A deadly avalanche struck the Castle Peak area near Lake Tahoe in California's Sierra Nevada mountains on Tuesday. At least eight skiers lost their lives, marking the incident as one of the deadliest avalanches in US history. The region is no stranger to avalanches, with the Sierra Avalanche Center noting at least 50 avalanches near Lake Tahoe since September 2025. According to the National Avalanche Center, the area currently has a high danger level of four out of five on the North American Public Avalanche Danger Scale, among the highest in the country at present. Avalanche fatalities have occurred in this region six times in the past decade. Earlier this year, a snowmobiler died in an avalanche near Castle Peak. Other recent deaths include a backcountry tourer on Powderhouse Peak in Colorado last February; one rider killed on KT-22 in the Sierra Nevadas in January 2024; and another snowmobiler killed near Frog Lake Cliffs in 2021. The Castle Peak avalanche is now the fourth deadliest avalanche event ever recorded in the United States. The deadliest was in Wellington, Washington, in 1910, which killed 96 people. The 1898 Chilkoot, Alaska avalanche killed around 65, while the 1981 Mount Rainier avalanche resulted in 10 deaths. Experts explain that avalanches occur when fresh snow falls onto an icy, weak snow layer. Nathalie Vriend, an associate professor at the University of Colorado Boulder, said, "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." This weak icy layer allows new snow to slide easily. Chris Feutrier, forest supervisor of the Tahoe National Forest, said the recent avalanche "resulted when a persistent weak layer" was loaded with a large amount of snow. He warned that this weak layer still exists and has accumulated three more feet of snow, keeping the avalanche risk very high.