File:Squirrel, Zion Canyon, Zion National Park, Utah (8096061967).jpg

Zion Canyon is a deep and narrow gorge in southwestern Utah, United States, carved by the North Fork of the Virgin River. Nearly the entire canyon is located within the eastern half of Zion National Park.

The beginning of the canyon is usually delineated as the Temple of Sinawava, a vertical-walled natural amphitheater nearly 3,000 feet (910 m) deep. The canyon actually begins much further upstream, however, and runs southward about 16 miles (26 km) through the Narrows to reach the Temple, where a seasonal tributary of the North Fork plunges over a tall waterfall during spring runoff and after heavy rain. The gorge then runs southwest through the national park, approaching 2,000 feet (610 m) deep in places. While the canyon rim is dominated by desert, the canyon floor supports a forest and riparian zone watered by the North Fork Virgin River. The gorge then merges with Pine Creek Canyon as it winds out of the national park and past the community of Springdale. The canyon's end is where it meets the Virgin River, some 100 miles (160 km) northeast of Lake Mead, which the river ultimately flows into.

Geologically Zion Canyon is part of the Navajo sandstone Colorado Plateau, which contained many joints and cracks when first uplifted, one of which was cut by the North Fork of the Virgin River to become Zion Canyon. The river was the largest force in cutting the canyon, mostly by flash floods, as the average flow of the river is very light. This relatively quick downcutting has left many seasonal tributaries with hanging valleys. Some of the largest tributaries have cut down to nearly an equal elevation as the valley floor.

Erosion continues to sculpt the canyon walls, creating natural arches and other rock formations. It is believed that there is another 1,000 feet (300 m) of vertical bedrock that the Virgin River can still erode. Mass wasting, often caused by ice wedging into cracks in the canyon walls, is another force that widens the valley. The Navajo Sandstone formation is easily eroded and is known to be very porous. Unstable geology is prevalent throughout the canyon, and occasional rockslides have formed impounded lakes in the canyon, the most recent of which was roughly 4,000 years ago. Owing to the extreme depth of the canyon, there are many springs fed by the surrounding groundwater, permitting water in the canyon to run year round.

en.wikipedia.org/wiki/Zion_Canyon