Wooden Shoe Arch formed thousands of years ago, but the rock it is made from is much older. Three hundred million years ago, an inland sea flooded this area, and as the sea evaporated it left a great salt basin that later filled with layers of sand and other sediments. Some of these red and white layers hardened into the sandstone of the Cedar Mesa Formation. Streams flowing westward from the ancestral Rocky Mountains brought the sediments that make up the red layers, and iron-rich minerals oxidized as these sediments washed into the area, giving them their red color. The white layers came from sand bars and coastal dunes left by an evaporating sea, and winds blew this sand into the area to create a vast plain of dunes, whose angled layering is still visible on cliff walls. An abundance of quartz gave these sandstone layers their white color. Over time, buried salt shifted and flowed under pressure from the overlying sandstone, causing the stone to break and split into parallel lines. Rain and the freezing and thawing of ice widened the cracks and eroded weaker rock, and over time water sculpted the sandstone into arches, fins, and spires, including Wooden Shoe Arch, while this erosion continues today.