Typically, a river flows over a large step in the rocks that may have been formed by a fault line. As it increases its velocity at the edge of the waterfall, it plucks material from theriverbed. This causes the waterfall to carve deeper into the bed and to recede upstream. Often over time, the waterfall will recede back to form a canyon or gorge downstream as it recedes upstream,and it will carve deeper into the ridge above it.
Often, the rock stratum just below the more resistant shelf will be of a softer type, meaning that undercutting due to splash back will occur here toform a shallow cave-like formation known as a rock shelter or plunge pool under and behind the waterfall. Eventually, the outcropping, more resistant cap rock will collapse under pressure to addblocks of rock to the base of the waterfall. These blocks of rock are then broken down into smaller boulders by attrition as they collide with each other, and they also erode the base of the waterfall byabrasion, creating a deep plunge pool or gorge.
Baatara gorge waterfall near Tannurin, Lebanon.
Streams become wider and shallower just above waterfalls due to flowing over the rock shelf, andthere is usually a deep pool just below the waterfall because of the kinetic energy of the water hitting the bottom. Waterfalls normally form in a rocky area due to erosion.
Waterfalls can occur alongthe edge of a glacial trough, whereby a stream or river flowing into a glacier continues to flow into a valley after the glacier has receded or melted. The large waterfalls in Yosemite Valley areexamples of this phenomenon. The rivers are flowing from hanging valleys
Five highest Waterfalls in the world
1. Salto Angel, (Salto Churún Merú)
Location: Canaima National parkRiver: Gauja (Rio Gauya), tributary of Rio Churún. The last in turn is tributary of Rio Caroni. The name - Gauja - to the river has been given by Latvian Alejandro Laime, who was the first to reach...