Rivers can slice remarkably deep into uplifted rock. A canyon is a steep-sided valley cut by running water, often exposing a thick sequence of rock layers. Arid climates favor canyon formation because sparse vegetation leaves the slopes vulnerable to erosion.

The Grand Canyon of the Colorado River is the classic example, but similar features appear wherever rivers maintain downcutting against tectonic uplift. Slot canyons form in particularly resistant rock when flash floods carve narrow, twisting passages.

Canyons provide natural cross-sections of regional geology. Hikers and scientists both use the exposed strata to read Earth history. The same steep walls that create scenic beauty also pose rockfall and flash-flood hazards for anyone traveling inside them.

• Deep valley with steep sides
• Carved primarily by river erosion
• Often reveals stratified rock layers
• Common in uplifted arid regions