Streams and Erosion : LUSENET : Introductory Geology, Oswego State : One Thread

How is flowing water in streams able to erode solid rock and deposit sediment?

-- Joseph Lewis Cook (, May 04, 2001


Rivers and streams are very capable of eroding the solid rock over which it flows. The force of water, especially during high water level periods, is very powerful. Solid bedrocks of granite and other hard, dense rock erodes at a very slow rate, whereas shales and sandstones erode at a much quicker rate. The higher the velocity of the water, the more erosion that may occur. When the river or stream comes to a wider area in the river, or approaches a more gentle slope, the water decelerates. This slowing down of water allows for all the suspended materials to be dropped. The sediments were only eroded and transported because of the initial force and speed of the water in the first place. Once the water loses its potential to carry heavy particles, they fall and build up on the river bed. Erosion and deposition cannot occur in the exact same spot. It can, however, occur nearby to each other. An example of this may be on a sharp river bend. On the outside of the curve, the water is accelerating and is flowing against the banks. It is here that erosion rates are very high. On the opposite side of the river, slowing, more shallow water will deposit suspended sediments, thus allowing erosion and deposition to occur in a close proximity. The link below is helpful in examining both of these processes.

-- Ron Testa, Jr. (, May 04, 2001.

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