A stress-rifting origin of Grand Canyon

The Grand Canyon is a massive rift in the Colorado Plateau. How and when it developed has been debated for nearly 150 years. Most geologists believe the unusual landscape was primarily shaped by water erosion. Here we propose a stress-rifting model to provide an alternative explanation for the origin of Grand Canyon. This paper adopts a brittle-ductile double layer model to simulate the deformation and rifting of the plateau due to the mantle-melting-induced expansion. Our results show that the uplift induced by thermal expansion and its associated horizontal extension can cause open fractures that extend from the brittle surface to the underlying ductile layer in a top-down way. In addition, we find that episodic uplift can deepen and connect multiple fractures together to form a larger fracture network. Our findings suggest that the formation of the Grand Canyon might have been driven by plateau uplift and its associated rifting under crustal extension, wherein water erosion played only a minor role in shaping the course of the Colorado River. The new paradigm provides simpler explanations to some of the long-standing geological mysteries surrounding the canyon.