What Are Avalanches?
There is something beautiful about the mountains, all covered in white snow. It’s relaxing to escape from the bustle of reality, spending winter surrounded by mountains. The snow is a terrific spot to go skiing and snowboarding. In the United States alone, almost 15 million people ski and 7 million people snowboard. However, despite its beauty, snow does pose a great risk. People must be constantly vigilant when on the slopes to avoid becoming buried in an avalanche.
A mass of snow, rock, ice, soil, and other debris flows down a mountainside quickly during an avalanche. Landslides are the common name for rock or soil avalanches. The most common type of avalanche, snow slides, can travel downhill faster than a skier. For those who enjoy spending their leisure time in the mountains, avalanche awareness is essential.
When an unstable snow mass detaches from a slope, a snow avalanche begins. As it descends, the snow accelerates, creating a river of snow and an icy cloud that rises far into the air. As it rushes downhill, the mass picks up even more snow. The weight of a huge, fully-grown avalanche can reach one million tons. It has a top speed of 200 miles per hour (320 kilometers per hour).
Avalanches begin when a snowpack’s layers slide off. A snowpack is an accumulation of layers of snow on a surface, like a mountainside. In the winter, constant snowfall creates a snowpack that is several feet thick. The thickness and texture of the layers differ.
A snowpack’s interlayer connections can be flimsy. A layer’s surface may develop a slippery layer of ice as a result of melting snow that refreezes. Fresh snowfall could slide off this slippery surface because it’s unable to adhere to it.
Melted snow can seep through a snowpack during the spring thaw, making the top of a lower layer slick. The upper snow layers can readily start sliding downhill if there is an increase in weight or vibration. Avalanches have been divided into four categories to make them easier to understand.
Loose Snow or Sluff Avalanche
Loose snow avalanches often occur following a recent snowfall and are common on steep hills.
The snowpack isn’t solid because it has not had enough time to fully settle or because sunlight has loosened it. A loose snow avalanche is an avalanche that begins at a point on the snow surface, builds mass gradually into the form of a fan, and is made of incohesive snow. Loose snow avalanches are more frequent than slab avalanches in extremely steep topography.
When a slab avalanche begins, the slab shatters into many different blocks. A slab avalanche is triggered when the weak layer lies lower down in a snowpack. Other compacted snow layers are placed on top of this one. The weak layer separates when the avalanche starts, pushing all the layers above it down the incline. These strata collapse into a massive slab or block. The snow chunks crumble into smaller and smaller fragments. Some of the fragments form a moving cloud of icy particles and ascend into the air. This fog moves at breakneck speed downward.
Loose snow avalanches can turn into slab avalanches. While thin slabs generally cause little harm, thick ones frequently result in deaths. Slab avalanches pose a risk to mountaineers, hikers, skiers, and snowboarders due to their thickness and speed.
Powder Snow Avalanche
Powder snow avalanches are a combination of slab and loose snow. This avalanche’s bottom half is made up of a slab, or a tightly packed mass of snow, ice, and air. An avalanche cloud of powdered snow can form above this and grow as it slides down the slope. This avalanche may travel over long distances at a pace of up to 190 miles per hour.
Wet Snow Avalanche
Wet snow avalanches are particularly hazardous since they move slowly due to friction, gathering debris from the path. This avalanche initially consists of water and snow, but further research on avalanches has shown us that it can quickly gain momentum.
When Does an Avalanche Occur?
To fully understand how to avoid avalanches, we must first know the three environmental factors needed for an avalanche:
- Slope – Generally, an avalanche will happen on slopes steeper than 30 degrees.
- Snowpack – Unstable snow is indicated by recent avalanches, shooting cracks, and “whompfing” or drum-like sounds under the snow.
- Trigger – It doesn’t take much to tip the scales; people, fresh snow, and winds frequently trigger the collapse of an avalanche.
Avalanches can be fatal and occur suddenly. 18,000 people were killed when a massive avalanche of rocks and ice devastated the Peruvian town of Yungay in 1970. A large avalanche compresses the air below it as it slides down a hillside, creating a strong wind that can tear a house apart, shattering windows, splintering doors, and ripping off the roof.
The human body will sink rapidly because it is three times denser than avalanche debris. This makes it much more challenging to locate and rescue avalanche casualties. When avalanches stop, they settle like concrete which can make it virtually impossible to move your body. The majority of avalanche victims are saved, but those who aren’t, suffocate to death as the snow hardens around them and buries them.
Avalanches are dangerous and can be deadly even while having a fun outing with friends or family. Yet, with training and education, you can know how to handle a situation in case you or your partner are involved in an avalanche.
