What you learned in school
Geography textbooks taught that the Grand Canyon formed through slow, uniform erosion over millions of years as a classic example of gradual geological processes. Students learned about the steady, consistent work of the Colorado River cutting through rock layers at a constant rate. This was presented as the definitive model of how major geological features form through imperceptibly slow changes over vast time periods. The uniformitarian principle suggested that current processes operating at current rates could explain all geological formations.
What we know now
Geography textbooks taught that the Grand Canyon formed through slow, uniform erosion over millions of years - a classic example of gradual geological processes. Students learned about the steady work of the Colorado River cutting through rock layers. While long-term erosion is still important, evidence suggests the canyon's formation involved more rapid processes including catastrophic flooding, rapid downcutting during specific geological periods, and complex interactions between different erosional processes. The formation was more episodic and dramatic than the simple gradual erosion model suggested.