A group of 3 snowmobillers were riding in the area near Aagard's cabin between Yamaha Hill and Aagard's Hill. The area is near a treeline on a sidehill with several washes running down the hill. Rider #1 crossed the hill near the bottom right above the treeline. As #2 started to cross near #1's tracks #3 passed and climbed up the hill. As #3 tried to turn around on the hill it started sliding. #3 was able to throttle up and jumped up hill from the first slide only to break off a second. The slide made it down into the trees just at the same time as #2 did. #2 did not get buried or know that the hill had slid until afterwords. #3 was swept down hill with the slide but was able to swim and popped out near the top of the snow. #3 was able to get out of the snow on his own power. He was near his snowmobile which was partially buried.