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Re: Vredefort



Well,..again, we`re probably talking (past each other) about different
orders of magnitude here. I still have to familiarize myself with the
terminology here (teratons of tnt and the like), but plan to look into it
further. Just wondering if the Permian-Triassic transition could have been a
somewhat larger bolide strike in the "pre-Pacific" region that didn`t cause
as much surface damage as it would penetrate the relatively thinner crust,
and <<perhaps>> set up some currents in the mantle that would initiate the
breakup of Pangea......just a thought.
-----Original Message-----
From: Stanley Friesen <sarima@ix.netcom.com>
To: dinosaur@usc.edu <dinosaur@usc.edu>
Date: Sunday, November 28, 1999 10:49 PM
Subject: Re: Vredefort


>At 07:37 AM 11/26/99 -0500, Larry Febo wrote:
>>>
>>>Certainly a large enough impact could wreak havoc on the crust, and even
>>>overturn large parts of the mantle.  No such impact has occurred in the
>>> last 3.5 billion years, of this we can be fairly certain.
>>>
>>
>>I`m not so sure. Much may be hidden because of erosion on the Earths
>>surface, or obliterated by subduction on the oceans floor.
>
>No doubt.  But an impact large enough to seriously disrupt the crust and
>overturn part of the mantle would do far more than just make a crater.  The
>effects would be unmistakable.  For one thing, the very existence of
>extensive early Archaean to early Proterozoic continental crust is evidence
>against large scale disruption on that scale has not occurred since the
>early Archaean.
>
>--------------
>May the peace of God be with you.         sarima@ix.netcom.com
>
>