How did continents and islands appear? What determines the name of the largest plates of the Earth? Where did our planet come from?
How it all began?
Everyone has thought at least once about the origin of our planet. For deeply religious people, everything is simple: God created the Earth in 7 days, period. They are unshakable in their confidence, even knowing the names of the largest ones formed as a result of the evolution of the planet’s surface. For them, the birth of our stronghold is a miracle, and no arguments of geophysicists, naturalists and astronomers can convince them.
Scientists, however, have a different opinion, based on hypotheses and assumptions. They make guesses, put forward versions and come up with a name for everything. This also affected the largest plates of the Earth.
At the moment, it is not known for certain how our firmament appeared, but there are many interesting opinions. It was the scientists who unanimously decided that there once existed a single gigantic continent, which, as a result of cataclysms and natural processes, split into parts. Scientists also came up with not only the names of the largest plates of the Earth, but also designated the small ones.
A theory bordering on science fiction
For example, Pierre Laplace, scientists from Germany, believed that the Universe emerged from a gas nebula, and the Earth is a gradually cooling planet, the crust of which is nothing more than a cooled surface.
Another scientist believed that the Sun, when passing through a gas and dust cloud, captured part of it with itself. His version is that our Earth was never a completely molten substance and was originally a cold planet.
According to the theory of the English scientist Fred Hoyle, the Sun had its own twin star, which exploded like a supernova. Almost all the fragments were thrown over vast distances, and the small number remaining around the Sun turned into planets. One of these fragments became the cradle of humanity.
Version as an axiom
The most common story of the origin of the Earth is as follows:
- About 7 billion years ago, the primary cold planet formed, after which its interior began to gradually warm up.
- Then, during the so-called “lunar era,” red-hot lava poured out onto the surface in gigantic quantities. This entailed the formation of the primary atmosphere and served as an impetus for the formation of the earth's crust - the lithosphere.
- Thanks to the primary atmosphere, oceans appeared on the planet, as a result of which the Earth was covered with a dense shell, representing the outlines of oceanic depressions and continental protrusions. In those distant times, the area of water significantly prevailed over the area of land. By the way, the upper part of the mantle is called the lithosphere, which forms lithospheric plates that make up the general “shape” of the Earth. The names of the largest plates correspond to their geographical location.
Giant rift
How did continents and lithospheric plates form? About 250 million years ago, the Earth looked completely different from what it does now. Then on our planet there was only one, simply gigantic continent called Pangea. Its total area was impressive and equal to the area of all existing continents, including islands. Pangea was washed on all sides by an ocean called Panthalassa. This huge ocean occupied the entire remaining surface of the planet.
However, the existence of the supercontinent turned out to be short-lived. Processes were seething inside the Earth, as a result of which the substance of the mantle began to spread in different directions, gradually stretching the continent. Because of this, Pangea first split into two parts, forming two continents - Laurasia and Gondwana. Then these continents gradually split into many parts, which gradually dispersed in different directions. In addition to new continents, lithospheric plates appeared. From the names of the largest plates, it becomes clear in which places giant faults formed.
The remains of Gondwana are the Australia and Antarctica we know, as well as the South African and African lithospheric plates. It has been proven that these plates are gradually moving apart in our time - the speed of movement is 2 cm per year.
The fragments of Laurasia turned into two lithospheric plates - North American and Eurasian. Moreover, Eurasia consists not only of a fragment of Laurasia, but also of parts of Gondwana. The names of the largest plates that form Eurasia are Hindustan, Arabian and Eurasian.
Africa takes a direct part in the formation of the Eurasian continent. Its lithospheric plate is slowly moving closer to the Eurasian plate, forming mountains and hills. It was because of this “union” that the Carpathians, Pyrenees, Alps and Sudetes appeared.
List of lithospheric plates
The names of the largest plates are:
- South American;
- Australian;
- Eurasian;
- North American;
- Antarctic;
- Pacific;
- South American;
- Hindustan.
Medium sized slabs are:
- Arabian;
- Nazca;
- Scotia;
- Philippine;
- Coconut;
- Juan de Fuca.
The lithosphere of planet Earth is the solid shell of the globe, which includes multi-layered blocks called lithospheric plates. As Wikipedia points out, translated from Greek it is “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 a limited amount of 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 touch 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 relative to the atmosphere. In places it has very low strength and is prone to fractures and ductility, especially if groundwater flows within 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, it is the solid shell of the Earth, which acts as an intermediate layer between fertile soil, mineral deposits, ores and the 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 Caucasus Mountains, the depth of this layer reaches 90 km.
