This region, rich in marine fossils from the Permian Period, was later buried and then uplifted by tectonic activity. Guadalupe Mountains National Park preserves this rare underwater-to-uplifted narrative, with hiking trails like the Permian Reef Trail offering a hands-on journey through Earth’s ancient marine environments. On the park’s western side, shimmering gypsum dunes contrast this geologic grandeur with a surreal, ever-changing desert landscape.

Ancient Sea to Sky-High Peaks

Rocks that once lay beneath an ancient sea now rise to form some of the tallest peaks in Texas. Towering above the Chihuahuan Desert in West Texas and southern New Mexico, the Guadalupe Mountains are part of one of the world’s best-preserved fossil reefs from the Permian Period. This hardened layer of ancient plant and animal remains provides a detailed snapshot of marine life just before the mass extinction that ended the Permian.

The Texas portion of the range lies within Guadalupe Mountains National Park, established in 1972. The park’s boundaries are visible in the satellite image above, captured by the OLI-2 (Operational Land Imager-2) aboard Landsat 9 on July 7, 2024. To the northeast, the fossil reef continues into New Mexico, where sulfuric acid has dissolved portions of the limestone, creating the vast underground chambers of Carlsbad Caverns National Park.

Life on the Edge of Pangea

During the Permian Period — roughly 300 to 250 million years ago — this region sat at the edge of a shallow inland sea along the coast of the supercontinent Pangea. Here, the Capitan Reef formed, made mostly of sponges and algae. Fossils of other ancient sea creatures, including ammonites, bivalves, brachiopods, crinoids, snails, and trilobites, have also been found throughout the area.

As sea levels dropped near the end of the Permian, the reef was buried beneath thousands of feet of sediment, preserving it for over 200 million years. Then, around 20 million years ago, tectonic activity pushed these layers upward. Over time, erosion stripped away the softer rock above, revealing the more durable fossil reef. In addition to the Guadalupe Mountains, exposed portions of the Capitan Reef also form the Apache and Glass Mountains in Texas.



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