At first glance, the ground under your feet seems absolutely motionless, but in fact it is not. The earth has a mobile structure that makes movements of a different nature. The movement of the earth's crust, volcanism in most cases can carry a colossal destructive force, but there are other movements that are 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 moves under the influence of the internal processes of the Earth. The movement of the earth's crust is a very slow, one might say, age-old phenomenon that is not perceptible by the human senses, and yet this process plays a huge role in our lives. A noticeable manifestation of the movement of tectonic layers is 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 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 mantle substance cannot increase in volume, the result is a steam boiler effect, when processes occurring in the bowels of the earth activate the movement of the earth's crust. At the same time, the movement of tectonic plates is stronger in areas with the highest temperature and mantle pressure on the upper layers of the lithosphere.
Study history
The possible displacement of the layers of the earth's surface was suspected long before our era. So, history knows the first assumptions of the ancient Greek scientist - the geographer Strabo. He put forward a hypothesis 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 also guessed about the movement of the earth's surface, who noticed that their villages, once founded in the coastal zone, turned out to be far from the sea coast through the centuries.
All the same, the movement of the earth's crust, volcanism began to be purposefully and large-scale studied during the active development of scientific and technological progress, which took place in the 19th century. 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 pattern of movement of the earth's crust is formed from 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 the 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 for 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 some sections of marine territories.
- Destroy primary relief structures of folded, inclined and discontinuous type, creating new ones in their place.
- Provides the exchange of substances between the mantle and the earth's crust, and also ensures the release 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, which host the continents and oceans. 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 largest layers of the earth's crust. When a tectonic plate shifts, the continent that sits on it shifts with it. Thus, the horizontal and at the same time very slow movements of the earth's crust led to the fact that the geographical map for many millions ofchanged over the years, the same continents moved away from each other.
The tectonics of the last three centuries has been most accurately studied. The movement of the earth's crust at the present stage is being studied with the help of high-precision equipment, thanks to which it was possible to find out that horizontal tectonic displacements of the earth's surface are exclusively unidirectional in nature and overcome only a few cm annually.
When shifting, tectonic plates converge in some places and diverge in others. Mountains form in the zones of plate collision, and cracks (faults) form in the zones of plate divergence. A striking example of the divergence of lithospheric plates observed at the present time is the so-called Great African faults. They are distinguished not only by the greatest extent of cracks in the earth's crust (more than 6000 km), but also by extreme activity. The breakup of the African continent is happening so fast that it is likely that in the not so distant future 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, unlike horizontal ones, have a double direction, that is, the land can rise and, after a while, fall. The rise (transgression) and fall (regression) of the sea level are also a consequence of the vertical movement of the lithosphere. The secular movements of the earth's crust up and down, which took place many centuries ago, can be traced by the lefttraces, namely: the Naples temple, built back in the 4th century AD, is currently located at an altitude of more than 5 m above sea level, but its columns are strewn with shells of mollusks. This is clear evidence that the temple was under water for a long time, which means that this piece of soil systematically moved in the vertical direction, either along the ascending axis or descending. This cycle of movements is known as the oscillatory modes of the earth's crust.
Regression of the sea leads to the fact that once the seabed becomes dry land and plains are formed, among which are the North and West Siberian plains, the Amazonian, Turanian, etc. Currently, land uplift is observed in Europe (Scandinavian Peninsula, Iceland, Ukraine, Sweden) and sinking (Holland, southern England, northern Italy).
Earthquakes and volcanism as a consequence of the movement of the lithosphere
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 is measured on the Richter scale. Seismic waves up to 3 points on this scale are not perceptible by a person, ground vibrations with magnitudes from 6 to 9 can already lead to significant destruction and death of people.
Due to the horizontal and vertical movement of the lithosphere, channels are formed at the boundaries of tectonic plates, through which the mantle matter under pressure erupts onto the earth's surface. This process is called volcanismwe can observe in the form of volcanoes, geysers and warm springs. There are many volcanoes on Earth, some of which are still active. they can be both on land and under water. Together with igneous rocks, they spew hundreds of tons of smoke, gas and ash into the atmosphere. Underwater volcanoes are the main cause of tsunamis, and they are stronger than land-based volcanoes. Currently, the vast majority of volcanic formations on the seafloor are inactive.
The importance of tectonics for humans
In the life of mankind, the movements of the earth's crust play a huge role. And this concerns not only the formation of rocks, the gradual impact on the climate, but also the very 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 are repeated in history, many ancient settlements went under water, and after a certain time they again found themselves above sea level.
