Volcanism in the Oregon segment of the Cascade Range results from intra-range rifts and the subduction of the Juan de Fuca tectonic plate under the North American tectonic plate. Mount Washington forms part of the High Cascades physiographic region in central Oregon, an arc of Pliocene to Quaternary lava flows, cinder cones, and fissure vents that trend from north to south, with occasional large stratovolcanoes. Near Mount Washington, the High Cascades form a lava field with high-alumina, diktytaxitic basalt erupted from cinder cones. These volcanoes have been eroded by glaciers and reduced to buttes in the Cascade arc, and much of the vents in the area were covered by Mount Washington. Some basalt lava flows occur on the edges of Mount Washington at the Cache Creek and Dry Creek canyons or as outcrops that form benches (long, relatively narrow strips of relatively level or gently inclined land bounded by distinctly steeper slopes above and below) about away from Washington from Patjens Lake to the McKenzie River.