Freshwater Falls Info Packet Waterfalls A waterfall is a river or other body of water's steep fall over a rocky ledge into a plunge pool below. Waterfalls are also called cascades. The process of erosion, the wearing away of earth, plays an important part in the formation of waterfalls. Waterfalls themselves also contribute to erosion. Often, waterfalls form as streams flow from soft rock to hard rock. This happens both laterally (as a stream flows across the earth) and vertically (as the stream drops in a waterfall). In both cases, the soft rock erodes, leaving a hard ledge over which the stream falls. A fall line is the imaginary line along which parallel rivers plunge as they flow from uplands to lowlands. Many waterfalls in an area help geologists and hydrologists determine a region's fall line and underlying rock structure. As a stream flows, it carries sediment. The sediment can be microscopic silt, pebbles, or even boulders. Sediment can erode stream beds made of soft rock, such as sandstone or limestone. Eventually, the stream's channel cuts so deep into the stream bed that only a harder rock, such as granite, remains. Waterfalls develop as these granite formations form cliffs and ledges. A stream's velocity increases as it nears a waterfall, increasing the amount of erosion taking place. The movement of water at the top of a waterfall can erode rocks to be very flat and smooth. Rushing water and sediment topple over the waterfall, eroding the plunge pool at the base. The crashing flow of the water may also create powerful whirlpools that erode the rock of the plunge pool beneath them. The resulting erosion at the base of a waterfall can be very dramatic, and cause the waterfall to "recede." The area behind the waterfall is worn away, creating a hollow, cave-like structure called a "rock shelter." Eventually, the rocky ledge (called the outcropping) may tumble down, sending boulders into the stream bed and plunge pool below. This causes the waterfall to "recede" many meters upstream. The waterfall erosion process starts again, breaking down the boulders of the former outcropping. Erosion is just one process that can form waterfalls. 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. Classifying Waterfalls There is not a standard way to classify waterfalls. Some scientists classify waterfalls based on the average volume of water in the waterfall. A Class 10 waterfall using this scale is Inga Falls, Democratic Republic of Congo, where the Congo River twists in a series of rapids. The estimated volume of water discharged from Inga Falls is 25,768 cubic meters per second (910,000 cubic feet per second). Another popular way of classifying waterfalls is by width. One of the widest waterfalls is Khone Phapheng Falls, Laos. At the Khone Phapheng Falls, the Mekong River flows through a succession of relatively shallow rapids. The width of the Khone Phapheng Falls is about 10,783 meters (35,376 feet). Waterfalls are also classified by height. Angel Falls, the world’s tallest waterfall, plummets 979 meters (3,212 feet) into a remote canyon in a rain forest in Venezuela. The water, from the Gauja River, often does not reach the bottom. The fall is so long, and so steep, that air pressure is stronger often than the water pressure of the falls. The water is turned to mist before it reaches the small tributary below. Types of Waterfalls One of the most popular, if least scientific, ways to classify waterfalls is by type. A waterfall's type is simply the way the descends. Most waterfalls fit more than one category. • A block waterfall descends from a wide stream. Niagara Falls, in the U.S. and Canada, is a block waterfall on the Niagara River. • A cascade is a waterfall that descends over a series of rock steps. Monkey Falls, in the Indira Gandhi Wildlife Sanctuary and National Park in Tamil Nadu, India, is a gently sloping cascade. The waterfall is safe enough for children to play in the water. • A cataract is a powerful, even dangerous, waterfall. Among the widest and wildest of cataracts are the thundering waters of the Iguazu River on the border between Brazil and Argentina. • A chute is a waterfall in which the stream passage is very narrow, forcing water through at unusually high pressure. Three Chute Falls is named for the three "chutes" through which the Tenaya Creek falls in Yosemite National Park, California. • Fan waterfalls are named for their shape. Water spreads out horizontally as it descends. Virgin Falls is a striking fan waterfall on Tofino Creek, on Vancouver Island, British Columbia, Canada. • Frozen waterfalls are just what they sound like. For at least part of the year, the waterfall freezes. Mountaineers often climb frozen waterfalls as a challenging test of their skill. The Fang is a single pillar of ice in Vail, Colorado that vertically plunges