Each river is unique in its own way. Everyone has a source - the place where it originates. The point of confluence into a larger water body is the mouth. Large waterways flow into the seas or oceans in different ways: an estuary or delta of the river is formed. The shape and shape of the mouth depends on many factors: the nature of the current, climatic conditions, the terrain, the presence of tides.
In nature, the circulation of water is constant. From the seas and oceans, it evaporates, gathers in the clouds and spills rain. On land, it absorbs into the soil or flows down in streams. Water collects in marshes, ponds, lakes, but sooner or later again falls into the rivers and again returns to the world ocean. The cycle ends. The rivers play an important role in this process.
Their source is sometimes difficult to determine reliably, but the place of the confluence into a larger object is seen from afar. However, each river, due to its characteristics, gives its waters in different ways. The mouth can be straight and deep with a sharply outlined coastline. And it happens that it is shallow and is divided into two, three or many branches (river delta).
The territory adjacent to the mouth can be permanent for many decades or every year to be flooded by tens or even hundreds of kilometers during the flood. And at each river a special character of the current. Exhaust water can be clean or cloudy due to the presence of a large number of organic particles. They flow with a rapid flow from the upper reaches or are washed out of muddy bottom sediments in the lower reaches. If most of them are not carried away at sea, then in such cases delta is most often formed.
River mouth: species
The degree of deposition of sedimentary particles is affected by tides. Often, the mouths of rivers flowing into open seas or oceans form an estuary. Salty sea water is heavier than fresh water. Streams of its tidal wave are recorded far along the channel. With low tide she returns. Constancy of motion prevents sediment particles from accumulating at the watershed boundary. The depth of the channel in such places reaches significant indicators. It often has sharply delineated boundaries, the area adjacent to the coastline is stable and relatively constant. Rivers with a mouth of this type are often navigable. On the shores of wide wedge-shaped estuaries, reminiscent of a convenient bay, large port cities are built up.
The river delta is usually formed when it flows into a lake, reservoir or sea of closed type without pronounced tides. Most of the organic matter carried away remains in the coastal zone, where the current is weakened. They settle down, gradually accumulating. This leads to an increase in the level of the bottom. Appearance islets appear, they turn into braids, dividing the channel into parts. So the sleeves are formed. Those in turn are divided - the river is constantly changing.
The delta of the river
This type of mouth has the form of a triangle. From the similarity with the Greek letter Δ, river formation and got such a name. It is believed that the pronounced form of the Nile mouth was first named in the ancient times by the delta. The type and configuration of the shoreline depends on the predominance of the opposing waves in the final reservoir or in the course of the current.
There are three characteristic types of deltas:
- Stretched when the density of the water of the river because of the abundance of alluvial particles is higher than in the receiving object.
- Conical at relatively equal water density and moderate flow (Nile).
- A finger-shaped mouth is formed (Mississippi).
The delta can form not only at the confluence of the river. Due to the peculiarities of the relief (when the channel leaves the plain) this type of formation can be in the middle course. In this case, the delta will be called internal. Downstream the streams are connected, and to the place of confluence the river carries the water in a single stream.
The change in the shape of the channel in the estuaries of large rivers leads to the formation of special ecosystems in such territories. Often they are characterized by the presence of a smooth, wide species diversity of the animal and plant world, an economic fish resource.
More often than not, more than one sleeve is formed. In the delta of the Lena River, for example, with a width of almost 400 km in the total area of about 45,000 km 2, there are countless of them. The processes of neoplasm are constantly, so it makes no sense to count their exact number in such a vast territory. Only three main channels are not interrupted to the sea, the others branch with the formation of many branches.