Lithosphere

The lithosphere is the outer solid shell of the Earth, which includes the entire earth's crust with part of the Earth's upper mantle and consists of sedimentary, igneous and metamorphic rocks. The lower boundary of the lithosphere is fuzzy and is determined by a sharp decrease in rock viscosity, a change in the propagation velocity of seismic waves, and an increase in the electrical conductivity of rocks. The thickness of the lithosphere on the continents and under the oceans varies and averages 25-200 and 5-100 km, respectively.

Consider in general terms the geological structure of the Earth. The third planet farthest from the Sun - the Earth has a radius of 6370 km, an average density of 5.5 g / cm3 and consists of three shells - the crust, mantle and core. The mantle and core are divided into inner and outer parts.

The Earth's crust is a thin upper shell of the Earth, which has a thickness of 40-80 km on the continents, 5-10 km under the oceans and makes up only about 1% of the Earth's mass. Eight elements - oxygen, silicon, hydrogen, aluminum, iron, magnesium, calcium, sodium - form 99.5% of the earth's crust. On the continents, the crust is three-layered: sedimentary rocks cover granitic rocks, and granitic rocks lie on basalt rocks. Under the oceans, the crust is of an "oceanic", two-layer type; sedimentary rocks lie simply on basalts, there is no granite layer. There is also a transitional type of the earth's crust (island-arc zones on the margins of the oceans and some areas on the continents, such as the Black Sea). The earth's crust has the greatest thickness in mountainous regions (under the Himalayas - over 75 km), the average - in the areas of platforms (under the West Siberian lowland - 35-40, within the boundaries of the Russian platform - 30-35), and the smallest - in the central regions of the oceans (5-7 km). The predominant part of the earth's surface is the plains of the continents and the ocean floor. The continents are surrounded by a shelf - a shallow-water strip up to 200 g deep and an average width of about 80 km, which, after a sharp steep bend of the bottom, passes into the continental slope (the slope varies from 15-17 to 20-30 °). The slopes gradually level off and turn into abyssal plains (depths 3.7-6.0 km). The greatest depths (9-11 km) have oceanic trenches, the vast majority of which are located on the northern and western margins of the Pacific Ocean.

The main part of the lithosphere consists of igneous igneous rocks (95%), among which granites and granitoids predominate on the continents, and basalts in the oceans.

The relevance of the ecological study of the lithosphere due to the fact that the lithosphere is the environment of all mineral resources, one of the main objects of anthropogenic activity (components of the natural environment), through significant changes in which the global ecological crisis develops. In the upper part of the continental crust, soils are developed, the importance of which for humans can hardly be overestimated. Soils - an organo-mineral product of many years (hundreds and thousands of years) of the general activity of living organisms, water, air, solar heat and light are one of the most important natural resources. Depending on the climatic and geological and geographical conditions, the soils have a thickness of 15-25 cm to 2-3 m.

Soils arose together with living matter and developed under the influence of the activities of plants, animals and microorganisms until they became a very valuable fertile substrate for humans. The bulk of organisms and microorganisms of the lithosphere is concentrated in soils, at a depth of no more than a few meters. Modern soils are a three-phase system (different-grained solid particles, water and gases dissolved in water and pores), which consists of a mixture of mineral particles (rock destruction products), organic substances (biota waste products of its microorganisms and fungi). Soils play a huge role in the circulation of water, substances and carbon dioxide.

Various minerals are associated with different rocks of the earth's crust, as well as with its tectonic structures: combustible, metal, construction, as well as those that are raw materials for the chemical and food industries.

Within the boundaries of the lithosphere, terrible ecological processes (shifts, mudflows, collapses, erosion) have periodically occurred and continue to occur, which are of great importance for the formation of ecological situations in a certain region of the planet, and sometimes lead to global ecological disasters.

The deep layers of the lithosphere, which are explored by geophysical methods, have a rather complex and still insufficiently studied structure, just like the mantle and core of the Earth. But it is already known that the density of rocks increases with depth, and if on the surface it averages 2.3-2.7 g / cm3, then at a depth of close to 400 km - 3.5 g / cm3, and at a depth of 2900 km ( boundary of the mantle and the outer core) - 5.6 g/cm3. In the center of the core, where the pressure reaches 3.5 thousand tons/cm2, it increases to 13-17 g/cm3. The nature of the increase in the deep temperature of the Earth has also been established. At a depth of 100 km, it is approximately 1300 K, at a depth of close to 3000 km -4800, and in the center of the earth's core - 6900 K.

