On the afternoon of September 20, a large volume of water surged down Mount Shasta's south flank into Mud Creek, entraining debris and inundating the drainage and roads near McCloud, California.
Mount Shasta debris flow not linked to volcanic activity
USGS seismologists have determined that the event was not triggered by volcanic or seismic activity. There is no visible change to the Konwakiton Glacier at the head of Mud Creek. The USFS reports that the debris flow was triggered either by rapid release of subglacial water or ponded water from the Mount Shasta Summit Plateau.