A fatal mudslide in rural northwestern Washington State over the weekend underscores the dangers of this fast-moving natural hazard.

On Saturday morning, a mudslide moved down the Stillaguamish River near the small former fishing village of Oso, Washington. Authorities have confirmed eight dead, eight injured, and as many as 108 people missing or unaccounted for as of Monday morning. The one-square-mile (2.6-square-kilometer) track of the mudslide also destroyed about 30 homes.

"This area has had slides in small increments over the last several years, but this took a huge bite of the hillslope this time," says O'Connor.

Not only has there been a lot of precipitation in the area over the past few months, but the Stillaguamish River also has been