Curious Nature: What’s under the snow?

Nathan Boyer-Rechlin
Walking Mountains Science Center
An avalanche in East Vail's Abraham's Bowl in an area known as Marvin's killed a local skier in February.
Provided by Vail Ski Patrol

By now, most of us are likely aware that Colorado’s snowpack is more dangerous than we have seen in recent years. Articles, warnings, and social media posts have all broadcasted a simple yet increasingly important message when it comes to backcountry recreation: This year isn’t normal.

However, what is it that actually makes our snowpack so dangerous this year? If you look below the snow’s surface, what will you find? These question bring us to the audience participation portion of this article, because the best way to understand what’s happening in our snowpack is to see for yourself!

If you live downvalley, or on the sunnier south facing slopes near Avon and Edwards, you may want to take a quick drive to one of our valley’s snowier trails. However, if you have over a foot or two of snow where you live, you can likely see many of this season’s problems right in your own backyard.

In order to take a peek into the snowpack, you will need to dig (with a shovel, or just your bare hands) or find a trail-side log or boulder where this season’s snow has piled up. As you look at this cross-section of snow what you’re really seeing is the history of our winter, a history written in layers that you can see and feel! As you dig into the snow, look for these common layers.

Near surface facets

If you’re ever found yourself admiring how Colorado’s snow often sparkles back at you on sunny days, congratulations — you’ve found this first layer. On clear and cold nights the snow at the top of our snowpack transforms from branched snowflakes into small angular ice crystals called facets.

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Anytime you see Colorado’s iconic sparkling snow you’re looking at faceted snow. Now, I know what some of you are likely thinking, hold on, the snow always sparkles.

Well, next time we get some fresh snow head outside right as the sun starts to break and you may notice that it’s not as sparkly as you remember. This is because fresh snow hasn’t faceted yet and the branched snowflakes do not reflect light in the same way as the angled faces of faceted crystals.

Crust layer

The next layer to look for is a crust layer. This will be a stiff and crunchy layer of snow that formed after a warm sunny day melted the surface of the snow, and then refroze overnight.

Depth hoar

To find this final layer of snow, you’ll need to dig all the way to the bottom of the snowpack. Hidden here is the ‘monster under the bed’ of Colorado’s snowpack. Take a handful of this snow and compare it to what is on the surface. If the snow you’re digging into has been around for a while, it likely resembles rock salt more than pristine snowflakes. These icy crystals are also faceted snow, just like the layer at the top of our snowpack, but they have had all season to transform and grow into what you see now.

This image from the Colorado Avalanche Information Center shows slabs over weak snow on a south aspect near treeline in the Vail-Summit zone. It is harder to affect the weak layers low in the snowpack, but if you did, the slab above is quite massive and the avalanche would be large.
Courtesy CAIC

What makes this year different?

Here in Colorado you would find these weak layers in almost any season. However, this year, the depth hoar at the bottom of the snowpack is larger and weaker than in years past. The early season snow that fell in September and October transformed and rotted for months until winter finally hit in force over the last six weeks.

The resulting snowpack is not unlike if you were to stack plywood on top of rows of dominos. After you’ve stacked enough plywood you may even be able to stand on it. However if you try to dance and accidentally knock over a domino — well you can imagine what would happen. As we start to see more and more yellow in the avalanche forecast (yellow represents moderate danger) remember that this season, as the Colorado Information Center reminds us “This is not your Grandmother’s moderate.”

To learn more about how these layers cause avalanches and why this year has proven so problematic, head over to the Colorado Avalanche Information center’s website at

Nathan Boyer-Rechlin is the Community Outreach Coordinator at Walking Mountains Science Center. He loves playing in, digging into, and just generally admiring snow.

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