This race is called the Mountain of Hell enduro mountain bike race. Boy did it lived up to its name when just as it stared as they began down the glacier some of the riders crashed causing a pileup.
This event has roughly 700 bikers who all start at the same exact time all going down a 15-mile slippery course of snow, ice, rocks, single tracks and sharp curves. They go down 8,530 feet. this race is a crazy.
This is what you call a domino effect. Once the first biker messed up the rest went down as well.
(video credit youtube.com/chabertonvideo)