Some of the youngest volcanic terrain found anywhere in the Cascade Range can be seen in the McKenzie Pass area of west-central Oregon. Above is a panorama visible from Dee Wright Observatory, a small rock tower built to provide travelers with an overlook of the numerous volcanoes and lava flows. The panorama here was shot in late Sept., 1997, and spans about 120 degrees centered roughly in a due north direction, looking subparallel to the axis of Cascade arc volcanism. The bare lava flows in the foreground issued mostly from the Belknap eruptive centers visible in the left side of the image, but lighter lavas on the far right side of the panorama descended from Yapoah cone positioned near Three Sisters volcanoes, several miles behind this view.
Nearly all the named mountains are constructive volcanic cones of various sorts, forming part of the High Cascades, a Quaternary volcanic arc. Notably, about 85% of the lavas erupted here are basalt in composition. A tectonic feature is evidenced in the morphology of Green Ridge, a north-trending normal fault escarpment 1500 ft high, that bounds the eastern side of the High Cascades.
Lavas erupted from Belknap Crater and Little Belknap Shield are likely about 1600-400(?) years old. Lavas immediately surrounding the observation point come from Yapoah cinder cone to the south. Youngest lavas in the area erupted from Collier Cone, a vent located near Yapoah. The Collier lavas have been dated at 400 years age with Carbon 14.