How to Do a Snow Compression Test
The snow compression test is a quick test for snow stability. It is a solid tool to help identify weak layers in the snow pack and it aids in the decision making process of deciding if the snow pack is stable or unstable. It should not be used alone, but it is an excellent and quick method for any backcountry user to test the snow. Through a progression of compressions on the snow , you'll be able to watch and visually locate dangerous weak layers in the snow and identify the quality of the break. The results from the snow compression test can aid in a decision making process that could save your life.
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Instructions
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Snow Compression Test
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1
Find a safe place to test the snow. It should be an area that is similar to where you want to ski. The snow must be undisturbed for accurate results.
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2
Dig out a snow column using your snow shovel. The column should measure 30 cm by 30 cm and be 100 to 120 cm tall. If your column width is larger, your readings will not be accurate because the shovel won't distribute the compression evenly. If it is taller, it may wobble and create false readings. Use your saw to cut out the back of the column. The sides of the column should be as smooth as possible. If the column fails during digging, it is classified as "very easy" and is very unstable.
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3
Place your shovel blade face down on the top of the column. Using only your finger tips, lightly tap the shovel 10 times. If the column fails, it is classified as "easy" and is unstable. Be sure to watch the column as you tap, so you can identify where and when a failure happens.
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4
Tap the shovel 10 more times from your elbow. The taps will be harder to simulate more compression. If the snow column fails here, it is "moderate" and unstable.
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5
Tap the shovel 10 more times from your shoulder. Use your fist to hit the shovel blade or it may hurt your hand. If it fails here it is called "hard" and is stable. If it does not fail, the snow is stable.
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Record your observations. Include the location of the failures, the number of hits it took, and the way it broke (uneven or smooth). Your observations, along with other tests and information, will help you make a decision about the safety of the snow in each area.
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Perform more compression tests and other snow stability tests in order to make the best decisions.
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Tips & Warnings
Always watch the snow column while you are tapping it because you will be able to see the failures.
Even if there is a failure early on in the process, complete ALL steps to see if there are more weak layers that will fail under greater force.
The compression test can be performed on any slope angle.
If you've never done this test, be sure to watch a trained professional so you have a better idea of what to look for.
The test sometimes gives inaccurate results depending on the hardness of the snow and location of the weak layer.
Multiple compression tests will give a more accurate picture of the area.
You are responsible for your own decisions in the backcountry. Never put yourself in a situation that you are not comfortable with.
