What causes this mountain landform?

[tvashtarkatena]

Located on the north side of West and Big Craggy peaks in the Pasayten Wilderness at about 7000'. There is a similar one located on the NE side of Bigelow in the Sawtooth Chelan Wilderness, at about the same elevation. It looks like a rock glacier, but both locations seem too far east for that (although the topo marks the Bigelow with a 'moraine' symbol)

 

Edited September 1, 2009 by tvashtarkatena

[Pete_H]

God, of course.

[Maine-iac]

Braided or anabranching stream bed (from meltwater)?

What was the surrounding area like? Was it in a Cirque, or other similar feature? Sorry I am not familiar with this area.

[Alasdair]

That is a glacial moraine. Or it certainly looks like one. This feature can be seen at the base of any glacier that has receded. A good place to see a feature just like that is from near the Harrison camp on the north side of Mt. Baker. At the terminus of the Colman Glacier the ground looks the same. Although the Pasayten does not have many glaciers now, it would have plenty not too long ago on a geological time frame. The ripple effect tends to form when the ice melts underneath the rock which is what happens at a terminal moraine. In addition the area above the trees on the upper left of the photo is a glacial carved slope.

[j_b]

Probably a rock glacier that are not uncommon in the Northeastern cascades (quite a few on the northern aspect of the ridge north of lake Chelan). They are understood to be either a glacier remnant covered by rock debris (that insulate ice from further melt) or more commonly, talus (from rockfall, lanslide and what not) mixed in with refrozen melt water in continental climate (i.e. not much peri-annual snow but cold enough for part of the day/year to allow refreezing of melt-rain below the surface). The surface ridges are caused by mixed medium (rock+ice) creep. This one doesn't look very active and/or healthy as the surface looks deflated except in the upper reaches of the photograph.

[tvashtarkatena]

Jessica Lundin of the UW Glaciology Dept was kind enough to send this prompt reply to my inquiry:

 

"I believe your photo is not a rock glacier for 2 reasons: (1) there appears to be a tree growing on it, which would not work on any glacier. (2) glaciers don't typically have a lumpy surface topography similar to soft ice cream, as in the photo. I'm not a geomorphology expert, but I diagnose this as debris flow (mud, rock, etc).

 

It dawned on me that this probably isn't a moraine feature, as it appears at the top, rather than the sides or bottom, of the cirque. It probably is the result of material coming directly off the peak...annual snow from the gulleys above and the resulting melt/slides, for example. I wonder if the top layer of rock rests on an underlayer of mud/silt, which sluffs underneath it during the spring melt.

 

 

 

Edited September 1, 2009 by tvashtarkatena

[j_b]

It's possible but a non-active rock glacier (or what's left over after the ice melts) could have trees on it and the surface would be irregular due to ground ice melting. There are lots of trees (even entire forests) growing on dead-ice topography, such as in the lower reaches of large alaskan glaciers.

[G-spotter]

I am a geomorphologist and it looks to me just like an inactive rock glacier. It's definitely not the moraine of a recently departed (ice) glacier, nor is it debris flow deposits.

[tvashtarkatena]

The debate rages on!

 

The real question is: who bakes a better apple pie?

[j_b]

trees on dead ice:

 

[tvashtarkatena]

Someone's gonna have to go back in there and get a core sample.

 

Klenke! Front and center!

[j_b]

It seems that it is way too big in extent to be a morainal complex for the puny glaciers in that part of the world.

[Pete_H]

I'm actually pretty sure God made it a few thousand years ago. I think I can make out the spot where Noah parked his boat to let a few dinosaurs on board.

[klenke]

If Scurlock calls it a rock glacier, it must be a rock glacier :

click here

(if this is the same feature as tvash's photo)

 

Other Scurlock "rock glacier" images:

near Silver Star Mountain

north side of Gilbert Mountain near Silver Star Mountain

lots more pictures here in this archive

 

 

The one on the north side of Bigelow Peak is a confirmed rock glacier. There is also one on the southeast side of Star Peak (photo of it is on this page).

[tvashtarkatena]

So, the question is, do any of these features still have ice underneath them, or are they dry fossils of previous glaciation?

[tvashtarkatena]

The answer here is clear. Not only is the feature a rock glacier; its also on Mars:

 

[Lowell_Skoog]

So, the question is, do any of these features still have ice underneath them, or are they dry fossils of previous glaciation?

 

See "Hunting for Eacas Glacier" in the following NWMJ article:

 

http://www.mountaineers.org/NWMJ/07/071_Post3.html

 

[tvashtarkatena]

Austin looks like he might have a hidden glacier or two in that beard.

 

Well, I guess that clinches it. What a cool surprise. No pun intended. Thanks for post.

 

Unfortunately, I forgot my camera during last year's (or was it the year before?) trip up Bigelow, so no pics of that one from me.

 

No Dice Lake (just below the rock glacier in my photo) is quite pretty and looks like it probably contains a few fish (white wine recommended)...a trip up to the Craggies 'glacier' would probably be a nice outing.

[tvashtarkatena]

BTW, I found a more complete pic of the Craggy feature in my folder. Turns out the meandering folds I thought were at head of the cirque (based on my originally posted photo) are actually at the terminus of a much larger feature.

 

[Choada_Boy]

Looks like Stone Man laid down for a nap and never got up.

[j_b]

In the new picture you can also see 3 lateral moraines. The furthest downstream that is lightly wooded in the upper 3rd, left half of the picture (also visible on your first pic), and 2 more in the right side mid-height of the newest picture. The point being that the surface of the rock glacier is now significantly lower than the innermost moraine (with a stream between the debris surface and the moraine), which suggests as mentioned before that this rock glacier is inactive and probably not cored with significant ice at the present (at least for the part we see in the picture). [/armchair speculation]

[tvashtarkatena]

This may require a double plus dot com secret mission of exploration

[olyclimber]

let me know. i'm in. i have a decoder ring from a crackerjack box.

[tvashtarkatena]

I have designed a personal robotic factotum to accompany me. A human can't be trusted. If you're serious, however, the launch will be next week, about 3 days after the weather clears a bit. It's a long space voyage for such a short hike, however. I'll be in the area on another mission...this would be a side trip.

Edited September 2, 2009 by tvashtarkatena

[John_Scurlock]

Here's a nice rock glacier I saw recently in the Absaroka-Beartooth Wilderness:

http://www.pbase.com/nolock/image/116908182 - click on 'original' (below the image) to see the largest uploaded size.

 

These are very common in this region. For example, in Idaho's Lost River range, around Borah peak, they are seen in virtually every drainage.