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Re: iridium



At 08:28 PM 5/6/98 -0700, Earl Wood wrote:
>     I would like to know if anyone has calculated the amount of Iridium
>needed to
>cover the entire earths surface , at the depth associated with the K C
>boundary ? and if so does anyone have these figures , or a reference
>that would be available to Joe citizen ?

You might check some of the original work by the Alvarez team, which was
published in Science and in Scientific American (both of which are available
at most public libraries).

Alvarez, L.W., W. Alvarez, F. Asaro & H.V. Michel.  1980.  Extraterrestrial
cause for the Cretaceous-Tertiary extinction. Science 208: 1095-1108.

Alvarez, W. & F. Asaro.  1990.  An extraterrestrial impact.  Scientific
American 263 (4): 78-84.

However, please note: the Earth wasn't "covered" with iridium: the planet
didn't glow silver.  It's not as if there is a visible layer of iridium at
the boundary!  Instead, the incredible miniscule amount of iridium that
normal falls on the Earth was increased to a vastly larger, but still
miniscule, amount.

Finally, it is the "K-T" boundary, not "K-C" (which would be the Cretaceous
Carboniferous boundary...).

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661