Isabella Carter
The lithosphere is the outermost layer of a terrestrial planet or natural satellite, composed of a rigid, rocky shell that includes the crust and the upper portion of the mantle. It is subdivided into tectonic plates, with two primary types: oceanic and continental. The oceanic lithosphere is denser and younger, associated with oceanic crust and ultramafic mantles, while the continental lithosphere is less dense and older, underlying the continents and continental shelves. The thickness of the lithosphere varies depending on the size of the planet, with small planets having thicker lithospheres and large planets having thinner ones due to retained heat. The study of the lithosphere is crucial for understanding the formation, evolution, and dynamics of terrestrial planets, and it also plays a vital role in supporting life on Earth by providing essential minerals and habitats for various ecosystems.
| Characteristics | Values |
|---|---|
| Definition | The rigid, outermost rocky shell of a terrestrial planet or natural satellite |
| Composition | Crust and the lithospheric mantle (the topmost portion of the upper mantle) |
| Crust | The outermost layer of the lithosphere, composed of hard rocks |
| Crust layers | Sedimentary (top), metamorphic (middle), and basaltic rocks (bottom) |
| Lithospheric mantle | The uppermost part of the mantle that behaves elastically on time scales of up to thousands of years or more |
| Asthenosphere | The weaker, hotter, and deeper part of the upper mantle that is able to convect |
| Plate tectonics | The lithosphere is subdivided horizontally into tectonic plates |
| Types | Oceanic and continental |
| Oceanic lithosphere | Associated with oceanic crust and found under the seas and oceans; composed of mafic crust and ultramafic mantle; denser than continental lithosphere |
| Continental lithosphere | Associated with continental crust and underlies the continents and continental shelves; less dense than oceanic lithosphere |
| Thickness | Varies depending on the planet's size and heat retention; small planets have thicker lithospheres, while large planets have thinner lithospheres |
| Heat | Heat is transported via conduction |
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What You'll Learn
The lithosphere is the outermost layer of a terrestrial planet
The lithosphere can be divided into two types: oceanic and continental. The oceanic lithosphere is associated with oceanic crust and is found in ocean basins. It is denser than the continental type and consists mainly of mafic crust and ultramafic mantle (peridotite). The continental lithosphere, on the other hand, is associated with continental crust and underlies the continents and continental shelves. It is less dense than the oceanic lithosphere. The oceanic lithosphere thickens as it ages and moves away from the mid-ocean ridge, while the continental lithosphere is older and thicker than its oceanic counterpart.
The thickness of a planet's lithosphere depends on its size. Small planets tend to have very thick lithospheres that extend almost to the core, whereas large planets have thin lithospheres due to retaining more heat. The Earth's lithosphere, for example, has an average thickness of about 100 kilometres, with oceanic plates being thinner than continental plates. The lithosphere of Venus is slightly thicker than that of Earth, while Mars' lithosphere is about 500 kilometres thick. Mercury's lithosphere may be up to 260 kilometres thick, but it could be thinner due to the presence of an asthenosphere.
The concept of the lithosphere as a strong outer layer of the Earth was first introduced by the English mathematician Augustus Edward Hough Love in 1911. It was further developed by American geologist Joseph Barrell, who coined the term "lithosphere". Canadian geologist Reginald Aldworth Daly expanded upon these concepts in 1940. The composition of the lithosphere varies depending on whether it is located on land or under the oceans. The Earth's crust, for instance, is composed of different layers of rock, including sedimentary, metamorphic, and basaltic rocks.
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It is composed of the crust and the uppermost mantle
The lithosphere of a terrestrial planet refers to the outermost layer of the planet, which is composed of the crust and the uppermost mantle. It is a rigid, brittle, and rocky shell that gradually turns into the softer, more pliable, and hotter asthenosphere. The lithosphere is subdivided horizontally into tectonic plates, which often include terranes accreted from other plates. The concept of the lithosphere as a strong outer layer was first introduced by mathematician A. E. H. Love in 1911, and further developed by geologist Joseph Barrell, who coined the term "lithosphere".
The crust and the upper mantle that make up the lithosphere are distinguished based on chemistry and mineralogy. The crust is the outermost layer of the Earth, composed of solid rocks. It is the only part of the Earth that humans can see. The crust is not homogeneous and is composed of different layers of rock, including sedimentary rock at the top, metamorphic rock in the middle, and basaltic rock at the bottom.
The uppermost mantle, also known as the lithospheric mantle or mantle lithosphere, is the topmost portion of the upper mantle that behaves elastically on time scales of thousands of years or more. It is the solid outer portion of the upper mantle, which becomes brittle and rocky. The uppermost mantle is not convecting, and its boundary with the asthenosphere is defined by a difference in response to stress. The asthenosphere, in contrast, is the weaker, hotter, and deeper part of the upper mantle that is able to convect.
The oceanic lithosphere is associated with the oceanic crust found under the seas and oceans. It is composed of mafic crust and ultramafic mantle (peridotite) and is denser than the continental lithosphere. The continental lithosphere, on the other hand, is associated with the continental crust that underlies the continents and continental shelves. The oceanic lithosphere thickens as it ages and moves away from the mid-ocean ridge, while the continental lithosphere is thicker and less dense.
