A canyons is also known as a Gorge.

A Canyon is a deep ravine between pairs of escarpments or cliffs and is the most often carved landscape by the erosive activity of a river over geologic timescales.

The Gandikota Canyon

Rivers have a natural tendency to cut through underlying surfaces so will eventually wear away rock layers to lessen their own pitch slowing their waters; given enough time, their bottoms will gradually reach a baseline elevation—which is the same elevation as the body of water it will eventually drain into.

This action, when the river source and mouth are at much different base elevations will form a canyon, particularly through regions where softer rock layers are intermingled with harder layers more resistant to weathering.

Canyons within mountains, or gorges that have an opening on only one side are called box canyons.

Slot canyons are very narrow canyons, often with smooth walls.

Canyons are much more common in arid than in wet areas because physical weathering has a more localized effect in arid zones. The wind and water from the river combine to erode and cut away less resistant materials such as shales.

Sometimes large rivers run through canyons as the result of gradual geological uplift. These are called entrenched rivers, because they are unable to easily alter their course.

Where the largest and deepest canyons of the World found?

The deepest canyon in the world is at the confluence of the Gilgit and Indus rivers, where the Karakoram Highway was constructed, the river flows at an elevation of about 1,000 m (3,300 ft) above sea level.

To the South by 15 km, rising in one continuous sweep above the Indus, the largest such rise on the planet, is the summit of the world’s 9th-highest mountain, Nanga Parbat, 8,126 m (26,660  ft) high. Rising to the north, also visible from the bridge over the Gilgit, is the westernmost of the great Himalayan peaks, Rakaposhi, 7,788 m (25,550 ft) high.

That makes the Indus gorge 7,120 m (23,360 ft) deep from river to peak at that point, more than 600 m (2,000 ft) greater than the depth of the Kali Gandaki Gorge and 1,500 m (5,000 ft) deeper than the Yarlung-Brahmaputra Gorge.

These are the three deepest canyons in the world. Only the largest mountain ranges of Asia have the scale for such canyons to have formed.