In this article we will talk about the delta. What does this sign look like, and where did it come from? What is the meaning of the word delta? In what sciences and spheres of human life is it used? We will pay special attention to what delta is in hydrology and geography. In particular, we will talk about the most famous river deltas of our planet.
Delta: what does the word mean?
The term and sign "delta" is used in various areas of human life. For example, in physics, mathematics, geography, anatomy, economics. The symbol itself does not even come from Greek, but from a more ancient language - Phoenician. There, this letter bore the name "delt", which translates as "entrance to the door."
Below are listed all areas of application, as well as the meanings of delta as a term and concept:
- Philology. First of all, the delta is the fourth letter of the Greek alphabet. By the way, it was from her that the Cyrillic letter “D” and the Latin D.
- Geography. In hydrological science, a delta is a type of river mouth. This will be discussed in more detail below.
- Astronomy. Delta is one of the names for the constellation Triangle, located in the northern celestial hemisphere.
- Maths. This is the name of one of the functions that allows you to record a point effect.
- Physics. The delta symbol is used to indicate the change between the values of two variables (for example, temperature).
- Economics and finance. In economic theory, there is such a thing as a delta coefficient. This is the level of change in the derivative to the value of the underlying instrument (for example, security or currency).
- Anatomy. This name has one of the muscles of the shoulder, which is directly involved in its extension or flexion.
The letter "delta" outwardly represents an equilateral triangle (see photo above). The uppercase version of the letter looks different - like a circle with a tail at the top. The character can be typed in the Microsoft Word editor. To do this, in the "Insert" tab, click on the "Symbol" button, and then - "Special characters". The sign should be sought in the section "Mathematical Operators". The second way to insert ∆ into the text is to use the keyboard shortcut “2206 Alt + X”.
What is delta in geography?
The surface of the earth's land is indented with beds of hundreds of thousands of rivers and streams. Each of them, of course, has its own source (the point where the watercourse begins) and its mouth (the place where the watercourse flows into the sea or lake). What is delta? This is one of the varieties of the river mouth.
In more detail, the delta is a geological formation that is formed by river sediments and is densely dissected by numerous arms and channels. Most often, it has a triangular shape in plan.
The delta is a separate ecosystem, which is distinguished by a rather complex hydrological regime, unique landscapes and a rich avifauna. As a rule, this area is well-moistened and often boggy (even if it is located in a desert area).
River Delta Formation
So, what is delta, we already know. Now let's find out how it is formed and what it consists of.
It should be said right away that for the formation of delta forms, certain geological, geomorphological and climatic conditions are necessary that would contribute to the accumulation of river sediments in the estuary part of the watercourse. The closer to the mouth, the lower the speed of the river. Therefore, it is here that the active deposition of solid rock particles carried by river waters occurs. Most often it is sand, clay, silt, limestone.
Gradually, too much rainfall accumulates at the mouth. In this regard, river water begins to look for alternative ways of moving towards the sea. And it finds, while forming a dense network of channels and duct. Over time, the river delta expands more and more, resembling a wide spreading fan.
As a rule, all river deltas consist of the same rocks. Basically, these are sandy-clay deposits, less often - coal and limestone. Often in the deltas of large rivers are deposits of iron or copper ores.
The main types of deltas
In modern science, several types of river deltas are distinguished:
- Classic multi-sleeve (example - Volga).
- Multi-lobed (Mississippi).
- Blocked (Murray).
- Coracoid (Tiber).
Separately, it is worth highlighting the so-called internal deltas. They arise in an arid climate, when the riverbed branches into several branches and is "lost" in its own sediment, never reaching the ocean. A striking example is the delta of the African Okavango River.
The largest deltas of the planet
The deltas of lowland rivers flowing into relatively calm bodies of water can be enormous. The largest of them are listed below (the area in thousands of square kilometers is indicated in brackets):
- Ganges (105.6).
- Amazons (100.0).
- Lena (45.5).
- Mekong (40.6).
- Mississippi (28.6).
- Nile (24.5).
- Volga (19.0).
- Danube (5.6).
The Ganges has the largest river delta on Earth. It has the shape of a triangle and consists of almost 250 sleeves. The Ganges Delta covers an area of 105,640 square meters. km, which is approximately comparable with the area of such a country as Bulgaria. There is also the world's largest mangrove forest - Sundarban.
One cannot but mention the Nile Delta. At one time, it was she who, with her ideal triangular shape, reminded the ancient Greek geographers the fourth letter of their alphabet. And so the term "delta" arose, which was firmly entrenched in geographical science. Since ancient times, the Nile Delta has been known for the exceptional fertility of its soils.