From Miller and others (1998) 
: "Mount Vsevidof is a symmetrical stratovolcano near the southwest end of Umnak Island. It is about 10 km wide at the base and steepens from 15 degrees at 300 m altitude to about 30 degrees near the summit. A circular crater, 1.2 km in diameter, occupies the summit. Glacial ice fills the crater and extends down the north and east flanks of the cone; some of these glacial tongues have incised narrow canyons up to 120 m deep.
"A chain of small cinder cones (unit Qc) below altitude 1220 m parallels a rift on the western flank 
. Young flows of andesite and dacite (unit Qvf) were extruded from this rift and from other vents on north and south flanks of the cone. Pyroclastic deposits, apparently products of a culminating summit eruption, attain a thickness of more than 30 m at the crater but thin downslope.
"The oldest Vsevidof flows (unit Qvba), are overlain by till of the last major glaciation, but the bulk of the cone is believed to be of post-glacial, i.e., Holocene, age. The cone is locally underlain by hypersthene-andesite lava flows and pyroclastic rocks of the more deeply eroded Mount Recheschnoi. Lava flows from both Recheschnoi and Vsevidof unconformably overlie a basement of probable early to middle Tertiary age including plutonic rocks (unit Tdp) and altered sedimentary and metamorphic rocks."