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Re: DINO EXTINCTIONS
The point that I have been trying to make is that something big hit the
earth, and caused quite a bit of damage. How much damage it caused directly
is up to debate. (For instance, you say that that you don't think a little
rock could cause that much damage, then you say that the damage would be too
severe for anything to survive).
1) A large object (size of Manhattan Island) DID hit the earth on
what is now the Yucatan Penisula of Mexico, near the modern town of
Chixilub. Based on geologic studies of the site, it came in at an angle.
This usually means more debris would be ejected from the crater than a
2) The object hit the earth around 65 mya.
3) Lots of things changed on earth around 65 mya - climate, land vs
sea ratios, etc.
4) Lots of creatures died, and lots of genera went extinct around
5) There is current no known other method that could destroy so many
genera, and yet leave survivors (in the pattern that we know exists).
6) NO EXTINCTION THEORY FOR K/T EXPLAINS ALL THE EFFECTS!!!
To me, it seems likely that a large object would cause all sorts of
changes throughout the world, yet not ALL of the changes, by themselves,
would be devastating. However, to many individuals, and to many genera the
sum total effects *were* devastating.
I, for one, think that the damage done by the impact was *sufficient* to
start a chain of events that led to the extinction as we see it today. It
did not need to cause the end of all life, or even the end of all vertebrate
life - which we know it did not do.
Someone wrote in one of the many replies to this series of topics, that
maybe what we should be looking at is what common factors the survivor
genera and species had that would enable them to survive such a cascade of
events triggered by a large impact. I heartily second that idea.
By the way, Peter, I don't think that the effects of dust in the
atmosphere lasted all that long - maybe 3-4 months, so that within a year
the sky would be nearly back to normal. (Except, as I said, the Oxygen
levels may have been reduced from 35% to 29%. This leads me to suggest that
the non-avian dinosaurs may have evolutionarily changed their lungs to
expect the higher O2 percentage, so that, if the baby dinos survived the
initial effects, they would have two problems facing them - Lack of parental
protections and help, and as they matured, their lungs wouldn't work
correctly, causing them to die as they grew older).
From: Tetanurae@aol.com <Tetanurae@aol.com>
To: email@example.com <firstname.lastname@example.org>; email@example.com
<firstname.lastname@example.org>; email@example.com <firstname.lastname@example.org>
Date: Tuesday, August 11, 1998 9:29 PM
Subject: DINO EXTINCTIONS
>Betty Cunningham wrote in reply to my doubts about the tiny rock killing
><<I have no difficulty imagining some natural disaster of an even larger
>Of course, yes, a rock falling from the sky would cause devistation in the
>area, local forest fires, tsunamis, etc and probably kill a lot of stuff
>locally. In fact, it would kill everything locally.
><<When Mt St. Helens' erupted ash was deposited across a 4 state swathe
>and we had red sunsets and haze due to the ash in the atmosphere.>>
>A slight red haze does not make a baking sky for months afterward. Oddly
>enough, I was very close to Mt Saint Helens when it errupted and got no ash
>my yard. The only reason it covered 4 states, is because the wind was
>Allan Edels wrote:
><<The multiple effects that I detailed (and there are more)
>are related to a sufficiently large rock (or whatever) hitting the earth.
>are in science), but that tiny speck could throw up into the atmosphere a
>HELL of a lot dust, etc.>>
>The point you fail to see, is that if you keep making the nuclear winter
>effects bigger and the atmospheric baking longer and hotter, and the forest
>fires greater, you simply exterminate everything. The greater the effects
>are, the more likely you will kill everything.
>No doubt a really really big rock from the sky would be devistating and
>everything, but it cannot be so selective as to kill say enantiornithines
>not neornithines, or ammonites and not nautiloids. Baking skies and
>forests do not selectively kill of basal ornithopods instead of basal
>primates, or avisaurids and hesperornithids instead of anseriformes: they
><<The effects listed need not have all ocurred to their greatest possible
>extent, but would be enough to upset the ecological balance of the entire
>planet, so that the extinctions would occur as an offshoot of the impact.>>
>But the extinctions would not have been selective, they would have
>or destroyed everything, not whole groups of taxa, while leaving others
><<Feel free to see no causative link, others will. Just as in some areas
>where you see a causative link, some others will not. I personally,
>obviously, lean towards seeing that link in this case.>>
>Your causitive link is flawed though. It would have debistated everything,
>not selective groups of taxa, while leaving closely related, and extremely
>similar ones untouched.