The lithosphere (IPA: [ˈlɪθ. ə. sfiɹ], from the Greek λίθος [líthos] for "rocky" + σφαίρα [sfaíra] for "sphere") is the solid outermost shell of a rocky planet. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly A planet, as defined by the International Astronomical Union (IAU is a celestial body Orbiting a Star or stellar remnant that is
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Earth's lithosphere
On the Earth, the lithosphere includes the crust and the uppermost mantle which is joined to the crust across the Mohorovičić discontinuity. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 In Geology, a crust is the outermost solid shell of a planet or moon The mantle is a part of an Astronomical object. The interior of the Earth, similar to the other Terrestrial planets, is Chemically divided The Mohorovičić discontinuity, usually referred to as the Moho, is the boundary between the Earth 's crust and the mantle. The lithosphere is underlain by the asthenosphere, the weaker, hotter, and deeper part of the upper mantle. The asthenosphere (from an invented Greek a + ' sthenos "without strength" and Greek word σφαίρα (sphera meaning globe is the The boundary between the lithosphere and the underlying asthenosphere is defined by a difference in response to stress: the lithosphere remains rigid for long periods of geologic time, whereas the asthenosphere flows much more readily. As the conductively cooling surface layer of the Earth's convection system, the lithosphere thickens over time. Convection in the most general terms refers to the movement of molecules within Fluids (i It is fragmented into tectonic plates (shown in the picture), which move independently relative to one another. This movement of lithospheric plates is described as plate tectonics. Plate tectonics (from Greek τέκτων tektōn "builder" or "mason" describes the large scale motions of Earth 's Lithosphere This is when plates move horizontally across the Earth's surface and the continents change their relative positions.
The concept of the lithosphere as Earth’s strong outer layer was developed by Barrell, who wrote a series of papers introducing the concept (Barrell 1914a-c). The concept was based on the presence of significant gravity anomalies over continental crust, from which he inferred that there must exist a strong upper layer (which he called the lithosphere) above a weaker layer which could flow (which he called the asthenosphere). These ideas were enlarged by Daly (1940), and have been broadly accepted by geologists and geophysicists. Although these ideas about lithosphere and asthenosphere were developed long before plate tectonic theory was articulated in the 1960s, the concepts that strong lithosphere exists and that this rests on weak asthenosphere are essential to that theory.
The division of Earth's outer layers into lithosphere and asthenosphere should not be confused with the chemical subdivision of the outer Earth into mantle, and crust. The mantle is a part of an Astronomical object. The interior of the Earth, similar to the other Terrestrial planets, is Chemically divided In Geology, a crust is the outermost solid shell of a planet or moon All crust is in the lithosphere, but lithosphere generally contains more mantle than crust.
There are two types of lithosphere:
- Oceanic lithosphere, which is associated with Oceanic crust
- Continental lithosphere, which is associated with Continental crust
Oceanic lithosphere
Oceanic lithosphere is typically about 50-100 km thick (but beneath the mid-ocean ridges is no thicker than the crust), while continental lithosphere has a range in thickness from about 40 km to perhaps 200 km; the upper ~30 to ~50 km of typical continental lithosphere is crust. Oceanic crust is the part of Earth's Lithosphere that surfaces in the Ocean basins The continental crust is the layer of granitic, Sedimentary, and Metamorphic rocks which form the Continents and the areas of shallow seabed A mid-ocean ridge or mid-oceanic ridge is an underwater Mountain range typically having a valley known as a Rift running along its axis formed by In Geology, a crust is the outermost solid shell of a planet or moon The mantle part of the lithosphere consists largely of peridotite. A peridotite is a dense coarse-grained Igneous rock, consisting mostly of the minerals Olivine and Pyroxene. The crust is distinguished from the upper mantle by the change in chemical composition that takes place at the Moho discontinuity. The Mohorovičić discontinuity, usually referred to as the Moho, is the boundary between the Earth 's crust and the mantle.
