Lithosphere composition and brief characteristics. What is the lithosphere made of and what is it
The lithosphere of the planet Earth is a solid shell of the globe, which includes multilayer blocks called lithospheric plates. As Wikipedia points out, translated from Greek This " stone ball". It has a heterogeneous structure depending on the landscape and the plasticity of the rocks located in the upper layers of the soil.
The boundaries of the lithosphere and the location of its plates are not fully understood. Modern geology has only limited number data about the internal structure of the globe. It is known that lithospheric blocks have boundaries with the hydrosphere and atmospheric space of the planet. They are in close relationship with each other and are in contact with each other. The structure itself consists of the following elements:
- Asthenosphere. A layer with reduced hardness, which is located in the upper part of the planet in relation to the atmosphere. In some places it has very low strength, is prone to fracture and viscosity, especially if groundwater flows inside the asthenosphere.
- Mantle. This is a part of the Earth called the geosphere, located between the asthenosphere and the inner core of the planet. It has a semi-liquid structure, and its boundaries begin at a depth of 70–90 km. It is characterized by high seismic velocities, and its movement directly affects the thickness of the lithosphere and the activity of its plates.
- Core. The center of the globe, which has a liquid etiology, and the preservation of the magnetic polarity of the planet and its rotation around its axis depends on the movement of its mineral components and the molecular structure of molten metals. The main component of the earth's core is an alloy of iron and nickel.
What is the lithosphere? In fact, this is a solid shell of the Earth, which acts as an intermediate layer between fertile soil, mineral deposits, ores and mantle. On the plain, the thickness of the lithosphere is 35–40 km.
Important! In mountainous areas, this figure can reach 70 km. In the area of such geological heights as the Himalayan or Caucasian mountains, the depth of this layer reaches 90 km.
Earth structure
Layers of the lithosphere
If we consider the structure of lithospheric plates in more detail, then they are classified into several layers, which form the geological features of a particular region of the Earth. They form the basic properties of the lithosphere. Based on this, the following layers of the hard shell of the globe are distinguished:
- Sedimentary. covers most top layer of all earth blocks. It is mainly composed of volcanic rocks, as well as residues organic matter, which over many millennia decomposed into humus. Fertile soils are also part of the sedimentary layer.
- Granite. These are lithospheric plates that are in constant motion. They mainly consist of heavy-duty granite and gneiss. The last component is a metamorphic rock, the vast majority of which is filled with minerals from among potassium spar, quartz and plagioclase. The seismic activity of this layer of the hard shell is at the level of 6.4 km/sec.
- Basaltic. Mostly composed of basalt deposits. This part of the solid shell of the Earth was formed under the influence of volcanic activity in ancient times, when the formation of the planet took place and the first conditions for the development of life arose.
What is the lithosphere and its multilayer structure? Based on the foregoing, we can conclude that this is a solid part of the globe, which has a heterogeneous composition. Its formation took place over several millennia, and its qualitative composition depends on what metaphysical and geological processes took place in a particular region of the planet. The influence of these factors is reflected in the thickness of the lithospheric plates, their seismic activity in relation to the structure of the Earth.
Layers of the lithosphere
oceanic lithosphere
This type of the earth's shell is significantly different from its mainland. This is due to the fact that the boundaries of the lithospheric blocks and the hydrosphere are closely intertwined, and in some of its parts the water space extends beyond the surface layer of the lithospheric plates. This applies to bottom faults, depressions, cavernous formations of various etiologies.
oceanic crust
That is why the plates ocean type have their own structure and consist of the following layers:
- marine sediments that have a total thickness of at least 1 km (may be completely absent in deep ocean areas);
- secondary layer (responsible for the propagation of medium and longitudinal waves moving at speeds up to 6 km / s, takes an active part in the movement of plates, which provokes earthquakes of various power);
- the lower layer of the solid shell of the globe in the region of the ocean floor, which is mainly composed of gabbro and borders on the mantle (the average activity of seismic waves is from 6 to 7 km/sec.).
A transitional type of lithosphere is also distinguished, located in the region of oceanic soil. It is characteristic of insular zones formed in an arcuate fashion. In most cases, their appearance is associated with the geological process of the movement of lithospheric plates, which were layered on top of each other, forming such irregularities.