Structure of the Earth
Layers of the lithosphere
If we consider the structure of lithospheric plates in more detail, 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 of the top layer of all earth blocks. It mainly consists of volcanic rocks, as well as the remains of organic substances, which over many millennia have decomposed into humus. Fertile soils are also part of the sedimentary layer.
- Granite. These are lithospheric plates that are in constant motion. They are predominantly composed of super-strong granite and gneiss. The last component is a metamorphic rock, the vast majority of which is filled with minerals such as potassium spar, quartz and plagioclase. Seismic activity of this layer of solid shell is at the level of 6.4 km/sec.
- Basaltic. It is predominantly composed of basalt deposits. This part of the Earth's solid shell was formed under the influence of volcanic activity back 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 above, we can conclude that this is the 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 lithospheric plates and their seismic activity in relation to the structure of the Earth.
Layers of the lithosphere
Oceanic lithosphere
This type of earth's shell differs significantly from its mainland. This is due to the fact that the boundaries of lithospheric blocks and the hydrosphere are closely intertwined, and in some parts of it the water space is distributed beyond the surface layer of lithospheric plates. This applies to bottom faults, depressions, cavernous formations of various etiologies.
Oceanic crust
That is why oceanic plates have their own structure and consist of the following layers:
- marine sediments that have a total thickness of at least 1 km (in the deep ocean, they may be completely absent);
- secondary layer (responsible for the propagation of medium and longitudinal waves moving at speeds of up to 6 km/sec, takes an active part in the movement of plates, which provokes earthquakes of varying power);
- the lower layer of the solid shell of the globe in the area where the ocean floor is located, which is mainly composed of gabbro and borders the mantle (average seismic wave activity is from 6 to 7 km/sec.).
A transitional type of lithosphere is also distinguished, located in the area of oceanic soil. It is characteristic of island zones formed in an arc. In most cases, their appearance is associated with the geological process of movement of lithospheric plates, which were layered on top of each other, forming this kind of irregularities.
Important! A similar structure of the lithosphere can be found on the outskirts of the Pacific Ocean, as well as in some parts of the Black Sea.
Useful video: lithospheric plates and modern relief
Chemical composition
The lithosphere is not diverse in terms of its content of organic and mineral compounds and is mainly presented in the form of 8 elements.
Most of these are rocks that were formed during a period of active eruption of volcanic magma and plate movement. The chemical composition of the lithosphere is as follows:
- Oxygen. Occupies at least 50% of the entire structure of the solid shell, filling its faults, depressions and cavities formed during the movement of plates. Plays a key role in the balance of compression pressure during geological processes.
- Magnesium. This is 2.35% of the Earth's solid shell. Its appearance in the lithosphere is associated with magmatic activity in the early periods of the planet’s formation. It is found throughout the continental, marine and oceanic parts of the planet.
- Iron. A rock that is the main mineral of lithospheric plates (4.20%). Its main concentration is in the mountainous regions of the globe. It is in this part of the planet that the highest density of this chemical element is found. It is not presented in pure form, but is found in lithospheric plates mixed together with other mineral deposits.
- Australian plate- 47,000,000 km²
- Antarctic plate- 60,900,000 km²
- Arabian subcontinent- 5,000,000 km²
- African plate- 61,300,000 km²
- Eurasian plate- 67,800,000 km²
- Hindustan plate- 11,900,000 km²
- Coconut Plate - 2,900,000 km²
- Nazca Plate - 15,600,000 km²
- Pacific Plate- 103,300,000 km²
- North American Plate- 75,900,000 km²
- Somali plate- 16,700,000 km²
- South American Plate- 43,600,000 km²
- Philippine plate- 5,500,000 km²
Then surely you would like to know what are lithospheric plates.
So, lithospheric plates are huge blocks into which the solid surface layer of the earth is divided. Given the fact that the rock beneath them is molten, the plates move slowly, at a speed of 1 to 10 centimeters per year.
Today there are 13 largest lithospheric plates, which cover 90% of the earth's surface.
Largest lithospheric plates:
Here it must be said that there is a continental and oceanic crust. Some plates are composed solely of one type of crust (such as the Pacific plate), and some are of mixed types, where the plate begins in the ocean and smoothly transitions to the continent. The thickness of these layers is 70-100 kilometers.
