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 used for 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.

Formation

Formation of a waterfall

Some waterfalls are the result of the underlying strata. 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.

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

• Angel Falls, the world's highest at 979 m (3230 ft), in Venezuela
• Victoria Falls, the world's largest, 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
• 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

Gallery

• Base of Tower Fall with rainbow-750px.JPG

  Tower Fall in Yellowstone National Park, USA

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  Godafoss in Iceland

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  Angel Falls, Venezuela

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  Wailua Falls in Hawaii, USA

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  Dettifoss in Iceland

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  Man-made waterfall at the Australian National Botanic Gardens in Canberra, Australia

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  Waterfall near Brienzersee, Switzerland

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  Earthen Dam Waterfall in Waverly, New York, USA

• Kaieteur.jpg

  Kaieteur Falls in Guyana

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  Niagara Falls, on the border between Canada and the USA

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  A small part of the Krimml Falls, Austria. Scale is given by the people on the right

External links

• World Waterfall Database
• Niagara Falls - Fullscreen QTVR Panorama