to fossils (preserved remains of organisms) found in the ground. It is suspected that the first dinosaur fossils were discovered over 2000 years ago, by the ancient Greeks and Romans. However, the first recorded dinosaur fossil found was in 1676, discovered in England. 1 Since then, the continuous fossil discoveries gave evidence that at some point above land meat-eaters and plant-eaters roamed the earth eating and sleeping, and sometimes hunting.From two different sources2, I have found out that the last of the dinosaurs were estimated to have become extinct over 65 million years ago.

However, although both sources state the same information on how long ago the dinosaurs were alive, they are not very reliable sources, as they are not well known or professional. Since they were first discovered the question of why they are not alive today has been debated again and again, with no definite answers.This Case StudyMany theories have been made, and I will include the major well known theories in this case study. I will include details about the theory as well as how believable they are in my opinion, and others opinion. I am aiming to find out details about each of the major theories, as well as how reliable and likely each theory is, and who believes in the theories. None of the theories that have been made are proved so this gives an opportunity to decide which of the possible theories that I believe to be the most likely.

This case study is aimed at the general public, and for people who do not know very much about dinosaurs, but are interested. This could include students as intelligent as the average year 9 or above as well as adults.One theory that explains why the dinosaurs became extinct is the Asteroid theory. This theory is one of the most common and widely believed theories about extinction of the dinosaurs. Although asteroids are rare, the theory is that an asteroid hit the Earth, ending dust and steam into the atmosphere. Scientists estimate that the asteroid was 4-9 miles (or 10km) wide and have found evidence supporting the theory that the asteroid hit the Yucatan Peninsula, in the Gulf of Mexico.

The asteroid is believed to have caused massive forest fires, tidal waves, and huge storms and perhaps most importantly blocked out the sunlight for at least six months. This left the dinosaurs no chance of surviving, as there was no sunlight and plant life, which is essential to life.EvidenceThere have been various pieces of evidence that suggest the asteroid impact theory is likely. One discovery that convinced many scientists was the discovery of rare elements such as osmium, gold, platinum, nickel, cobalt, palladium and idium in the deep layer of rock, where the asteroid is thought to have landed. These elements are rarely found on Earth, but are often found in asteroids. This evidence suggests that an asteroid collided with Earth, supporting the asteroid impact theory.

Also, as the elements were found deep below the surface, this suggests that the asteroid hit the Earth a long time ago, also supporting the asteroid impact theory. These claims are supported fairly in the evidence given.Another piece of evidence that suggests that the asteroid theory is likely is that the fossils of dinosaurs, reptiles and sea animals are all found above the layer of sediments that the asteroid is thought to have created. The leader of the research team that discovered this evidence, Gerta Keller of Princeton university said "we know that between four and nine meters of sediments were deposited at about two or three centimetres per thousand years after the impact.

The mass extinction level can be seen in the sediments above this interval." This evidence suggests that there was a major extinction after the asteroid impact theory. The claim that Gerta Keller has made - that it was the asteroid that caused the extinction - is supported in the evidence given.Arguments ForThe Asteroid theory overall seems like a likely theory, as many scientists believe it, and the evidence shows that the idea has proof to back it up.

The discoveries about the asteroid impact continue, as the research is not over. This shows that scientists are still investigating the matter. From this, I can tell that the theory seems likely, as if it were not; scientists would not spend any time researching it. Excluding the views of others, including scientists, the asteroid impact theory still seems likely, as the dinosaurs were such a successful and strong species and would therefore it would take a large impact or event to kill out the entire species.

Arguments AgainstHowever, 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.3ComparisonBoth 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.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.EvidenceSome 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 ForThe 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 AgainstHowever, 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.4 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.

EvidenceThere 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 ForThe 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 AgainstAlthough 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.5This graph (taken from www.

casualpc.com/HistoryInThrees/charts.htm) 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."