Waimea Canyon, also known as the Grand Canyon of the Pacific, is a large canyon, approximately ten miles (16 km) long and up to 3,000 feet (900 m) deep, located on the western side of Kauaʻi. Waimea is Hawaiian for "reddish water", a reference to the erosion of the canyon's red soil. The canyon was formed by a deep incision of the Waimea River arising from the extreme rainfall on the island's central peak, Mount Waiʻaleʻale, among the wettest places on earth.
Geologically the canyon is carved into the tholeiitic and post-shield calc-alkaline lavas of the canyon basalt. The lavas of the canyon provide evidence for massive faulting and collapse in the early history of the island. The west side of the canyon is all thin, west-dipping lavas of the Napali Member, while the east side is very thick, flat-lying lavas of the Olokele and Makaweli Members. The two sides are separated by an enormous fault along which a large part of the island moved downwards in a big collapse.
--- http://en.wikipedia.org/wiki/Waimea_Canyon_State_Park