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Avalanche Situation

James

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Latest in CO near Silverton. Looks big. Three killed.Four of seven buried, one dug out.
I would think the situation would get worse with snow moving in.

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A total of 10 skiers, snowboarders and snowmobilers have been caught in avalanches in Colorado this season, with eight people buried and now seven deaths, according to the Colorado Avalanche Information Center.
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CAIC Report

87398124-FCAC-4CC4-89E5-5A15C70102AF.jpeg

 

LiquidFeet

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An overview of the avalanche accident site near Silverton on Monday, Feb. 1. The red line marks the general path of the group, down the slope and then down the gully. The blue lines mark the approximate boundaries of the avalanche. The large avalanche on the left caught the group of skiers. The small avalanche on the right released simultaneously.

That's the caption for that image above. Elsewhere it says they triggered it.

For those of you who understand these things, how could skiers on the red line trigger that avalanche? It looks like it started beside them and above them, not under them. It came down on them from above when they were crossing the mountain, so they must have been down below when it released. How could they be the trigger?
 
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James

James

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It came down on them from above when they were crossing the mountain, so they must have been down below when it released. How could they be the trigger?
The fault can propagate up, then destroying the weak bond between the snow above and below. Mostly I think in hard slab avalanches. There would be nothing holding a huge mass to the ground.
The Sheeps Creek slide in Loveland propagated some 1,000 ft up iirc. It was far, anyway. They were crossing near the bottom.

In this situation maybe just that lower steep area slid, then causing the whole slope to go. We await the report. Could take a week.
 
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jmeb

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How could they be the trigger?

I'd like to wait for the CAIC report before speculating, but I would guess it was a remote trigger from the valley/terrain trap at the bottom.

If when crossing through that valley, they triggered a slab, that slab may have been supporting the slope above them. As the slab in the valley failed, then the slab on the steep entrance failed, and with that gone there was no support of the slab above all the way up the face. An example of why it is so critical to think no just strictly about overhead terrain, but overhead terrain that is potentially "connected" -- i.e. the snowpacks are supporting one another.

Here are two illustrations that sort of demonstrate it -- both these types would've been at play in this case.
1413664797880.jpg


avi-transceivers-01.jpg



So unbelievably tragic.
 

SBrown

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An overview of the avalanche accident site near Silverton on Monday, Feb. 1. The red line marks the general path of the group, down the slope and then down the gully. The blue lines mark the approximate boundaries of the avalanche. The large avalanche on the left caught the group of skiers. The small avalanche on the right released simultaneously.

That's the caption for that image above. Elsewhere it says they triggered it.

For those of you who understand these things, how could skiers on the red line trigger that avalanche? It looks like it started beside them and above them, not under them. It came down on them from above when they were crossing the mountain, so they must have been down below when it released. How could they be the trigger?

Imagine a house of cards, and they pulled one out of the bottom.
 

HardDaysNight

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Remote triggering is typically associated with hard slab instability. It’s one of the spookiest phenomena one can imagine and, unless one has seen it happen, really beggars belief!
 

Tricia

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I'm not as savvy as many others here, but I get the idea that the low tide year we've been having in general this season, through much of the west, compouded with the new snow that is coming in with different temps is creating some crazy layers.
 

martyg

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I was shoveling out a rock wall feature that has landscape lights. Its pretty at night. I'm down with an injury this year, so it seemed like a good use of tine.

The snow just felt like absolute junk as I dove my shovel into the snow. Layers of hard crust interspersed with layers of nothing but honeycombed snow.

Our #snowpack is just so sketch right now. If I were to go backcountry skiing it would just be ridge walking with my dog, and zero danger from terrain above,
 
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James

James

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1FC5B530-0BDE-4708-87BE-1F1E1A12E5D7.jpeg

The depth of snow in that ravine where the skiers were buried could be very deep.
 

pais alto

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The depth of snow in that ravine where the skiers were buried could be very deep.
From TGR.
PRESS RELEASE San Juan County, Colorado
Silverton Colo.: Wednesday February 3rd. The Ophir Pass avalanche recovery operation accomplished extracting the three missing skiers from Monday’s avalanche. The victims have been recovered but still need to be removed from the area via helicopter. The weather was too adverse for helicopter operations on Wednesday. Ground teams worked all day from 6:00AM to 6:00PM