Map of lithospheric plates
Largest lithospheric plates (13 pcs.)At the beginning of the 20th century, American F.B. Taylor and the German Alfred Wegener simultaneously came to the conclusion that the location of the continents was slowly changing. By the way, this is, to a large extent, what it is. But scientists were unable to explain how this happens until the 60s of the twentieth century, when the doctrine of geological processes on the seabed was developed.
Map of the location of lithospheric plates It was fossils that played the main role here. Fossilized remains of animals that clearly could not swim across the ocean were found on different continents. This led to the assumption that once all the continents were connected and animals calmly moved between them.
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Together with part of the upper mantle, it consists of several very large blocks called lithospheric plates. Their thickness varies - from 60 to 100 km. Most plates include both continental and oceanic crust. There are 13 main plates, of which 7 are the largest: American, African, Indo-, Amur.
The plates lie on a plastic layer of the upper mantle (asthenosphere) and slowly move relative to each other at a speed of 1-6 cm per year. This fact was established by comparing images taken from artificial Earth satellites. They suggest that the configuration in the future may be completely different from the present one, since it is known that the American lithospheric plate is moving towards the Pacific, and the Eurasian plate is moving closer to the African, Indo-Australian, and also the Pacific. The American and African lithospheric plates are slowly moving apart.
The forces that cause the divergence of lithospheric plates arise when the material of the mantle moves. Powerful upward flows of this substance push the plates apart, tearing apart the earth's crust, forming deep faults in it. Due to underwater outpourings of lavas, strata are formed along faults. By freezing, they seem to heal wounds - cracks. However, the stretching increases again, and ruptures occur again. So, gradually increasing, lithospheric plates diverge in different directions.
There are fault zones on land, but most of them are in the ocean ridges, where the earth's crust is thinner. The largest fault on land is located in the east. It stretches for 4000 km. The width of this fault is 80-120 km. Its outskirts are dotted with extinct and active ones.
Along other plate boundaries, plate collisions are observed. It happens in different ways. If plates, one of which has oceanic crust and the other continental, come closer together, then the lithospheric plate, covered by the sea, sinks under the continental one. In this case, arcs () or mountain ranges () appear. If two plates that have continental crust collide, the edges of these plates are crushed into folds of rock, and mountainous regions are formed. This is how they arose, for example, on the border of the Eurasian and Indo-Australian plates. The presence of mountainous areas in the internal parts of the lithospheric plate suggests that once there was a boundary of two plates that were firmly fused with each other and turned into a single, larger lithospheric plate. Thus, we can draw a general conclusion: the boundaries of lithospheric plates are mobile areas to which volcanoes, zones, mountain areas, mid-ocean ridges, deep-sea depressions and trenches are confined. It is at the border of lithospheric plates that they are formed, the origin of which is associated with magmatism.
lithospheric plate- A large rigid block of the Earth’s lithosphere, bounded by seismically and tectonically active fault zones, according to plate tectonics, such blocks move along the asthenosphere. → Fig. 251, p. 551 Syn.: tectonic plate… Dictionary of Geography
A large (several thousand km across) block of the earth’s crust, including not only the continental crust, but also the associated oceanic crust; bounded on all sides by seismically and tectonically active fault zones... Big Encyclopedic Dictionary
A large (several thousand kilometers in diameter) block of the earth’s crust, including not only the continental crust, but also the oceanic crust associated with it; bounded on all sides by seismically and tectonically active fault zones. * * * LITHOSPHERIC… … encyclopedic Dictionary
A large (several thousand km in diameter) block of the earth’s crust, including not only the continental crust, but also the oxanic layer associated with it. bark; bounded on all sides by seismically and tectonically active fault zones... Natural science. encyclopedic Dictionary
The Juan de Fuca lithospheric plate (named after the navigator Juan de Fuca, a Greek by nationality who served Spain) is tectonic ... Wikipedia
A 3D model showing the position of the remnants of the Farallon plate deep in the Earth's mantle... Wikipedia
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- (Spanish: Nazca) lithospheric plate located in the eastern part of the Pacific Ocean. The plate got its name from the name of the area of the same name in Peru. The earth's crust is of oceanic type. On the eastern border of the Nazca plate... Wikipedia was formed
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