Today a recreational party triggered a cornice above our group gathered at 1900 m along the climber's right Xmas tree trim line on the left feeder gully of the Emerald Lake slide path. The debris stopped about 350 m above us, and in hindsight we were not threatened by it considering our position in low frequency terrain along the trim line, although a refrigerator sized cornice chunk rolled past us and continued 1500 m down the path. We are uncertain if the cornice triggered a slab, but assume so based on characteristics of the avalanche flow and debris.