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Chickenheads and Knobs on Snow Creek Wall


catbirdseat

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It's the sediment-filled subglacial water that does all the erosion!!!! wazzup.gif

 

which is why glaciers tend to sink into narrow, stream-chiseled gorges... wait a second

 

you see that stream-chiseled stuff way out away from glaciers, such as Box Canyon in MRNP, but not under the glacier itself, eh? not that I'm an expert, I'm just Satan's advocate.

 

Personally I believe the rock is on the left and the glacier is on the right: smileysex5.gif

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Fern, that's not how glaciers grind down mountains. Stones and grit get embedded in the ice and moves with it. THAT is what grinds down solid rock.

 

That theory has been discredited since the 1950s. Wake the fuck up and read the science before you spout off numbnuts the_finger.gif

 

It's the sediment-filled subglacial water that does all the erosion!!!! wazzup.gif

 

That IS what he was saying, that the streams do "all" (most) of the erosion. I certainly can't prove anything, but I don't believe it until someone proves my theory wrong smileysex5.gif

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here's a nice PhD position for anyone interested from an email I received today.

 

The PhD project entitled "Miocene intrusions in Southern Patagonia - a possible link to ridge subduction ?" is funded by the Swiss National Science Foundation for a period of 3 years. Potential candidates should have a strong interest in igneous petrology and geochronology. Hands-on experience in geochemistry is a plus. Serious interest in field work is important.

The objective of this project is to study the Miocene plutonism in Southern Patagonia (Fitz Roy in Argentina; Cerro Donoso and Cerro Balmaceda in Chile), examining to which extent this plutonism is linked to the subduction of the Chile ridge during the Miocene. This study aims to (a) document the geochemical composition of these intrusive bodies to determine source regions and magmatic evolution, and (b) to better constrain intrusion ages, and to unravel the ages of individual intrusion cycles. A petrological characterization in combination with major and trace element studies will form the basis for more advanced geochemical investigations using rare earth elements and radiogenic isotopic analyses. Stable isotope analyses will complement this analytical approach. A second important aspect of the study is age determination. Emphasis will be on Ar-Ar geochronology, combined with high precision U-Pb zircon dating.

 

PLUS the fact you'll get paid to live in the Alps.

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That may be so but you don't mean to say that liquid water is the main erosive force of glaciers. It's the ice.
Your reading comprehension suggests you failed highschool English. If there was just ice there with no liquid water the erosion rate would be pretty much zilch dumbass. I mean to say it's the water. the_finger.gif
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Dru, it is clear that you are not a complete idiot like kevbone because you form very coherent writings. However, I think you must be joking on this one...? Anybody who takes the ever-present cc.com advice (search the interweb) will find that glaciologists recognize two key forms of erosion, neither of which are silty sub-glacial streams. It's always abrasion (rock in glacier against rock under glacier) and quarrying (freeze-thaw popping loose chunks of sub-glacial rock which are then picked up).

 

http://en.wikipedia.org/wiki/Glacier#Glacial_erosion

http://gemini.oscs.montana.edu/~geol445/hyperglac/eroproc1/

http://www.gi.alaska.edu/ScienceForum/ASF4/416.html

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Abrasion is silty glacial water, not rocks frozen in ice. Rock frozen in ice idea is 50's science. It can't be observed, modelled or duplicated or proven. In short it is bunk!

 

I'd expect silty water to result in more uniform erosion rather than the longitudinal striations that I see on slabs that glaciers have run across. It seems to me those features would more likely result from rocks gouging into the bedrock as they are pushed along by the glacier.

 

But of course, I'm not a geologist.

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Striations are microscale. Microscale features are all that frozen rocks can do. Even there it is moving till, not moving ice, that makes the microfeatures... and the till is saturated. Dry till won't abrade worth shit.

 

See at the bottom of a continental glacier the pressure is enough to plasticize both the rocks in the ice and the rock the ice is resting on. Can you wear through a brick of butter by rubbing it with margarine? Hell no. But run some water across it and it will melt. Same deal.

 

How come you don't see any plucking or quarrying, say, in the Bypass Glacier cirque on Slesse? Cause there is not enough water. The ice is just a reservoir for the erosive water.

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Ask Mauri

 

Great info at his faculty website about North Cascades Glaciers. Especially the stuff about the chronology of glacier advance and retreat from the time of the continental glaciers onward.

 

I had no idea that the Little Ice Age was a period of significant glacial advance relative to proceding 2,3,4 eons.

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