here is why - 1300 feet blown off the top of mt st. hlens. it's a stand memory for most people. not locals. they witnessed house-sized boulders falling from the sky and thought the world was coming to an end. >> this morning things were calm over mt st. helen's volcano. the sun cracked the horizon, various wildlife were spotted in the cracks of the radar. a giant slice was missing from the side wall, blown to smithereens 35 years ago today. for two months back then. mt st. helens was rumbling, then at 8:32am what sounded like a sonic boomerang throughout the pacific north-west. the mountain blew sideways. mt st. helen scientist back in 2010 on the anniversary recalled the moment the mountain blew its top. >> superheated groundwater and gases flashed out in a side way motion, and ultimately killing trees up to 17 miles north-west of the volcano. >> reporter: they remembered it happened quickly. >> in about 3 minutes time, 200 square miles of forest was toppled, scorches or killed in a standing position and took 57 lives in a matter of minutes. >> ice melted rivers clogged. buildi