more than 30 meters (100 feet). • Horsetail waterfalls maintain contact with the hard rock that underlies them. Reichenbach Falls, a fall on the Reichenbach Stream in Switzerland, is a horsetail waterfall where legendary detective Sherlock Holmes allegedly fell to his doom. • Multi-step waterfalls are a series of connected waterfalls, each with their own plunge pool. The breathtaking "falling lakes" of Plitvice Lakes National Park, Croatia, are a series of multi-step waterfalls. • Plunge waterfalls, unlike horsetail falls, lose contact with the hard rock. The tallest waterfall in Japan, Hannoki Falls, is a plunge waterfall that stands 497 meters (1,640 feet). Hannoki Falls is seasonally fed by snowmelt from the Tateyama Mountains. • Punchbowl waterfalls are characterized by wide pools at their base. Wailua Falls is a punchbowl waterfall on the island of Kauai, Hawaii. Although the plunge pool is tranquil and popular for swimming, the area around Wailua Falls itself is dangerous. • The water flowing over segmented waterfalls separate as distinct streams. Huge outcroppings of hard rock separate the streams of Nigretta Falls, a segmented waterfall in Victoria, Australia, before they meet in a large plunge pool. Cascade Tanks West African Lungfish – Protopterus annectens Diet: Feeds on plants, mollusks, frogs and fish Habitat: Found in backwater areas of rivers and lakes in Africa around the Congo. Did You Know? The West African Lungfish lives in areas with a dry season. To survive from one wet season to the next, it hibernates in a burrow surrounded by slime which acts as a cocoon. Elephantnose – Gnathonemus petersii Diet: Feeds on worms and insects Habitat: Found in muddy bottom areas of the Niger and Congo River basins. Did you know? The long snout is actually an extension of its mouth. This part is covered with electroreceptors used for finding food and navigation. Freshwater Pufferfish – Tetradon mbu Diet: Feeds on small fish, mollusks, and crustaceans Habitat: Found in both fresh and brackish waters in the Congo River basin Did you know? This pufferfish can grow up to 2 feet long! Like all pufferfish, they have the ability to puff themselves with water or air when threatened. African Knifefish – Xenomystus nigri Diet: Feeds on worms, crustaceans, insects, and snails Habitat: Found in quiet waters with a lot of vegetation Did you know? The African Knifefish can produce a bark-like sound from their swim bladders. Buffalohead Cichlid – Steatocranus casuarius Diet: Feeds of insects and other fish Habitat: Lives in areas of the Congo River Basin with strong water flow Did you know? Buffalohead Cichlids move by hopping along the bottom rather than swimming because of their larger body size. Reedfish – Erpetoichthys calabaricus Diet: Feeds on worms, crustaceans, and insects, primarily at night Habitat: Found in slow flowing rivers and standing water Did you know? Moves like a snake over the bottom and is able to breathe air in times of low oxygen in the water. Giraffe Catfish – Auchenoglanis occidentalis Diet: Feeds on plankton, mollusks, seeds, and detritus Habitat: Found in lakes and rivers across a large area of Africa Did you know? Male Giraffe Catfish guard the nest of eggs and will even guard eggs of other species. Ornate Birchir – Polypterus ornatipinnis Diet: Feeds on worms and insect larvae when young. Eats mostly small fish as an adult Habitat: Found in calm waters of swamps and rivers Did you know? The females will lay eggs in a cup formed by the male’s fin. He will then spread the eggs out on plants to grow and hatch. Cuvier’s Bichir – Polypterus senegalus Diet: Feeds on small fish, insects, crustaceans, and frogs Habitat: Found in muddy and inshore areas of the Congo River basin Did you know? Courtship starts with either the male or female jumping out of the water to impress the other. Spotted Leaf Fish – Ctenopoma acutirostre Diet: Feeds on crustaceans, worms, insects, and small fish Habitat: Found in the middle and lower areas of the Congo River basin Did you know? These fish are ambush predators. They stay very still in plants and dead trees until a prey item swims close enough for them to grab. African Freshwater Butterflyfish – Pantodon buchholzi Diet: Feeds on crustaceans and fish, also on terrestrial insects, aquatic larvae and nymphs of insects Habitat: Found in calm waters such as swamps, creeks and backwater areas in West and Central Africa Did you know? These fish always hang out at the surface of the water and will jump out to look for insects to eat, or to get away from a predator. Rainbow Krib – Pelvicachromis pulcher Diet: Feeds on worms, insects, and plant material Habitat: Found in heavily vegetated areas of both slow and fast moving water Did you know? Unlike other fish that attach their eggs to vegetation, Rainbow Kribs are cave brooders.