Why are the rock formations at the bottom of the canyon older?
As a rule, the oldest rocks of layered rock strata are always at the bottom, the youngest at the top. The rock at the bottom was the first to form. Layers of weathered and eroded particles (sediments) or igneous material in the form of lava, add additional weight over time, which causes the mass to sink and compress, forming new rock layers. When running water erodes a canyon, the geologic history of the land is revealed in the rock layers.
