Avalanche: Steam Mill #2 1/7/2010

Mon, 01/11/2010 - 6:14am

Submitted by Toby

Observer Name:

David Rosenberg (1-9-10).........Toby Weed (1-11-10)

Observation Date:

01/10/2010

Occurrence Date:

01/07/2010

Occurrence Time:

Unknown

Region:

Steam Mill #2
Hells Kitchen
Logan River
Logan

Location

41° 57' 19.5732" N, 111° 37' 17.328" W

Avalanche Characteristics

Elevation:

9000'

and below

Aspect:

Northeast

East

Slope Angle:

Alpha Angle:

Trigger:

Natural

Trigger: additional info:

Sympathetic Release

Avalanche Type:

Hard Slab

Weak Layer:

Facets

Depth (avg):

18"

Depth Range:

12" to

Width:

800'

Width Range:

100' to

400'

Vertical:

500'

Vertical Range:

450' to

600'

Snow Profile

Snow Profile Comments:

The avalanche ran on 2-3mm faceted snow near the ground. Not quite depth hoar and elevated about 10 cms off the actual ground surface by basal hard October ice layer......

David's snow profiledescription, (1-10-11):

On Sunday, we did a tour from the Yurt along the top of the ridge all the way over to steam mill peak. On the middle peak above where the slide occurred, I dropped down about 100 vertical ft below the ridge and 200 vertical feet above the crown to do a snow profile and an extended column test and found:

Elevation: 9,100 ft, 36" snow depth, 20 degree slope angle, aspect East - ENE, Date/Time: Jan 10, 12 pm-ish.

Top inch, 35" - 36": ice crust, pen hard
35" - 10": mixtures of 1 finger and 4 finger snow hard, with a distinct layer 1 finger - pen layer sandwiched by 4-finger layer about halfway down
10" - 6": buried facets / depth hoar, fist hard
6" - 0": frozen ice, pen - knife hard, Oct/Nov snow?

With the extended column/shovel test in the same pit, the 1st test failed on the buried facets (i.e., 6"-10" above ground) as I finished isolating the block. Not very clean nor energetic shear. The second test (right next to the first) failed on the 11th shovel tap on the same facet layer with a very clean and energetic shear.

Note that the slope where I did the test was above the crown, but much less steep, and there was a significant convexity between where I did the test and the crown so that I couldn't see the crown from the test location. We also didn't go down nor look closely at the debris or toe.

General Comments

From Beaver Mt, Could see 3 large recent avalanches in Steam Mill #2 in upper Hells Kitchen Canyon...From a distance these looked quite f

Video 1:

General Comments 2

The photo is looking up the Southern Flank of the south of three avalanches, which appear to have been natural sympathetic avalanches from late last week....

Video 2:

General Comments 3

Debris from the large avalanches ran quite a distance through deadly trees in the obvious run-out zone of the large avalanche-prone slope...

General Comments 4

We encountered deep piles of chunky debris stacked on the sparse trees high in the path of the middle avalanche...

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