From Wood and Kienle (1990): "Mount Drum, the westernmost
volcano in the Wrangell volcanic field, was formed between ~0.65 and 0.24 Ma during at least two cycles of cone-building and ring-
dome extrusion. The first cycle began with the construction of a cone consisting chiefly of andesite and
dacite lava flows, breccias, lahars, and tuffs, and culminated with the emplacement of a series of
rhyolite ring domes around the cone's southeast flank. The second cycle of activity, following without an apparent time break, continued to build the cone but with more dacitic flows and fewer
pyroclastic and
volcaniclastic deposits. This stage was followed by the emplacement of at least nine dacitic domes that lie on 270 degrees of arc, crudely defining a circle ~12-13 km in diameter centered approximately at the present summit of Mount Drum. The
rhyodacite dome of Snider Peak and its massive dacite flows erupted late in the second cycle, probably marking the end of major constructive activity. Following the second cycle, paroxysmal explosive activity, probably from the central
vent area, destroyed the south half of the
stratovolcano and deposited ~7 cubic km of hot and cold
avalanche debris over an area >200 square km."