Cotahuasi Canyon in Peru and Hell' Canyon on the
Oregon-Idaho border are deeper — but Grand Canyon
is known for its overwhelming size and its intricate and
colorful landscape. Geologically it is significant because
of the thick sequence of ancient rocks that are beautifully
preserved and exposed in the walls of the canyon.
These rock layers record much of the early geologic
history of the North American continent. Grand Canyon
is also one of the most spectacular examples of natural
erosion in the world.
The principal consensus among geologists is that the
Colorado River basin (of which the Grand Canyon
is a part) has developed in the past 40 million years
and that the Grand Canyon itself is probably less than
five to six million years old (with most of the downcutting
occurring in the last two million years). The result of all
this erosion is one of the most complete geologic columns
on the planet.
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