<P> Nearly two billion years of Earth 's geological history have been exposed as the Colorado River and its tributaries cut their channels through layer after layer of rock while the Colorado Plateau was uplifted . While some aspects about the history of incision of the canyon are debated by geologists , several recent studies support the hypothesis that the Colorado River established its course through the area about 5 to 6 million years ago . Since that time , the Colorado River has driven the down - cutting of the tributaries and retreat of the cliffs , simultaneously deepening and widening the canyon . </P>
<P> Nearly two billion years of Earth 's geological history have been exposed as the Colorado River and its tributaries cut their channels through layer after layer of rock while the Colorado Plateau was uplifted . While some aspects about the history of incision of the canyon are debated by geologists , several recent studies support the hypothesis that the Colorado River established its course through the area about 5 to 6 million years ago . Since that time , the Colorado River has driven the down - cutting of the tributaries and retreat of the cliffs , simultaneously deepening and widening the canyon . </P>
when did the colorado river start to form the grand canyon
when did the colorado river start to form the grand canyon
about 5 to 6 million years ago
about 5 to 6 million years ago