What is the Lithosphere (Parts, Characteristics and Types)

It is called lithosphere or lithosphere. most superficial layer of the earth’s sphere, formed by the crust and the outermost area of ​​the Earth’s mantle. This layer is delimited by the Earth’s surface (upper limit) and the asthenosphere (lower limit). The lithosphere is approximately 50 to 100 km thick, although it varies depending on location.

The word lithosphere is of Greek origin, formed by the words lithoswhich means ‘stone’, and sphaira, which expresses ‘sphere’. The term was introduced by Joseph Barrell, an American geologist who published in 1914 a series of articles in which he delves into this concept, titled The Strength of the Earth’s Crust.

Parts of the lithosphere

The lithosphere is a rock layer that varies in thickness in the deep sea and in mountainous regions. This formed by an earth’s crust, which in turn is divided into continental and oceanic crust; and the outer part of the earth’s mantle, called residual mantle. The lithosphere rests on the asthenosphere, a soft layer that is part of the Earth’s upper mantle.

The lithosphere is subdivided into tectonic plates. These plates act as physical boundaries for each other, and move as rigid blocks on Earth’s upper mantle. Geological phenomena such as seismicity, magmatism, volcanism or orogenesis occur at the edges.

Tectonic plates are classified into:

Major or main plateswhich are: Eurasian, North American, South American, Pacific, African, Australian and Antarctic;
Minor or secondary plates, like the Arabian plate or Nazca plate; and
Microplateslike the Northern Andes plate.

Characteristics of the lithosphere

The lithosphere is characterized by its rigidity. It is the coldest inner layer of the Earth. The density of the lithosphere is approximately 3 t/m3. The lithosphere is chemically composed of oxygen, sulfur, aluminum, iron, calcium, sodium, potassium , magnesium and silicon. Likewise, it is formed by minerals and rocks that can be igneous, sedimentary and metamorphic. The lithosphere is also composed of organic compounds that are buried in the crust, such as oil, coal or natural gas. Life on Earth develops in part of the Earth’s crust and above the lithosphere. The lithosphere is related to other layers such as the hydrosphere, the atmosphere and the biosphere, undergoing various alterations as a result of them. Depending on the location, the lithosphere can be less than 50 km deep and extend beyond 100 km. The movement of the lithosphere is produced by the displacement of the tectonic plates that form the crust, and on whose edges geological phenomena are formed. The lithosphere can be classified into continental and oceanic lithosphere.

Types of lithosphere

The lithosphere can be classified into continental and oceanic lithosphere.

The continental lithosphere It is made up of the continental crust and the external part of the Earth’s mantle. It has up to 70 km thick of plutonic and metamorphic rocks and is made up of mountains, mountain ranges, hills, plateaus, plains, valleys and depressions.

For its part, the oceanic lithosphere It is formed by the oceanic crust and the external part of the Earth’s mantle. It has a thickness between 5 and 10 km of basalt, plutonic rock, sediments and minerals that are denser than the previous crust. The oceanic lithosphere is formed through volcanism in the form of fissures in the mid-ocean ridges, which are located in the middle of the oceans.

Depending on the characteristics of parts of the lithosphere, we can also talk about three other types:

Elastic lithosphere: It is the upper layer of the lithosphere and the one that moves with the tectonic plates. It is thicker than the seismic and thermal lithosphere.
seismic lithosphere: is the base of the lithosphere, characterized by the attenuation of primary waves and a reduction in the propagation speed of secondary waves.
Thermal lithosphere: constitutes the thermal limit part of the lithosphere where heat conduction predominates over heat convection (of which the asthenosphere is characterized).

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