Geologically, the history of Sedona began about 500 millions years ago. Over a period of 300 million years, the land was alternately ocean bottom and coastal plain. Sedimentary layers of sandstone formed. Between 200 and 65 million years ago, dinosaurs roamed the land. From 65 to 20 million years ago, there were uplifts in southern Arizona and down faulting and wind erosion in northern Arizona. From 20 to 12 million years ago, volcanic activity caused the Verde Valley to down fault into a deep basin with lakebeds, creating the Mogollon Rim.
About 3 million years ago, the Colorado Plateau uplifted. Since then, erosion by wind, rain and snowmelt has created Oak Creek Canyon and exposed the layers of sediment (Schnebly Hill Formation sandstone) to form the spectacular red rock formations we now see in Sedona. Vegetation and wildlife evolved and migrated. The process continues today, however slowly.