What are Plate Tectonics - Summary

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Plate tectonics, a theory that is part of the geological sciences, makes it possible to explain a vast variety of natural phenomena that occur on planet Earth. The theory is based, in very general terms, in that the lithosphere or lithosphere is fragmented in what we call tectonic plates, that is, they are the parts that make up the lithosphere.

Following this line, if you want to know more about what are tectonic plates We recommend you read this interesting Green Ecologist article in which you will find all the explanation you need and you will also discover what types of tectonic plates there are, why they move and much more.

What are plate tectonics and which are the main ones

In a simple way we can define tectonic plates as fragments of the lithosphere, that is, fragments of the solid surface layer of the Earth, which can be up to 100 kilometers thick. Tectonic plates are suspended in a viscous layer called asthenosphere, layer that allows the movement or lateral displacement of the tectonic plates. The plates are considered rigid, since when moving laterally they interact with each other without deforming, except their edges, which undergo considerable modifications.

Furthermore, the lithosphere is composed of 14 main tectonic plates and 46 secondary tectonic plates. The difference between the main and secondary plates lies in their size, the main ones being the largest. Next we will name the 14 main plates:

  • North American plate
  • South american plate
  • Pacific Plate
  • African plate
  • Eurasian plate
  • Australian license plate
  • Antarctic plate
  • Caribbean plate
  • Plate of Coconuts
  • Nazca plate
  • Philippine license plate
  • Arabic plate
  • Scotia Badge
  • Juan de Fuca plaque

Here you can learn more about what is the lithosphere and below you can see the plate tectonic map.

Types of tectonic plates

Depending on the kind of earth's crust that forms them, the tectonic plates can be:

  • Ocean plates: composed of oceanic crust, which is thin and basic composition with iron and magnesium in greater proportion. In general, it is completely submerged in the water of the oceans.
  • Mixed plates: composed mostly of continental crust and to a lesser extent oceanic crust. As the continental crust predominates in its composition, some call them continental plates. Most plate tectonics are of this type.

In turn, tectonic plates can be classified according to the type of limit or edge they present:

  • Divergent limit: tectonic plates separate due to the movement that moves them away. This type of limit occurs in both oceanic and continental plates. As the plates separate, the magma rises and seeps through the fractures, giving rise to the formation of new crust.
  • Convergent limit: tectonic plates collide head-on, and as a result, one plate sinks below the other. The sinking process is known as subduction. Generally, the subduced plate is the most dense and once in the mantle, it partially melts and creates magma. On the contrary, when two plates have the same density as, for example, in the collision of two continental plates, the obduction process occurs. In this process, no plate sinks, but rather there is a deformation of the edges of both plates in a vertical direction, being joined by a suture zone.
  • Sliding limit: tectonic plates slide in parallel but in opposite directions. Here neither the creation nor fracture of the cortex occurs as in the previous cases. These limits are characterized by strong friction between plates.

Why tectonic plates move

Why plate tectonics move is not yet known exactly. The truth is that plate tectonics is a modern theory that emerged between 1960 and 1970 and is still in full development. What has been proven is the existence of factors that promote the sliding of the plates.

One of the key factors in plate movement is related to temperature, more precisely the geothermal gradient, as it creates conditions conducive to movement: a very viscous lithosphere capable of flowing over an asthenosphere with lower viscosity.

Likewise, the geothermal gradient across the planet is completely heterogeneous and, as a consequence, the crust is made up of materials with different densities. Precisely, from the materials with different densities that make up the crust, the gravitational forces they are capable of generating the different movements of the tectonic plates.

Consequences of the movement of tectonic plates

The movements of the plates have multiple effects, mainly on the edges of the plates and in the areas close to the edges. Let's see here:

  • Rift Valleys: They are geological fractures that originate from the separation caused by two plates with divergent boundaries.
  • Volcanism: Volcanoes can be caused by magma that rises during separation caused by plates with divergent boundaries, as well as subduction of plates with convergent boundaries. To better understand volcanism, a consequence of tectonic movement, you can read about How volcanoes are formed and Types of volcanoes.
  • Earthquakes: tremors, earthquakes or earthquakes are produced by the collision of plates with convergent limits and also by friction between plates with sliding limits. If you want to learn more about this topic, here you can read about the Difference between earthquakes, tremors and earthquakes and Earthquake: what it is, how it occurs and types.
  • Mountain formations: During the obduction process of plates with convergent boundaries, they collide with each other, producing folds and distortions at their edges. As a result of the folds and distortions, mountains and mountain ranges originate.
  • Transforming faults: they are observed as geological discontinuities in the terrain or also as heavily fractured rocky areas. Failures are produced by friction between plates with sliding limits.

Once you have learned all this about what tectonic plates and their movements are, you may be curious to understand more about how continents were formed.

If you want to read more articles similar to What are tectonic platesWe recommend that you enter our Nature Curiosities category.

  • Fernández, C., Alfaro, P., Alonso, G. G., & Chaves, F. M. A. (2022). What moves tectonic plates? Earth Sciences Teaching, 27 (3), 238-245
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