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
1980 eruption of Mount St. Helens
1980 eruption of Mount St. Helens
West Crater