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Unformatted text preview: large extinction event that killed off 90% of all species on Earth. Would you expect to find a crater? C. No - the crater would have eroded away by now. Clicker Question #3: If something like Tunguska happens every ~100 years, how come we haven't heard about it [in previous events, say 200 or 300 or 400 years ago]? C is the current best guess, though one could argue that A and B are possible answers....
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- Fall '08