AY Honors/Waterfalls/Answer Key

Hopetoun Falls near Otway National Park, Victoria, Australia

A waterfall is usually a geological formation resulting from water, often in the form of a stream, flowing over an erosion-resistant rock formation that forms a sudden break in elevation. Waterfalls may also be artificial, and they are sometimes created as garden and landscape ornament.

Some waterfalls form in mountain environments where erosion is rapid and stream courses may be subject to sudden and catastrophic change. In such cases, the waterfall may not be the end product of many years of water action over a region, but rather the result of relatively sudden geological processes such as thrust faults or volcanic action.

The hobby of falls bagging is blossoming in many parts of the world.

Formation

Formation of a waterfall

Typically, a stream flow across an area of formations strata will form shelves across the streamway, elevated above the further stream bed when the less erosion-resistant rock around it disappears. Over a period of years, the edges of this shelf will gradually break away and the waterfall will steadily move upstream. Often, the rock strata just below the more resistant shelf will be of a softer type, and will erode out to form a shallow cave-like formation known as a rock shelter (also known as a rock house) under and behind the waterfall.

Waterfalls can also form due to glaciation, 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 are examples of this phenomenon.

Streams often become wider and more shallow just above waterfalls due to flowing over the rock shelf, and there is usually a deep pool just below the waterfall due to the kinetic energy of the water hitting the bottom.

Types of waterfalls

Cascade-style waterfall in Oregon, United States.

Block: Water descends from a relatively wide stream or river.
Cascade: Water descends a series of rock steps.
Cataract: A large waterfall. See Cataracts of the Nile for a well-known sequence of six.
Fan: Water spreads horizontally as it descends while remaining in contact with bedrock.
Horsetail: Descending water maintains some contact with bedrock.
Plunge: Water descends vertically, losing contact with the bedrock surface.
Punchbowl: Water descends in a constricted form, then spreads out in a wider pool.
Segmented: Distinctly separate flows of water form as it descends.
Tiered: Water drops in a series of distinct steps or falls.
Multi step: A series of waterfalls one after another of roughly the same size each with its own sunken plunge pool.

Examples of large waterfalls

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Angel Falls, the world's highest at 979 m (3230 ft), in Venezuela
Tugela Falls, the world's second highest at 947 m (3110 ft), in KwaZulu-Natal province, Republic of South Africa.
Ramnefjellsfossen, the world's third highest at 808m (2685 ft), at Stryn, Nesdalen, Norway.
Victoria Falls, the world's widest, on the Zambezi River, on the border between Zambia and Zimbabwe
Boyoma Falls, with the world's highest volume, 17,000 m³/s (600,000 ft³/s), on the Congo River, Democratic Republic of the Congo
Gocta, the fifth highest in the world at 771 m (2533 ft), located in the province Chachapoyas, Peru
Yosemite Falls, the tallest in North America, located in Yosemite National Park, United States
Niagara Falls, most voluminous in North America, on the border between the United States and Canada
Rhine Falls, Europe's largest, located in Switzerland
Iguazu Falls, a tall and extremely wide fall located in South America on the Argentina/Brazil border
Jog Falls, India's highest and second highest in Asia, located in Karnataka state, India
Jurong Falls in Singapore is said to be the tallest man-made waterfall in the world