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The all-time greatest photo of a snow bridge?

 Poster: A snowHead
Poster: A snowHead
This is the most beautiful ski photo I've seen in many a moon. It was captured only a month ago (27 May, in fact) on the Watkins Mountains, Greenland, by Norwegian ski adventurer Arnt Flatmo.

It shows his friend Per Ove Oppedal Torstein skiing over a snow bridge on the way down from Brekruna. Probably a snow bridge best crossed at speed - how do you ever judge the strength of these things? - but what a fabulously beautiful piece of natural snow sculpture. [You can enlarge the photo with the zoom button, bottom right] There are more spectacular photos on Arnt Flatmo's site hordafjell.com, including the Cairngorms and Mont Blanc. I wonder if he sells prints, or if he's producing a book - this is brilliant stuff.

[Acknowledgements to 'Big Sly' on the Winterhighland site for spotting it]
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 Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
Absolutely stunning photography. Thanks for that DG.
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 Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
Gosh. Good question about the bridge strength. Amazing photo - as are the others. Thanks for flagging them up, DG
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Beautiful photo - looks like he's telemarking...
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 Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
Excellent. TVM DG.
For others - The snow bridge shot is in 'Moments 2004' on Arnt's site and there are also other Greenland mountain views in 'European Mountains' which also has the Scottish stuff.
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 You'll need to Register first of course.
You'll need to Register first of course.
I could look at those for hours. Best not, though. Not yet.
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 Then you can post your own questions or snow reports...
Then you can post your own questions or snow reports...
You might be surprised at the strength of that snow bridge, it looks to be about 10 M deep by 16 M long and about 6 M wide, which works out to 960 cubic meters of snow, now if snow is roughly 1/10 the density of water then that means about 100 tons of snow in that bridge ! 65Kg of fast moving skier will not have any effect on it
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 After all it is free Go on u know u want to!
After all it is free Go on u know u want to!
surley every structure has abreaking point?
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You'll get to see more forums and be part of the best ski club on the net.
I think we're dealing with a number of interesting points here, which are beyond my grasp of physics and engineering.....however, we know that a massively heavy slab of snow can be in such a delicate state of equilibrium that a 65kg skier can start it sliding.

We also know (or do we?) that the beating wings of a butterfly can set of a chain reaction that results in a hurricane.

That said, I think DGO is right. I'd trust that massive snow bridge more than a potential avalanche slope, so long as I didn't hang around admiring the depth of the crevasse below it....

...on that topic, how deep is that crevasse? Any offers?
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 Ski the Net with snowHeads
Ski the Net with snowHeads
Quote:

We also know (or do we?) that the beating wings of a butterfly can set of a chain reaction that results in a hurricane.


I think we know that it very probably can't. The butterfly effect was a theoretical illustration of the atmosphere being a chaotic system. However, the very small draught created by the butterfly would easily be subsumed in a larger scale system to the point where it would not have an effect that wouldn't have been very likely anyway.

An aircraft contrail however, I could be persuaded about.

As to the snow bridge and structures, it is theoretically impossible for a structure to be built that can support only it's mass, yeah? If so, it could be 100 tons and still collapse with the addition of 65Kg (though surely an adult male skier with climbing equipment would weigh more than that?). However, I'd have thought that the likelihood of a 100 ton snowbridge naturally forming at such a delicate balance of forces, would be very small? In that case a moderate wind or temperature change would bring it down, surely?
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 snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
oh blimey - are we getting into another physics problem solving scenario? Shocked
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 And love to help out and answer questions and of course, read each other's snow reports.
And love to help out and answer questions and of course, read each other's snow reports.
Quote:

The strength of a snow bridge varies tremendously with temperature. An arch that might support a truck in the cold of winter or early morning may collapse under its own weight during an afternoon thaw. Cross every bridge with caution every time. Don?t assume that because it held in the morning during the ascent that it?s safe as you head down in the afternoon.


from here: http://www.getoutdoors.com/go/golearn/442
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 So if you're just off somewhere snowy come back and post a snow report of your own and we'll all love you very much
So if you're just off somewhere snowy come back and post a snow report of your own and we'll all love you very much
Also:

Quote:

h. Snow Bridges. Snow bridges are formed by windblown snow that builds a cornice over the empty interior of the crevasse. As the cornice grows from the windward side, a counter drift is formed on the leeward side. The growth of the leeward portion will be slower than that to the windward so that the juncture of the cornices occurs over the middle of the crevasse only when the contributing winds blow equally from each side. Bridges can also be formed without wind, especially during heavy falls of dry snow. Since cohesion of dry snow depends only on an interlocking of the branches of delicate crystals, such bridges are particularly dangerous during the winter. When warmer weather prevails the snow becomes settled and more compacted, and may form firmer bridges.

