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Rock Glaciers in the Cascades?


Jake

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I was there and I couldn't really tell. It was October and there was no snow anywhere. It looked just like smal talus and scree. The rocks all moved very easily underfoot. We were never sure about exactly what a rock glacier was.

 

I was able to find this definition:

rockglacier.jpg

"Rock glaciers like this one, in the San Juan Mountains of Colorado, are rarer than ice glaciers. A rock glacier takes a combination of cold climate, a copious supply of rock debris, and just enough of a slope. Like ordinary glaciers, there is a large amount of ice present that allows the glacier to flow slowly downhill, but in a rock glacier the ice is hidden. Sometimes an ordinary glacier is simply covered by rockslides. But in many other rock glaciers, water enters a pile of rocks and freezes underground—that is, it forms permafrost between the rocks, and ice builds up until it mobilizes the rock mass.

 

Rock glaciers may move very slowly, only a meter or so per year. There is some disagreement over their significance: while some workers consider rock glaciers a kind of dying stage of ice glaciers, others hold that the two types are not necessarily related. Certainly there's more than one way to create them. For more photos of rock glaciers and a taste of current research, visit this page at Queen's University of Belfast. " Link

Edited by catbirdseat
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I'm not sure where the rock glacier is on Star Peak but there are a couple of candidate locations (brown dotted areas on the map).

This photo hints at what it would look like (bottom-right):

39929.jpg

 

There is also a rock glacier below the macroscian North Face of Mt. Bigelow nearby to Star Peak. It doesn't look like much but you can tell where it is (the forested prow cleaves it):

46425.jpg

 

There are some others in the Pasayten I believe, but I can't recall off-hand where they are. I could be mistaken, though.

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This is the south side of Ptarmigan Peak:

38046.jpg

There is no rock glacier there and I would find it highly unusual to find a rock glacier on a south-facing slope--especially in the Pasayten where glacier ice is hard to come by. The south slope is rolly polly tundra-like land (heather and rock and dirt, etc..). However, there may well be a rock glacier on the north side. I don't remember reading of one being there.

 

Here's the largest glacier in the central Pasayten (east side of Mt. Lago). Not much, is it? And this was taken in 1998. No telling what shell of this is left now:

37917.jpg

Or maybe the one below Lago's North Face:

37918.jpg

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MisterMo: Indeed. I was unaware of this one on Stuart.

It is in the old brown Beckey and is mentioned in a variation for the W. Ridge (p. 307):

"Variation: North Side of Lower Ridge:

From north side of Stuart Pass or from lower west ridge before its N.W. face traverse and climb scree N.W., then into the large gully at the head of the rock glacier."

 

It must be the talusy slope with the snow aprons in this photo:

13231.jpg

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Ptarmigan Peak has a nice rolling rock glacier on south side. I called it Physiological Peak because you could never see the summit until you actually got there from the base.

 

I remember there to be lot of rock on Ptarmigan - and a nice case of dehydration as well...

 

This is all interesting though. What other curious geological features are out there in them thar mountains?

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Except, of course, that a regular glacier can't become a rock glacier at some future date from recession or whatever. A rock glacier forms in its own special way (see CBS's post above).

eh...if you read cbs post with proper level of reading comprehension you will see a regular glacier CAN become a rock glacier. wave.gif

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