Name: The Science Behind Colorado’s Deadly Avalanche Season
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What causes particularly deadly seasons like this one? Does climate change have a role? Rocky Mountain PBS spoke with scientists and avalanche experts to find answers.This video was produced in collaboration with NOVA and is made possible in part by the Corporation for Public Broadcasting, a private corporation funded by the American people.

The 2020-21 avalanche season has been the deadliest season in modern history, according to data from the Colorado Avalanche Information Center.

The 2020-21 avalanche season has been the deadliest season in modern history, according to data from the Colorado Avalanche Information Center.

With 36 deaths in the U.S., the 2020-21 avalanche season has been the deadliest season in modern history, according to data from the Colorado Avalanche Information Center.

What causes particularly deadly seasons like this one? Does climate change have a role? Rocky Mountain PBS spoke with scientists and avalanche experts across North America to find answers.

How researchers are studying a particularly deadly avalanche season

The science behind Colorado’s deadly avalanche season

science behind Colorado’s deadly avalanche season

The Science Behind Colorado’s Deadly Avalanche Season

Planet Earth

The Science Behind Colorado’s Deadly Avalanche SeasonPublished: April 28, 2021Jason Foster: It's been a deadly winter in Colorado's back country: 12 avalanche fatalities so far. That's twice as many as all of last season. Colorado is on pace for its deadly season in a hundred years. But why has this season been so bad?Dr. Ethan Greene: One factor has just been how sensitive our snowpack is. We have a fairly thin snow pack this year. Uh, we have some very weak snow near the ground that formed early in the season. And as we're continuing to pile snow on top of that later in the winter, uh, we're seeing a lot of avalanche. So here in Colorado, we record somewhere between 4,000 and 5,000 avalanches a year. Wow. In north America, the most deadly avalanches are dry slab avalanches. Uh, what happens is that crack shoots across that weak layer and detaches that slab of snow that then goes rolling down the hill. Avalanches are driven by the weather, both the summation of weather events over a particular year, and then also, uh, specific weather events that can sometimes trigger avalanches. In March of 2019, we had a large avalanche cycle in Colorado. Because this was such a large event, we wanted to understand it a little bit better. The way that we're doing that is through dendrochronology. Dendrochronology is the study of tree rings. My specialty is avalanches and not, um trees.Dr. Erich Peitzsch: I use dendrochronology as a tool to study avalanches. I like trees, trees are great. And when an avalanche hits a tree it'll impact the tree and leave a signal within the tree rings. So it's basically a mechanical damage that stays within the tree ring. From that year with more samples, we can say, oh, well, that tree was hit in this year, this year and this year. And then we can look at the sample nearby and say, oh, that tree was hit in these years,Dr. Ethan Greene: Looking at a bunch of trees in a particular area, we can start to get a better idea of how often large avalanches run in these particular areas,Dr. Erich Peitzsch: Which allows us to then develop an avalanche chronology through time.Jason Foster: And that brings us to climate change. Does it play a role?Dr. Erich Peitzsch: Right now, we're sort of in the beginning of trying to look at some of the climate drivers for these large magnitude avalanche events.Dr. Ethan Greene: It certainly makes sense that climate change will affect avalanches. But exactly how is something that we don't really know?Jason Foster: So, how do we reduce avalanche fatalities?Dr. Ethan Greene: In North America, we use a lot of active mitigation. And so that is avalanche forecasting, where we look at how avalanche conditions are developing over time and recognize certain places where we can trigger an avalanche. We move the asset out of the way, whether it's skiers at a ski area or closing a highway and then release an avalanche, typically with some type of explosiveCoulter Austin: For avalanche control, the type of explosive we use is a bag ammonium, nitrate, diesel fertilizer. And within that bag, we put a stick of dynamite and attached to that you have a two and a half minute safety fuse, assembly. Yeah. I mean, it's pretty surreal thing to throw bombs out of a helicopter. The main purpose of our job is the safety of the public below. We are here to protect the public, cause avalanches when we can control them. As a back country, skier or snowboarder, you never want to be alone because if something happens, there's no one there to get you.Dr. Ethan Greene: So getting some training is extremely useful. Little education can save your life.Coulter Austin: If you're buried in avalanche at 10 minutes, you'll have about a 90% chance of survival, uh, past that. It's a very steep drop-off.Dr. Ethan Greene: Anytime you're going into the mountains, you want to be prepared for avalanche safety. Uh, that means carrying an avalanche rescue transceiver, uh, pro pole and a shovel.Coulter Austin: If you find yourself ever caught in an avalanche, try and backpedal, keep your head as close to the surface as you can, as you feel the avalanche slow down, what you're gonnna wan to do is put your hands over your face.Dr. Ethan Greene: In North America, most people die in avalanches from asphyxia.Coulter Austin: If you can get your hands over your face, you can maybe create yourself a little air bubble.Dr. Ethan Greene: So they get buried in the snow.Coulter Austin: You're caught under the snow and you're exhaling. The CO2 creates an ice bubble over your mouth. And that's how you suffocate.Dr. Ethan Greene: The other way that people die in avalanches is from trauma. So that's sustaining some injury as you're moving down the hill in the back country, invest in airbag, protects your neck, protects your headA very small percentage of people that die in avalanches die from hypothermia. With that freedom to go where we want to go and do what we want to do comes the responsibility to take care of ourselves. And in the mountains in the wintertime, avalanche safety is a really important aspect of being prepared. So you can go out, come home safe.

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The science behind Colorado’s deadly avalanche season

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How Do Avalanches Form?

Avalanche Town

Making North America