Each brook flows from the source, where it originates, and, gaining strength, ends at the mouth of the river, where it flows into another body of water (ocean, sea, lake, other river or reservoir). It follows that the mouth of the river - this is the place of its connection with another body of water. Some do not have a permanent mouth, sometimes they lose it in the swamp, so it is not always possible to trace the end of the brook.
There is the concept of the so-called blind mouth. It can appear as a result of drying or when water seeps into the ground, sand, or a river flows into a closed lake.
It is customary to distinguish such types of estuaries as delta and estuary:
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the river delta owes its appearance to deposits of erosive products and their removal in large quantities;
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estuary - the flooded lower part of the valley.
If the sea is shallow at the mouth of the river, tidal or tidal currents are not expressed and the river carries a sufficiently large amount of sediment, then we can safely say that nature created all the conditions for the appearance of the delta.
An example of the world's largest delta is the mouth of the Amazon. Its area is more than one hundred thousand km². Just in this delta there is another record holder - Marajo, a huge river island that exceeds Scotland in area. The Amazon River is staggering with its mouth, it is ten times the width of the English Channel. Therefore, it is not surprising that in the rainy season the river begins to leave its banks and thereby floods the adjacent forests. She is very rich in fish and vegetation. There are some species of animals that live only in the Amazon. Because of the width, crossing it is not so easy, it will take about four hours to do this.
Estuaries are formed where the descent of the coast is observed at the mouth of the river. The Ob River boasts the largest estuary. It is called the Gulf of Ob, its length is about 800 km, 50-70 km wide and 25 m deep.
Rivers that flow into the cold seas of the Arctic differ in the types of their mouths. For example, the Lena River and others to the east have deltas. They are pronounced and go far into the sea. Those to the west form estuaries.
The mouth of the Dniester River, which carries its waters into the Black Sea, is characterized by such a formation as a estuary. And her neighbor Danube formed a delta at the confluence. What factors have contributed to this, still remain a mystery to scientists, the light on which they managed to shed only partially.
A very simple view of the delta is the coraco delta. It consists of two braids that are located on both sides of the channel. This type can only be seen on small rivers, for example, in Italy - p. Tiber Similar braids appeared when the flow velocity in the river became small, but the current remained on the rod.
Also not too common type is the lobed delta. An example of this can be seen on the Mississippi River. Its delta arose due to the furcation of the channel, in this case it was on several sleeves. The prerequisites can be different: starting from the roughness of the area, ending with the influence of the human factor.
These types of deltas form when they flow into the seas. There is another species that is characterized by flowing into shallow bays. Such deltas still have a name - run. An example is the Danube River. The Niger Delta is very interesting, because its edge received a smooth contour. The surf of the sea put a lot of effort into this.
