Cascade Volcano Observatory Check out the latest on the Cascade volcanoes. By the end of the Miocene a high region with a variety of eruptons. As was the case with the Sierra Nevada, the Cascades alss rotate to the southwest as a result of extension to the east. Increased uplift and composite volcano building. Pliocene-Holocene, frequent eruptions built modern peaks which have been modified by glaciation.
Volcanism shuts off from south to north as the transform boundary migrates northward.
Mt. Lassen is just north of the shut-off zone. B.P., unlike others most eruptions in form of lava flows, ash eruptions 1840-1890. Mt. Shasta- erupts on avg. Mt. Lassen-largest in the world. The greatest hazard the population and property in the Cascades is between Mt. Rainer and Seattle, Washington.