Important! A similar structure of the lithosphere can be found on the outskirts Pacific Ocean, as well as in some parts of the Black Sea.
Useful video: lithospheric plates and modern relief
Chemical composition
In terms of filling with organic and mineral compounds, the lithosphere does not differ in diversity and is mainly represented in the form of 8 elements.
For the most part, these are rocks that were formed during the period of active eruption of volcanic magma and the movement of plates. The chemical composition of the lithosphere is as follows:
- Oxygen. It occupies at least 50% of the entire structure of the hard shell, filling its faults, depressions and cavities that form during the movement of plates. plays key role in the balance of compression pressure during the course of geological processes.
- Magnesium. This is 2.35% of the solid shell of the Earth. Its appearance in the lithosphere is associated with magmatic activity in the early periods of the formation of the planet. It is found throughout the continental, marine and oceanic parts of the planet.
- Iron. Rock, which is the main mineral of lithospheric plates (4.20%). Its main concentration is the mountainous regions of the globe. It is in this part of the planet that the highest density of this chemical element. It is not presented in a pure form, but is found in the composition of lithospheric plates in a mixed form, along with other mineral deposits.
- Philippine plate.
- Australian.
- Eurasian.
- Somali.
- South American.
- Hindustan.
- African.
- Antarctic Plate.
- Nazca plate.
- Pacific;
- North American.
- Scotia plate.
- Arabian plate.
- Cooker Coconut.
The stone shell of the Earth - the earth's crust - is firmly fastened to the upper mantle and forms a single whole with it -. The study of the earth's crust and lithosphere allows scientists to explain the processes occurring on the surface of the Earth and to predict changes in the appearance of our planet in the future.
The structure of the earth's crust
The earth's crust, consisting of igneous, metamorphic and sedimentary rocks, on and under the oceans has a different thickness and structure.
In the continental crust, it is customary to distinguish three layers. The upper one is sedimentary, in which sedimentary rocks predominate. The two lower layers are conditionally called granite and basalt. The granite layer consists mainly of granite and metamorphic basalt layer - of denser rocks, comparable in density to basalts. The oceanic crust is two-layered. In it, the upper layer - sedimentary - has a small thickness, the lower layer - basalt - consists of basalt rocks, and there is no granite layer.
The thickness of the continental crust under is 30 50 kilometers, under the mountains - up to 75 kilometers. The oceanic crust is much thinner, its thickness is from 5 to 10 kilometers.
There is bark on other planets terrestrial group, on the Moon and on many satellites of the giant planets. But only the Earth has two types of crust: continental and oceanic. On other planets, in most cases it consists of basalts.
Lithosphere
The stone shell of the Earth, including the upper part of the mantle, is called the lithosphere. Under it is a heated plastic layer of the mantle. The lithosphere seems to float on this layer. The thickness of the lithosphere in different regions of the Earth varies from 20 to 200 kilometers or more. In general, it is thicker under the continents than under the oceans.
Scientists have found that the lithosphere is not monolithic, but consists of. They are separated from each other by deep faults. There are seven very large and several smaller lithospheric plates that constantly but slowly move along the plastic layer of the mantle. The average speed of their movement is about 5 centimeters per year. Some plates are entirely oceanic, but most have different types of crust.
Lithospheric plates move relative to each other in different directions: either move away, or, conversely, approach and collide. As part of the lithospheric plates, their upper "floor" - the earth's crust - also moves. Due to the movement of lithospheric plates, the location on the Earth's surface changes. The continents either collide with each other, or move away from each other for thousands of kilometers.
Engineering geology, its tasks and place in the system of engineering disciplines.
