What killed off the dinosaurs?

Thirty years ago, UC Berkeley geologist Walter Alvarez offered his revolutionary answer to that question and incited one of the liveliest controversies in modern science.

Now, an international team of scientists says today the issue is settled: Alvarez was right.

In 1980, Alvarez and his colleagues at Berkeley theorized that a monstrous asteroid 10 miles wide slammed into Mexico’s Yucatan Peninsula about 65 million years ago and dug a crater 60 miles wide and 15 miles deep. The impact sent up a huge cloud of ash, soot, pulverized rock and sulfurous steam that darkened the skies for years like a nuclear winter, dooming more than half the world’s life on land and in the oceans – microorganisms, plants and animals.

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