The geologic story of Red Rock Canyon began nearly 300 million years ago when sand and gravel washed down from the ancestral Rocky Mountains, forming vast alluvial deposits that eventually became the Fountain Formation. About 50 million years later, shifting desert dunes blanketed the area, creating the striking red Lyons Sandstone that gives Red Rock Canyon much of its distinctive character today.

Over the next 100 million years, the landscape changed dramatically as shorelines advanced and retreated across the region. At various times, the future canyon was a tidal flat, a delta, a sandy shoreline, and eventually the floor of a shallow inland sea. Layers of sand, mud, seashells, and even shark teeth accumulated over millions of years, forming the Morrison, Purgatoire, Dakota, Colorado Group, Fort Hays Limestone, Smoky Hill Shale, and Pierre Shale formations that can still be seen throughout the area.

Then came a period of powerful mountain-building known as the Laramide Orogeny. Beginning about 70 million years ago, immense forces deep within the earth uplifted the Rocky Mountains and tilted the sedimentary rock layers of Red Rock Canyon into the dramatic formations visible today. Along the Ute Pass Fault, these younger sedimentary rocks meet much older rocks, including the 1.7-billion-year-old Idaho Springs Gneiss and the billion-year-old Pikes Peak Granite found in nearby Section 16. In some locations, ancient cracks in these igneous rocks were filled with sand during the Cambrian Period, creating unusual sandstone dikes that stand apart from the surrounding rock layers.

Over millions of years, erosion carved the uplifted rock layers into the parallel ridges, valleys, and canyons that define Red Rock Canyon today. Sand and gravel carried down from the mountains accumulated in lower areas, forming the mesas and rolling landscapes that complete this remarkable geologic story.