45 years ago, Mt. St. Helens' eruption solved a California mystery

For over a century, geologists were baffled by the rolling mounds scattered across Northern California's Shasta Valley. Travelers along Interstate 5 can glimpse these unusual hills and ridges, often mistaking them for volcanic cones or natural terrain. It wasn't until the eruption of Mount St. Helens that scientists realized the landscape was carved by the sheer might of what is thought to be one of the largest landslides ever discovered, an...