Re: Discovery of Antarctic subglacial rivers may challenge excavation plans


"Daryl Krupa" <icycalmca@xxxxxxxxx> skrev i en meddelelse
news:1146548033.043095.131870@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Carsten Troelsgaard wrote:
<snip>
It may have this sentiment of 'catastrophisme'
that could make it a geological 'darling' in the eye of the public
(said the dull sedimentologist)

Carsten:
Theories that much of the landscape of western Canada is
the result of outbursts from subglacial lakes under the
Laurentide Ice *** have attracted very little attention
outside of the ranks of professionals.

I always figured that it was meltwater-lakes on top of the ice.
A local adventurer John Andersen cayacs north Greenland and makes a glacial
travers passed the Humbolt Glacier, for fear that they won't be able to land
their cayacs along the icy coast. I recall him to describe a glacial lake,
on top of the glacier, in the order of 50 km across. (Maybe the glacial
outlet of the vast icy interior 'compresses' the ice from the side and
prevent cracking open some conduites for the correct boyant position of the
water ..)

The main result seems to have been the elimination of the
university department from which the theories originated.

:o/

I wonder what sort of sedimentary succession the release of such a major
volume of pressurized water would produce .. it would already be present
at
the head of the outlet.

John Shaw, the last Chairman of the Department of Geography
at the University of Alberta, thought that the sediment mobilised by
Laurentide megafloods would be found in the offshore Mississippi delta,

where they have proven to be difficult to conclusively identify.
That, of course, would be at or below the mouth of the outlet;
at the heads of outlets of Laurentide sub-glacial lakes one finds
eworked and scoured boulder deposits that look superficially like
drumlins or sand dunes. These bouldery deposits seem to have
accumulated in the early stages of the outburst, as elongated hollows
were scoured out of the sole of the glacier above at a drainage divide,

then choked with large sediment grains as flow waned, then partially
re-opened as the sediment supply was reduced and erosion dominated
again. There are sometimes smaller-grain-size deposits similar in
morphology to, and parallel to, the bouldery "dunes".

The concept of large-scale subglacial jokuhlaups is not new.
What is surprising to me is that the researchers who found the
inter-lake water movement were surprised at what they found.

Would you like me to look up some references on sediments
associated with subglacial mega-floods for you?

Interesting Daryl. Don't jump for me. Reading your post I started frasing
something like 'any book on morphology ought to have imagery from this end
of the sedimentary scale'. Maybe more than I though would be curious about
the bouldery deposits/drumlins of the outburst.
I promised myself to go look at a local outburst (Goeteborg, Sweden), but
havn't got to it yet.

Daryl Krupa



I assume that they've got some idea of where the
outlet would be.



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