Were These Enormous Class 4 Avalanches Set off by CMH Necessary? Skip to 1:48 for the avalanches. At 6:20, there is a class 4 avalanche that runs 3,300 vertical feet and 2.2 miles. It’s one thing to control avalanches and make sure terrain is safe for skiers and riders. It’s another thing to set of class 4 avalanches with enormous destructive potential hurdling down and destroying 300-year-old forests. If the avalanches […] Avalanche Miles Clark | April 11, 2013 4 Comments