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From: agranok@udenva.UUCP
Newsgroups: sci.bio,sci.astro
Subject: Re: Mass extinctions
Message-ID: <3345@udenva.UUCP>
Date: Thu, 2-Apr-87 12:13:10 EST
Article-I.D.: udenva.3345
Posted: Thu Apr  2 12:13:10 1987
Date-Received: Sat, 4-Apr-87 19:46:35 EST
References: <6760@alice.uUCp> <496@uokmax.UUCP>
Reply-To: agranok@udenva.UUCP (Alexander Granok)
Organization: U of Denver
Lines: 30
Keywords: Iridium, Osmium, Ash
Xref: utgpu sci.bio:219 sci.astro:798
Summary: Nuclear Winter Analogy

In article <496@uokmax.UUCP> david@uokmax.UUCP (David Lee Cox) writes:
>I really like this discussion, but am a little confused about a couple of
>things,  What would volcanoes, or meteors do that could cause mass extinctions?
>
Even though this will probably be answered by a zillion people, here 'goes 
anyway.  It has been hypothesized that the phenomenon which did away with the
dinosaurs (and many of the other life forms on earth) was something akin to
nuclear winter, as *it* has been theorized.  A large cloud of debris so cut down
on the available light to the planet that the climate changed drastically.  
This change not only killed the food sources of the now-extinct animals, but
probably had some serious affects on their reproductive and behavioral lives
as well.  The source of this cloud?  Well, primarily due to the large concen-
trations of the elements Iridium and Osmium which are in the strata of about
this time, it was decided that some sort of meteor (boy, what a meteor!) 
impacted the earth and caused the cloud.  These elements are very rare on the
earth, but do appear with greater frequency in meteoric rock.  

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
been suggested as the source of the island of Iceland.  The meteor fell on a
weak point in the earth's crust, and the rest is, well...history. This discus-
sion will probably expand greatly over the next week or so, and I'll be inter-
ested in seeing what other people have to say.

-- 
                                           
                              Alex Granok 
                              hao!udenva!agranok
                              "Wait a minute.  Strike that.  Reverse it."