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Re: craters and the k/t (Norm King)



[My apologies if this went out before, but I didn't see it in the
 archives.  -- MR ]

Norm King wrote:

> I think the presumed tsunami deposits are actually more in dispute than 
> the subsurface feature that is hypothesized to be the impact crater. 

Can't tsunamis also be caused by the movments of the ocean plates? There
was quite a bit of volcanic activity around the K-T...

> It just happens to be so close to the K-T boundary that its position
> is indistinguishable from that level.

As I understand it, Chixalub is a bit too old for the K-T. Didn't they
find undisturbed sediment from the later Maastrican (sp?) *inside* the
thing? If it was volcanic or extraterrestrial, anything from that age
should have been *blown out*.

> The data suggest a classic impact crater, with many (all?) of the 
> subtleties that should be observable for a buried impact crater.  People 
> who know how to assess these things claim that the presumed crater is 
> large enough for the impact to have had an effect on the environment that 
> could have adversely affected life on a global scale.

Of course, this is were we get to the parts of the impact theories I have
the most trouble with. Where is the evidence that an impact would cause
such long term damage?? Large impacts in the past have never caused mass
extinctions-or any extinctions. It's all guesswork backed up with more
guesswork.

> Recently, a chunk of meteorite was brought up in a core from the eastern 
> Pacific from a location that would have been almost directly down range 
> from the impact, given the trajectory which had been calculated for the 
> impacting object based on independent data.

But we find meteorites all the time all over the Earth. How can they
really tell?

> I don't know about the rest of you, but finally the number of 
> observations that fit together so nicely in the impact scenario become so 
> great that I find it impossible to believe that they are all 
> coincidences. 

Well, I think if you take into consideration volcanic activity and the
fossil record, the impact theory is pretty weak. As far as the fossil
record goes, we find a history of decreasing diversity and numbers
approching the K-T. We also never have found an increase of fossils after
the K-T that would suggest a sudden massive death event. Also, why would
the effects of the impacts effect some animals and not others?

I still think the best bet was simple, geological changes and the
resulting enviromental changes *over time* was the cause of the mass
extinctions. We have solid proof of the effects such changes, and proof
of such activites. 

If there was an impact, it could have occured after everything was dead.
In this case, to prove cause and effect, the timing has to be *just
right*. That is really hard to pin down. 

Oh well, there has to be a skeptic in every crowd, huh? It's nice to talk
about this stuff without fistfights occurring for a change. My biggest
gripe about the article is that it is dangerous to assume theories that
are still under considerable research. Also, I'd like to see a few
non-impact articles in these magazines. But hey, it's not as dramatic. You
need those exploding dinosaurs on the cover to sell issues. :)

-Sherry