West Crater has erupted at least two large lava flows since Quaternary time, each of which extend about from the volcano. Emplaced into canyons on the sides of the crater, the flows have just started to be eroded by local streams. The flows have a gray color, and they consist of a platy, olivine basalt lava interspersed with olivine phenocrysts. The western flow has ridges perpendicular to its flow with heights of , as well as two levees that reach heights of which span of the deposit. The eastern flow has at least ten subunits with a rough surface; it was more viscous than the western flow. Both deposits have impeded soil development. In addition to the lava flows, hornblende andesite can also be found near West Crater to the northwest of the Trout Creek Hill.