The buff-colored cliffs and canyons of Cathedral Gorge, called the Panaca Formation, are remnants of a Pliocene-era lakebed. About one million years ago, much of Meadow Valley (the area along US 93 from Caliente to Panaca) was covered by a freshwater lake. Sediments and gravel settled on the lake floor. As the climate changed over centuries, the lake gradually drained, and erosion started working on the exposed sediments. Rainwater and melting snow carved rivulets in the siltstone and clay shale, working their way down and widening the cracks into gullies and canyons. The "caves" area designated on the east side of the Gorge are not true caves but the canyon walls narrow down so much that explorers feel like they are in caves.