While hiking on the ridge to the summit our party noticed remnants of a large avalanche on the eastern face of Mt Nebo. The fracture line went all along the southern boarder of the face starting at around 10400', up to about 11200', across the bowl and to the northern edge (we could not see the northern edge of the crown therefore total width estimate is difficult, perhaps about 1/4 - 1/3 mile?). Depth appeared to vary but the crown looked to be about 1 foot for most of it. The debris appeared to have stopped mostly at the bench around 9700', but it looked like some debris ran into the gully far below. We decided to cut a cornice to see what affect it would have on the slope. With people C and D spotting, A and B approached the chosen cornice. Right where/when spotter C said to 'stop' the cornice released between A and B's feet. Luckily both stepped back onto the ridge. The cornice was about 20 feet wide, perhaps 10 feet out. It triggered another 200+ foot wide avalanche on the east face of Mt Nebo (it was very hard to see just how far the new crown propagated due to our extreme hesitation to get too close to the edge). This slide was above the fracture already observed and was thought to be the same new snow/old snow layer. It looked to be about the same thickness and ran to the obvious bench at about 9700'. At this time our party decided to retreat. Another Note/Observation A natural cornice fall had occurred sometime the night before in the NW couloir. This cornice fall then triggered a slide which propagated all the way down the chute to the apron. From afar we were not sure what exactly had happened but as we gained elevation we could see the point where the cornice had fallen from above a large cliff and landed in the couloir. As we got even closer we could see sympathetic crowns/fractures all the way down the chute on the looker's right side and we began to really understand and appreciate how huge the resulting debris pile in the apron was.