The predominant part of the Earth's matter is in a solid state, but on the border of the earth's crust and upper mantle (depths of 100-150 km) lies a stratum of softened, pasty rocks. This thickness (100-150 km) is called the asthenosphere. Geophysicists believe that other parts of the Earth can also be in a rarefied state (due to decompaction, active radio decay of rocks, etc.), in particular, the zone of the outer core. The inner core is in the metallic phase, but today there is no consensus on its material composition.

Bibliography

For the preparation of this work, materials from the site http://ecosoft.iatp.org.ua/ were used.

The lithosphere is the outer solid shell of the Earth, including the earth's crust and the upper part of the mantle. The lithosphere includes sedimentary, igneous and metamorphic rocks. The lower boundary of the lithosphere is indistinct and is determined by a decrease in the viscosity of the medium, the speed of seismic waves and an increase in thermal conductivity. The lithosphere covers the earth's crust and the upper part of the mantle several tens of kilometers thick to the asthenosphere, in which the plasticity of rocks changes. The main methods for determining the boundary between the upper boundary of the lithosphere and the asthenosphere are magnetotelluric and seismological. The thickness of the lithosphere under the oceans is from 5 to 100 km (the maximum value is at the periphery of the oceans, the minimum is under the Mid-ocean ridges), under the continents - 25-200 km (maximum - under ancient platforms, at least - under relatively young mountain ranges, volcanic arcs). The structure of the lithosphere under the oceans and continents has significant differences. Under the continents in the structure of the earth's crust of the lithosphere, sedimentary, granite and basalt layers are distinguished, the thickness of which as a whole reaches 80 km. Beneath the oceans, the Earth's crust has repeatedly undergone partial melting processes during the formation of the oceanic crust. Therefore, it is depleted in fusible rare compounds, devoid of a granite layer, and its thickness is much less than that of the continental part of the earth's crust. The thickness of the asthenosphere (a layer of softened, doughy rocks) is about 100-150 km. Currently, on the ocean floor in the middle ridges, the process of formation of the earth's crust continues, which is accompanied by the release of gases and small volumes of water. Oxygen is present in high concentrations in the composition of the modern earth's crust, followed by silicon and aluminum in percentage. Basically, the lithosphere is formed by compounds such as silicon dioxide, silicates, aluminosilicates. Crystalline substances of igneous origin took part in the formation of most of the lithosphere. They were formed during the cooling of magma that came to the surface of the Earth, which is in the bowels of the planet in a molten state. In cold regions, the thickness of the lithosphere is the greatest, and in warm regions it is the smallest. The thickness of the lithosphere can increase with a general decrease in the heat flux density. The upper layer of the lithosphere is elastic, and the lower layer is plastic in terms of the nature of the reaction to constantly acting loads. In tectonically active areas of the lithosphere, horizons of reduced viscosity are distinguished, where seismic waves travel at a lower speed. According to scientists, according to these horizons, some layers “slip” in relation to others. This phenomenon is called stratification of the lithosphere. In the structure of the lithosphere, mobile areas (folded belts) and relatively stable areas (platforms) are distinguished. Blocks of the lithosphere (lithospheric plates) move along the relatively plastic asthenosphere, reaching sizes from 1 to 10 thousand kilometers in diameter. At present, the lithosphere is divided into seven main and a number of small plates. The boundaries separating the plates from each other are the zones of maximum volcanic and seismic activity.

Add your price to the database

Comment

The lithosphere is the stone shell of the Earth. From the Greek "lithos" - a stone and "sphere" - a ball

The lithosphere is the outer solid shell of the Earth, which includes the entire earth's crust with part of the Earth's upper mantle and consists of sedimentary, igneous and metamorphic rocks. The lower boundary of the lithosphere is fuzzy and is determined by a sharp decrease in rock viscosity, a change in the propagation velocity of seismic waves, and an increase in the electrical conductivity of rocks. The thickness of the lithosphere on the continents and under the oceans varies and averages 25 - 200 and 5 - 100 km, respectively.

Consider in general terms the geological structure of the Earth. The third planet farthest from the Sun - the Earth has a radius of 6370 km, an average density of 5.5 g / cm3 and consists of three shells - bark, robes and i. The mantle and core are divided into inner and outer parts.

The Earth's crust is a thin upper shell of the Earth, which has a thickness of 40-80 km on the continents, 5-10 km under the oceans and makes up only about 1% of the Earth's mass. Eight elements - oxygen, silicon, hydrogen, aluminum, iron, magnesium, calcium, sodium - form 99.5% of the earth's crust.

