Why do canyons form?
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Answer: Rivers erode rock over time
Rivers erode rock over time ✓ — Correct! Canyons form when rivers cut downward through rock layers over millions of years. The Grand Canyon formed as the Colorado River eroded through sedimentary rock. Downcutting happens faster when land uplifts or sea level drops. Soft rock erodes faster, creating the characteristic stepped canyon walls!
Wind carves deep valleys — Wrong. Wind can erode canyons in dry areas, but most major canyons form from river erosion cutting through uplifted rock.
Glaciers dig trenches — Wrong. Glaciers carve U-shaped valleys, not V-shaped canyons. River erosion creates the deep, narrow canyons like the Grand Canyon.