Data Bases • Custom Term Papers • Free Term Papers • Free Research Papers • Free Essays • Free Book Reports • Plagiarism? Links • Top 100 Term Paper Sites • Top 25 Essay Sites • Top 50 Essay Sites • Search 97,000 Papers @ DirectEssays.com • Search 101,000 Papers @ ExampleEssays.com • Search 90,000 Papers @ MegaEssays.com Free Essays • Term Paper Sites • Chuck III's Free Essays • Free College Essays • TermPaperSites.com • My Term Papers • Get Free Essays • Essay World • Planet Papers	Search Lots of Essays Back to Subjects - Science Dino Dino Controversy surrounds the extinction of the dinosaurs. According to one theory, dinosaurs were slowly driven to extinction by environmental changes linked to the creeping withdrawal of shallow seas from the continents at the end of the dinosaur era. Proponents of this theory propose that dinosaurs dwindled in number and variety over several million years. An opposing theory proposes that the impact of asteroid or comet caused catastrophic destruction of the environment, leading to the extinction of the dinosaurs. Evidence to support this theory includes the discovery of a buried impact crater (thought to be the result of a large comet striking the earth) that is 200 km (124 mi.) in diameter in the Yucatan Peninsula of Mexico. The spray of debris was blown from the edge of the crater. The debris has been found over large regions of North America. Comet enriched material from the impact’s fiery explosion was spread all over the world. With radiometric dating, scientists have used the decay rates of certain atoms to date the crater, spray of debris, and fireball layer. Using similar techniques to date the dramatic changes in the record of microscopic fossils, they have found that the impact and the dinosaur extinction occurred nearly simultaneously. Although great amounts of ash suggest that most of North and South America was devastated by fire from the impact, the longer-term environmental effects of the impact were ultimately more deadly to life than the fire. Dust blocked sunlight from the earth’s surface for many months. Burned sulfur from the impact site, water vapor and chlorine from the oceans, and nitrogen from the air combined to produce a worldwide fallout of intensely acidic rain. Scientists postulate that darkness and acid rain caused plant growth to die. As a result, both the herbivorous dinosaurs, which were dependent on plants for food, as well as the carnivorous dinosaurs, which fed on the herbivores, died out. On the other hand, animals such as frogs, lizards, and small insect-eating turtles and mammals, which were dependent on organisms that fed on decaying plant material, were more likely to live. Their survival indicates that, in most areas, the surface of the earth did not freeze. These our just some of the many theories about the extinction of the dinosaurs. It is hard to pick one theory over the other due to how confident people are with the theory they think is true. I am more lenient toward the theory that states that an asteroid or comet hit the earth but I could be wrong, it is just a theory. Bibliography: Word Count: 424
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