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Why don't we get tree wells in Europe?

post #1 of 10
Thread Starter 

I could be wrong, but most people here don't know what I'm talking about. I only found out about them from my canadian colleagues. We have a two meter  base on the lower slopes, and 4 meters up top. There aren't nearly as  many trees as in the states, but I thought for sure we'd have some. Maybe the trees need to be a certain size ie have a certain circumference trunk, I don't really know, but it's not something we worry about here.

Any ideas?

post #2 of 10

A couple of hypotheses:

 

  1. Skiers in Eruope tend to stay between the piste poles, so many will never encounter a tree well
  2. A lot of the terrain is above tree line - no trees, no tree wells
  3. Tree wells depend on the type of tree and how the branches keep snow form accumulating under the tree.  Deciduous trees don't make tree wells.  Some conifers are more efficient at making them than others.  I don't know enough about forrestry to comment on the differences between the tree populations, but this is probably a factor.
  4. You need deep soft fluffy snow - the kind that you can sink in up to your waist - for a tree well to be dangerous.  That may be less prevalent where you ski than in the Canadian Rockies.

 

 

 

post #3 of 10

Are all of your trees big and old?  If the branches don't touch the snow there is little chance of a tree well forming.

post #4 of 10
Thread Starter 

Some of the trees have the branches touching the snow, especially this year, as we're got such great snow, although looking out my winder righ tnow, the ones I see don't seem to have too many lower down branches. I agree we don't get as often the dry snow. Now that I think about it, we usually get a mix, like three weeks ago, before the super big cold snap, we had 60cm, then it rained briefly, and was like cement, then we had three weeks of dry fluffy snow, with cold sunshine days. I'm guessing the heavy stuff  helps create a solid base around the tree -  a theory only.

post #5 of 10
Quote:

Originally Posted by Walt View Post

 

  1. You need deep soft fluffy snow - the kind that you can sink in up to your waist - for a tree well to be dangerous.  That may be less prevalent where you ski than in the Canadian Rockies.

 


Don't tell the tree wells in the PNW. smile.gif  What is this 'fluffy' that you speak of?

 

 

post #6 of 10
Quote:
Originally Posted by skiingaround View Post
 I'm guessing the heavy stuff  helps create a solid base around the tree -  a theory only.


We have similar snow conditions around here and we have lots of tree wells.  They're only a problem if you ski close to the trees.  Never having been to Europe, I wonder if skiers there are doing lots of skiing through the trees or if they are staying a safe distance from them, generally?  Or do they ski only through mature forests without lower foliage?

post #7 of 10

I was in St. Anton during the second big dump (not the great big dump) of January. It was the dry stuff that you can sink to your waist in, and we were skiing in the trees because of the low visibility. What I noticed was that a lot of the lower branches were not close enough to the ground and thick enough to cause tree wells, so the snow was more easily able to pile up right up next to the trunk.

 

I can't remember any resorts I've been to in the Alps in the last few years that have had a lot of trees with branches lower than my chest or waist. Usually, it's just a few here and there that you can easily push out of your way. I'm not sure if it's from tree grooming or a natural feature of the species of trees in the area.

post #8 of 10

aside from a low hanging canopy which might effectively shield snow from accumulating near a truck; a major contributor to tree wells are the tree trunks themselves.

 

Tree trunks absorb the sun's energy and build up heat, greater than the surrounding area, in their surface. This is especially true where the trees have large trunks and sunshine in winter is common - the Western States, Canada, etc. The heat buildup in the trunk melts the snow closest at a faster rate, hence the funnel shapes. There is additional heat radiation which helps the well become broader.

Tightly bunched trees which shield the sun more - like many of the heavily managed European forests, allow less sun intrusion down to the trunk snowline interface, hence less melting, so less well development. Areas, regions, climates which have less sun during winter will also not develop as strong wellling.

Deciduous forests, even tightly forested ones, will develop more welling because there is no winter canopy.

