Tectonic Plates

We explain what tectonic plates are, their types and which are the main ones. Also, what happens when they move, separate or push each other.

What are tectonic plates?

Tectonic plates or lithospheric plates are the different fragments into which the earth's crust is divided. Intense seismic, volcanic and orogenic activity is concentrated on its edges.

This is because the tectonic plates are in constant motion above the asthenosphere, which is the layer of the upper mantle closest to the crust and is mainly composed of magma. This magma moves inside the planet due to temperature differences, which causes the tectonic plates above to also move.

The shifts of tectonic plates produce geological phenomena such as earthquakes and volcano eruptions. They can also cause the formation of mountain chains and sedimentary basins, where plains are then formed.

Plate tectonics theory: The theory of plate tectonics, which explains these phenomena, was formulated in the late 1960s. Its main contributions were based on other studies carried out during the 20th century on the geological nature of the planet, among them, the theory of continental drift. by Alfred Wegener (1912) and the theory of ocean floor spreading by Harry Hess (1960).

Characteristics of tectonic plates

Tectonic plates have the following characteristics:

• They are fragments of the earth's crust.
• They are located above the asthenosphere, the part of the upper mantle closest to the Earth's crust.
• There are fourteen main tectonic plates.
• There are three types: oceanic, continental and mixed.
• They move slowly, but steadily.
• Their movements produce earthquakes and volcanic eruptions.

Types of tectonic plates

There are three types of tectonic plates: oceanic, continental and mixed.

• oceanic plates. They are composed entirely of oceanic crust, that is, the floor of the oceans, so they are submerged throughout their entire length.
• continental plates. They are composed mainly of continental crust, that is, of the continents themselves.
• mixed plates. They have a continental part and an oceanic part, and are the predominant type of plate.

Main tectonic plates

The main tectonic plates into which the Earth's surface is divided are:

• African plate. It covers the entire African continent and extends towards the Indian and Atlantic oceans.
• Antarctic plate. It covers the entire Antarctic and extends into the surrounding oceans.
• Arabic plate. It covers the Arabian Peninsula. In its subsoil, there are the largest oil and gas reserves on the planet.
• Coconut Plate. It is located in the Pacific Ocean, in the western coastal region of Central America. Together with the Caribbean plate, it is responsible for the formation of the volcanic arcs of the Central American region.
• Nazca Plate. It is located in the eastern Pacific Ocean, off the coasts of Peru, Ecuador, Colombia and Chile. It is responsible, together with the South American plate, for the formation of the mountains and volcanoes that make up the Andes mountain range.
• Juan de Fuca Plate. It is a small oceanic plate located on the coasts of the Pacific Ocean, north of the United States.
• Caribbean plate. As its name indicates, it is located in the Caribbean region. It covers the Central American continental portion and all of the islands in the Caribbean Sea.
• Pacific Plate. It is one of the largest tectonic plates on the planet. It covers almost the entire ocean of the same name and has on its edges the so-called “Pacific Ring of Fire”, the area of ​​greatest seismic and volcanic activity in the world.
• Eurasian plate. It is a huge tectonic plate that covers all of Europe and Asia (with the exception of India), the Arabian Peninsula and part of Siberia. It also extends over the North Atlantic Ocean and the Arctic Ocean.
• Filipino plate. It is located in the Pacific Ocean, east of the Philippines. It is responsible for the formation of some of the islands of Japan and is part of the Pacific ring of fire.
• Indo-Australian plate. It extends from India's border with China and Nepal, across the entire Indian subcontinent and the entirety of Australia and New Zealand. Includes sectors of the Indian and Pacific oceans.
• North American plate. It is the largest plate on the planet. It contains North America in its entirety, including Greenland, as well as the archipelagos of Cuba, the Bahamas, half of Iceland and a sector of Siberia. It also covers part of the North Atlantic and Arctic Glacier oceans.
• Scotia Plate. It is located at the junction of the Pacific and Atlantic oceans, south of South America. It is an oceanic plate of intense seismic activity.
• South American plate. It extends over South America and the western portion of the Atlantic Ocean. Together with the Nazca plate, it is responsible for the formation of the Andes mountain range.

Tectonic plate movements

Tectonic plates move on the asthenosphere, the fluid portion of the Earth's upper mantle composed of magma. They move at a constant but very slow speed, so that it is imperceptible to human beings.

Plates move because the magma beneath the crust also moves. The differences in temperature and pressure in the asthenosphere produce movements of rise and fall of magma, and this explains why the plates that are on the mantle also move.

There are three types of plate movements:

• Convergence. It occurs when tectonic plates move in opposite directions and push against each other. This movement causes the so-called “subduction edges”, in which mountain chains and volcanoes form.
• Divergence. It occurs when tectonic plates move in opposite directions and tend to separate. This movement causes the formation of new oceans (since water occupies the space left between the continents that separate) and mountain ranges of underwater volcanoes.
• Transformation. It occurs when tectonic plates move laterally relative to each other. This movement does not cause the formation of high relief, but rather tectonic faults, which are large fissures in the crust resulting from friction between the plates.

The edges of tectonic plates

The most significant tectonic events occur in the contact zones between the plates. Regions away from the edges tend to be much less active in tectonic terms.

In plate boundary regions, the following tectonic events are usually frequent:

• Tremors and earthquakes. They are produced due to the energy accumulated by the friction of tectonic plates, and are transmitted through seismic waves. When these waves reach the surface of the Earth, they manifest themselves in the form of strong and sudden vibrations. If these vibrations occur in the continental crust, they are called earthquakes; If they occur in the oceanic crust, they are called tidal waves or tsunamis.
• mountainous formations. They are produced by the folding and deformation of the continental crust at the edges of convergent plates. They are also called folds. They are usually grouped in mountain ranges called mountain ranges.
• volcanic eruptions. They are formed by the heat and pressure that accumulates inside the planet as a result of the movement of tectonic plates. The magma rises from the asthenosphere and reaches the surface in the form of an eruption, which comes out of the crater of the volcanoes.

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References

• Gil, A. (2020). The map of tectonic plates. The World Order. https://elordenmundial.com/
• National Geographic. (2023). What are tectonic plates and what causes their movements?. https://www.nationalgeographic.es/
• Tarbuck, E. and Lutgens, F. (2005). Earth Sciences. An introduction to physical geology. Prentice Hall.