According to scientific research, scientists were able to establish that the lithosphere consists of:

• Oxygen - 49%;
• Silicon - 26%;
• Aluminum - 7%;
• Iron - 5%;
• Calcium - 4%
• The composition of the lithosphere includes many minerals, the most common are feldspar and quartz.

On the continents, the crust is three-layered: sedimentary rocks cover granitic rocks, and granitic rocks lie on basalt rocks. Under the oceans, the crust is "oceanic", two-layered; sedimentary rocks lie simply on basalts, there is no granite layer. There is also a transitional type of the earth's crust (island-arc zones on the outskirts of the oceans and some areas on the continents, such as the Black Sea).

The earth's crust is thickest in mountainous regions.(under the Himalayas - over 75 km), the middle one - in the areas of the platforms (under the West Siberian lowland - 35-40, within the boundaries of the Russian platform - 30-35), and the smallest - in the central regions of the oceans (5-7 km). The predominant part of the earth's surface is the plains of the continents and the ocean floor.

The continents are surrounded by a shelf - a shallow-water strip up to 200 g deep and an average width of about 80 km, which, after a sharp steep bend of the bottom, passes into the continental slope (the slope varies from 15-17 to 20-30 °). The slopes gradually level off and turn into abyssal plains (depths 3.7-6.0 km). The greatest depths (9-11 km) have oceanic trenches, the vast majority of which are located on the northern and western margins of the Pacific Ocean.

The main part of the lithosphere consists of igneous igneous rocks (95%), among which granites and granitoids predominate on the continents, and basalts in the oceans.

Blocks of the lithosphere - lithospheric plates - move along the relatively plastic asthenosphere. The section of geology on plate tectonics is devoted to the study and description of these movements.

To designate the outer shell of the lithosphere, the now obsolete term sial was used, which comes from the name of the main elements of rocks Si (lat. Silicium - silicon) and Al (lat. Aluminum - aluminum).

Lithospheric plates

It is worth noting that the largest tectonic plates are very clearly visible on the map and they are:

• Pacific- the largest plate of the planet, along the boundaries of which constant collisions of tectonic plates occur and faults form - this is the reason for its constant decrease;
• Eurasian- covers almost the entire territory of Eurasia (except Hindustan and the Arabian Peninsula) and contains the largest part of the continental crust;
• Indo-Australian- It includes the Australian continent and the Indian subcontinent. Due to constant collisions with the Eurasian plate, it is in the process of breaking;
• South American- consists of the South American mainland and part of the Atlantic Ocean;
• North American- consists of the North American continent, part of northeastern Siberia, the northwestern part of the Atlantic and half of the Arctic Oceans;
• African- consists of the African continent and the oceanic crust of the Atlantic and Indian oceans. It is interesting that the plates adjacent to it move in the opposite direction from it, therefore the largest fault of our planet is located here;
• Antarctic Plate- consists of the mainland Antarctica and the nearby oceanic crust. Due to the fact that the plate is surrounded by mid-ocean ridges, the rest of the continents are constantly moving away from it.

Movement of tectonic plates in the lithosphere

Lithospheric plates, connecting and separating, change their outlines all the time. This allows scientists to put forward the theory that about 200 million years ago the lithosphere had only Pangea - a single continent, which subsequently split into parts, which began to gradually move away from each other at a very low speed (an average of about seven centimeters per year ).

It is interesting! There is an assumption that due to the movement of the lithosphere, in 250 million years a new continent will form on our planet due to the union of moving continents.

When the oceanic and continental plates collide, the edge of the oceanic crust sinks under the continental one, while on the other side of the oceanic plate its boundary diverges from the plate adjacent to it. The boundary along which the movement of the lithospheres occurs is called the subduction zone, where the upper and plunging edges of the plate are distinguished. It is interesting that the plate, plunging into the mantle, begins to melt when the upper part of the earth's crust is squeezed, as a result of which mountains are formed, and if magma also breaks out, then volcanoes.

In places where tectonic plates come into contact with each other, there are zones of maximum volcanic and seismic activity: during the movement and collision of the lithosphere, the earth's crust collapses, and when they diverge, faults and depressions form (the lithosphere and the Earth's relief are connected to each other). This is the reason that the largest landforms of the Earth are located along the edges of the tectonic plates - mountain ranges with active volcanoes and deep-sea trenches.

Problems of the lithosphere

The intensive development of industry has led to the fact that man and the lithosphere have recently become extremely difficult to get along with each other: pollution of the lithosphere is acquiring catastrophic proportions. This happened due to the increase in industrial waste in combination with household waste and fertilizers and pesticides used in agriculture, which negatively affects the chemical composition of the soil and living organisms. Scientists have calculated that about one ton of garbage falls per person per year, including 50 kg of hardly decomposable waste.