When going out on the slopes, whether skiing, snowboarding, snowmobiling, or sledding, you need to be aware of the signs of a potential avalanche. We’ll go into more detail about these warning signs later in the article. By studying and educating yourself on this information, you can protect yourself and your partner from danger.
10 Signs of Avalanche Risk
An avalanche is most often caused when a snowpack’s gravitational pull is greater than its stability which causes the snow to slide down the slope. As we’ve discussed, weather, human activity, landscape topography, and snowfall all increase the risk of an avalanche.
Consider taking an avalanche safety course if you want to traverse the backcountry safely. Avalanche risk is present even when it is not predicted, so this list is by no means comprehensive. Prior to any adventure, always check the proper resources for information regarding risk forecasts.
To help you stay safe, The Colorado Avalanche Information Center has listed 10 signs of avalanche risk. Before we start, a word of caution, while this list is a helpful resource, it does not take the place of avalanche safety training.
- Avalanche Forecasts – The avalanche threat and related snowpack conditions are evaluated via avalanche forecasts. For example, The Colorado Avalanche Information Center notifies backcountry users of avalanche threats in all parts of the state. Check to see if your state has similar resources.
- Unstable Snow – Cracked or crumbling snow might be a sign that weak layers are present beneath the snowpack’s surface. Watch for signs of a developing avalanche through “whompfing” or drum-like sounds under the snow which signal the snowpack is collapsing. Heavy rain or snowfall in the previous 24 hours can also cause unstable snow. Snowpack can become unstable for several days after significant snowfall or rain.
- Recent Heavy Snowfall – In older, weaker snow layers, recent snowfall can create a heavy snowpack. Layers may become unstable for several days due to the fresh snow.
- Wind-blown Snow – Avalanche activity is significantly influenced by snow drifts and wind-blown snow. On steep slopes, stay clear of snowdrifts and cornices. Strong winds will leave surface patterns on the snow. This can be a sign that snow has been moved and dumped in potentially dangerous drifts.
- Steep Slopes – Usually, avalanches happen on slopes greater than 35 to 50 degrees. Use an inclinometer to gauge the slope’s steepness.
- Flagged Trees – Trees that have broken or split branches on the upward-facing side of the trunk are flagged trees. Slopes with few trees or only small trees increase the likelihood of an avalanche path because avalanches hinder the growth of trees.
- Connected Environment – Take into account the terrain around and above you. Be mindful of the slopes as steep slopes near flat ground can have a significant impact on how an avalanche progresses. Gullys, cliffs, boulders, trees, water sources, and flat transitions all contribute to the likelihood of an avalanche.
- Persistent Slabs – Even after a snowstorm has passed, persistent slabs of snow can still form. Find out if there are any in your area by looking at avalanche prediction websites.
- Recent Avalanches – Avalanches that have recently occurred in your area indicate that the snowpack is unstable.
- Sudden or Rapid Melting – Heavy amounts of rain, intense sunlight, or prolonged above-freezing temperatures can increase the avalanche risk.
Unstable Snow and Other Triggers
Both weak and strong snow layers make up an unstable snowpack. Snow that is poorly bonded or unconsolidated makes up a weak layer, while snow that is well consolidated, like a slab, makes up a strong layer. A stable snowpack often has less noticeable density variations and is more homogenous.
Each year, there are roughly 100,000 avalanches in the mountains of western North America, claiming the lives of over 150 individuals. Recent studies revealed that Colorado presents the most risk of avalanches in comparison to other states. The research shows that one-fourth of all avalanche-related deaths in the U.S. since 1950 occur in Colorado. In Canada, avalanches present a frequent risk in the highlands of Alberta, British Columbia, and Yukon.
A snowpack gains a new layer following snowfall, increasing the likelihood of snow avalanches. During a storm, further snowfall could overflow the snowpack, causing an avalanche. Earthquakes can also trigger avalanches.
But you don’t need something as catastrophic as an earthquake to cause an avalanche; smaller vibrations, such as from construction equipment and snowmobiles, can cause avalanches too. Even a single skier has the power to start a slide by creating enough vibrations. In fact, it is skiers or other snow activity goers that causes 90% of avalanche incidents involving people.
Right now, it is impossible for experts to say with absolute accuracy when and where avalanches will happen, but, by monitoring the snowpack, temperature, and wind conditions, they can gauge the level of risk.
Ski resorts commonly use avalanche control teams to decrease the risk by triggering slides before skiers hit the slopes. Patrols at some ski resorts use explosives to cause avalanches. Alternatively, they may fire a cannon to shake loose any sizable, fresh snow accumulations on dangerous slopes.
In Canada and Switzerland, avalanche control teams are part of special military units. Stationed in the high mountains, they construct large, sturdy structures to anchor snowpacks. These structures protect homes against slides.
