lithosphere

Geographic

2022

We explain what the lithosphere is, its layers and its importance. Also, the continental lithosphere and the oceanic lithosphere.

The lithosphere includes the earth's crust and the upper part of the mantle.

What is the lithosphere?

The lithosphere or lithosphere is the most solid and superficial layer of planet Earth, that is, the most rigid and external of all. It is formed by the Earth crust and the top layer of terrestrial mantle and it is the coldest surface on the planet, on which all the living beings.

The term lithosphere comes from the Greek words lithos ("Stone") and sphaíra ("sphere"). This layer is part of the geosphere (which is the solid part of the planet) and varies in thickness. It is not easy to determine exactly where the lithosphere begins and ends, although the atmosphere and the asthenosphere (upper mantle zone) are often used as limits.

There are two types of lithosphere:

  • Continental lithosphere. It is made up of the continental crust (that is, the continents) and the outermost region of the earth's mantle. It is mostly composed of granite-type stones and reaches around 120 km thick.
  • Oceanic lithosphere. It is the portion of the earth's crust that makes up the ocean floor. It is a much thinner layer than the continental one (barely 65 km thick) and is made up mostly of basaltic rocks.

The lithosphere is fragmented into different blocks known as tectonic plates (or lithospheric plates) on which the earth's crust is found. These plates move a few centimeters a year. The movement of the plates is given by convection currents and can cause friction or separation between plates, which generates processes such as orogenesis (formation of moutains and landforms) and the magmatism or volcanism.

Characteristics of the lithosphere

Some characteristics of the lithosphere are:

  • Location. The lithosphere is one of the layers of the Earth and it is formed by the terrestrial surface and the external layer of the terrestrial mantle. These two are the outermost layers of the planet.
  • Size. The lithosphere has a variable extension, which usually ranges from 100 to 150 km deep.
  • Temperature. The lithosphere has temperatures that vary according to the different locations and depths of the Earth: on the Earth's surface, for example, the temperature is similar to that of the environment. The temperature of the lithosphere increases as it descends and in the outer zone of the mantle it can exceed 1000 ° C.
  • Function. The lithosphere is a fundamental layer for the development of life on planet Earth because it includes the earth's surface, which is the layer that houses living organisms. It is thanks to the physical and chemical conditions provided by this layer that plants, animals and humans can develop on Earth.
  • Structure. The lithosphere is a solid and rigid layer formed by different types of materials, such as silicates or metals. It is made up of tectonic plates that are large pieces of solid rock that are in continuous movement.

Layers of the lithosphere

The lithosphere is made up of two main layers:

  • Earth's crust. It is the outermost solid region of the globe, in which living beings inhabit. It can be of two types: continental crust, when it is part of the continents, and oceanic crust, when it is part of the seabed.
  • The upper region of terrestrial mantle. It is the outer zone of the inner layer of the planet called the terrestrial mantle. The terrestrial mantle is the most abundant layer on the planet (it occupies 84% ​​of the Earth) and is composed of the upper mantle and the inner mantle. The mantle is made up of silicates (materials made of oxygen and silicon) and extends from the end of the earth's crust to the outer part of the planet's core (about 2,900 km deep). The upper mantle is a very dense and viscous layer, over which the tectonic layers move.

Tectonic plates

The Tectonic plates is the theory that maintains that the lithosphere is made up of tectonic plates, which are rock fragments that slide over the asthenosphere. These plates are in continuous movement and can move closer to or separate from each other, causing phenomena such as the formation of mountains, the formation of volcanoes, seismic phenomena, the formation of depressions, among others.

The movement of the plates is generated by convection currents (variations in temperature and density) and generates interaction between the edges of the plates in phenomena known as:

  • Divergent limits. Tectonic plates separate and magma emerges from inside the Earth, causing the formation of volcanoes.
  • Convergent limits. Tectonic plates collide with each other and mountains are formed. The process of subduction can also occur, when one plate sinks under the other, which generates the appearance of mountain ranges.
  • Transformative limits. Tectonic plates slide laterally without destruction of the lithosphere. These movements generate earthquakes or faults.

There are 14 main tectonic plates and more than 40 secondary ones.Among the most prominent are: the African plate, the South American plate, the Nazca plate, the Indo-Australian plate, the Eurasian plate, the North American plate, the Caribbean plate and the Pacific plate.

Importance of the lithosphere

The lithosphere is a very important layer of planet Earth, because it is the one that contains the earth's crust on which living beings inhabit, such as animals, plants, bacteria, mushrooms and the human being. It plays a fundamental role because it provides the environment conducive to the development of life and makes resources and nutrients available that allow the feeding and the development of living organisms.

Regarding the human development, the lithosphere is of great importance because it is a source of resources and natural goods that humans use for different purposes and that are the basis of many industries. The earth's surface provides human beings with materials and resources for the development of the textile industry, food, automotive, oil, metallurgical, among many others.

The lithosphere is the outermost layer of planet Earth and it is there where movements and phenomena that modify the life of organisms take place, such as seismic activity (tremors, earthquakes, seismic faults), magmatic activity (volcanoes) or the formation of mountains (orogenesis). In addition, it is the only terrestrial layer that humans have been able to study directly, so it is the layer that has the most information and the one that is best known. The other layers are found deep below the earth's surface and are only known from measurements, experimentations and scientific deductions.

The geosphere, hydrosphere, atmosphere, and biosphere

The different systems that make up planet Earth are known as "spheres". One of them is the geosphere, of which the lithosphere is part, which is the solid part of the planet and is made up of:

  • Earth's crust. It is a solid layer and is the outermost and superficial layer of the Earth. It is the layer on which all living beings inhabit.
  • The mantle. It is a layer that is located between the earth's crust and the core, which is why it is considered an intermediate layer made up mostly of silicates and with a temperature that varies according to its proximity to the core. This layer is made up of the upper mantle and the lower mantle (which is at a higher temperature and is denser than the upper one).
  • The nucleus. It is a solid sphere located in the center of the Earth with temperatures higher than 4000 ° C and made up mainly of iron. The core is made up of the inner core (it is solid) and the outer core (it is liquid).

The lithosphere is part of the geosphere because it is a layer formed by the crust and part of the mantle.

In addition to the geosphere, the Earth is composed of:

  • Hydrosphere. Part of the planet Earth formed by water, that is, oceans, rivers, seas, lagoons, among others.
  • Atmosphere. Part of the planet Earth made up of gases, among which oxygen, nitrogen and carbon dioxide.
  • Biosphere. It is the set of living beings that inhabit and interact on planet Earth.
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