Washington Mudslide's Speed Led to High Death Toll
Slide's large size and unstable conditions also make recovery difficult.
Rescue teams, search dogs, and volunteers continued to search for survivors for a sixth day in the aftermath of the devastating mudslide in Washington's Snohomish County. The mudslide, which occurred Saturday morning, crashed down a hillside and destroyed more than 30 homes in the town of Oso. More than 90 people are still unaccounted for.
The mudslide was likely caused by prolonged rainfall, according to Rex Baum, a research geologist with the U.S. Geological Survey. "We know that there have been landslides in that area for a long time, and it's not unusual for deposits from old landslides to be reactivated by prolonged rainfall," he told National Geographic. (See "Mudslides Explained: Behind the Washington State Disaster.")
"This particular landslide has a