Ignoring Avalanche Warning Signs
Recently, in Colorado, there have been four avalanche deaths. According to the Colorado Avalanche Information Center, avalanches injure and kill between 25 and 30 individuals in the United States every year. Recognizing warning signs that an avalanche may occur is crucial if you want to stay safe and even stay alive.
Avalanches: Don’t Take the Risk
Just this year, in Pole Canyon, the Utah County Sheriff’s Office discovered the corpse of a man who had been caught in an avalanche. According to Utah County Sheriff’s sergeant, two men were out snowmobiling in the area when one of them got trapped and buried in the slide.
The avalanche occurred in a mountain’s open bowl region and was extremely large. The witness, a relative of the deceased, informed rescuers that the two were returning up the mountain from the bowl after riding along when the avalanche began. The avalanche started at a height of 8,000 feet and covered a distance of roughly 1,500 feet.
According to the witness, one of the two men was able to pivot and get out of the avalanche’s way. His friend, however, was discovered days later buried beneath more than 22 feet of snow. Rescuers dug snowy terraces to recover his corpse.
We hope that no one is ever caught in an avalanche, but despite the efforts to stay safe, the risk is ever-present. If you or your partner are ever caught in an avalanche, there are some steps of rescue to prevent death.
If You Are in an Avalanche
While predicting avalanches is not an exact science, there are still methods you can use to survive an avalanche. First, angle yourself to reach the edge of the avalanche flow. Try to escape the mountain’s slab and grab onto something solid such as the downhill sides of trees or rocks.
To prevent injury, push heavy objects, machinery, or other equipment away from you. This means, if you are skiing or snowboarding, try to discard your skis, pole, or your board. Skiers and snowboarders can accelerate by traveling straight downward before turning to the side to avoid sliding.
If you are snowmobiling, try to stay on your machine and ride to the edge of the avalanche. Keep your pack on if you are wearing one. It can help with flotation. In the event that you fall off your snowmobile, push yourself as far away from the vehicle as possible, so you don’t get hurt.
While in the moving avalanche, attempt to roll onto your back with your feet facing downhill. To avoid being swept away, grab onto anything solid (trees, rocks, etc.). Close your lips and clench your teeth. If the avalanche begins to move you downward, use a swimming motion to remain on the surface.
When the avalanche begins to slow down, or even before it begins to slow, propel your body toward the surface of the snow. You should also try to create an air pocket in front of your face with one arm. See if you can push the other arm toward the surface.
Lastly, if you end up being completely buried underneath the avalanche, stay calm. Try to dig yourself out, if possible. Relax your breathing, especially if you can’t dig your way out. Maintain your composure and only shout when a searcher is approaching.
If Your Partner Is in an Avalanche
If you see someone in an avalanche, don’t leave the scene. The window of time to rescue a person from an avalanche is 15 minutes. If there are others, alert them to the situation. Watch for the victim. Make sure you create a point where they were last seen. Do not just jump into a search, but instead make sure that the area is safe first. Do not allow yourself to become a victim as well.
Look for any surface indicators of the victim: gloves, boots, or equipment. Be quiet, and listen for auditory clues. Conduct a beacon search, get close to the area, and begin probing before you begin digging. If the victim is not wearing a beacon, don’t give up. If necessary, administer first aid if you are capable of doing so.
Here’s Your Sign: Get the Right Tools
While many may feel safe in the controlled world of ski resorts, it is always better to be prepared if you find yourself on an untracked run or in the backcountry. For that, it’s crucial to pack the necessary protection equipment.
When it comes to protection, you should never compromise; these are the essentials for avalanche safety equipment:
- Avalanche Transceiver – An avalanche transceiver sends a local signal from the victim in send mode and receives that signal from the victim’s companions in search (or receive) mode.
- Snow Probe – This long tent-pole-like wand folds down into pieces to fit in a pack and is used to locate a buried person after the transceiver search. You’ll want a longer overall length as it makes it easier to locate someone buried deeply. Longer probes also increase efficiency because you can frequently probe to the necessary depth.
- Snow Shovel – The majority of snow shovels disassemble to store away. Bigger is usually better as recovering a victim can require moving lots of snow.
Keep Safe Follow the Warning Signs
Getting caught in an avalanche is preventable. By making sure you are aware of the dangers of an avalanche and how to spot the signs, you can prevent the risk to your life and those traveling with you. No matter what fun you might have, taking the chance on a slope that shows avalanche warning signs is not worth the risk.
If you want more safety training, visit us at hardhattraining.com, where we have training and certification courses on Snowmobile Drivers and Snowcat Operators.