GEOGRAPHY.
when the river flows across a zone of rocks with different resistant,
the less resistant rocks get eroded much faster.
this cause a sudden change in gradient and causes the water to plunge thus forming a waterfall.
(formation of waterfall)
During faulting, rocks are uplifted. This results in a displacement of rocls where one layer of rock is higher than the other.
When a river flows across an area where faulting has occured, the gradient of the river bed drops suddenly and a waterfall is formed.
(formation of waterfall by faulting)
As the river overflows its banks and water is spread out over a larger area, the speed of flow is reduced.
It begins to deposit is load, especially when the flood starts to subside.
The heavier and caorser materials will be deposited first on the immediate banks of the river while the finer and lighter materials such as silts and clay will be carried farther away from the banks before they are deposited.
In this way, the deposition process helps to sort out the load carried by the river according to size and weight.
Over a series of floods, sediments aer deposited layer upon layer.
As a result, a floodplain is formed.
(formation of floodplain)
The accumulation of coarser materials on the banks of the river helps to raise the banks higher than the floodplain. forming leeves.
(formation of leeves)
When a river enters a body of water like a lake or the sea, its speed of flow is reduced.
This results in a decrease in the energy of the river and deposition of sediment takes place.
At the river's mouth, sand is deposited close to the shore, while fine silt and clay are carried farther out before being deposited. Over a long period of time, layers of sediment build up and eventually form an extensive platform at the river mouth called a delta.
(formation of delta)
The formation of delta depends on several factors.
First the river must carry a lot of sediment when entering the open sea.
Secondly, the tidal currents must not be too strong.
otherwise, the sediments will be washed out into the sea or pushed along the coast much faster than the river can deposit them.
Third, the coastal water should not be too great or else the sediment will not be deposited on the sea floor and will be dispersed into the sea instead.
(conditions for forming deltas)
Meanders are most common in the lower course of the river.
As erosion and deposition continue on the concave and convex banks respectively, a meander may become more and more pronounced and is separated by a narrow neck.
Eventually, the river breaks through the neck and flows through a straight channel.
The meander is eventually cut iff and us seperated fron the main river channel, thus forming an oxbow lake.
(formation of meander and oxbow lake)
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