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A waterfall is any point in a river or stream where water flows over a vertical drop or a series of steep drops. Waterfalls also occur where meltwater drops over the edge of a tabular iceberg or ice shelf.
Waterfalls can be formed in several ways, but the most common method of formation is that a river courses over a top layer of resistant bedrock before falling onto softer rock, which Erosion faster, leading to an increasingly high fall. Waterfalls have been studied for their impact on species living in and around them.
Humans have had a distinct relationship with waterfalls since prehistory, travelling to see them, exploring and naming them. They can present formidable barriers to navigation along rivers. Waterfalls are religious sites in many cultures. Since the 18th century, they have received increased attention as tourist destinations, sources of hydropower, andparticularly since the mid-20th centuryas subjects of research.
Waterfalls are sometimes interchangeably referred to as "cascades" and "cataracts", though some sources specify a cataract as being a larger and more powerful waterfall and a cascade as being smaller. A plunge pool is a type of stream pool formed at the bottom of a waterfall.Robert L Bates, Julia A Jackson, ed. Dictionary of Geological Terms: Third Edition, p. 391, American Geological Institute (1984) A waterfall may also be referred to as a "foss" or "force".
A river sometimes flows over a large step in the rocks that may have been formed by a fault line. Waterfalls can occur along the edge of a glacial trough, where 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 are examples of this phenomenon, which is referred to as a hanging valley. Another reason hanging valleys may form is where two rivers join and one is flowing faster than the other.
When warm and cold water meets by a gorge in the ocean, large underwater waterfalls can form as the cold water rushes to the bottom.
A process known as "potholing" involves local erosion of a potentially deep hole in bedrock due to turbulent spinning stones around on the bed, drilling it out. Sand and stones carried by the watercourse therefore increase erosion capacity. 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. The rate of retreat for a waterfall can be as high as one-and-a-half metres per year.
Often, the rock stratum just below the more resistant shelf will be of a softer type, meaning that undercutting due to splashback will occur here to form a shallow cave-like formation known as a rock shelter under and behind the waterfall. Eventually, the , more resistant cap rock will collapse under pressure to add blocks 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 by abrasion, creating a deep plunge pool in the gorge downstream.
Streams can become wider and shallower just above waterfalls due to flowing over the rock shelf, and there is usually a deep area just below the waterfall because of the kinetic energy of the water hitting the bottom. However, a study of waterfalls systematics reported that waterfalls can be wider or narrower above or below a falls, so almost anything is possible given the right geological and hydrological setting. Waterfalls normally form in a rocky area due to erosion. After a long period of being fully formed, the water falling off the ledge will retreat, causing a horizontal pit parallel to the waterfall wall. Eventually, as the pit grows deeper, the waterfall collapses to be replaced by a steeply sloping stretch of river bed. In addition to gradual processes such as erosion, earth movement caused by or or can lead to the formation of waterfalls.
Waterfalls also affect terrestrial species. They create a small microclimate in their immediate vicinity characterized by cooler temperatures and higher humidity than the surrounding region, which may support diverse communities of and liverworts. Species of these plants may have disjunct populations at waterfall zones far from their core range.
Waterfalls provide nesting cover for several species of bird, such as the Black Swift and white-throated dipper. These species preferentially nest in the space behind the falling water, which is thought to be a strategy to avoid predation.
/a> Ephemeral waterfall seen from inside cave. Mammoth Cave National Park.
/a> About Horsetail Falls, One of Yosemite's Ephemeral Waterfalls.
/a> Bird Rock Falls. Waterfalls can also be found underground and in oceans.
As late as 1985 a scholar felt that "waterfalls remain a very much neglected aspect of river studies". Studies of waterfalls increased dramatically in the second half of the 20th century. Numerous waterfall guidebooks exist, and the World Waterfall Database is a website cataloging thousands of waterfalls.
Some countries that were colonized by European nations have taken steps to return names to waterfalls previously renamed by European explorers. Exploration of waterfalls continues; the Gocta Cataracts were first announced to the world in 2006.
Waterfalls can pose major barriers to travel. Canals are sometimes built as a method to go around them, other times Portage or Portage railway.
Human development has also threatened many waterfalls. For instance, the Guaíra Falls, once one of the most powerful waterfalls in the world, were submerged in 1982 by a human-made dam, as were the Ripon Falls in 1952. Conversely, other waterfalls have seen significantly lower water levels as a result of diversion for hydroelectricity, such as the Tyssestrengene in Norway. Development of the areas around falls as tourist attractions has also destroyed the natural scene around many of them.
Waterfalls are included on thirty-eight World Heritage Sites and many others are protected by governments.
Many artists have painted waterfalls and they are referenced in many songs, such as those of the Kaluli people in Papua New Guinea. Michael Harner titled his study of the Jivaroan peoples of Ecuador The Jivaro: People of the Sacred Waterfalls. Artists such as those of the Hudson River School and J. M. W. Turner and John Sell Cotman painted particularly notable pictures of waterfalls in the 19th century.
One of the versions of the Shinto purification ceremony of misogi involves standing underneath a waterfall in ritual clothing. In Japan the Nachi Falls are a site of pilgrimage, as are falls near Tirupati, India, and the Saut-d'Eau, Haiti. The Otavalos use Piguchi waterfall as part of the Churru ritual which serves as a coming of age ceremony. (2025). 9780444637871 ISBN 9780444637871 Many waterfalls in Africa were places of worship for the native peoples and got their names from gods in the local religion.
"In China tradition, the waterfall represents" the season of autumn, yin, and the Chinese dragon's power over water that comes from the former two.
Artificial waterfalls are or that imitate a natural waterfall.Susan C. Anderson (Editor), Bruce Tabb (Editor), Water, Leisure and Culture: European Historical Perspectives, Berg Publishers, 2002, , page 122 The Cascata delle Marmore is the tallest artificially built waterfall at .
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