Tectonics is a branch of geology that studies the structure of the earth's crust and the movement of lithospheric plates. But it is so multifaceted that it plays a significant role in many other geosciences. Tectonics is used in architecture, geochemistry, seismology, in the study of volcanoes and in many other areas.
Science tectonics
Tectonics is a relatively young science, it studies the movement of lithospheric plates. For the first time, the idea of plate movement was voiced in the theory of continental drift by Alfred Wegener in the 20s of the XX century. But it only received its development in the 60s of the XX century, after conducting studies of the relief on the continents and the ocean floor. The material obtained allowed us to take a fresh look at previously existing theories. The theory of lithospheric plates appeared as a result of the development of the ideas of the theory of continental drift, the theory of geosynclines and the contraction hypothesis.
Tectonics is a science that studies the strength and nature of the forces that form mountain ranges, crush rocks into folds, stretch the earth's crust. It underlies all geological processes occurring on the planet.
Contract hypothesis
The contraction hypothesis was put forward by the geologist Elie de Beaumont in 1829at a meeting of the French Academy of Sciences. It explains the processes of mountain building and folding of the earth's crust under the influence of a decrease in the volume of the Earth due to cooling. The hypothesis was based on the ideas of Kant and Laplace about the primary fiery-liquid state of the Earth and its further cooling. Therefore, the processes of mountain building and folding were explained as processes of compression of the earth's crust. Later, cooling down, the Earth reduced its volume and crumpled into folds.
Contract tectonics, the definition of which confirmed the new doctrine of geosynclines, explained the uneven structure of the earth's crust, became a solid theoretical basis for the further development of science.
Geosyncline theory
Existed at the turn of the late XIX and early XX centuries. She explains tectonic processes by cyclic oscillatory movements of the earth's crust.
Geologists' attention was drawn to the fact that rocks can occur both horizontally and dislocated. Horizontal rocks were assigned to platforms, and dislocated rocks were assigned to folded areas.
According to the theory of geosynclines, at the initial stage, due to active tectonic processes, a deflection and lowering of the earth's crust occurs. This process is accompanied by the removal of sediments and the formation of a thick layer of sedimentary deposits. Subsequently, the process of mountain building and the appearance of folding occurs. The geosynclinal regime is replaced by the platform regime, which is characterized by insignificant tectonic movements with the formation of a small thickness of sedimentary rocks. The final stage is the formation stage.continent.
Geosynclinal tectonics dominated for almost 100 years. The geology of that time experienced a shortage of factual material, and subsequently the accumulated data led to the creation of a new theory.
Theory of lithospheric plates
Tectonics is one of the directions in geology, which formed the basis of the modern theory of the movement of lithospheric plates.
According to the theory of lithospheric plates, part of the earth's crust - lithospheric plates, which are in continuous motion. Their movement is relative to each other. In zones of stretching of the earth's crust (mid-ocean ridges and continental rifts), a new oceanic crust (spraying zone) is formed. In the zones of submergence of the blocks of the earth's crust, the absorption of the old crust occurs, as well as the subsidence of the oceanic under the continental (subduction zone). The theory also explains the causes of earthquakes, the processes of mountain building and volcanic activity.
Global plate tectonics includes such a key concept as the geodynamic setting. It is characterized by a set of geological processes, within the same territory, in a certain period of geological time. The same geological processes are characteristic of the same geodynamic setting.
The structure of the globe
Tectonics is a branch of geology that studies the structure of the planet Earth. The earth in a rough approximation has the shape of an oblate ellipsoid and consists of several shells(layers).
The following layers are distinguished in the structure of the globe:
- Earth's crust.
- Robe.
- Core.
The Earth's crust is the outer solid layer of the Earth, it is separated from the mantle by a boundary called the Mohorovich surface.
The mantle, in turn, is divided into upper and lower. The boundary separating the mantle layers is the Golitsin layer. The Earth's crust and upper mantle, down to the asthenosphere, are the Earth's lithosphere.
The core is the center of the globe, separated from the mantle by the Gutenberg boundary. It splits into a liquid outer core and a solid inner core, with a transition zone between them.
The structure of the earth's crust
The science of tectonics is directly related to the structure of the earth's crust. Geology studies not only the processes occurring in the bowels of the Earth, but also its structure.
The Earth's crust is the upper part of the lithosphere, is the outer solid shell of the Earth, it is composed of rocks of different physical and chemical composition. According to physical and chemical parameters, there is a division into three layers:
- Bas altic.
- Granite-gneiss.
- Sedimentary.
