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 a 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 spheres of human activity. For example, in physics, mathematics, geography, anatomy, economics. The symbol itself does not even come from Greek, but from an older language - Phoenician. There, this letter was called "delt", which translates as "entrance to the door."
All fields of application are listed below, as well as delta values as a term and concept:
- Philology. First of all, 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 one of the types of river mouth. Moremore on this later.
- Astronomy. Delta is one of the names of the constellation Triangulum, located in the northern celestial hemisphere.
- Mathematics. This is the name of one of the functions that allows you to record a point impact.
- Physics. The delta symbol is used to indicate a change between the values of two variables (eg temperature).
- Economy and finance. In economic theory, there is such a thing as the delta coefficient. This is the rate at which a derivative instrument changes to the value of an underlying instrument (such as a 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" looks like an equilateral triangle (see photo above). The capital version of the letter looks different - like a circle with a tail at the top. The symbol can be typed in the Microsoft Word editor. To do this, in the "Insert" tab, you need to click on the "Symbol" button, and then - "Special characters". The sign should be looked for in the Mathematical Operators section. The second way to insert the ∆ symbol into the text is to use the keyboard shortcut "2206 Alt+X".
What is a delta in geography?
The surface of the earth's land is indented by the channels 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, delta isa geological formation that is formed by river sediments and is densely dissected by numerous branches and channels. Most often it has a triangular shape in plan.
Delta is a separate ecosystem, characterized by a rather complex hydrological regime, unique landscapes and the richest avifauna. As a rule, this area is well moistened and often marshy (even if it is located in a desert area).
Formation of a river delta
So we already know what delta is. Now let's find out how it is formed and what it consists of.
It should be said right away that the formation of deltaic forms requires certain geological, geomorphological and climatic conditions that would contribute to the accumulation of river sediments in the estuarine part of the watercourse. The closer to the mouth, the lower the speed of the river. Therefore, it is here that active sedimentation of solid particles of rocks carried by river waters takes place. Most often it is sand, clay, silt, limestone.
Gradually, too much precipitation accumulates at the mouth. In this regard, river water begins to look for alternative ways to move to the sea. And it finds, while forming a dense network of channels and channels. 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 there are deposits of iron orcopper ores.
Main types of deltas
In modern science, there are several types of river deltas:
- Classic multi-arm (example - Volga).
- Multi-bladed (Mississippi).
- Blocked (Murray).
- Beak-shaped (Tiber).
It is worth highlighting the so-called internal deltas. They occur in an arid climate, when the riverbed forks into several branches and is "lost" in its own sediment, never reaching the ocean. A striking example is the African Okavango Delta.
The largest deltas of the planet
Deltas of lowland rivers flowing into relatively calm water bodies can reach colossal proportions. The largest of them are listed below (the area in thousands of square kilometers is indicated in brackets):
- Ganga (105, 6).
- Amazons (100, 0).
- Lena (45, 5).
- Mekong (40, 6).
- Mississippi (28, 6).
- Nile (24, 5).
- Volga (19, 0).
- Danube (5, 6).
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 sq. km, which is roughly comparable to the area of a country like Bulgaria. It is also home to the world's largest mangrove forest, the Sundarbans.
Not to mention the Nile Delta. At one time, it was she who, with her ideal triangular shape, reminded the ancient Greek geographers of the fourth letter of their alphabet. So andthe term "delta" arose, which is firmly entrenched in geographical science. Since ancient times, the Nile Delta has been known for the exceptional fertility of its soils.