(1) Once a crevasse has been completely bridged, its detection is difficult. Bridges are generally slightly concave because of the settling of the snow. This concavity is perceptible in sunshine, but difficult to detect in flat light. If the presence of hidden crevasses is suspected, the leader of a roped team must probe the snow in front of him with the shaft of his ice ax. As long as a firm foundation is encountered, the team may proceed, but should the shaft meet no opposition from an underlying layer of snow, a crevasse is probably present. In such a situation, the prober should probe closer to his position to make sure that he is not standing on the bridge itself. If he is, he should retreat gently from the bridge and determine the width and direction of the crevasse. He should then follow and probe the margin until a more resistant portion of the bridge is reached. When moving parallel to a crevasse, all members of the team should keep well back from the edge and follow parallel but offset courses.

(2) A crevasse should be crossed at right angles to its length. When crossing a bridge that seems sufficiently strong enough to hold a member of the team, the team will generally move at the same time on a tight rope, with each individual prepared to go into self-arrest. If the stability of the snow bridge is under question, they should proceed as follows for a team of three glacier travelers:

(a) The leader and second take up a position at least 10 feet back from the edge. The third goes into a self-belay behind the second and remains on a tight rope.

(b) The second belays the leader across using one of the established belay techniques. The boot-ax belay should be used only if the snow is deep enough for the ax to be inserted up to the head and firm enough to support the possible load. A quick ice ax anchor should be placed for the other belays. Deadman or equalizing anchors should be used when necessary.

(c) The leader should move forward, carefully probing the snow and evaluating the strength of the bridge, until he reaches firm snow on the far side of the crevasse. He then continues as far across as possible so number two will have room to get across without number one having to move.

(d) The third assumes the middle person's belay position. The middle can be belayed across by both the first and last. Once the second is across, he assumes the belay position. Number one moves out on a tight rope and anchors in to a self-belay. Number two belays number three across.

(3) In crossing crevasses, distribute the weight over as wide an area as possible. Do not stamp the snow. Many fragile bridges can be crossed by lying down and crawling to the other side. Skis or snowshoes help distribute the weight nicely.


From: http://www.globalsecurity.org/military/library/policy/army/fm/3-97-61/ch10.htm
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 You know it makes sense.
You know it makes sense.
Here are some more snow bridges. All interesting and original, but less beautiful than that magnificent Greenland example:

1 A family snowbridge, with what looks like a turtle to the left of them, but surely it can't be?

2 Heavy vehicle stuck on collapsing snowbridge (sorry this one's only available as a thumbprint)

3 A rare hump-backed snowbridge in the Cascade mountains (from http://www.peakspeak.net/PeakPhoto.asp?PhotoID=115&PeakID=12

4 Sheltering under a Swiss snowbridge (no chance of a Swiss snowbridge collapsing, presumably). (Interestingly, this one was carved out by a snowfall, according to the caption on http://www.kitchak.com/Switz-02-046.html
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 Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
David, that's an Alsatian not a turtle!
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 Poster: A snowHead
Poster: A snowHead
Seems it's got a better idea of how to cross one than the humans in that photo. I wonder what the "after" shot looked like?
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 Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
"Unbeknowst to the Jones family, Rover was chewing a line across the to speed their demise"
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 Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
Lassie suddenly realised that when they plummeted to their deaths, the (s)he would be on the wrong side of the abyss from the dog biscuits.
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Thanks very much, Ian. I was never cut out to be a zoologist. Despite that, I can't quite make out how I mistook the tail of an Alsatian for the head of a turtle.
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 Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
Great photo David, already have it saved as my wallpaper on the PC for July. The first one I mean, not the one with the Turtle.
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