Area traveled began around 7k and went up to 8400 feet; Upon approaching 8100 feet snow stratigraphy and avalanche hazard changed drastically. Shooting cracks occurred on slopes of about 25 degrees; At 8400 feet I was traversing vertically across the slope on a NNW facing slope, and I was actually on a flat bench when I remotely triggered Chute number 7 in the Argenta chutes. It broke 7 feet below the bench I was traveling on. Collapse failure occurred from collapsing on the bench with shooting cracks extending below me, the slope directly below me was no greater than 25 degrees with a roll over 80 feet down hill. Catastrophic Failure appeared to occur as a result of a failure in compression because of the slope being tied into the 35 to 38 degree rollover directly down hill. Cracks shot out to riders left to where the slope ties into a contour shoulder/nose that has a 35 to 38 degree side hill aspect facing NE. Width at the starting zone was approximately 80 feet. Slope checker-boarded below me and took off. Soft slab, yet in the low angel starting zone it left soft chunks scattered about. Weak layer was obviously surface hoar. No need for a hand lense here. The slope had a shimmer and served as a great slippery bed surface. Upon observing slope upon descent when heading back down ascending route it obviously continued down hill propagating at each opening of the gully area. Slope ran 1300 vertical, full course, It remained contained in the gully without propagating to adjacent slopes. At it's widest apex it was about 120 feet wide. Crown face was between 12 and 14 inches. Slope did not gouge in to older snow. Ran to with in 20 feet of the creek, 1350 vertical. Debris at the toe was minimal...2 to 2.5 feet deep.