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Was: SPECULATION: pterosaur extinction versus bird survival
This list is really not the place for disputes about impact science, and
I did not start any discussion along that line; but I feel it incumbent upon
me to offer the following corrections to what Marilyn Wegweiser said (to the
list) on the topic, today:
>Sorry..... but recent discussions I have been having with several
astrophysicists lead me to currently say, despite popular depictions,
that there are good chances are that "it" probably didn't "impact" at
vaporized some distance above the earth, large chunks of it falling
out spectacularly, etc. (e.g., Tunguska)...<
Wrong. You will get reliable information on the K/T event by studying
the published works on this matter by impactologists who have devoted years
to related studies. All the evidence contradicts any idea that the K/T
object just vaporized in the atmosphere. Sure, the object totally
vaporized, but on and within earth's surface, not high in the atmosphere.
My knowledge of the crater-forming K/T event does not originate in what you
call "popular depictions", and "popular depictions" is an unfair way to
characterize the quality and extent of the scientifically published analysis
of the impact under discussion. Have you ever seen the gravity map images
of the K/T impact structure? The effect of a purely atmospheric
vaporization of a cosmic body? LMAO, and the community of impact researchers
laughs with me.
Those who think a 5 to 6 mile-in-diameter chondritic mass (the
calculated size range and type of the K/T object) would be completely
vaporized by passing at virtually unimpeded cosmic velocity through anything
so relatively thin as the earth's 20-mile-thick densest atmospheric layer
(only about four times thicker than the cosmic body, itself), simply have
not done their home work, "astrophysicists" or not.
Incidentally, the K/T impact energy was several orders of magnitude
greater that the energy released during the relatively 'pipsqueak' Tunguska
event, in which an object (possibly a small comet) almost totally vaporized
in the atmosphere.
You say, "...large chunks of it falling out spectacularly, etc. (e.g.
Tunguska)..." [Your parenthetical example.]
If I'm reading your intended meaning correctly, wrong again. No
large chunks of any kind fell out of the sky (to earth) in the Tunguska
event. Tiny spherules of magnetite (an ablation condensate) and some of
tiny spheres and/or fragments of metallic iron were found and seem to have
been associated with the atmospheric explosion there. That's about all that
reached the ground, excepting the massive shock wave. (Yes, I've read the
official Russian reports, etc. and watched all updates carefully via the
official publication the Meteoritical Society, namely Meteoritics and
So, there you have it: The impact of earth's surface by a chondritic
body, resulting in the extinction of all species of non-avian dinosaurs and
pterosaurs (plus a vast array of other organisms, large to microscopic).
The track record in South America indisputably shows an abundance of
non-avian dinosaur species living right up to the K/T impact. At least one
bone census in North America tells the very same story. It is repeated
If that extinction had not happened, you and I might not be here. Come
to think of it, maybe that awesome, fateful event 65 million years ago
really was our luckiest day of all.