Why does the Sierra Madre Occidental appear steeper from the west than from the east?

The Sierra Madre Occidental appears steeper from the west because its western margins have been deeply dissected into formidable escarpments, with benched flanks that drop into deep canyons known as barrancas. In contrast, when viewed from the east, the mountains present a relatively slight but broken relief.1

This rugged western landscape is the result of the dissection of the plateau's margins, which created a deeply gouged, angular terrain. These canyons, such as the famous Barranca del Cobre (Copper Canyon), can feature local relief exceeding 5,000 feet (1,500 metres). While the range was once assumed to be a structurally simple feature of horizontal lavas, it is now understood to have a complex history involving deformation, faulting, and significant volcanic deposition during the Cenozoic Era.21