At first glance, the soil under my feet seems completely motionless, but in fact it is not. The earth has a moving structure, which makes movements of a different nature. The movement of the earth's crust, volcanism in most cases can carry a tremendous destructive force, but there are other movements too slow and invisible to the naked human eye.
The concept of the movement of the earth's crust
The earth's crust consists of several large tectonic plates, each of which makes movements under the influence of the Earth's internal processes. The movement of the earth's crust is a very slow, we can say, secular phenomenon, which is not noticeable by the human senses, and yet this process plays a huge role in our life. Noticeable manifestations of the movement of tectonic strata are the formation of mountain ranges, accompanied by earthquakes.
Causes of tectonic movements
The solid component of our planet - the lithosphere - consists of three layers: the core (the deepest), the mantle (intermediate layer) and the earth's crust (surface part). In the core and mantle, too high a temperature causes the solid matter to pass into a fluid state with the formation of gases and an increase in pressure. Since the mantle is limited by the earth’s crust, and the substance of the mantle cannot increase in volume, the result is the effect of a steam boiler when the processes occurring in the bowels of the earth activate the movement of the earth’s crust. Moreover, the movement of tectonic plates is stronger in the areas with the highest temperature and pressure of the mantle on the upper layers of the lithosphere.
Study history
About the possible displacement of the layers of the earth's surface was guessed long before our era. So, history knows the first assumptions of the ancient Greek scientist - geographer Strabo. He hypothesized that some parts of the Earth periodically rise and fall. Later, the Russian encyclopedist Lomonosov wrote that the tectonic movements of the earth's crust are earthquakes that are invisible to humans. The inhabitants of medieval Scandinavia, who noticed that their villages, once founded in the coastal zone, were centuries away from the sea coast, also guessed about the movement of the earth's surface.
Nevertheless, the movement of the earth's crust, volcanism began to purposefully and extensively study during the active development of scientific and technological progress, which took place in the XIX century. The research was carried out both by our Russian geologists (Belousov, Kosygin, Tetyaev, etc.) and foreign scientists (A. Wegener, J. Wilson, Gilbert).
Classification of types of movement of the earth's crust
The motion pattern of the earth's crust is formed of two types:
- Horizontal
- Vertical movements of tectonic plates.
Both of these types of tectonics are self-sufficient, independent of each other and can occur simultaneously. Both the first and second play a fundamental role in shaping the relief of our planet. In addition, the types of movement of the earth's crust are the primary object of study of geologists, since they:
- They are the direct cause of the creation and transformation of the modern relief, as well as the transgression and regression of certain sections of marine territories.
- Destroy the primary relief structures of the folded, inclined and explosive type, creating new ones in their place.
- They provide a metabolism between the mantle and the earth's crust, and also provide the exit of magmatic matter through channels to the surface.
Horizontal tectonic movements of the earth's crust
As mentioned above, the surface of our planet consists of tectonic plates on which continents and oceans are located. Moreover, many geologists of our time believe that the formation of the current image of the continents was due to the horizontal displacement of these very huge strata of the earth's crust. When the tectonic plate shifts, the mainland that is on it shifts along with it. Thus, horizontal and at the same time very slow movements of the earth's crust led to the fact that the geographical map was transformed over many millions of years, the same continents were moving away from each other.
The tectonics of the last three centuries have been most accurately studied. The movement of the earth's crust at the present stage is studied using high-precision equipment, thanks to which it was possible to find out that the horizontal tectonic displacements of the earth's surface are exclusively unidirectional in nature and overcome only a few cm annually.
When displaced, the tectonic plates converge in some places, but diverge in some places. Mountains form in plate collision zones, and cracks (faults) form in plate divergence zones. A striking example of the divergence of lithospheric plates observed at the present time are the so-called Great African Faults. They are distinguished not only by the greatest length of cracks in the earth's crust (more than 6000 km), but also by their extreme activity. The rupture of the African continent is taking place so quickly that it is probably not in such a distant future that the eastern part of the mainland will separate and a new ocean will form.
Vertical movement of the earth's crust
Vertical movements of the lithosphere, also called radial, in contrast to horizontal, have a double orientation, that is, land can rise and fall after some time. The vertical movement of the lithosphere also results in a rise (transgression) and lowering (regression) of sea level. The centuries-old movements of the earth's crust up and down that took place many centuries ago can be traced by the traces left, namely: the Naples temple, built as early as the 4th century AD, is currently located at an altitude of more than 5 m above sea level, however its columns are strewn with mollusk shells. This is clear evidence that the temple has been under water for a long time, which means that this section of soil has systematically moved in the vertical direction, either along the ascending axis or then descending. This cycle of movements is known as the oscillatory forms of motion of the earth's crust.
Regression of the sea leads to the fact that once the seabed becomes land and plains form, among which are the North and West Siberian plains, the Amazon, Turan and others. At present, there is a rise in land in Europe (Scandinavian Peninsula, Iceland, Ukraine, Sweden) and lowering (Holland, south of England, north of Italy).
Earthquakes and volcanism as a result of lithosphere movement
Horizontal movement of the earth's crust leads to a collision or fracture of tectonic plates, which is manifested by earthquakes of various strengths, which are measured on the Richter scale. Seismic waves of up to 3 points on this scale are not noticeable by a person, soil vibrations with magnitudes of 6 and 9 can already lead to significant damage and loss of life.
Due to the horizontal and vertical movement of the lithosphere, channels are formed at the boundaries of the tectonic plates, through which the material of the mantle erupts under pressure to the earth's surface. This process is called volcanism, we can observe it in the form of volcanoes, geysers and warm sources. There are many volcanoes on Earth, some of which are still active. they can be both on land and under water. Together with igneous vapors, they spew hundreds of tons of smoke, gas and ash into the atmosphere. Submarine volcanoes are the main cause of tsunamis; they are superior to terrestrial ones in terms of eruption force. Currently, the vast majority of volcanic formations on the seabed are inactive.
The value of tectonics for humans
In the life of mankind, the movements of the earth's crust play a huge role. And this applies not only to the formation of rocks, the gradual impact on the climate, but also to the life of entire cities.
For example, the annual transgression of Venice threatens the city with the fact that in the near future it will be under water. Such cases in history are repeated, many ancient settlements went under the water, and after a certain time again found themselves above sea level.