For many years now, the depths of the sea have attracted people. Water, as you know, occupies more than 2/3 of the Earth's surface. Therefore, you can explore it for a very long time. Deep sea trenches today attract many scientists. It is not surprising, since mankind has long sought to know the unknown. In addition, deep-sea trenches on the map appeared relatively recently.
However, not always technical capabilities allow us to satisfy our curiosity. Oceans still reliably keep many secrets hidden under the water. People only at the end of the 19th century began to study deep-sea depressions and plains. And this means that for a long time we will have enough objects for research.
Where are the deep-sea basins located?
It is known that the bottom of the oceans is a plain that lies at a depth of about two meters to 6 thousand meters. The bottom in some areas is covered with wrinkles and hollows. They have different depths. These depressions are located mainly in zones of geological activity. More than 8 thousand meters is their depth.
How did the deep sea troughs
Their occurrence is associated with processes that took place in ancient times, when our Earth was just forming. Nowadays it is difficult to imagine those years when the ocean did not exist on the planet. However, there were such times.
Many knowledge about the processes taking place in the universe is still not accessible to man. Nevertheless, we know something about the origin of planets. Let us leave the divine theory aside and talk about what science thinks about this. Gravity, which had tremendous power, twisted the tangles of planets from a cold cloud consisting of gas and dust. This process can be better understood by imagining how the mistress rolls the bun from dough. Of course, these balls were not of perfect shape. However, they still went to travel throughout the universe.
Volcano formation
The bowels of our planet during the first billion years of such a space journey were very hot. This was influenced by the force of gravitational compression, as well as the radioactive decay of isotopes with a long life. In those days, there were a lot of such isotopes. Apparently, the bowels of our planet then were a kind of nuclear firebox - the upper part of the Earth’s mantle melted . And it was at that time that volcanoes began to operate. Huge masses of gases, ash and water vapor, they began to throw up. And on the slopes of volcanoes flowed fire-breathing lava.
The emergence of lakes and the primary ocean
Our planet as a result of these processes was shrouded in fog. She hid behind the clouds, which carried, in addition to volcanic gases, large masses of water vapor. It should be said that in those days on Earth it was not hot. Scientists conducted research, which revealed that the temperature on the planet about the first billion years of its life did not exceed 15 ° C.
Cooling water vapor fell on the surface of the earth with droplets of condensate . As a result of this, at first it was covered only by individual ponds and puddles. Initially, the surface of the Earth, as you now know, was not smooth and even. However, these irregularities increased as a result of volcanic activity. Water filled the troughs of different depths. Separate lakes became larger and larger until they merged together. So the primary ocean was formed. The explanation presented above was given by Otto Yulievich Schmidt, a Soviet scientist. Of course, this is a controversial hypothesis, like any others like her. However, no one has yet put forward a more plausible version.
Tectonic basins
Now you know how the depressions formed. They represent the lowering of the earth's surface. Where are the deep-sea basins located? They are found both on land and at the bottom of the seas and oceans. Their origin is mainly tectonic. In other words, it is connected with the activity of volcanoes on our planet. Therefore, tectonic depressions are especially numerous. They represent areas in which a prolonged lowering of the Earth's crust is observed due to processes occurring in the mantle (its upper part, which is called the asthenosphere).
Asthenosphere
The word "asthenosphere" comes from two Greek words. One of them translates as "weak", and the second - "ball". Approximately 800-900 km is the thickness of the asthenosphere. It is the most mobile part of the Earth's surface. The asthenosphere is less dense than the lower part of the mantle. In addition, it is more elastic, since its mass is filled with molten magma, which has a deep origin. In the asthenosphere, either outflow or compaction of a substance regularly occurs. Therefore, magma moves all the time. It then goes down, then goes up.
Lithosphere
The mantle is reliably hidden by a solid, solid shell of the earth's crust, the thickness of which is up to 70 km. The earth's crust, as well as the upper part of the mantle together form the lithosphere. This name also has Greek origin and consists of two words. The first of these is “stone,” and the second is “sphere.” Molten magma, which rises up from the depths, stretches (up to a gap) the earth's crust. Most often, such gaps occur precisely in the ocean depths. Sometimes the movements of magma even lead to a change in the speed of rotation of the Earth, and therefore its figures.
The lithosphere is not a uniform continuous cover. It consists of 13 large plates - blocks, the thickness of which is from 60 to 100 km. All of these lithospheric plates have both oceanic and continental crust. The largest of them are American, Indo-Australian, Antarctic, Eurasian and Pacific.
Plate movement and deep-sea troughs
In the distant past, there were different outlines of the oceans and continents, which is explained by the movement of plates. Nowadays, American and African are gradually diverging. The American plate slowly floats to the Pacific, and the Eurasian approaches to the African, Pacific and Indo-Australian.
The movements of the earth's crust due to tectonic activity were observed in all periods of the history of our planet. Troughs also formed at different times. They are characterized by different geological age. Volcanogenic and sedimentary deposits fill ancient depressions. And the youngest are clearly expressed in the relief of our planet. Therefore, it is not difficult for scientists to determine where the deep-sea basins are located.
The shape of the troughs
Lowering the earth's crust can be closed both on all sides, and on most of them. Usually across they reach tens and hundreds of kilometers, less often thousands. As a rule, their shape in relatively calm parts of the crust of our planet is more or less round, sometimes oval. But in the moving belts, where the deep-sea troughs are located, they have a linear shape. They are also often limited here by faults.
Deep water troughs
Depressions are not the only designation of geological objects of interest to us. Recently, pointing to them, they are increasingly saying "deep-sea troughs." The fact is that this concept more accurately conveys the shape of depressions of this kind. There are many of them in the transition zone between the ocean and the mainland. Especially numerous are the deep-sea trenches of the Pacific Ocean. There are 16 troughs here. Also known are the deep-sea trenches of the Atlantic Ocean (there are 3 of them). As for the Indian, there is only one hollow.
The depth of the most significant gutters exceeds 10 thousand meters. They are located in the Pacific Ocean, which is the oldest. The Mariana Trench (on the map above), the deepest known trench, is located here. "Challenger Abyss" is the name of its deepest point. Its depth is about 11 thousand meters. This depression got its name from the Mariana Islands located near it.
The history of the study of the Mariana Trench
Scientists began to explore this object since 1875. It was then that the Challenger, a British corvette, lowered a deep-water lot into it, which determined that its depth was 8367 m. The British repeated their experience in 1951, but this time they used an echo sounder. The maximum depth that he determined was 10,863 meters. A new mark was recorded in 1957. It was established by the Russian expedition, which went to the cavity on the ship "Vityaz". The new record was 11,023 m. Relatively recently, in 1995 and 2011, studies were conducted that showed the following results - 10 920 and 10 994 meters, respectively. It is possible that the depth of the Mariana Trench is even greater.