The thickness of the lithosphere varies depending on the planet. Small planets tend to have very thick lithospheres that extend from the surface to the core. Large planets, on the other hand, have thin lithospheres due to retaining more heat. For example, the Earth's lithosphere is thin and has an average thickness of about 100 kilometers, with oceanic plates being thinner than continental plates. Mars' lithosphere is about 500 kilometers thick, while Mercury's lithosphere may be up to 260 kilometers thick.
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The lithosphere is subdivided into tectonic plates
The lithosphere is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. It is composed of the crust and the lithospheric mantle, the topmost portion of the upper mantle. The crust and upper mantle are chemically and mineralogically distinct. The Earth's lithosphere, for instance, is around 100 kilometres thick on average, with the oceanic plates being thinner than the continental plates.
The lithosphere is horizontally subdivided into tectonic plates, which often include terranes accreted from other plates. These plates are composed of the oceanic lithosphere and the thicker continental lithosphere, each topped by its own kind of crust. The oceanic lithosphere is associated with oceanic crust and exists in the ocean basins, while the continental lithosphere is associated with continental crust and underlies the continents and continental shelves.
The oceanic lithosphere has a mean density of about 2.9 grams per cubic centimetre, while the continental lithosphere has a mean density of about 2.7 grams per cubic centimetre. The oceanic lithosphere thickens as it ages and moves away from the mid-ocean ridge, with the oldest oceanic lithosphere being approximately 140 kilometres thick. This thickening occurs through conductive cooling, which transforms the hot asthenosphere into lithospheric mantle.
The tectonic plates may include both continental and oceanic crust or just one of the two. The location where two plates meet is called a plate boundary, and it is where geological events such as earthquakes and the creation of topographic features like mountains, volcanoes, mid-ocean ridges, and oceanic trenches occur. Tectonic plates move relative to each other at different rates due to the convection of the asthenosphere and lithosphere, leading to the formation of various geological formations such as the Himalaya mountain range and the East African Rift.
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There are two types of lithosphere: oceanic and continental
The lithosphere is the outermost layer of a terrestrial planet, composed of the crust and the uppermost portion of the mantle. It is subdivided horizontally into tectonic plates, which often include terranes accreted from other plates. The lithosphere is rigid and brittle, gradually turning into the softer, more pliable asthenosphere below it. The thickness of the lithosphere varies depending on the size of the planet, with small planets having thicker lithospheres and large planets having thinner lithospheres.
The continental lithosphere, on the other hand, is associated with continental crust and underlies the continents and continental shelves. It has a lower mean density of about 2.7 grams per cubic centimetre. The thickness of the continental lithosphere ranges from about 40 kilometres to 280 kilometres, with the upper portion consisting mostly of the crust.
The distinction between oceanic and continental lithosphere is important in the theory of plate tectonics. Tectonic activity occurs at the boundaries of these plates, where they may collide, tear apart, or slide against each other. Rift valleys and ocean ridges, where the lithosphere is thinnest, are areas where tectonic plates are shifting apart. Tectonic activity is responsible for significant geological events such as earthquakes, volcanoes, orogeny, and deep ocean trenches.
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The thickness of the lithosphere varies across different planets
The lithosphere is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. It is composed of the crust and the lithospheric mantle, the uppermost portion of the upper mantle. The lithosphere–asthenosphere boundary is defined by a difference in response to stress. The asthenosphere is the ductile, semi-solid layer beneath the lithosphere.
The oldest oceanic lithosphere is about 140 kilometers (87 miles) thick. This thickening occurs by conductive cooling, which converts hot asthenosphere into lithospheric mantle and causes the oceanic lithosphere to become increasingly thick and dense with age. The thickness of the mantle part of the oceanic lithosphere can be approximated as a thermal boundary layer that thickens as the square root of time.
The lithosphere can be divided into oceanic and continental lithosphere. The former is associated with oceanic crust and exists in the ocean basins. The latter is associated with continental crust and underlies the continents and continental shelves. The oceanic lithosphere is denser than the continental lithosphere. Young oceanic lithosphere, found at mid-ocean ridges, is no thicker than the crust, but it thickens as it ages and moves away from the mid-ocean ridge.
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Frequently asked questions
The lithosphere is the rigid, rocky outermost layer of a terrestrial planet or natural satellite. It is composed of the crust and the uppermost portion of the mantle.
The composition of the lithosphere varies depending on whether it is located on land or under the oceans. The oceanic lithosphere is made of mafic crust and ultramafic mantle (peridotite) and is denser than the continental lithosphere. The Earth's crust is made up of sedimentary rock at the top, metamorphic rock in the middle, and basaltic rock at the bottom.
The lithosphere is formed through the cooling and solidification of the outermost layer of a planet or natural satellite. This process is driven by the loss of gravitational potential energy as denser materials sink to the core during the early stages of a planet's formation.
