The avalanche that killed at least eight skiers in California’s Sierra Nevada mountains occurred in the Castle Peak area, near Lake Tahoe – an area where deadly avalanches are not uncommon.

The Sierra Avalanche Center, which provides forecasts for the region, has observed at least 50 avalanches in the area near Lake Tahoe since September 2025. And according to the National Avalanche Center, which maintains a map of locations where avalanche danger is highest, risk is currently particularly high in the Lake Tahoe area.

As of Wednesday, the region ranks a four out of five on the North American Public Avalanche Danger Scale, making it among the areas with the greatest avalanche risk in the US at this time.

People have died in avalanches in the Lake Tahoe area in six out of the past 10 years. Most recently, a snowmobiler was killed earlier this year when an avalanche occurred in the same area near Castle Peak.

According to the Colorado avalanche information center, a backcountry tourer was killed on Powderhouse Peak in February last year.

In January 2024, two riders were caught in an avalanche on KT-22 in the Sierra Nevadas, killing one. And in March of 2021, one snowmobiler was killed in an avalanche near Frog Lake Cliffs, north of Donner Pass.

Other fatal avalanches occurred in the area in 2020, 2018 and 2016.

Perhaps the most well-known avalanche to occur in the region was the Alpine Meadows avalanche of 1982.

That March, a wall of snow crashed into the Alpine Meadows ski resort, killing seven. Although the resort had closed due to weather, four employees who had remained on site were among the dead. The incident was memorialized in the film Buried: The 1982 Alpine Meadows Avalanche and the book A Wall Of White by Jennifer Woodlief.

Avalanche deaths are more likely to occur in the backcountry than within a ski resort. Last year, the Colorado avalanche information center recorded 19 avalanche deaths across the US in the backcountry during the 2024-2025 ski season.

Although avalanches are not uncommon in the Sierras, the death toll of Tuesday’s avalanche makes it among the deadliest in US history.

The deadliest avalanche in US history occurred in Wellington, Washington, in 1910, when an avalanche swept two passenger trains into a gorge, killing 96 people. The second deadliest took place in 1898 in Chilkoot, Alaska, when snow slides killed about 65 people during the Klondike gold rush. The third highest death toll due to an avalanche was recorded in 1981 after an avalanche on Ingraham Glacier swept down Mount Rainer, killing 10.

The avalanche on Castle Peak on Tuesday is now the fourth deadliest in US history.

Avalanches can occur when fresh snow falls on an area where snowfall has already been packed into an icy layer.

“When snow falls, it’s a fluffy crystal structure. But when the temperature rises and the snow starts to melt and then refreezes, it turns more granular,” Nathalie Vriend, associate professor of thermo fluid sciences at the University of Colorado Boulder, wrote in an article for the Conversation.

“That granular, icier snow is a weak layer. When a new snowfall dumps on top of it, the grains in the weak layer can shear, creating a surface for an avalanche to slide on.”

Tuesday’s avalanche “resulted when a persistent weak layer” was covered in a “large load of snow”, Chris Feutrier, forest supervisor of the Tahoe national forest, said at a press conference on Wednesday. That weak layer remains, and has reloaded with another three feet of snow, he said.