Engineering geology studies the natural, geological situation of the area before the start of construction, and also determines the changes that will occur during the operation and construction of structures. Currently, before designing any structure, it is necessary to carry out engineering and geological surveys, which determine the main design tasks: Selection of the most geologically favorable location for this structure. Identification of engineering and geological conditions in order to select the most rational foundations, as well as the technological process of implementation construction works. Recommendations of the necessary measures for the engineering improvement of the selected territory (these are: soil soaking, fixing, melioration, etc.). At present, engineering geology is called upon to solve the most complex problems under any construction conditions. The need for engineering-geological study of our country in order to justify the regional location of national economy facilities and the correct development of new territories is also supplemented not only by the requirements for studying engineering-geological conditions, but also by the need to develop forecasts for the development of modern geological processes and phenomena in order to prevent natural disasters. Geology is the science of the Earth, its structure, composition, and history of development. She happens to be integrated science, consisting of various numerous disciplines: crystallography - the study of crystals and the crystalline structure of substances; mineralogy - the science of minerals; petrography - the science of rocks; dynamic geology - the science of processes occurring on the surface and inside the earth; historical geology - the science of the history of the development of the earth; hydrogeology - the science of groundwater; geomorphology - the science of the development of the relief of the earth's crust. Engineering geology is a science that studies the geological processes of the upper layers of the earth's crust and the physical and mechanical properties of rocks in connection with human engineering and construction activities. The main object of study of geology is the lithosphere and the earth's crust. The founder of geology is M. V. Lomonosov, V. M. Severgin. We will study the most significant section of geology for construction "Engineering Geology"
Structure of the Earth, geosphere.
The shape of the Earth is close to a sphere, but flattened at the poles. This shape is called a spheroid, but due to the fact that the earth's surface has depressions and mountains, it was called the geoid. Our planet has a concentric structure and consists of a core and shells. On the surface of the earth is a water shell - the hydrosphere and atmosphere. The core of the earth (see Figure 1) is believed to have a silicate composition with a high iron content. The radius of the core is about 3500 km, the temperature of the core is 2000 ... 25000. Intermediate shell - the boundary is a depth of 2900 km (see Figure 2). Consists mainly of silicon, iron, magnesium. Behind the intermediate shell, lies peridotite, consisting of silicate rocks, with a predominance of silicon and magnesium. Its upper part contains molten masses. Seismic phenomena are born here. The outer part of the earth up to 50 ... 70 km deep is called the lithosphere, it is a source of mineral raw materials.
Hydrosphere - water shell covers up to 70% of the earth's surface. The greatest depth is 11521 meters ( Mariana Trench). The water temperature depends on the latitude and depth of the area. The highest +35.60 in the Persian Gulf, the lowest -2.80 in the Arctic Ocean.
The biosphere is the living environment of organisms and is associated with the lithosphere, hydrosphere and atmosphere.
Atmosphere - surrounds the earth at an altitude of 3000 km. It consists of 3 shells: troposphere, stratosphere, ionosphere.
Troposphere - the surface layer from 6 km to 18 km (near the equator). With distance from the surface, the temperature drops sharply and at an altitude of 10 - 12 km is 50 degrees.
The stratosphere is the next layer with a height of 80 - 90 km.
Ionosphere - the upper part of the atmosphere, passing at an altitude of 3000 km into interplanetary space. It has a low density and high ionization.
The structure of the lithosphere. The concept of tectonic plates.
The deep crust and the upper (solid) part of the mantle form the lithosphere. It is a "ball" of solid matter with a radius of about 6400 km. The earth's crust is the outer shell of the lithosphere. Consists of sedimentary, granite and basalt layers. Distinguish between oceanic and continental crust. The first one lacks a granite layer. The maximum thickness of the earth's crust is about 70 km - under the mountain systems, 30-40 km - under the plains, the thinnest earth's crust - under the oceans, only 5-10 km.
The rest we call inner lithosphere, which also includes central part called the kernel. We know almost nothing about the inner layers of the lithosphere, although they account for almost 99.5% of the entire mass of the Earth. They can only be studied with the help of seismic surveys.
The lithosphere is divided into blocks - lithospheric plates are large rigid blocks of the earth's crust that move along the relatively plastic asthenosphere. The lithosphere under oceans and continents varies considerably.
The lithosphere under the oceans has undergone many stages of partial melting as a result of the formation of oceanic crust, it is highly depleted in low-melting rare elements and mainly consists of dunites and harzburgites.
The lithosphere under the continents is much colder, more powerful and, apparently, more diverse. It does not participate in the process of mantle convection, and has undergone fewer cycles of partial melting. In general, it is richer in incompatible rare elements. Lherzolites, wehrlites and other rocks rich in rare elements play a significant role in its composition.
The lithosphere is split into about 10 large plates, the largest being the Eurasian, African, Indo-Afstralian, American, Pacific, and Antarctic. Lithospheric plates move with the land rising on them. The theory of the movement of lithospheric plates is based on the hypothesis of A. Wegener about the drift of the continents.
