What to know about avalanches, what causes them and how to stay safe

Avalanches, masses of snow moving down a slope, happen most often in the wilderness

An avalanche — a mass of snow moving down a slope — happens most often in the wilderness. Watching for forecasts, bringing the proper gear and getting training to prepare for them can help with outings, according to the National Avalanche Center.

Each winter, about 25 people on average die in avalanches in the United States, the center says, adding, “Some days are dangerous and some days are not.”

Here’s a look at avalanches, how they occur and some tips on how to stay safe:

It generally takes just two ingredients to create dangerous conditions: A slope of 30 degrees or more and layers upon layers of snow.

Extra pressure on top of that snowpack from weight, wind, rain, heavy snow or motion can cause some of the layers to shear off and slide downhill.