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Written by Administrator
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Monday, 05 October 2009 |
 Flowing water, even though only a small part of the hydrosphere, its activities affect the earth's surface sculpture. This activity is associated with the movement of water, which flow through the power of gravity. The speed of water flow depends on the decline, mostly decreasing with the passage of the river oases, water flowing, which increases its course.
In most rivers distinguishes three sections: the upper course, middle, bottom. In each course indicate the different activities of varying intensity. It is a destructive activity, transporting and judging. Water flowing through the manger kindle haul rock material to form a trough and valley. The destructive activity of the deepening and widening the river bed is called erosion. Erosion activity varies from one cross country. Water flowing indented in depth and increases or cuts off the edges of the trough and the trough extends. There are, therefore: the erosion of bottom, side and backward.
In the upper reaches of the river is the largest decline. Overridden by strong erosion of the plunge. River strongly crib rocks, widening the riverbed and creating steep valley V-shaped With intensification of the erosion of river indented deep-seated deeper in the bottom of the valley, and remnants of the old river terraces form a bottom (erosion). The rate of erosion depends on the type of river rocks. The rocks are harder, more resistant, the processes of erosion taking place more slowly. Differences in bedrock resistance, after which the river flows, cause that arise: thresholds, rapids and waterfalls.
The speed of the river is not the same across the width of the trough. As soon as it flows over the deepest place of your bed - in the mainstream. Trend shifts from one side to the other bed, destroying the undermining of their shores - is a lateral erosion. The river transports a lot of loose, coarse rock material from the slopes and troughs. In the middle course of the river drop decreases. River by more water. Over the erosion Plunge prevailing transportation rock material. Begins to dominate erosion Side - formed meanders. The river begins to flow . Meanders constantly increasing, and comes to them breaking down and the river straightens its course. Cut and bend of the old lake is called the old river bed. Formed flat-bottomed valley, ie the V-shaped valley transformed by lateral river erosion widens its valley. The river begins - flat-bottomed valley (U).
In the lower reaches of the river water flow is very large. a small decline. River transports more slowly carried the material accumulating it on or flood plain at the mouth. In this section of the river valley is (U). Transportation of material is him on the bottom, the material flows in suspension, dissolved on the surface of the river flows.
Along the river followed by segregation of the material:
- In the throat remains material
- In the valley - gravel, sand,
- At the bottom of the sand and mules.
- Within the estuary mud and fine sand.
The nature of the estuary depends not only on the river itself, but also from the bottom of the reservoir formation, which is considered and the movements of marine waters:
- mouth - when the tank, which passes the river is shallow and does not occur at the edges of its strong currents or tides. The material is deposited when the river near the shore, bottom of the tank until the water surface. River then extends its course, divides into several arms, and sediment builds up on the surface of Alluvial fan - delta.
- Funnel-shaped mouth - formed in the intertidal zone, forcing the river bed tidal wave destroys the edges and expands them, giving them the shape of a funnel. With the outflow of material is far from the shore. The estuary formed when a river ends its course in the deep sea.
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Last Updated ( Tuesday, 27 October 2009 )
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