Remotely triggered avalanche on the lower east/southeast face of peak 10420 going down into the adjacent Lake Lackawaxen flats. There were no ski or snowboard or snowmobile tracks going into or out of the slide path. It appears that the slide was remotely triggered by a snowmobile climbing the hillside skiers right of the slide by about 30 yards. This avalanche was observed from the Hidden Canyon Saddle accessed from Brighton Resort.