San Juan County Sheriff’s Dept., Office of Emergency Management, San Juan County Search & Rescue, La Plata County Search & Rescue, Silverton Mountain Medical crew, and CAIC were all involved in today's operation. La Plata County SAR brought in a snowcat to remove 12-foot-high avalanche debris on the road from yesterday’s avalanche that ran naturally in the area. Avalanche activity impeded the recovery mission and needed to be removed in order to retrieve the trapped snowmobiles and equipment that were used on Tuesday’s operations. All equipment was successfully extracted from the accident area today and the recovery mission ended with the successful goal of retrieving the three skiers. The skiers were wearing beacons which enabled a successful identifiable location. They were buried in 20 plus feet of avalanche debris. Due to the rugged terrain and avalanche debris, a helicopter retrieval of the three skiers is now required. The next open window of weather permitting will allow the final step of this recovery mission to happen and complete this operation. The final step will be transferring the persons to the San Juan County Coroner's office for positive identification.

PLEASE CONTINUE TO AVOID THE OPHIR PASS AREA

Avalanche danger in the backcountry is always unpredictable regardless of your avalanche knowledge and skills. It is critical to check the avalanche forecast and avalanche danger prior to venturing into the backcountry. Check the Colorado Avalanche Information Center (CAIC) for avalanche conditions, have your equipment of beacon, shovel, probe and make a plan for communications with your ski group.
”...buried in 20 plus feet of avalanche debris...”
 
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James

James

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Wow. That’s some serious shoveling/tunneling. Takes a lot of people. Without beacons on the victims I can’t see how they would find them till May or June.

This guy’s using a chainsaw-
65E48A10-F40E-45A4-9CA0-3F53CE02B60E.jpeg

From the CAIC facebook page.
 

locknload

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I'd like to wait for the CAIC report before speculating, but I would guess it was a remote trigger from the valley/terrain trap at the bottom.

If when crossing through that valley, they triggered a slab, that slab may have been supporting the slope above them. As the slab in the valley failed, then the slab on the steep entrance failed, and with that gone there was no support of the slab above all the way up the face. An example of why it is so critical to think no just strictly about overhead terrain, but overhead terrain that is potentially "connected" -- i.e. the snowpacks are supporting one another.

Here are two illustrations that sort of demonstrate it -- both these types would've been at play in this case.
1413664797880.jpg


avi-transceivers-01.jpg



So unbelievably tragic.
Really good graphic to show how features affect snow stability. Put this together with yet another death right outside the gate at Park City and we have the makings of an incredibly scary and dangerous year. I do not know what the CO avvy report said that day (I follow UT) but I'll guess it was high at the altitude and aspect where they were. The weak layer has been there since early season and the recent snow and wind events have just made it worse. Very sorry for everyone involved.

This is a great year just to practice avoidance. If you go out (with proper training and gear) just stay in low angle stuff and remove the risk. The terrain trap at the bottom gives me the chills....ugh.
 

Ken_R

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An overview of the avalanche accident site near Silverton on Monday, Feb. 1. The red line marks the general path of the group, down the slope and then down the gully. The blue lines mark the approximate boundaries of the avalanche. The large avalanche on the left caught the group of skiers. The small avalanche on the right released simultaneously.

That's the caption for that image above. Elsewhere it says they triggered it.

For those of you who understand these things, how could skiers on the red line trigger that avalanche? It looks like it started beside them and above them, not under them. It came down on them from above when they were crossing the mountain, so they must have been down below when it released. How could they be the trigger?

Persistent slab avalanches (VERY typical here in Colorado) are a lot of times triggered from below and from a distance. If the slab you are skiing on is connected to the one on the steep slope you can cause a colapse where you are and a crack (or cracks) will propagate very very quickly to the rest of the slope and the slab will break like a pane of glass and come crashing down.

Wide open, Alpine terrain is where you will find just immense slabs that might be only a few feet thick on average but cover entire slopes.
 

Erik Timmerman

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20' of debris. I wonder how deep the survivor was buried. Most probes are only 240 ish cm long. Better be careful with the chainsaw!
 

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