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What are the main theories of how and what killed the dinosaurs?

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Introduction

what killed the dinosaurs INTRODUCTION What were dinosaurs? over 165 million years; from the late Triassic period (about 230 million years ago) until the end of the Cretaceous period (65 million years ago). Dinosaurs have varied in size, with some known to have grown to a massive 15 meters tall and others to be only the size of a chicken. What does extinction mean? Extinction is the complete disappearance of a species. Extinction usually occurs if a specie on Earth cannot adapt quickly enough to a serious change in the environment, which causes death. Extinction can naturally occur; through an asteroid hitting the Earth, a huge volcanic eruption, disease or an ice age. However modern extinctions are mainly caused by human activity, directly or indirectly. For example the passenger pigeon of North America was hunted to extinction; this was directly due to human activity. As I stated before sometimes animals can become extinct due to human activity indirectly. A good example of this would be the Blue pike from the Great Lakes in Canada that became extinct in the 1970's. ...read more.

Middle

However when a volcano erupts it releases poisonous gasses into the atmosphere that could be responsible for the deaths of all dinosaurs. So, what is the evidence for and against each theory? And, which is most likely to be the actual cause of the mass extinction 65 million years ago? ASTEROID THEORY What is the background information of this theory? 1980 by Luis Alvarez and his son Walter Alvarez. Luis was a physicist and Walter was a geologist and together they claimed that an asteroid (that was somewhere between 4 and 9 miles in diameter) had hit the Earth around 65 million years ago, causing the extinction of the dinosaurs. It also killed plants (though not roots or seeds) leading to, ultimately, many species of animals and dinosaurs dying and becoming extinct. The above diagram is the scientific speculation of the Alvarezes. Luis Alvarez said also that 'the pollution in the atmosphere would settle on the ground all over the Earth, creating the layer of iridium that he and his son discovered in Italy.' ...read more.

Conclusion

This would have decreased the temperature of the Earth dramatically. After this, global fires would release considerable amounts of CO2, resulting in the temperature of the Earth increasing. This CO2 would later cause chemical reactions that would have created acid rain that covered the entire Earth. VOLCANIC THEORY What is the background information of this theory? volcanoes in India 65 million years ago all erupting consecutively, CO2 was released into the atmosphere. Which let no oxygen to the dinosaurs. CONCLUSION I believe that there is very strong and plausible evidence for both the Asteroid Impact theory, put forward by Luis Alvarez and Walter Alvarez, and the Volcanic - Greenhouse Effect Theory, put forward by Dewey McLean. I have looked carefully at the evidence for both of the theories and come to the conclusion that they both caused a mass extinction 65 million years ago. I think that the only way that a mass extinction could have been caused 65 million years ago is if both events happened in a relatively short amount of time. ...read more.

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