#WATERFALL RULES WIKI SERIES#

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. Eventually, the outcropping, more resistant cap rock will collapse under pressure to add blocks of rock to the base of the waterfall. 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. The rate of retreat for a waterfall can be as high as one-and-a-half metres per year. 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. This causes the waterfall to carve deeper into the bed and to recede upstream. Sand and stones carried by the watercourse therefore increase erosion capacity. Ī process known as 'potholing' involves local erosion of a potentially deep hole in bedrock due to turbulent whirlpools spinning stones around on the bed, drilling it out. Horseshoe-shaped falls focus the erosion to a central point, also enhancing riverbed change below a waterfalls. Hydraulic jets and hydraulic jumps at the toe of a falls can generate large forces to erode the bed, especially when forces are amplified by water-borne sediment. As the watercourse increases its velocity at the edge of the waterfall, it may pluck material from the riverbed, if the bed is fractured or otherwise more erodible. The caprock model of waterfall formation states that the river courses over resistant bedrock, erosion happens slowly and is dominated by impacts of water-borne sediment on the rock, while downstream the erosion occurs more rapidly. When warm and cold water meet by a gorge in the ocean, large underwater waterfalls can form as the cold water rushes to the bottom. Another reason hanging valleys may form is where two rivers join and one is flowing faster than the other. The large waterfalls in Yosemite Valley are examples of this phenomenon, which is referred to as a hanging valley. 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. Ī river sometimes flows over a large step in the rocks that may have been formed by a fault line.

Waterfalls are commonly formed in the upper course of a river where lakes flow into valleys in steep mountains. A waterfall may also be referred to as a 'foss' or 'force'. A plunge pool is a type of stream pool formed at the bottom of a waterfall. 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. What actually constitutes a waterfall continues to be debated. Some scholars have included rapids as a subsection. In 2000 Mabin specified that 'The horizontal distance between the positions of the lip and plunge pool should be no more than c 25% of the waterfall height.' There are various types and methods to classify waterfalls. Since the 18th century they have received increased attention as tourist destinations, sources of hydropower, and-particularly since the mid-20th century-as subjects of research.Ī waterfall is generally defined as a point in a river where water flows over a steep drop that is close to or directly vertical. Waterfalls are religious sites in many cultures. They can present formidable barriers to navigation along rivers. Humans have had a distinct relationship with waterfalls for years, travelling to see them, exploring and naming them. Waterfalls have been studied for their impact on species living in and around them. 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 on to softer rock, which erodes faster, leading to an increasingly high fall. Waterfalls also occur where meltwater drops over the edge

#WATERFALL RULES WIKI SERIES#

A point in a river or stream where water flows over a vertical drop Geli Ali Beg Waterfall in Erbil Pearl Waterfall, Jiuzhaigou, Sichuan, ChinaĪngel Falls in Venezuela is the world's tallest waterfall at 979 m (3,212 ft).Ī waterfall is any point in a river or stream where water flows over a vertical drop or a series of steep drops.

Waterfall rules wiki