One of 13 volcanic cones in the West Crater-Soda Peaks zone, which covers an area of , West Crater is part of a monogenetic volcanic field with basaltic to andesitic volcanic edifices that vary from 360,000 years old to 2,000 years old. It has a summit crater with a width of and a depth of . West Crater's lava dome formed on the floor of a glacial cirque, and has a similar size to the lava dome formed after the 1980 eruption of Mount St. Helens. West Crater has erupted at least two large lava flows within the Holocene epoch, about 8,000 years Before Present, each of which extend about from the volcano. Emplaced into canyons on the sides of the crater, the flows are being eroded by local streams. The lava dome likely formed before the lava flows erupted.