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Re: More Than Meteor Killed The Dinos
At 04:32 2006-10-25, Deinonychus47@aol.com wrote:
Based upon the stream of comet impacts on Jupiter, could not a pair of large
meteorites or comet fragments) have impacted the Yucatan at the end of the
Cretaceous Period and the evidence for what would have been the first crater
been obliterated by the close-behind second object? If a comet, it could
been torn apart by the gravity of Jupiter or even Saturn and a couple of
fragments sling-shotted at the Earth.
Multiple asteroids are fairly common, so multiple impacts certainly
happens. However these would usually occur within seconds of each other,
and not be noticeable as multiple except near the impact sites. Co-orbital
comet fragments could certainly impact over a period of several hours in
different parts of the World. However it is doubtful if the fallback
deposits far from the impact sites would be separable in this case either.
In any case the Chicxulub impactor was a chondrite, not a comet as shown by
the composition of the impact debris.
The only two mechanisms that would result in multiple impacts spread out
over a longish period (e. g. 300 000 years) are:
1). A comet shower caused by disturbance of the Oort cloud (e. g. by
another sun passing close to the solar system)
2). A largish collision in the asteroid belt
3). A change in the orbit of one or more of the outer planets causing
"resonance sweeping" in the Kuiper and/or asteroid belt.
It seems likely that either 1) or 2) may have caused the striking
concentration of impacts in the late Eocene.
3) might seem outlandish but is the most likely explanation for "the late
heavy bombardment" ca 3800-3900 MYA BP
For that matter, what proof is there that the initiation of the Deccan Trap
lava flows was not caused by a meteorite/comet fragment impact?
It is indeed possible that *very* large impacts might generate lava on a
large scale. There is no definite proof that this has happened on Earth
(except on a small scale at Sudbury), but there is one clear case on Venus,
so it can happen.
It has been suggested that The Siberian Traps, the Ontong Java Plateau or
the Bushveld complex of South Africa might have originated in this way, but
the arguments aren't very strong.
In any case, as others have already pointed out, Deccan volcanism started
well before the end of the Cretaceous. Also note that there are dinosaurs
and other typical maastrichtian fossils in the intertrappan beds, so at
least the early part of the Deccan eruptions did not have too catastrophic
effects even on the (then insular) Indian continent. However it is clear
that even fissure eruptions of modest size have severe effects over
considerable areas as shown by the Laki eruption 1783 which caused mass
mortality in sheep and cattle and a consequent famine on Iceland.