waterfalls

A waterfall is a place where water flows over a vertical drop or series of drops in the course of a river or stream. They commonly form where a layer of hard rock overlies a softer layer; the softer rock erodes more quickly, creating a step over which the water plunges. Erosion at the base undercuts the lip, and the waterfall can retreat upstream over time.

Waterfalls are categorized by how the water moves down the rock face: plunge waterfalls descend vertically with little contact with the rock; horsetail retain some contact while descending; cascades break the fall into a series of smaller steps; tiered or multistep waterfalls consist of two or more distinct drops.

Key features include the crest or lip where the water begins to fall, the plunge pool at the base, and the face or wall of rock over which the water flows. The height and width vary widely, and flow can be seasonal, increasing during wet periods and decreasing in droughts.

Ecology and hydrology: Waterfalls create humid microhabitats and influence downstream sediment and nutrient transport. They can act as barriers to fish migration, though some species can pass via pools and fast-flow channels; in many locations, human-made ladders or bypass channels aid passage.

Human use and conservation: Waterfalls attract tourism and can be sources of hydroelectric power, especially where river flow is reliable. They may be protected within national parks or nature reserves to preserve landscapes, wildlife, and safety.

Notable examples include Niagara Falls on the border of Canada and the United States; Victoria Falls on the Zambezi River in southern Africa; Angel Falls in Venezuela, the world’s highest uninterrupted waterfall; Yosemite Falls in California; Gullfoss in Iceland.