From: Mike Lorrey (mlorrey@datamann.com)
Date: Tue Jun 26 2001 - 13:01:49 MDT
Technotranscendence wrote:
>
>
> > * it wasn't all birds. Actually birds were almost
> > entirely wiped out. Only one group of shore birds
> > survived. They then radiated to current bird niches.
> > The near-elimination of birds *may* have provided the
> > opportunity for bats to emerge.
>
> I was not aware of this.
>
> > I just heard yesterday of a discovery of a suspicious
> > carbon layer at the Triassic/Jurassic mass extinction
> > boundary.
>
> This might support a global wildfire resulting from an impact.
THe fact that this layer also has a significant iridium layer says it
cannot be explained by volcanic activity.
>
> > An interesting point is that the end-
> > Cretaceous and end-Permian extinction match up with
> > *both* massive bolide impacts *and* bogglingly large
> > flood basalts.
>
> Yeap. Archibald does not dispute this, though there is some disagreement
> over timing. On page 145 of the book, he even charts the level of eruption,
> but argues on 144 that the "eruptions... were episodic -- not continuous."
> The flood basalts range in age from 69 to 65 million years old. If the
> impact is placed at 65 million years ago, this means a good portion of high
> level volcanic activity was already happening before the impact. This does
> not completely rule out an impact as the [nonavian] dinosaur killer, though
> it might point to an accomplice.
Significant volcanic activity would have resulted from a change in the
orbit of the moon caused by the influence of a number of close flybys
over several million years of the object that wound up colliding at 65
million years. For example, an impact or flyby of the moon which would
have caused it to either come closer to earth (increasing tidal stress
but decreasing tortional stress on earth's rotational velocity) on a
faster orbit or else move away from earth into a slower orbit (thus
decreasing tidal stress but increasing tortional stress on earth's
rotational velocity) would have significantly affected tectonic forces
during that period. Also a change in the moon's angle of inclination
would have caused similar release of tectonic forces.
If the body that impacted the Yucatan was a fragment of a calved body
that impacted or grazed the moon on previous occasion, this would
explain the time disparity.
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