The cone-shaped edifice of the Iliinsky stratovolcano with a base diameter of 8 km on the northeastern slope is complicated by a large explosion funnel 800x1200 m in size and 200-450 m deep, formed during the eruption of 1901. At the top of the volcano there is a double explosive crater. Two large lava flows descend along the northern slope of the volcano. Several small effusive and extrusive domes are noted at the southwestern foot of the volcano.