The Cascade Anticlinorium is a prominent feature from southern British Columbia to northern California that formed from regional folding during the Cascade Orogeny. Extensive research has been conducted across the anticlinorium and its parasitic folds, but little focus has been given to the erosion surface that truncates the anticlinorium. Outcropping along parasitic folds on the western flank of the Cascade Anticlinorium, Mount St. Helens is an excellent location to assess erosion. An examination of regional stratigraphy and structure of the anticlinorium, as well as the parasitic folds that comprise the deformed basement underlying Mount St. Helens, reveals that at least 7,850 m of strata were eroded along the truncated Lakeview Peak Anticline, while exhumed intrusives in the adjacent Pole Patch Syncline suggest a greater value. Because this erosion surface can be traced across the entire Cascade Anticlinorium, significant erosion occurred across the entire anticlinorium, much of which happened after regional folding. Such massive denudation is only explicable by the Genesis Flood.