What three states are covered by the volcano range including the North Cascades?
Cascades Volcano Observatory The David A. Johnston Cascades Volcano Observatory is the volcano observatory that monitors volcanoes in the northern Cascade Range. Its territory covers Oregon, Washington, and Idaho. The Cascade range's southernmost reaches extend into Northern California, and Cascade volcanoes south of the Oregon-California border—such as Mt. Shasta—previously fell into CVO's jurisdiction. However, as of February 2012, these volcanoes fall under the jurisdiction of the newly formed California Volcano Observatory (CalVO), based in Menlo Park, CA which monitors and researches volcanic activity throughout California and Nevada.
Twin Buttes (California) The Twin Buttes are a group of volcanic cinder cones located in the Cascade Mountain Range of Shasta County, California.