Re: Large animal extinctions - part 1

Wallace Neslund (morbidia@chattanooga.net)
Tue, 09 Jul 1996 17:43:16 -0700

Thomas R. Holtz, Jr. wrote:
>
> timo.niroma@tilmari.pp.fi (Timo Niroma) wrote:
>
> > 1. "Where is the impact crater?"
> > A: There are three possibilities: a. in the bottom of the Atlantic
> > ocean, b. originally a, but distorted as to having been become
> > unrecognizable during these intervening 11600 years and c. there never
> > was any crater.
> >
> > a. Of the 150 or so meteorite craters known on Earth (the amount is
> > increasing in average by 2-3 craters per year) only 1 or possibly 2 are
> > found in sea despite the fact that 70% should be found in oceans. The
> > bottom of the oceans, at least in the depth of kilometers, outside the
> > continent shelves, are very difficult to investigate. So one possibili
> > ty is that the crater is deep in the North Atlantic out of the reach
> > of detectability.
>
> Except of course the seafloor has been radar mapped so that most large
> scale surficial structures are well resolved.
> >
> > b. The bottom of the Atlantic Ocean is moving about 3 cm per year,
> > which makes almost 400 m since the end of the ice age and the supposed
> > catastrophe. If we take the most likely figure for the crater, it would
> > be at most 2 to 4 km in diameter, so it would now be greatly distorted,
> > and difficult to find even if it exists in the shallower parts of the
> > western North Atlantic. This supposition is based on the assumption
> > that the extraterrestrial was an iron one. If it was stony, it should
> > have been very big (say half a kilometer in diameter).
>
> 400m distortion of a 2-4 km object would still be a pretty circular
> structure. Also, the whole seafloor is moving together, and except at
> the transverse faults, there isn't a whole lot of distortion anyway.
> >
> >
> > 2. "Where's the corollary extinction events among smaller animal &
> > plant fauna?"
> >
> > The dinosaur-killer 65 million years ago left after it no animals whose
> > weight exceeded 23 kg.
>
> Except for turtles, crocodilians, champsosaurs, and lot of fish.
>
> > The smaller the animals the more shelter they
> > could get 65 million and 11600 years ago and the smaller the animal the
> > less food in average they needed. The dinosaur-killer killed also the
> > tiny trilobites which hade thrived hundred of millions of years since
> > Cambrian, but that was most probably the result of breakup of the chain
> > of flood, boiling and poisonous oceans made a great havoc amongst
> > plankton.
>
> The trilobites died off 200 million years or so earlier, at the Permian-
> Triassic boundary. The main invertebrate extinctions at or near the
> K-T boundary are the loss of the ammonoids, inoceramids, rudistids, some
> other bivalves, many coccolithophorid linneages, some foraminifera, and
>
> In fact, all major mass extinctions save the Pleistocene-Holocene ones are
> characterized primarily by the loss of marine invertebrate lineages,
> and only secondarily of terrestrial vertebrates and other forms.
>
> > Plant fauna near the epicenter is of course burnt by the tremendous
> > heat, but the seeds in the ground survive, as can be seen after forest
> > fires.
>
> Where is the evidence for the fires? There are no known vast contemporaneous
> ash beds from this geologically recent interval. For that matter, there
> is no evidence for basinwide tsunami deposits or other correlates of
> the hypothesis. Why would the coastal terminal morraines, such as
> those on Long Island, withstand this massive, megafauna killing onslaught,
> when ordinary human activities and erosion destroy them so easily?
>
> > 3. "Your (and Brian Fagan's) hypothesis is UTTERLY ABSURD."
> >
> > As I already implied, all new hypothesis that contain odd features to
> > the recipients, may sound absurd to them.
>
> Illogical jump. Just because some hypotheses which were later accepted
> were first considered absurd does not mean all hypotheses which are
> considered absurd are later accepted.

(silly stuff cut out)

This discussion seems to be centered around the merits of an ocean or land
meteor impact. What if the meteor hit on the North Polar icecap? The ice is
both deep and firm. The supposed meteor could blow away a mile or more of
the ice and leave no crater. There would be no fires, nothing to burn. It
would, though, melt a LOT of ice and possibly initiate the end of the ice
age. How does this affect the discussion?

Wally

-- 

God knows, I don't. - Thomas Aquinas



He's so dumb, he not only doesn't know anything,

   He doesn't suspect anything. - unknown