Nobody knows for sure exactly how the dinosaurs became extinct. However scientists have speculated for decades about possible events that caused the dinosaurs to die out. Possibilities range from asteroids, to volcanoes, to climate changes. One of the more popular or well-known extinction theories involves the belief that an asteroid struck the Earth, causing devastating effects, and triggering mass extinctions around the end of the Cretaceous period.
The asteroid impact extinction theory began in 1980 with Luis and Walter Alvarez, a father and son team. They theorized that an asteroid struck the Earth at the close of the Cretaceous period, causing devastating effects and mass extinctions (Botzer 2004). Then, in the early 1990s, Alan Hildebrand, an associate professor at the University of Calgary, discovered the Chicxulub crater on the Yucatan peninsula in Mexico. This crater was 186 miles in diameter and six miles deep, and it was created when an asteroid hit the Earth approximately sixty-five million years ago. This asteroid is said to have strike the Earth with a force of 100 million to 300 million megatons of TNT (Recer 1993). With the discovery of the crater came the theory that this particular asteroid killed the dinosaurs and caused other mass extinctions. It was believed that the impact of the asteroid increased temperatures to above 20,000 degrees, sent massive tidal waves and earthquakes across the Earth, and filled the atmosphere with dust and chemicals, which blocked the sun. It was then hypothesized that the blocking of the sun led to drastic climate changes, allowing the Earth to cool, and creating a climate too cold for the warm-blooded dinosaurs (Re...
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...me 300,000 years after the impact. We still don’t know for sure what happened to the dinosaurs, and there is a possibility that we never will know. However, several signs indicate that the Chicxulub asteroid probably created conditions that begin the decline of the dinosaurs. This was most likely followed by a second large impact, or several smaller impacts that caused drastic changes in the environment and resulted in the mass extinction.
Botzer, Angela. “That Asteroid Didn’t Kill Dinosaurs, Study Says.” National Geographic News. 9 Mar 2004. 31 Mar 2004 http://news.nationalgeographic.com/news
Keller, Gerta, et al. “Chicxulub Impact Predates the K-T Boundary Mass Extinction.” PNAS Online. 2 Mar 2004. 5 Apr. 2004 http://www.pnas.org/cgi
Recer, Paul. “Crater Theory: Big Space Rock Did in Dinosaurs.” Times 17 Sep. 1993: National.
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