Episodic eruptions during this phase of activity produced andesite and dacite lavas, as well as pyroclastic flows from Peléan activity. Later, the volcano was overridden by the Cordilleran Ice Sheet, which covered a large portion of western North America during glacial periods of the Quaternary.
This phase of volcanic activity produced andesite and dacite lava flows, along with pyroclastic flows from Peléan activity.  The volcano was subsequently buried by the Cordilleran Ice Sheet, which covered a large portion of western North America during glacial periods of the Quaternary.