The Laurel Caverns area was once a shallow sea rich with life. Layers of sand were laid down upon one another over time. Each layer included the calcium-rich exoskeletons (shells) of sea life, like corals, crustaceans, brachiopods, and more. Under crushing weight, this mixture fused into Loyalhanna limestone, a unique sedimentary rock that is roughly 50% sand held together by the calcium carbonate formed from shells. During a visit, particularly lucky visitors might even spot a fossil of one of these bygone creatures.
Deep underground, this limestone formed into layers of rock until colossal tectonic forces thrust the stone up to form the Appalachian Mountains, and buckled the layers. As wind and weather stripped away the surface, erosion exposed the limestone. This began a slow-motion masterpiece: mildly acidic rainwater seeped into ancient fractures, dissolving the calcium carbonate and sweeping away some of the sand. This process continues to carve and widen these passages today.
A defining feature of Loyalhanna limestone is its cross-bedding. As you explore, look for angled, rippled, or cross-hatched layers within the cavern that create striking geometric patterns of different textures and color.