Waterfall

Waterfalls, also known as cascades, are notable for being “a river or other body of water’s steep fall over a rocky ledge into a plunge pool below,” where the plunge pool is just a landing spot for the cascading water [1]. This collection of feature most set waterfalls apart.

The location of waterfalls is oftentimes particular, with “waterfalls commonly formed in the upper course of a river where lakes flow into valleys in steep mountains” [2]. Waterfalls form in a variety of different ways, with multiple visual features resulting from how they formed, but they “often form as streams flow from soft rock to hard rock. The soft rock erodes, leaving a hard ledge over which the stream falls such as granite formations forming cliffs and ledges” from the “stream’s channel cutting deep into the stream bed” [1]. With this erosion, the stream will carry along sediment, such as silt, pebbles, or even boulders.

Erosion continues throughout the existence of a waterfall, with “a stream's velocity increasing as it nears a waterfall, increasing the amount of erosion taking place and eroding rocks in the waterbody above waterfalls to be very flat and smooth, and eroding the plunge pool at the base." This erosion may be contributed to through “whirlpools” created by the crashing flow as well. This erosion, high velocity flow, and vertical drop of water combine to lead to this rapid, turbulent, foamy water present in whirlpools. With this erosion, ‘the area behind the waterfall may be worn away, creating a hollow, cave-like structure called a "rock shelter,”’ which is easy to recognize. Finally, aside from erosion, a “waterfall may form across a fault, or crack in the Earth’s surface. An earthquake, landslide, glacier, or volcano may also disrupt stream beds and help create waterfalls” [1].

References

[1] National Geographic Society. (2012, October 9). Waterfall. Retrieved (2021, July 21), from https://www.nationalgeographic.org/encyclopedia/waterfall/

[2] Carreck, Rosalind. (1982). The family encyclopedia of natural history. Windward. The Hamlyn Publishing Group. pp. 246–248. ISBN 978-0711202252