Lithospheric plates are constantly changing their outlines, they can split as a result of rifting and solder, forming a single plate as a result of collision. On the other hand, the division of the earth's crust into plates is not unambiguous, and as geological knowledge accumulates, new plates are identified, and some plate boundaries are recognized as non-existent. The movement of lithospheric plates is due to the movement of matter in the upper mantle. In rift zones, it breaks the earth's crust and pushes the plates apart. Most rifts are found at the bottom of the oceans, where the earth's crust is thinner. On land, the largest rifts are located in the African Great Lakes and Lake Baikal. The speed of movement of lithospheric plates is -1-6 cm per year.
When lithospheric plates collide, the following are formed at their boundaries: mountain systems, if in the collision zone both plates carry the continental crust (Himalayas), and deep-sea trenches, if one of the plates carries the oceanic crust (Peru Trench). This theory is consistent with the assumption of the existence of ancient continents: southern - Gondwana and northern - Laurasia.
The boundaries of the lithospheric plates are mobile areas where mountain building occurs, earthquake areas and most active volcanoes (seismic belts) are concentrated. The most extensive seismic belts - Pacific and Mediterranean - Trans-Asian.
At a depth of 120-150 km under the continents and 60-400 km under the oceans lies a layer of the mantle, called the asthenosphere. All lithospheric plates seem to float in the semi-liquid asthenosphere, like ice floes in water.
Currently, plate tectonics is the following picture. The modern lithosphere is divided into many lithospheric plates, but 90% of the earth's surface falls on eight main plates. The earth's surface is of two types: oceanic crust (younger, as it is constantly being updated) and continental crust (older). Lithospheric plates can carry out various types of movement relative to each other, there are three main types of movement: first, divergence, that is, a divergence between plates; secondly, convergence, that is, convergence, convergence between the plates; thirdly, shear movements along transform geological faults. Currently, scientists believe that plate tectonics does not play a decisive role in global climate change, but may have an auxiliary effect on these processes.
And any negative lithospheric changes can exacerbate the global crisis. From this article you will learn about what the lithosphere and lithospheric plates are.
Concept definition
The lithosphere is the outer hard shell of the globe, which consists of the earth's crust, part of the upper mantle, sedimentary and igneous rocks. It is rather difficult to determine its lower boundary, but it is generally accepted that the lithosphere ends with a sharp decrease in the viscosity of rocks. The lithosphere occupies the entire surface of the planet. The thickness of its layer is not the same everywhere, it depends on the terrain: on the continents - 20-200 kilometers, and under the oceans - 10-100 km.
The Earth's lithosphere mostly consists of igneous igneous rocks (about 95%). These rocks are dominated by granitoids (on the continents) and basalts (under the oceans).
Some people think that the concepts "hydrosphere" / "lithosphere" mean the same thing. But this is far from true. The hydrosphere is a kind of water shell of the globe, and the lithosphere is solid.
Geological structure of the globe
The lithosphere as a concept also includes geological structure of our planet, therefore, in order to understand what the lithosphere is, it should be considered in detail. The upper part of the geological layer is called the earth's crust, its thickness varies from 25 to 60 kilometers on the continents, and from 5 to 15 kilometers in the oceans. The lower layer is called the mantle, separated from the earth's crust by the Mohorovichich section (where the density of matter changes dramatically).
Earth consists of the earth's crust, mantle and core. The earth's crust is a solid, but its density changes dramatically at the boundary with the mantle, that is, at the Mohorovichic line. Therefore, the density of the earth's crust is an unstable value, but the average density of a given layer of the lithosphere can be calculated, it equals 5.5223 grams / cm 3.
The globe is a dipole, that is, a magnet. Earthly magnetic poles located in the southern and northern hemispheres.
Layers of the Earth's lithosphere
The lithosphere on the continents consists of three layers. And the answer to the question of what the lithosphere is will not be complete without considering them.
The upper layer is built from a wide variety of sedimentary rocks. The middle one is conditionally called granite, but it consists not only of granites. For example, under the oceans, the granite layer of the lithosphere is completely absent. The approximate density of the middle layer is 2.5-2.7 grams/cm 3 .
