The northeasternmost volcano is Mount Rees, which reaches a summit height of at Tasch Peak. Volcanic rocks crop out at Trabucco Cliff on its northeastern flank. Glacial erosion has cut deep cirques into the eastern flank of Mount Rees, and volcanic outcrops indicate that volcanic rocks alternate between subglacial formations and subaerial formations. Outcrops consist of breccia and lavas, which in one case are intruded by a dike.