According to the National Park Service, "Capitan Reef is now recognized as one of the most well-preserved fossil reefs in the world ... Movement of faults over the last 20 million years caused a long-buried portion of the Capitan Reef to rise several thousand feet above its original position. This uplifted block was then exposed to wind and rain causing the softer overlying sediments to erode, uncovering the more resistant fossil reef and forming the modern Guadalupe Mountains. Today the reef towers above the desert floor as it once loomed over the floor of the Delaware Sea 260 to 265 million years ago."