Acronyms in the MIN

Snowpack tests involve digging a large square hole in the snow (aka a pit), then isolating a column of snow to test the reactivity of weak layers within it. Watch this video by forecaster Mike Conlan for instructions on a variety of snowpack tests:

Snowpack tests are indicative of a specific location only. The snowpack can vary tremendously across different elevations, aspects, and even the same slope. If you see test results in a MIN report, consider them as one piece of a much larger avalanche conditions puzzle.

We often see compression test results in MIN reports, as it is the easiest snowpack test to perform. This test is used to identify weak layers in the snowpack and assess their strength. Conducting a CT involves isolating a 30x30 cm column, placing the flat part of the shovel on top of the column, and applying a series of taps to the shovel blade with increasing strength.

There are three topics of interest: the number of taps required to cause a fracture; the character of the fracture; and the depth of the layer that fractured.

Results are ususally recorded in this style: CTM15 down 32, SP.

In this example:

• CTM15 means compression test moderate that took 15 taps to trigger a fracture
• Down 32 is the depth of the weak layer that failed
• SP indicates the fracture character.

Fracture character is a description of how the weak layer responds to the load of the compression test. There are five types of fracture character broken into three major classes: sudden, resistant, or break. Sudden failures indicate a greater likelihood of slab avalanches than resistant failures and breaks. Watch this video by Dr. Bruce Jamieson, a leading avalanche researcher, to learn more about fracture character.

We also see these extended column test (ECT) results in the MIN. The ECT assesses both initiation (how much force it takes a weak layer to fail) and propagation (how far the failure will spread across the column, and, possibly, across the slope). The ECT involves isolating a column 90cm x 30cm, placing the shovel blade on top of the column at one end, and applying the same series of taps as the compression test. Results are recorded in this style:

• ECTP15 means a fracture propagated across the entire column on the 15th tap (from the elbow).
• ECTN25 would mean a fracture occurred on the 25th tap (from the shoulder), but it did not propagate.

Snow hardness, or density, is a common measurement taken during a snow profile and indicates the relative strength of various layers throughout the snowpack. The person conducting the snow profile will first identify the separate layers, and then assess each layer’s hardness using their hand, a pencil, or a knife.