The Cause of the Mass Extinction in the Late Cretaceous Period
Dinosaurs first appeared around 245 million years ago, and they lived for 180 million years. Then suddenly, 65 million years ago they went extinct. Not only did all the dinosaurs die out, but also up "to 75% of all marine genera were lost" ("mass extinction"). This leaves scientists wondering about what could have led to this mass extinction in the Cretaceous Period. They have collected evidence from fossils and earth’s geography, to propose some theories Scientists believe that the dinosaur extinction was due to either the collision of a massive asteroid, the eruptions of the Deccan Trap volcanos, or the epidemic of diseases.
The collision of a massive asteroid is believed to be have instigated the dinosaur elimination. First of all an asteroid is a "minor planet, small body orbiting the sun" ("asteroid”) .There are many asteroids in space. Scientists believe that earth was hit by an asteroid that was over six miles wide, or that earth was hit by a comet travelling 18 miles per second. They contemplate that when the asteroid hit earth’s surface, a great amount of debris and sulfur rose into the air. They believe that this blocked the suns light from hitting the earth. In result, all the dinosaurs and 70 percent of all animals and plants died (“What Killed the Dinosaurs").
Scientists have backed up their theory that earth was hit by an asteroid, with a great amount of evidence. In 1980, Walter Alvarez of the University of California at Berkeley discovered deposits of iridium in sediments that dated back from the Cretaceous period, which was when the mass extinction occurred. "Iridium is rare on earth, but is concentrated in meteors and comets" ("mass extinction").This led to proposal of the asteroid theory since the discovery of the iridium sediments proves that an asteroid had hit earth. Then in 1991, the Chicxulub crater was found on the Yucatan peninsula in Mexico. This crater was 112 miles wide and was large enough to be created by an asteroid with a diameter of 6 miles, which would have caused a mass extinction (“mass extinction”). They also discovered a great amount of sulfur in the craters soil which has brought up the idea that sulfuric acid rose to the atmosphere after the asteroid hit earth. This many have created a thick haze which would have made earth temperature decrease by 20-30*F (“mass extinction”). Therefore, many plants would die which would lead to the extinction of herbivores. Then the carnivores would die. The eruption of the Deccan Trap volcanos may have also triggered the mass extinction. ("Volcanoes, Not Meteorite, Killed Dinosaurs, Scientist Argues"). Some scientists believe that about 70 million years ago, huge volcanic eruptions in the Deccan Traps in India, which at the time, was located off of East Africa coast in the southern hemisphere, led to the mass extinction (Ward 170). The Deccan Trap Volcanos cover up 6000 miles on India and if they had erupted, it would have definitely caused a mass extinction (“mass extinction”). Scientists have
proof that they erupted for 800,000 years ("mass extinction").They believe when the asteroid hit the earth, its impact shook earth’s crust and generated volcanic eruptions. They also believe that volcanic ash made of carbon and sulfur dioxide rose into the air. This would have blocked the sunlight from hitting the earth and would have led to the dying out of many plants and animals. When the sunlight was blocked from hitting the earth, this caused the sea water to get trapped in the polar caps, due to global cooling. In result, inland bodies of waters lowered, which changed the environment (“mass extinction”). The dinosaurs and other animals would not have been able to adapt to this sudden change. Furthermore, gases that were released into the air because of these eruptions created acid rain and exhausted the ozone layer (“mass extinction”). This would have also caused the mass...
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