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Re: "Forensic" Evidence Of Dinosaur Killer

Toby White wrote
>jwoolf@erinet.com wrote:
>><sigh> Another expert hypnotized by the Doomsday Scenario.  Doomsday
>>impact theories are disproved by the fossil evidence.  Burn away the
>>surface vegetation and you wreck the terrestrial ecosystem completely. 
>>The ecological collapse shown in the fossil record is extensive,
>>claiming all animals over about ten kilos in mass and many smaller ones,
>>but it is _not_ complete.  Some groups survived.  And the survivors
>>included a large number of small endothermic animals, which require
>>_lots_ of food.  No plants, no food.  No food, all those little mammals
>>and birds would have starved.  They didn't starve.  Ergo, there must
>>have still been plants around. 
>>Not convinced?  Consider oxygen.  Firestorm = lots of oxygen suddenly
>>gone from the air.  It would have taken decades or centuries for the
>>oxygen to build back.  In the meantime, what happened to all those
>>oxygen-breathing animals?
>There seems to be a substantial hole in your reasoning.  That hole is
>approximately 300 km in diameter and is located in the Yucatan.  
The original article on which the Guardian story was based, was published in
Nature (Morgan J, Warner M & The Chicxulub Working Group, Size and
morphology of the Chicxulub impact crater, Nature 1997; 390: 472-76). In that
the authors claimed that the diameter of the transient crater was only 100 km.
The size of the transient crater is correlated closely with the amount of energy
released. More interestingly, the prominent 170-195-km ring is not the crater's
slumped rim, but instead a fault scarp with a vertical offset of about 0.5 km.

See also the review in the same issue of Nature (Melosh H J, Multi-ringed
revelation, Nature 1997; 390: 439-40).

Gautam Majumdar                 gautam@majumdar.demon.co.uk