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 Post subject: Snow Pit Data confusion
PostPosted: Mon Jan 24, 2011 6:20 pm 
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Cap'n Wingspan
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Joined: Thu Apr 26, 2007 3:08 pm
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Location: Wallingford
Can someone explain this to me? This is a chart plotting the data from a snow pit dug on Mazama Ridge on Rainier last wednesday from the Rainier Climbing blog (a blog maintained by the park/rangers on climbing conditions and MRNP news).
I'm not sure if it's just confusing as hell or if I'm just not understanding it or both, but could someone tell me what I'm looking at so I can form some reasonable and reasoned thoughts?

http://2.bp.blogspot.com/_VjLLPPQFH1c/T ... ow+Pit.jpg

thanks


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PostPosted: Mon Jan 24, 2011 7:13 pm 
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Longshanks
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Location: Denver
It's a super confusing, badly made graphic. I don't understand all of it, but I can make a decent guess.

The vertical axis is depth beneath the surface in centimeters. There are two horizontal axes: the top one is snow temperature in Celsius; the bottom is snow hardness. The letters on the hardness axis indicate weather the snow can be penetrated with: F (fist), 4F (four fingers), 1F (one finger), P (pen), K (knife), or I (for in-penetrable ice, I think.).

The left-hand edge of the blue bars on the graph indicate the hardness of each layer, while the faint red line indicates the snow temperature (mostly 0 C).

The bar just to the right of the graph seems to indicate roughly what shape the snow crystals are, and how large they are, in each layer of the snow-pack.

I have no idea what the stability test codes are in the far right hand bar.


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PostPosted: Mon Jan 24, 2011 7:30 pm 
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Cap'n Wingspan
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Hey thanks Obadiah, that makes a lot of sense. I could have spent all night guessing the meaning of the letters that turned out to be snow hardness indicators without ever getting it.


Last edited by Evan Jewett on Mon Jan 24, 2011 8:45 pm, edited 1 time in total.

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PostPosted: Mon Jan 24, 2011 7:44 pm 
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Mountain Rhombus
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the lack of units on the vertical is annoying.

I looked into the right hand codes and this document has absolutely everything: http://www.fsavalanche.org/Default.aspx ... ntLinkId=3
I'm hoping to get around to reading it all shortly.

Here is some quick explanation of the CT and Q numbers: http://www.fsavalanche.org/Default.aspx ... ntLinkId=3

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PostPosted: Mon Jan 24, 2011 8:20 pm 
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UW Climber
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Joined: Thu May 15, 2003 9:00 am
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The (In)Stability Test results are

A Rutschblock test failed at level 6 (RB6 -jumped up and down on it) with a shear quality of 3 (Q3 - irregular shear layer) at a depth of 20 cm from the surface.

A Compression Test showed failure after 19 taps (Score 19 is 10 taps from the wrist and 9 taps from the elbow) with a shear quality of 3. In this test, however, the failure was on a different weak layer at a depth of 50 cm.

These tests do not indicate instability.

The confusion for me is that the hardness measures (the purple blocks) don't line up with the scale at the bottom (P, 1F, 4F, etc.) .


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PostPosted: Tue Jan 25, 2011 12:06 pm 
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UW Climber
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Joined: Wed Oct 07, 2009 9:23 pm
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Location: Portland (on the way to Smith)
Response to Tom:

From my understanding, as having just finished avy 1 yesterday (it was awesome and HIGHLY recommended), is that you can have 1F+ i.e. it's between the hardness of 1 finger and the pencil (P), so that's probably what they're indicating.

Also, here is a snow crystal card that shows what the symbols mean:
http://www.backcountry.com/backcountry- ... ystal-card


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