Today, pollution of the lithosphere has become an urgent problem, since nature is not able to cope with it on its own: the self-purification of the earth's crust is very slow, and therefore harmful substances gradually accumulate and eventually negatively affect the main culprit of the problem - man.

The state of rest is unknown to our planet. This applies not only to external, but also to internal processes that occur in the bowels of the Earth: its lithospheric plates are constantly moving. True, some sections of the lithosphere are quite stable, while others, especially those located at the junctions of tectonic plates, are extremely mobile and constantly shudder.

Naturally, people could not leave such a phenomenon unattended, and therefore, throughout their history, they studied and explained it. For example, in Myanmar, the legend is still preserved that our planet is entwined with a huge ring of snakes, and when they begin to move, the earth begins to tremble. Such stories could not satisfy inquisitive human minds for a long time, and in order to find out the truth, the most curious drilled the earth, drew maps, made hypotheses and put forward assumptions.

The concept of the lithosphere contains the solid shell of the Earth, consisting of the earth's crust and a layer of softened rocks that make up the upper mantle, the asthenosphere (its plastic composition makes it possible for the plates that make up the earth's crust to move along it at a speed of 2 to 16 cm in year). It is interesting that the upper layer of the lithosphere is elastic, and the lower layer is plastic, which makes it possible for the plates to maintain balance when moving, despite constant shaking.

During numerous studies, scientists came to the conclusion that the lithosphere has a heterogeneous thickness, and largely depends on the terrain under which it is located. So, on land, its thickness ranges from 25 to 200 km (the older the platform, the larger it is, and the thinnest is under the young mountain ranges).

But the thinnest layer of the earth's crust is under the oceans: its average thickness ranges from 7 to 10 km, and in some regions of the Pacific Ocean it even reaches five. The thickest layer of the crust is located along the edges of the oceans, the thinnest - under the mid-ocean ridges. Interestingly, the lithosphere has not yet fully formed, and this process continues to this day (mainly under the ocean floor).

What is the earth's crust made of

The structure of the lithosphere under the oceans and continents is different in that there is no granite layer under the ocean floor, since the oceanic crust has undergone melting processes many times during its formation. Common to the oceanic and continental crust are such layers of the lithosphere as basalt and sedimentary.

Thus, the earth's crust consists mainly of rocks that are formed during the cooling and crystallization of magma, which penetrates into the lithosphere through cracks. If at the same time the magma could not seep to the surface, then it formed such coarse-grained rocks as granite, gabbro, diorite, due to its slow cooling and crystallization.

But the magma that managed to get out, due to rapid cooling, formed small crystals - basalt, liparite, andesite.

As for sedimentary rocks, they were formed in the Earth's lithosphere in different ways: detrital rocks appeared as a result of the destruction of sand, sandstones and clay, chemical ones were formed due to various chemical reactions in aqueous solutions - these are gypsum, salt, phosphorites. Organic were formed by plant and lime residues - chalk, peat, limestone, coal.

Interestingly, some rocks appeared due to a complete or partial change in their composition: granite was transformed into gneiss, sandstone into quartzite, limestone into marble. According to scientific research, scientists were able to establish that the lithosphere consists of:

• Oxygen - 49%;
• Silicon - 26%;
• Aluminum - 7%;
• Iron - 5%;
• Calcium - 4%
• The composition of the lithosphere includes many minerals, the most common are feldspar and quartz.

As for the structure of the lithosphere, stable and mobile zones are distinguished here (in other words, platforms and folded belts). On tectonic maps, you can always see the marked boundaries of both stable and dangerous territories. First of all, this is the Pacific Ring of Fire (located along the edges of the Pacific Ocean), as well as part of the Alpine-Himalayan seismic belt (Southern Europe and the Caucasus).

Description of platforms

The platform is practically immovable parts of the earth's crust that have gone through a very long stage of geological formation. Their age is determined by the stage of formation of the crystalline basement (granite and basalt layers). Ancient or Precambrian platforms on the map are always located in the center of the continent, young ones are either on the edge of the mainland, or between the Precambrian platforms.

Mountain-fold area

The mountain-folded region was formed during the collision of tectonic plates, which are located on the mainland. If the mountain ranges were formed recently, increased seismic activity is recorded near them, and all of them are located along the edges of the lithospheric plates (the younger massifs belong to the Alpine and Cimmerian stages of formation). Older areas related to the ancient, Paleozoic folding, can be located both on the edge of the mainland, for example, in North America and Australia, and in the center - in Eurasia.