The lower layer is also conditionally called basalt. It consists of heavier rocks, its density, respectively, is greater - 3.1-3.3 grams / cm 3. The lower basalt layer is located under the oceans and continents.
The earth's crust is also classified. There are continental, oceanic and intermediate (transitional) types of the earth's crust.
The structure of lithospheric plates
The lithosphere itself is not homogeneous, it consists of peculiar blocks, which are called lithospheric plates. They include both oceanic and continental crust. Although there is a case that can be considered an exception. The Pacific lithospheric plate consists only of oceanic crust. The lithospheric blocks consist of folded metamorphic and igneous rocks.
Each continent has at its base an ancient platform, the boundaries of which are defined by mountain ranges. Plains and only individual mountain ranges are located directly on the platform area.
Seismic and volcanic activity is quite often observed at the boundaries of lithospheric plates. There are three types of lithospheric boundaries: transform, convergent, and divergent. The outlines and boundaries of lithospheric plates change quite often. Small lithospheric plates are connected to each other, while large ones, on the contrary, break apart.
List of lithospheric plates
It is customary to distinguish 13 main lithospheric plates:
So, we gave a definition of the concept of "lithosphere", considered the geological structure of the Earth and lithospheric plates. With the help of this information, it is now possible to answer with certainty the question of what the lithosphere is.
The earth's crust and the upper (solid) part of the mantle form the lithosphere. It is a "ball" of solid matter with a radius of about 6400 km. The earth's crust is the outer shell of the lithosphere. Consists of sedimentary, granite and basalt layers. Distinguish between oceanic and continental crust. The first one lacks a granite layer. The maximum thickness of the earth's crust is about 70 km - under the mountain systems, 30-40 km - under the plains, the thinnest earth's crust - under the oceans, only 5-10 km.
The rest we call the inner lithosphere, which also includes the central part, called the core. We know almost nothing about the inner layers of the lithosphere, although they account for almost 99.5% of the entire mass of the Earth. They can only be studied with the help of seismic surveys.
The lithosphere is divided into blocks - lithospheric plates are large rigid blocks of the earth's crust that move along the relatively plastic asthenosphere. The lithosphere under oceans and continents varies considerably.
The lithosphere under the oceans has undergone many stages of partial melting as a result of the formation of oceanic crust, it is highly depleted in low-melting rare elements and mainly consists of dunites and harzburgites.
The lithosphere under the continents is much colder, more powerful and, apparently, more diverse. It does not participate in the process of mantle convection, and has undergone fewer cycles of partial melting. In general, it is richer in incompatible rare elements. Lherzolites, wehrlites and other rocks rich in rare elements play a significant role in its composition.
The lithosphere is split into about 10 large plates, the largest being the Eurasian, African, Indo-Afstralian, American, Pacific, and Antarctic. Lithospheric plates move with the land rising on them. The theory of the movement of lithospheric plates is based on the hypothesis of A. Wegener about the drift of the continents.
Lithospheric plates are constantly changing their outlines, they can split as a result of rifting and solder, forming a single plate as a result of collision. On the other hand, the division of the earth's crust into plates is not unambiguous, and as geological knowledge accumulates, new plates are identified, and some plate boundaries are recognized as non-existent. The movement of lithospheric plates is due to the movement of matter in the upper mantle. In rift zones, it breaks the earth's crust and pushes the plates apart. Most rifts are found at the bottom of the oceans, where the earth's crust is thinner. On land, the largest rifts are located in the African Great Lakes and Lake Baikal. The speed of movement of lithospheric plates is -1-6 cm per year.
During the collision of lithospheric plates, mountain systems are formed at their boundaries: mountain systems, if both plates carry the continental crust in the collision zone (Himalayas), and deep-sea trenches, if one of the plates carries the oceanic crust (Peru Trench). This theory is consistent with the assumption of the existence of ancient continents: southern - Gondwana and northern - Laurasia.
The boundaries of the lithospheric plates are mobile areas where mountain building occurs, earthquake areas and most active volcanoes (seismic belts) are concentrated. The most extensive seismic belts - Pacific and Mediterranean - Trans-Asian.
At a depth of 120-150 km under the continents and 60-400 km under the oceans lies a layer of the mantle, called the asthenosphere. All lithospheric plates seem to float in the semi-liquid asthenosphere, like ice floes in water.
lithosphere crust anthropogenic