Basics on how to interpret snow profiles

Sample Snow Profile
Sample Snow Profile

This is a quick and dirty explanation of Snow Profiles. For in depth information, see Snow, Weather, and Avalanches: Observational Guidelines for Avalanche Programs in the United States (S.W.A.G.), most of the snow profile information is covered in Chapter 2, and is available online.

The first thing you would want to understand is whether a pit was from top to bottom or bottom to top. Typically if you are not digging to the ground the pit would represent top to bottom. In the case of the of the snow profile above, I was not able to dig to the ground so the profile is top to bottom.

Column one from left to right show the following:
1. Temperature in Celsius represented by the red line. Temperature numbers are at the top of the graph.
2. Each of the blue rows in column one represents layers and the respected density in each layer. At the bottom of the graph you will see the hardness scale of (F) fist (4F) four fingers (1F) 1 finger (P) pencil (K) knife.
3. Often you will see the crust layers in this area as well represented as solid black lines.

Column two shows the height of the snow pack in centimeters. In this case the pit was dug to 180cm. On a profile, look at the notes at the top to see if it was dug to the ground. This information was not entered in this pit diagram and you should assume this was dug to the ground with the top being the top of the snowpack.

Crystal_Grain_Symbols-1024x876
Crystal Grain Symbols

Column three shows the crystal form symbols (referenced in S.W.A.G).  What is important here is the crystal forms above and below temperature gradients (i.e. +1.0 degree celsius change in 10cm). In addition you want to look at the crystal forms above and below the failures found in the stability test column.

Column four shows the size of the grains in mm for each layer.

Column five typically shows the density of the snow similar to column one. In this pit the information was not entered.

Column six shows the failures and the stability test performed. In this case an ECT (extended column test) failed Depth: 80(cm) ECTN score 19 (Translation) Compression test was performed with a medium score of 19 from the elbow, fracture initiates but does not propagate across the entire column (ECTN). This tested was repeated twice with the same results.

At other depths it was recorded as ECTPV. Translation: fracture propagates across the entire column during isolation.

Keep in mind snow profiles should be one of the last tools used in decision making. You should pretty much know what kind of results you are going to get and what snow they will be seeing in their pits before they dig them. You will occasionally get surprises and this should factor into your decision making process.

Again, this is a very quick and brief explanation of snow profiles.

Post a Reply