See the context of this sign.

Canyon Formation

The River that Cut Through Mountains

Long before and through the Age of Dinosaurs, layers
of sediments were deposited in ancient oceans,
deserts, and lakes that once covered this land. Heat
and pressure over the years compressed the sediments
into rock layers called formations. Over millions
of years the Green River carved through the rock
layers. Then shifts in the earth's crust bent the
formations upward to form the Uinta Mountains. As the
gradual uplift of the mountains occurred, the Green
River held its place, cutting down through 1,700 feet
of Red Canyon.

Don't miss the rest of our virtual tour of Flaming Gorge National Recreation Area in 1127 images.