Did a Meteorite Cause the Extinction of the Dinosaurs?

Did a Meteorite Cause the Extinction of the Dinosaurs?

Introduction

This case study will try to answer the often debated question: did a meteorite cause the extinction of the dinosaurs? This report will be split into three sections: Scientific theory, evidence and the conclusion. In the scientific theory section, I will talk about the basic outlines and concepts that brought this theory about. The evidence section will tell readers of what evidence is there to support the theory, ranging from the discovery of the K-T boundary to meteorite impact craters. Finally, the conclusion will summarise all the information I have gathered concerning the subject and I'll be giving my own opinion of the matter of “Did a meteorite wipe out the dinosaurs?”

Scientific Theory

This theory of the dinosaur's extinction was developed by Walter Alvarez and his father, Luis Alvarez. Sixty-five million years ago, at the end of the Cretaceous, nearly fifty percent of all life on Earth along with all non-avian dinosaurs suddenly became extinct. Walter Alvarez and his father suggested that a large asteroid collided with the Earth causing large dust clouds to gather around the atmosphere. This would block the sun's rays and cause plants to die; the herbivorous dinosaurs would starve to death and carnivores would have feasted on the corpses but when that food supply ran, out the carnivores had to look for an alternate food source. They resorted to cannibalism. In order for a meteorite to cause such damage it would need to be a considerable size, roughly about the size of a large city or even that of the moon.

Evidence

While digging in an Italian gorge in the 1970's, the Alvarez' discovered limestone in the walls of the gorge; the limestone was dated to 65 million years ago. This wall is dubbed the K-T boundary as it represents the end of the cretaceous and the dawn of the tertiary period.

In the late 1970's, geophysicist Glen Penfield discovered a large crater that is more than 180Kms in diameter, near the Mexican village of Chicxulub. This is known as the Chicxulub crater and it has been dated back to 65 million years ago. As expected some discrepancies have arisen concerning the subject such as scientists argue whether a meteorite impact really is to blame for the dinosaurs' demise. Other opposing theories are that sea levels began to rise and this would have drowned most land animals. Another is that the dinosaurs simply could not adapt to the climate changes and it has been proven that there was increased volcanic activity towards the end of the cretaceous period.

The increased volcanic activity may have been brought on by the meteorite impact, because the theory states that, like an earthquake, the impact would send a huge seismic wave through the planet and push up mountain ranges from within the Earth. Evidence from the fossil record also suggests that two million years before the end of the cretaceous period, at least 15 dinosaur families had already died out.

Conclusion

In conclusion, I think the most likely theories are either the meteorite impact or increased volcanic activity. Most scientists agree that one of the two theories , if not both of them, are to blame for the extinction of the dinosaurs and those who do not believe in either theory still try to find evidence to support their own concepts. As for my opinion, I think that volcanic activity is initial cause for the extinction but the meteorite colliding with the Earth increased the volcanic activity and blocked the sun's rays; causing all plants to die. The herbivores would die from starvation and the carnivores would then consume the corpses. However, once this food source had diminished, the predators would have to look for an alternate food source and resort to cannibalism. The idea of cannibalism also supports the theory of the dinosaurs not being able to adapt to changes in their environment.

Bibliography

• en.wikipedia.org/wiki/Cretaceous-Tertiary extinction event -Accessed 06/10/ 09

• en.wikipedia.org/wiki/K-T boundary-Accessed 06/10/09

• en.wikipedia.org/wiki/Chicxulub crater - Accessed 08/10/09

• en.wikipedia.org/wiki/Luis Walter Alvarez - Accessed 08/10/09

• en.wikipedia.org/wiki/Walter Alvarez - Accessed 08/10/09