Extinction of Dinosaurs Essay Example | Topics and Well Written Essays - 1250 words - 1

Extinction of Dinosaurs - Essay Example The disappearance of the dinosaurs is in some ways a great mystery. During the time the dinosaurs lived, many new kinds developed and other older kinds died out. Not all kinds died out at once, but by the end of the Cretaceous period, the last of the dinosaurs had disappeared. Scientists have proposed several theories to explain the disappearance of the dinosaurs. There are two main theories of Dinosaur extinction as follows: the Asteroid Theory. In 1980 the asteroid theory was proposed by Luis and Walter Alvarez. This theory is based on the discovery of unusually high concentrations of the rare metal iridium at rock levels close to the level of the last dinosaur remains. Iridium is more common in meteorites than in rocks found in the earth's crust. According to this theory, a large asteroid crashed into the earth about the time the dinosaurs disappeared. The force of the collision caused a huge cloud of dust to circle the earth. The dust blocked the sun's light for as long as five y ears. This killed many plants, and without food, the dinosaurs died too.