The formation is well-known among hikers and photographers for its colorful, undulating forms and the difficult hike required to reach it. Due to the fragile nature of the formation and the large number of people wishing to visit it, a daily lottery system is used to dispense only ten next-day permits in person at the Kanab visitor center. Additionally, ten online permits for each date are available four months in advance of a planned trip. A map and information about the hike are supplied to those who have obtained permits.
The Wave consists of intersecting U-shaped troughs that have been eroded into Navajo Sandstone of Jurassic age. The two major troughs which comprise this rock formation are 62 feet (19 m) wide by 118 feet (36 m) long and 7 feet (2 m) wide by 52 feet (16 m) long. Initially, infrequent runoff eroded these troughs along joints within the Navajo Sandstone. After their formation, the drainage basin, which fed rainwater to these troughs, shrank to the point that the runoff became insufficient to contribute to the cutting of these troughs. As a result, the troughs are now almost exclusively eroded by wind, as indicated by the orientation of erosional steps and risers cut into the sandstone along their steep walls. These erosional steps and risers are oriented relative to the predominant direction of the wind as it is now naturally funneled into and through these troughs.
According to wikipedia