The tectonic or lithospheric plates are the blocks or fragments in which the lithosphere is divided, which move dragged by the Earth's mantle . These plates have been formed from the mantle and reintegrated into it in a constant process since the last 3,000 million years. The lithosphere has several dozen tectonic plates of varying magnitude and 8 of the largest are the Eurasian, African, Australian, North American, South American, Nazca, Pacific and Antarctic.
These plates move thanks to the dynamics of the mantle and the lithosphere, by the convection currents generated by the thermal flow. The tension of the flow of the mantle drags the rigid crust, which cracks and separates forming the plates. When ocean plates move apart, magma (molten basalt) rises to the surface and a new ocean floor forms.
Types of tectonic plates There are basically two types of tectonic plates, oceanic and continental, thus generating three possibilities of converging boundaries between plates. These are continental plate convergence against an oceanic one, an oceanic one against another oceanic one and a continental one against another continental one. Oceanic plates They are formed by oceanic crust (denser than continental crust) and is made up of silicates of iron and magnesium (mafic rocks).
The crust of these plates is thinner (7 km on average) compared to the continental crust and is always covered by marine waters. Continental plates The continental crust is formed by sodium, potassium and aluminum silicates (felsic rocks), being of lower density than the oceanic crust. It is a plate with thicker crust, reaching up to 70 km thick in mountain ranges.
It is really a mixed plate, in which although the continental crust predominates, there are also oceanic portions. Tectonic plates of the world Traditionally, 7 major tectonic plates are recognized: the Eurasian, the African, the Australian, the North American, the South American, the Pacific and the Antarctic. Likewise, there are intermediate plates such as the Nazca, Philippine, Coco and Caribbean plates, and other very small ones.
Some of small size are the Anatolian and the Aegean and only in the western Pacific there are more than 20 small tectonic plates. Some of the major tectonic plates are described below: Eurasian Plate This tectonic plate includes Europe, most of Asia, part of the North Atlantic Ocean, and the Arctic. Asia excludes Hindustan, Southeast Asia, and the Far East of Siberia, Mongolia, and China.
African Plate This covers the eastern Atlantic and almost the entire African continent, except for its eastern fringe which corresponds to the Arabian and Somali plates. The limits of this plate are divergent in all its perimeter, except in its contact with the Eurasian plate that is convergent. Australian Plate The Australian tectonic plate includes Australia, New Zealand, and parts of the Southwest Pacific.
The Australian plate shows divergent boundaries to the south and west, while its boundaries to the north and east converge. North American Plate Includes the entire North American subcontinent up to the Yucatan Peninsula, Greenland, part of Iceland, western North Atlantic and Arctic areas. The boundaries of this plate diverge from the Atlantic ridge to the east and converge in the Pacific.
South American Plate Includes the subcontinent of the same name and has divergent limits from the Atlantic ridge. While on the western side it shows convergent limits with the Nazca plate, to the southwest with the Antarctic and to the north it interacts with the Caribbean plate. Pacific Plate It is an oceanic plate with divergent boundaries from the Pacific ridge separating it from the Nazca plate.
On the other hand, to the north and west it has convergent boundaries with the North American, Eurasian, Philippine and Australian plates. Antarctic Plate This tectonic plate includes the entire Antarctic continental shelf and the ocean of the same name, with divergent boundaries on its perimeter. Nazca Plate It consists of an oceanic plate that subducts on the western coast of the South American plate (convergence).
While it presents divergence to the north with the Coco plate and to the south with the Antarctic. On the other hand, to the west it diverges from the Pacific plate from its ridge and its collision with the South American plate gave rise to the Andes mountain range. Movements of the tectonic plates The tectonic plates or delimited fragments of the lithosphere move transported by the movement of the asthenosphere.
Convection currents cause the displacement of the viscous material in the mantle, forming circulation cells. The "conveyor belt" The material of the mantle of the upper layer (asthenosphere), at a lower temperature, descends pushing the hot material from below. This hotter material is less dense and rises, displacing matter and causing it to move horizontally, until it cools down and descends again.
This current of viscous flow from the mantle drags the tectonic plates formed of solid material (lithosphere). New ocean floor When tectonic plates move, magma (molten basalt) from inside the mantle outcrops at the separation points. This emerging basalt creates new ocean floor, pushing the old substrate horizontally and the crust expands.
Subduction As the ocean floor expands, it collides with the continental masses. As this bottom is denser than the continental shelf, it sinks below it (subduction), so it melts and becomes part of the mantle again. In this way the material follows the cycle driven by convection and the tectonic plates drift across the planet's surface.
Continental drift The movement of the mantle caused by convection and that of the tectonic plates of the lithosphere, causes continental drift. This is the relative displacement of the continents with respect to each other. Since the origin of the tectonic plates about 3,000 million years ago, they have merged and divided at various times.
The last great confluence of most of the continental masses occurred 300 million years ago with the formation of the supercontinent Pangea. Then, as the displacements continued, Pangea fragmented again forming the current continents, which continue to move. Consequences of plate movement The movement of tectonic plates releases energy from the interior of the planet at the plate boundaries mechanically (earthquakes) and thermally (volcanism).
In turn, the displacements, shocks and frictions model the terrestrial and oceanic relief. Volcanic activity The thermal flow of the mantle and its circulation by convection pushes the molten magma or basalt towards the surface causing volcanic eruptions. These in turn cause catastrophes by expelling lava, gases and particles that pollute the environment.
Volcanic island arcs and continental volcanic arcs The convergence of two oceanic plates can produce chains of volcanoes that, when emerging , originate island arcs. At the convergence of an oceanic plate with a continental one , continental volcanic arcs are formed, such as the Trans-Mexican volcanic belt. Seismic activity The collision of tectonic plates and especially the transformation limits, cause seismic movements or earthquakes.
Some of them reach great magnitude and negatively affect human beings, destroying infrastructure and causing the death of people. Among the consequences of these phenomena are tidal waves or tsunamis, when the seismic movement occurs in the ocean. Relief of the Earth The movement and interaction of the tectonic plates with each other shapes the relief of the earth and the ocean floor.
The great continental mountain ranges, such as the Andes and the Appalachians, are the product of the convergence of tectonic plates by subduction and those of the Himalayas by obduction. In turn, due to isostatic or gravitational balance, when one area rises, another is formed as a depression or plain. Diastrophic processes, such as faults, folding and others, are caused by the movements of tectonic plates.
Climate The distribution of continental masses affects the regime of marine currents and the global climate. Large continental masses due to the convergence of plates form drier continental interiors, in turn affecting the agusa cycle. In the same way, the mountainous elevations produced by the subduction and obduction processes affect the wind regime and the distribution of rainfall.
