Aracar is a polygenetic volcanic cone with a diameter of and a rectangular basis , covering a surface area of . Four lava domes extend southeast from the volcano. Grey basaltic lava flows descend from its summit and form a gentle western flank and much steeper eastern, northern and southern flanks. West of the main summit a wide and several hundred meters deep crater forms Aracar's main crater. Snowmelt occasionally forms small ephemeral lakes in the main crater. A shallow deep secondary crater is surmounted by a flat semilunar wide surface. Small southbound andesitic lava flows are associated with the main crater. Some deep gorges cut into the volcano, and erosion has removed of rock. Moraines, mainly occurring on the eastern side of the volcano, descend to .