ANCHORAGE, Alaska — It is feared that three skiers have died after an avalanche in the Alaskan wilderness carried them away and buried them under approximately 10 stories of snow.
The National Avalanche Center reports that, on average, about 25 people die in avalanches each winter in the U.S., mostly in backcountry areas. Avalanches are uncommon at ski resorts because they manage their slopes and intentionally trigger smaller slides when no one is present.
Here’s a breakdown of avalanches, their causes, and some safety recommendations:
What were some recent avalanches?
The heli-skiers are presumed dead after being swept away and buried on Tuesday afternoon close to Girdwood, a skiing town roughly 40 miles (64 kilometers) south of Anchorage. Heli-skiing involves using a helicopter to reach isolated areas and slopes with untouched snow for backcountry skiing.
If these three deaths are confirmed, it would be the deadliest avalanche event in the U.S. since 2023, when three climbers died in Washington’s Cascade Mountains.
Experts have stated that it is very unlikely the helicopter triggered the avalanche because its vibration or noise doesn’t generate sufficient force.
Before this week, avalanches had claimed the lives of 15 individuals in the U.S. this winter: 10 backcountry skiers and snowboarders, four snow machine users, and one ski patroller, according to the Colorado Avalanche Information Center.
The most recent incident occurred on Feb. 28 in the Harts Pass area of Washington, where an avalanche caught three snowmobilers. One person died, and another was injured.
On Feb. 22, a skier-triggered avalanche in a steep area above Berthoud Pass in central Colorado resulted in one death. According to the Colorado Avalanche Information Center, it was the state’s third avalanche death this winter and the second in less than a week, following the death of a Crested Butte snowboarder west of Silverton on Feb. 20.
Elsewhere, on Feb. 17, avalanches caused three fatalities: one near Lake Tahoe, on the California-Nevada border, and two backcountry skiers in Oregon’s Cascade Mountains. On Feb. 8, a well-known outdoor guide died in a Utah avalanche.
How do avalanches occur?
Generally, only two elements are needed to create dangerous conditions: a slope of at least 30 degrees and multiple layers of snow.
Additional pressure on the snowpack from weight, wind, rain, heavy snowfall, or movement can cause some layers to break off and slide downhill.
Sometimes a slide occurs as loose snow, known as a sluff. According to the Sierra Avalanche Center, sluffs account for a small percentage of avalanche-related deaths and property damage.
Other avalanches are slab avalanches, which occur when a large snow layer breaks away. These account for the majority of fatalities.
Another type of avalanche occurs when wind forms a snow cornice that hangs over a ridge or the edge of a steep slope. The Colorado Avalanche Information Center notes that the overhang can suddenly collapse, surprising anyone underneath or on top of it.
What triggers an avalanche?
Movement, rapidly changing weather, and wind can all trigger an avalanche. However, experts say that victims or their companions trigger 90% of slides that result in injury or death.
This means that people who ski, snowmobile, snowshoe, or participate in other winter backcountry activities should check the avalanche forecast before heading out and ensure they have the appropriate safety equipment.
Most ski resorts have avalanche protocols or mitigation systems, which often involve checking snowpack stability. Remote detonations are also used to intentionally trigger slides and eliminate dangerous buildup before skiers are allowed on the slopes, according to Chris Lundy, an avalanche specialist.
Lundy stated that the helicopter that dropped off the skiers in Alaska’s backcountry was very unlikely to have triggered the avalanche.
“The common belief that sounds or vibrations trigger avalanches is incorrect. Physical force on the snowpack is required for an avalanche to occur,” he said.
How can one avoid an avalanche?
Don’t think you can outrun one. The Sierra Avalanche Center reports that dry slab avalanches commonly reach speeds of up to 80 mph (129 kph) within seconds. Wet avalanches typically travel at around 20 mph (32 kph).
In comparison, Usain Bolt, an eight-time Olympic gold medalist, set a record of just under 28 mph (45 kph) in the 100-meter dash in 2009 – on a flat track, not a snow-covered slope. Most people caught in avalanches are on the slope when they happen.
The best strategy is to avoid areas where avalanches are likely to occur. Outdoor enthusiasts can consult forecasts at regional avalanche centers or .
If you do venture out, using the buddy system and knowing wilderness first aid is advisable. Experts recommend three essential pieces of equipment: an avalanche beacon or transceiver, which transmits location signals; a shovel for snowpack testing and rescue; and a thin, folding pole for probing the snow to locate buried individuals. An avalanche airbag backpack that inflates when triggered can help the wearer stay on or near the surface during an avalanche.
What if you get caught in an avalanche?
Try to cover your mouth and nose with your hands as quickly as possible. If your arms are outstretched when buried, you will be unable to move them.
Cupped hands provide a small air pocket. Your breath is warm when you exhale, which can help melt the snow. If you’re lucky, you may be able to wiggle a finger or two to slowly create space in the otherwise cement-like snow for more air and eventually escape.