Latitude has a lot to do with this also - high altitude but lower latitude forests like the Western US develop strong wells because of the more direct sun rays in winter coming thru less atmosphere..

Lower altitude and higher latitude forests like Europe, Scandinavia, Russia and the like, receive less direct sun rays coming through more atmosphere.

Predominant winds also have an affect on how a well develops.

For large trunked trees like Ponderosa Pines with high branching the well can be suprisingly symetric - the shady side of the truck still seems to pick up heat from the sunny side and have almost as much welling.

Last season I stared down a well of a particularly large Ponderosa and the well, which easily stood off from the trunk some 8 feet - I swear I couldn't make out the bottom which was at least 25 ft down.

When I'm skiing on the sunny side of a hill, in glades of large trees, I'm particularly wary of wells, because they can be broad and deep and not easy to spot until you;re almost upon them.

post #9 of 10

interesting description and explanation. Is it the water in the tree that holds the heat? would a dead tree function that way?

 

We were pausing in the woods and saw a man ski up to a tree and start to unzip, then zip, he was gone. whoa!

 

I've seen what looks like wells around large dead snags that have formed by the wind swirling around the base of the tree. Is this a common formation?

 

I read a description of an equally eerie scene. A once forested area became buried in sand. The trees eventually died and slowly rotted out. The tree trunk was now like a well, a 60 foot vertical tunnel, barely covered at the top with some rotten wood and some sand. Kids would be lost in them sometimes.

post #10 of 10
Quote:
Originally Posted by moreoutdoor View Post

aside from a low hanging canopy which might effectively shield snow from accumulating near a truck; a major contributor to tree wells are the tree trunks themselves.

 

Tree trunks absorb the sun's energy and build up heat, greater than the surrounding area, in their surface. This is especially true where the trees have large trunks and sunshine in winter is common - the Western States, Canada, etc. The heat buildup in the trunk melts the snow closest at a faster rate, hence the funnel shapes. There is additional heat radiation which helps the well become broader.

Tightly bunched trees which shield the sun more - like many of the heavily managed European forests, allow less sun intrusion down to the trunk snowline interface, hence less melting, so less well development. Areas, regions, climates which have less sun during winter will also not develop as strong wellling.

Deciduous forests, even tightly forested ones, will develop more welling because there is no winter canopy.

Latitude has a lot to do with this also - high altitude but lower latitude forests like the Western US develop strong wells because of the more direct sun rays in winter coming thru less atmosphere..

Lower altitude and higher latitude forests like Europe, Scandinavia, Russia and the like, receive less direct sun rays coming through more atmosphere.

Predominant winds also have an affect on how a well develops.

For large trunked trees like Ponderosa Pines with high branching the well can be suprisingly symetric - the shady side of the truck still seems to pick up heat from the sunny side and have almost as much welling.

Last season I stared down a well of a particularly large Ponderosa and the well, which easily stood off from the trunk some 8 feet - I swear I couldn't make out the bottom which was at least 25 ft down.

When I'm skiing on the sunny side of a hill, in glades of large trees, I'm particularly wary of wells, because they can be broad and deep and not easy to spot until you;re almost upon them.


This all may be true, but I doubt that these wells offer the same danger as the ones made from loose, fresh snow.  As the snow melts away from the trunk it becomes more ice than snow, which leads me to suspect that these wells do not have the same danger factor as the ones built from loose snow sloughing off of tree branches.  If you fall into one of these you're facing suffocation from snow in your face while you're immobilized.  In the sun created wells, while you might really slam into the trunk and hurt or kill yourself, you won't have fluffy snow fall in around you.  This is the greatest danger of tree wells.  It's like an immobile avalanche.  The sun created ones should be relatively easier to extract yourself from as well.

 

I can't remember ever seeing this type of sun created well that was of any size, though I don't ski in California so I might just need a widening of my horizons.

 

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