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Hi Frederic
The reasons there is found so many meteorites in
Antartica, are many. I will try to give e few here:
1- The climat is extremely dry, so even old ones
are well
preserved.
2- The meteorites that fall far far inland are
transported
toward the shores with the
movement of the ice.
When snow keeps faling -
meter after meter and covering
the meteorites - and there
is very litle evaporation - the
layer should just get thicher
and thicker. It cant.
The pressure builds up and the
snow turns to ice.
The pressure builds up even
more, and the whole thing
start to sink as the lower
layers - under high pressure -
turns
plastic.
So so the icecap is moving
all the time, from the center
and out, and eventualy
falls into the ocean as icebergs.
BUT, in some places (the
famous locations like Allan
Hills etc.) the ice is
forced up to the surface by rock
formations beneath. Here
the ice is worn down by
ablation, and you see the
famouse "blueice fields".
Over time meteorites will
just keep comming up on these
locations.
The eception is the
meteorites that are very heavy.
They just sink to
the bottom of the ice, and will only be
seen when all
the ice is melted.
Can you see the picture ?
Else I can make a drawing, and send you, it is not
easy to explane in words alone :-)
Best wishes
Lars Pedersen
----- Original Message -----
Sent: Tuesday, December 16, 2003 10:02
AM
Subject: Re: [meteorite-list] Dry Lake
Stewnfields??
Hi Doug and List,
I also wonder about another point on
meteorite falls... Since I started hunting them, I thought that they can fall
anywhere, the location of their landing place depending on their orbit around
the sun and the angle they meet the Earth with. Is that right or are there any
areas on our planet where they get more "attracted" ?
There have been more finds in Antarctic than
anywhere else, but I guess that it's simply because people have been searching
for them there for a longer time, but can it be for another reason ? Has the
magnetic field linking the poles any effect (like for boreal auroras) ?
...
I'm not a scientist and maybe my question sounds
strange, but should anybody have a clear and easy to understand explanation,
thanks in advance for sending it, just for my knowledge.
Kind regards
----- Original Message -----
Sent: Tuesday, December 16, 2003 5:49
AM
Subject: Re: [meteorite-list] Dry Lake
Stewnfields??
Hi John, I think if we get back to basic
definitions, a strewn field is an ellipsoid shape caused by a mid air
explosion raining down material, as far as I understand. What happens
afterwards to the material is irrelevant. And the strewn field is a
geometric representation fitted to the fall in practice, not the actual
individual stones. If some gets moved, picked clean, the boundaries of
the strewn field can't change, from their original
definition.
Perhaps some of the hunters among us will not see it that
way...as strewn tends to bring a connotation of waltzing in and cleaning
up. And an empty strewn field sounds odd...
So I would think
that the technical "set one straight answer" you want is that:
Mathematically it takes at least four border points to make an ellipse, but
to actually be able to fit one with any confidence in an area, you need
plenty more, to fill in the area. A neat statistical definition seems
impractical, so it will come down top the field researcher's opinion.
If the one who did the research wants to call it a strewn field and their is
evidence for a mid air explosion...then we should have one. And if
there are a few rocks...in the desert, or in Chicago, and the principal
investigator(s) don't feel there is enough for an ellipse, then its not,
because they say so. An it is a good assumption if we happen upon an
old scattered field, we can say...this might be a strewn field, but lacking
a good cause-effect ellipse explanation there can't be a right answer for
lack of data. In the end one can probably collect opinions on this
until blue in the face...and who calls what a what...but for
what?
Strewn fields are simply human categories so we can make sense
out of natural events that don't have to conform to our neat, ways of
nomenclature. Just like the concept of a species or a race in
biology. You know an obvious one when you see it...but when you start
taking it as gospel and look at the limits of the definition, the whole
think breaks down, and mass consensus isn't reached...plus air resistance
already distorts a strewn field to a researcher. So there has got to
be a little eyeballing going on since tiny particles don't fall
nicely. If it looks like a strewn field, (tastes like one),
...
Sipping my hot chocolate...Saludos
Doug
Dawn
Mexico
En un mensaje con fecha 12/15/2003 10:17:15 PM Mexico
Standard Time, [EMAIL PROTECTED] escribe:
To Rob, Bob, Adam, and others:
Recent finds
from the Nevada dry lakes were grouped in a small area within a
dry
lake. The finding of three apparent pieces from same fall created a
description by Adam that these finds might constitute a new
strewnfield.
Questions/observations in regards to desert
strewnfields.
1. Obvious groupings of fallen masses would make the
likelihood of the area
being a meteorite stewnfield. Do multiple finds
in desert locale usually get
described as a stewnfield?
2. Does
the fact that many rocks get moved around in these environments take
the strewnfield idea down a notch with rocks being scattered?...or
does their
proximity within the bounds of normal surface movements
qualify them to be
still within the original strewnfield?
3.
Is the idea of stating a location has a new strewnfield more about this
location being a new place to find more than one meteorite of the same
apparent fall?...and not so much about the actual fall
characteristics?
I guess I'm just curious about the use of word
strewnfield in this case?
Yearning to be set
straight,
John
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