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To: cogitator

I have no idea what you just said, but it does seem ironic.


11 posted on 11/28/2005 7:41:24 PM PST by ChocChipCookie (Democrats: soulless minions of orthodoxy.)
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To: ChocChipCookie
I have no idea what you just said, but it does seem ironic.

I can explain. The controversy regards the cause of the extinction of the dinosaurs. For a long time, the main idea was climate change near the end of the Cretaceous, basically a slow process. The Alvarez team determined that the K/T boundary (Cretaceous/Tertiary -- I've never known why K was the Cretaceous letter) had an iridium anomaly most likely caused by an asteroid impact, so they suggested that an asteroid impact wiped out the dinos. This was initially viewed as crackpot, slowly gained credibility, and took the lead when the big Chicxulub impact structure on the Yucatan was identified as being just the right age. But there are problems with the theory -- mainly that not everything died out right then, and though catastrophic, an impact is so short-lived that it doesn't seem that it could accomplish full extinctions. So it's been noted that the Deccan Trap flood basalt period -- when the Indian subcontinent passed over the "plume" of volcanic activity currently located on the island of Reunion, east of Madagascar -- took place for about 1 million years just before the Chicxulub impact. Flood basalts are huge outpourings of lava, accompanied by large releases of volcanic gas.

Put the two together, and it appears there was a million-year long period of altered climate caused by volcanic activity, finishing with a powerful impact that could have pushed a lot of species with tenuous holds on existence over the edge to extinction.

This crater is a recent impact on the Deccan Trap flood basalts, so it superimposes the two active factors that appear to have caused the end of the dinosaurs and which mark the end of the Cretaceous period.

13 posted on 11/29/2005 8:27:20 AM PST by cogitator
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