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Rivers. Text References. Planet Earth pages 255-_____ Bunnett Orange Pages 46-48. Introduction. Source: A river source is the beginning of a river. These are located in mountains, and the source may be fed by an underground spring, or by run-off from rain, snowmelt, or glacial melt.
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Text References Planet Earth pages 255-_____ Bunnett Orange Pages 46-48
Introduction • Source: A river source is the beginning of a river. These are located in mountains, and the source may be fed by an underground spring, or by run-off from rain, snowmelt, or glacial melt. • Mouth: A river mouth is the place where a river flows into a larger body of water, like another river, a lake, or an ocean. • Rivers are most effective in humid climates because they carve out valleys as they mature. • Rivers do so much for people and the land. Three specific types of work that rivers do are erosion, transportation and deposition. • A peneplain is the result of river erosion, transportation, and deposition. These three things make a peneplain, which is a level plain.
The River as an Energy System • Energy is the ability to do work. The amount of energy that a river has determines whether it can erode a valley, transport materials and deposit them. • Friction plays a huge role in the flow of the river. A wide and flat river is not good for transporting water because the friction slows the water down. However; a river that is deep and narrow is perfect for transporting water because there is much less friction. • Erosion in a river is caused by attrition, corrasion, hydraulic action, and chemical solution. Attrition is when pebbles are eroded by hitting each other as they roll down the river bed. Corrasion is the wearing away of the river bed and banks by all the material passing through. Hydraulic action is the same as corrasion, but instead of erosion being caused by materials, it is from the weight and pressure of water. Chemical solution is the dissolving of minerals from rock materials.
Drainage Patterns • Watershed: A ridge of high land dividing two areas that are drained by different river systems. • River Basin: The land area drained by a river and its tributaries. • Tributaries: A stream that flows into a larger stream or other body of water.
Information about Rivers • Three sections of a mature river are denudation, deposition, and division. A mature river starts to carve the landscape out more. The deposition occurs when the river flows and carries materials along with it. The river eventually starts to divide and branch off. • There are three names for each of the river stages. • Youth Torrent Stage Upper Course • Mature Valley Stage Middle Course • Old Plain Stage Lower Course
Other information about rivers • There are four types of erosion in rivers. Abrasion is when materials grind against the river edges. Attrition is when loads carried by the river are tossed against the sides and they break apart. There is also hydraulic action and solution. • Rivers speed can decrease because of the water entering a lake, water entering a sea, or water entering a gently sloping plain. • Three reasons why rivers volume may decrease is that it could be dry season, there are permeable rocks which soak in the water, or evaporation may be very high in a region. • A youth staged river will most likely begin in the mountains and have a very steep slope. Mature rivers tend to be between the mountains and land and therefore, the slope is not steep, but not level. On the other hand, an old river will be fairly level to the ground.
Contour Lines and Elevation • The gradient for the young portion of a river is steep, for a mature portion it is not as steep, and for an old portion it is almost flat. • The valley shape for a young river is steep, for a mature river it is rolling, and for an old river it is flat, like a flood plain. • Contour lines for young rivers will be close together, for mature rivers, somewhat close and for old portions they will be very far apart.
Youth River Stage • Potholes are deep round holes worn in by loose stones spinning in strong rapids or waterfalls.
Interlocking spurs are when erosion takes place on alternate sides of the rivers bank.
Rapids are moving water with great speed. Waterfalls are steep cliff like surfaces
Concave and convex banks are determined by whether the bank slants in or out.
Gorges occur where valleys have very steep sides and are both narrow and deep.
Canyons are very similar to that of a gorge. The only thing that separates a canyon from a gorge is the size of it.
Erosion • Headward erosion causes the river valley to grow in length. • Vertical erosion makes the river deeper. • Lateral erosion causes the river to widen.
Mature River Stage • Meanders are broad, curving bends in a river.
Slip off slopes are gentle slopes on the banks off a river. They are either concave or convex.
Old Age River Stage • Flood plains are layers of sediment that are dropped by a river. This extends over the entire valley and creates a flood plain.
Braided channels are when the river is divided into branches because of deposited material that cut off the river.
Ox Bow lakes are formed when a river is running through a valley and a lake stretches and connects with the river.
Levees and raised beds are when a river builds up its bed and banks with deposit and the river then flows between elevated banks.
A delta is a level area of deposits formed at the mouth of a river, where it enters a shallow and/or calm water body.
