Great information, Thanks! Ruben Garcia Phoenix, Arizona http://www.mr-meteorite.com http://www.youtube.com/profile_videos?user=meteorfright&p=v
--- On Thu, 7/24/08, Mr EMan <[EMAIL PROTECTED]> wrote: > From: Mr EMan <[EMAIL PROTECTED]> > Subject: Re: [meteorite-list] A question about Antarctica vs Alaska meteorite > hunting. > To: [email protected], [EMAIL PROTECTED] > Date: Thursday, July 24, 2008, 4:24 PM > Hello Ruben Good question. > > What makes the recovery in Antarctica is a combination of > rare processes and not just glaciers catching up > meteorites. It takes a rare combination of bedrock, ice > and wind to expose the meteorite fields in Antarctica. > > Meteorites falling into the main flow are likely lost > forever. But if it falls along the edge of the field in a > side lobe-- not in the main glacial flow--there is a chance > it can be exposed again. Sometimes thousands of years > later. The ice in the top portion of the lobe doesn't > scour the bedrock and stir up rock fragments like the main > flow does and has minimal inclusions of earth rock in the > load carried by the ice. A lobe occurs near a bottleneck > and is like a slow motion wave getting sloshed out of a bath > tub-- being pushed out of the "tub" itself by the > main flow and rising bedrock. When the lobe hits the > valley rim-- a gentle slope or buried ridge-line, the ice > is forced up and over it, exposing the ice to very high > velocity and extremely dry winds. This action scours away > the ice matrix --perhaps even sublimates some ice directly > into water vapor. In any event, the ice is removed by > wind action leaving the meteorites concentrated on > the surface. "Concentrated" implies a placer > deposit but in fact means that in fives and tens meteorites > are exposed each season before the ice flows over the slope > and they are reburied in ice unless recovered by the annual > meteorite search teams. > > I believe that a few iron meteorites have been recovered in > glacial moraines elsewhere but that is a different > concentration mechanism and they certainly aren't > separated out from the earth rock!. Active glaciers such > as associated with caving icebergs carry whatever load they > have inside them into the sea. > > Meteorites don't seem to survive long in moist frequent > freeze thaw environments making finding stone meteorites > remote. I don't know the circumstances of recent > Canadian meteorites and couldn't say if they were > related to glaciers. The environment in glacial fields is > against stones but favors irons, IMHO, so long as the ice > doesn't make icebergs but ends in annual moraine > building piles of debris. > > Elton > > --- On Thu, 7/24/08, Ruben Garcia > <[EMAIL PROTECTED]> wrote: > Hi all, > I know that many of you follow the work done in Antarctica > a lot more closely > than I do. I know that meteorites have been recovered there > for over two > decades and more recently in eastern Manitoba, Canada. All > due to ancient > glaciers and their movements. My questions are as follows: > > 1)Has anyone really searched for meteorites in other > glacial areas such as > Alaska? > > 2)Is there any reason to believe that meteorites > wouldn't be found there? > 3)Are the Alaskan glaciers old enough to sufficiently > "catch"meteorites? ______________________________________________ http://www.meteoritecentral.com Meteorite-list mailing list [email protected] http://six.pairlist.net/mailman/listinfo/meteorite-list