It is interesting that scientists determine the age of mountain-folded areas according to the youngest folds. Since mountain building is ongoing, this makes it possible to determine only the time frame of the stages of development of our Earth. For example, the presence of a mountain range in the middle of a tectonic plate indicates that the border once passed here.

Lithospheric plates

Despite the fact that ninety percent of the lithosphere consists of fourteen lithospheric plates, many do not agree with this statement and draw their own tectonic maps, saying that there are seven large and about ten small ones. This division is rather arbitrary, because with the development of science, scientists either identify new plates, or recognize certain boundaries as non-existent, especially when it comes to small plates.

It is worth noting that the largest tectonic plates are very clearly visible on the map and they are:

• The Pacific is the largest plate on the planet, along the boundaries of which constant collisions of tectonic plates occur and faults form - this is the reason for its constant decrease;
• Eurasian - covers almost the entire territory of Eurasia (except Hindustan and the Arabian Peninsula) and contains the largest part of the continental crust;
• Indo-Australian - consists of the Australian continent and the Indian subcontinent. Due to constant collisions with the Eurasian plate, it is in the process of breaking;
• South American - consists of the South American mainland and part of the Atlantic Ocean;
• North American - consists of the North American continent, part of northeastern Siberia, the northwestern part of the Atlantic and half of the Arctic Oceans;
• African - consists of the African mainland and the oceanic crust of the Atlantic and Indian oceans. It is interesting that the plates adjacent to it move in the opposite direction from it, therefore the largest fault of our planet is located here;
• The Antarctic Plate is made up of the mainland Antarctica and the nearby oceanic crust. Due to the fact that the plate is surrounded by mid-ocean ridges, the rest of the continents are constantly moving away from it.

Movement of tectonic plates

Lithospheric plates, connecting and separating, change their outlines all the time. This enables scientists to put forward the theory that about 200 million years ago the lithosphere had only Pangea - a single continent, which subsequently split into parts, which began to gradually move away from each other at a very low speed (an average of about seven centimeters per year). ).

There is an assumption that due to the movement of the lithosphere, in 250 million years a new continent will form on our planet due to the union of moving continents.

When the oceanic and continental plates collide, the edge of the oceanic crust sinks under the continental one, while on the other side of the oceanic plate its boundary diverges from the plate adjacent to it. The boundary along which the movement of the lithospheres occurs is called the subduction zone, where the upper and plunging edges of the plate are distinguished. It is interesting that the plate, plunging into the mantle, begins to melt when the upper part of the earth's crust is squeezed, as a result of which mountains are formed, and if magma also breaks out, then volcanoes.

In places where tectonic plates come into contact with each other, there are zones of maximum volcanic and seismic activity: during the movement and collision of the lithosphere, the earth's crust collapses, and when they diverge, faults and depressions form (the lithosphere and the Earth's relief are connected to each other). This is the reason that the largest landforms of the Earth are located along the edges of the tectonic plates - mountain ranges with active volcanoes and deep-sea trenches.

Relief

It is not surprising that the movement of the lithospheres directly affects the appearance of our planet, and the diversity of the Earth's relief is amazing (the relief is a set of irregularities on the earth's surface that are above sea level at different heights, and therefore the main forms of the Earth's relief are conditionally divided into convex (continents , mountains) and concave - oceans, river valleys, gorges).

It is worth noting that the land occupies only 29% of our planet (149 million km2), and the lithosphere and the Earth's relief consist mainly of plains, mountains and low mountains. As for the ocean, its average depth is a little less than four kilometers, and the lithosphere and the relief of the Earth in the ocean consist of a continental shelf, a coastal slope, an oceanic bed, and abyssal or deep-sea trenches. Most of the ocean has a complex and varied relief: there are plains, basins, plateaus, hills, and ridges up to 2 km high.

Problems of the lithosphere

The intensive development of industry has led to the fact that man and the lithosphere have recently become extremely difficult to get along with each other: pollution of the lithosphere is acquiring catastrophic proportions. This happened due to the increase in industrial waste in combination with household waste and fertilizers and pesticides used in agriculture, which negatively affects the chemical composition of the soil and living organisms. Scientists have calculated that about one ton of garbage falls per person per year, including 50 kg of hardly decomposable waste.

Today, pollution of the lithosphere has become an urgent problem, since nature is not able to cope with it on its own: the self-purification of the earth's crust is very slow, and therefore harmful substances gradually accumulate and eventually negatively affect the main culprit of the problem - man.