What caused the formation of the Grand Canyon?

• A. A meteor impact created the canyon.
• B. Glacial carving alone formed the canyon.
• C. Volcanic activity created a canyon.
• D. The Grand Canyon was formed primarily by the erosion of the Colorado River cutting through layers of rock over millions of years.

Answer: (D)

The influence most responsible for the Grand Canyon is long-term river erosion. Over millions of years, the Colorado River carved downward through the layered rock of the Colorado Plateau, deepening the canyon as the land above slowly uplifted. This uplift increased the river’s gradient and its power to cut, so the canyon could widen and expose walls of different rock types. The result is a deep, stepped gorge where softer rocks wear away faster than harder ones, creating the distinct, colorful layers we see today.

Meteor impacts would create a crater, not a linear, river-cut canyon with exposed sedimentary layers. Glacial carving alone doesn’t fit the Grand Canyon’s profile, even though glaciers shaped landscapes in nearby regions; the canyon’s structure and scale are best explained by river incision over a long time. Volcanic activity would leave volcanic rocks and different landforms rather than the expansive, layered canyon carved primarily by erosion from the river.