250 Million Years Ago, Rising Greenhouse Gas Levels Set Off Catastrophic Changes
In 1980, scientists Luis Alvarez and his son, Walter, proposed a new explanation for the dinosaurs' disappearance 65 million years ago: a meteor strike. Initially, the idea was met with resistance. But the evidence was convincing: a sediment layer high in iridium, an element common in asteroids, was found the world over, along with a 110-mile-wide impact crater in the Yucatán of the same age. What started as a fringe idea has gone mainstream.
Now scientists are rethinking another of earth's... Full Story
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