There is also a division in the structure of the earth's crust. There are four main types of the earth's crust:
- Continental.
- Oceanic.
- Subcontinental.
- Suboceanic.
The continental crust is represented by all three layers, its thickness varies from 35 to 75 km. The upper, sedimentary layer is widely developed, but, as a rule,has little power. The next layer, granite-gneiss, has a maximum thickness. The third layer, bas alt, is composed of metamorphic rocks.
The oceanic crust is represented by two layers - sedimentary and bas alt, its thickness is 5-20 km.
The subcontinental crust, like the continental one, consists of three layers. The difference is that the thickness of the granite-gneiss layer in the subcontinental crust is much less. This type of crust is found on the border of the continent with the ocean, in the area of active volcanism.
Suboceanic crust is close to oceanic. The difference is that the thickness of the sedimentary layer can reach 25 km. This type of crust is confined to deep foredeep of the earth's crust (inland seas).
lithospheric plate
Lithospheric plates are large blocks of the earth's crust that are part of the lithosphere. The plates are able to move relative to each other along the upper part of the mantle - the asthenosphere. The plates are separated from each other by deep-sea trenches, mid-ocean ridges and mountain systems. A characteristic feature of lithospheric plates is that they are able to maintain rigidity, shape and structure for a long time.
Earth tectonics suggests that the lithospheric plates are in constant motion. Over time, they change their contour - they can split or grow together. To date, 14 large lithospheric plates have been identified.
Tectonics of the lithospheric plates
The process that forms the appearance of the Earth is directly related to the tectonics of the lithosphericplates. The tectonics of the world implies that there is a movement not of continents, but of lithospheric plates. Colliding with each other, they form mountain ranges or deep oceanic depressions. Earthquakes and volcanic eruptions are the result of the movement of lithospheric plates. Active geological activity is confined mainly to the edges of these formations.
The movement of lithospheric plates has been recorded by satellites, but the nature and mechanism of this process is still a mystery.
Ocean tectonics
In the oceans, the processes of destruction and accumulation of sediments are slow, so tectonic movements are well reflected in the relief. The bottom relief has a complex dissected structure. Tectonic structures formed as a result of vertical movements of the earth's crust, and structures obtained due to horizontal movements are distinguished.
The structures of the ocean floor include landforms such as abyssal plains, oceanic basins, and mid-ocean ridges. In the zone of basins, as a rule, a calm tectonic situation is observed, in the zone of mid-ocean ridges, tectonic activity of the earth's crust is noted.
Ocean tectonics also includes structures such as deep sea trenches, ocean mountains and giyots.
Causes moving plates
The driving geological force is the tectonics of the world. The main reason for the movement of plates is mantle convection, which is created by thermal gravitational currents in the mantle. This is due totemperature difference between the surface and the center of the earth. Inside the rocks are heated, they expand and decrease in density. Light fractions begin to float, and cold and heavy masses sink in their place. The heat transfer process is continuous.
There are a number of other factors that affect the movement of plates. For example, the asthenosphere in the zones of ascending flows is elevated, and in the zones of subsidence it is lowered. Thus, an inclined plane is formed and the process of "gravitational" sliding of the lithospheric plate takes place. Subduction zones also have an impact, where cold and heavy oceanic crust is pulled under hot continental.
The thickness of the asthenosphere under the continents is much less, and the viscosity is greater than under the oceans. Under the ancient parts of the continents, the asthenosphere is practically absent, so in these places they do not move and remain in place. And since the lithospheric plate includes both continental and oceanic parts, the presence of an ancient continental part will impede the movement of the plate. The movement of purely oceanic plates is faster than mixed, and even more so continental.
There are many mechanisms that set the plates in motion, they can be conditionally divided into two groups:
- Mechanisms that set in motion under the action of the mantle current.
- Mechanisms associated with the application of forces to the edges of the plates.
The set of processes of driving forces reflects the whole geodynamic process, which covers all layers of the Earth.
Architecture and tectonics
Tectonics is not only a purely geological science related to the processes occurring in the bowels of the Earth. It is also used in everyday life. In particular, tectonics is used in the architecture and construction of any structures, be it buildings, bridges or underground structures. This is where the laws of mechanics come into play. In this case, tectonics refers to the degree of strength and stability of a structure in a given particular area.
The theory of lithospheric plates does not explain the connection between plate movements and deep processes. We need a theory that would explain not only the structure and movement of lithospheric plates, but also the processes occurring inside the Earth. The development of such a theory is associated with the unification of such specialists as geologists, geophysicists, geographers, physicists, mathematicians, chemists and many others.
