The large, fast-moving mudslide that buried much of Oso, Washington in March 2014 was the deadliest landslide in U.S. history. Since then it’s been revealed that this area has experienced major slides before, but it’s not known how long ago they occurred. University of Washington geologists analyzed woody debris buried in earlier slides and used radiocarbon dating to map the history of activity at the site. The findings, published online Dec. 22 in the journal Geology, show that a massive…







































