Bryce Canyon National Park is home to some bizarre rock formations known as hoodoos. Bryce Canyon is not actually a "real" canyon formed by flowing water. The hoodoos are instead formed by chemical weathering and frost wedging of sedimentary rock. A hoodoo is a tall, thin spire of rock that rises from the bottom of an arid, or desert basin. They are different from pinnacles or spires due to their unusual or variable shape. Pinnacles and spires are smooth and taper from the ground upward, while hoodoos take on a more "totem pole" shape.
For much of the year, Bryce Canyon experiences temperatures both above and below freezing each day. Water seeps into cracks in the mudstone, limestone and siltstone, and expands by nearly 10% as it freezes at night. Over time, the ice breaks the rock apart, creating the unusual structures. Acid from rain water also helps dissolve some of the limestone. The unusual shapes are caused by differing erosion rates of the different types of sedimentary rock in the basin.