Party of 4 arrived at the top of the Porter Fork Pass approx 10 am and just as we started up the ridge to the north, the slope gave way below us at the very start of the ridge, ran about 350' broke at the PWL about 4', ran into the gut and then down. Serious, unsurvivable. Took a few trees out. We went back down and around to have a better look and then came back to the saddle. Obviously we were at this point disinclined to ski anything along the ridge but we walked up to investigate and saw many fracture lines continuing along the ridge.