Hoodoos are carved from the Claron Formation, whose rock was deposited by ancient rivers, streams, and lakes over a period of 20 million years. State shapes are shown for reference. On the Colorado Plateau, the high elevations and mountains create micro-climates where forests may grow surrounded by arid lowlands. The Cretaceous Seaway moved northward from the Gulf of Mexico into this region of North America. Sediments deposited as the sea invaded and retreated became the brown and gray marine rocks now exposed at the park's lowest elevations and across the Paria Valley.
Edges exposed by uplift are susceptible to erosion.
In Utah the southern edge of the High Plateaus has eroded into the cliffs of the Grand Staircase . Hoodoos and eroding fins.