 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.