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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
May the peace of God be with you. firstname.lastname@example.org