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Currently, the main suspect behind this catastrophe is a cosmic impact from an asteroid or comet, an idea first proposed by physicist Luis Alvarez and his son geologist Walter Alvarez. Scientists later found that signs of this collision seemed evident near the town of Chicxulub (CHEEK-sheh-loob) in Mexico in the form of a gargantuan crater more than 110 miles (180 kilometers) wide. The explosion, likely caused by an object about 6 miles (10 km) across, would have released as much energy as 100 trillion tons of TNT, more than a billion times more than the atom bombs that destroyed Hiroshima and Nagasaki.
However, further work suggested the Chicxulub impact occurred either 300,000 years before or 180,000 years after the end-Cretaceous mass extinction. As such, researchers have explored other possibilities, including other impact sites, such as the controversial Shiva crater in India, or even massive volcanic eruptions, such as those creating the Deccan Flats in India.
http://news.yahoo.com/asteroid-impact-ki...46621.html