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From: jon@oddhack.UUCP
Newsgroups: sci.bio,sci.astro
Subject: Re: Mass extinctions
Message-ID: <2212@cit-vax.Caltech.Edu>
Date: Fri, 3-Apr-87 03:47:34 EST
Article-I.D.: cit-vax.2212
Posted: Fri Apr  3 03:47:34 1987
Date-Received: Sun, 5-Apr-87 02:27:25 EST
References: <6760@alice.uUCp> <496@uokmax.UUCP> <3345@udenva.UUCP>
Sender: news@cit-vax.Caltech.Edu
Reply-To: jon@csvax.Caltech.EDU (Jon Leech)
Organization: California Institute of Technology
Lines: 14
Keywords: Iridium, Osmium, Ash
Xref: utgpu sci.bio:222 sci.astro:800

In article <3345@udenva.UUCP> agranok@udenva.UUCP (Alexander Granok) writes:
>One of the things that had bothered scientists was the evidence of the impact.
>Something that large would leave visible scars for some time, wouldn't it?
>Unless it landed in the ocean, which is an interesting idea which has recently

	Depending on the nature of the target material (shield rock lasts
about the longest), large craters are eroded away on timescales on the order
of ten million years. Any given impact is likely to have taken place in an 
area that is currently covered by water, anyway (after all, the Earth is ~70%
oceans!)

    -- Jon Leech (jon@csvax.caltech.edu || ...seismo!cit-vax!jon)
    Caltech Computer Science Graphics Group
    __@/