Oceanic lithosphere consists mainly of mafic crust and ultramafic mantle (peridotite) and is denser than continental lithosphere, for which the mantle is associated with crust made of felsic rocks. Mafic is an adjective describing a Silicate mineral or rock that is rich in magnesium and iron the term was derived by contracting "magnesium" and "ferric" Ultramafic (also referred to as ultrabasic) rocks are igneous and meta -igneous rocks with very low Silica content (less than 45% generally A peridotite is a dense coarse-grained Igneous rock, consisting mostly of the minerals Olivine and Pyroxene. Felsic is a term used in Geology to refer to Silicate minerals, Magma, and rocks which are enriched in the lighter elements such as Silicon Oceanic lithosphere thickens as it ages and moves away from the mid-ocean ridge. This thickening occurs by conductive cooling, which converts hot asthenosphere into lithospheric mantle, and causes the oceanic lithosphere to become increasingly dense with age. Oceanic lithosphere is less dense than asthenosphere for a few tens of millions of years, but after this becomes increasingly denser than asthenosphere. The gravitational instability of mature oceanic lithosphere has the effect that at subduction zones the oceanic lithosphere invariably sinks underneath the overriding lithosphere, which can be oceanic or continental. In Geology, a subduction zone is an area on Earth where two tectonic plates meet and move towards one another with one sliding underneath the other New oceanic lithosphere is constantly being produced at mid-ocean ridges and is recycled back to the mantle at subduction zones. As a result, oceanic lithosphere is much younger than continental lithosphere: the oldest oceanic lithosphere is about 170 million years old, while parts of the continental lithosphere are billions of years old. The oldest parts of continental lithosphere underlie cratons, and the mantle lithosphere there is thicker and less dense than typical; the relatively low density of such mantle "roots of cratons" helps to stabilize these regions (e. A craton ( Greek kratos / κρἀτος ( neut. "strength" is an old and stable part of the Continental crust that has survived g. , Jordan, 1978).
Mantle
Another distinguishing characteristic of the lithosphere is its flow properties. Under the influence of the low-intensity, long-term stresses that drive plate tectonic motions, the lithosphere responds essentially as a rigid shell and thus deforms primarily through brittle failure, whereas the asthenosphere (the layer of the mantle below the lithosphere) is heat-softened and accommodates strain through plastic deformation. Plate tectonics (from Greek τέκτων tektōn "builder" or "mason" describes the large scale motions of Earth 's Lithosphere The asthenosphere (from an invented Greek a + ' sthenos "without strength" and Greek word σφαίρα (sphera meaning globe is the
Geoscientists can directly study the nature of the subcontinental mantle by examining mantle xenoliths brought up in kimberlite and other volcanic pipes. This article concerns the geologic term for other uses see Xenolith (disambiguation A xenolith ( Greek: 'foreign rock' is a rock Kimberlite is a type of potassic Volcanic rock best known for sometimes containing Diamonds It is named after the town of Kimberley in South Africa The histories of these xenoliths have been investigated by many methods, including analyses of abundances of isotopes of osmium and rhenium. Osmium (ˈɒzmiəm is a Chemical element that has the symbol Os and Atomic number 76 Rhenium (ˈriːniəm is a Chemical element with the symbol Re and Atomic number 75 Such studies have confirmed that mantle lithospheres below some cratons have persisted for periods in excess of 3 billion years, despite the mantle flow that accompanies plate tectonics (e. A craton ( Greek kratos / κρἀτος ( neut. "strength" is an old and stable part of the Continental crust that has survived g. , Carlson et al. , 2005).
References
- Earth's Crust, Lithosphere and Asthenosphere
- Crust and Lithosphere
- Barrell, J. 1914a The strength of the Earth's crust. Journal of Geology. 22, 425-433.
- Barrell, J. 1914b The strength of the Earth's crust. Journal of Geology 22, 441-468.
- Barrell, J. 1914c The strength of the Earth's crust. Journal of Geology 22, 655-683.
- Carlson, R. W. , Pearson, D. G. , and James, D. E. , 2005, Physical, chemical, and chronological characteristics of continental mantle. Reviews of Geophysics 43, 8755-1209/05/2004RG000156
- Daly, R. 1940 Strength and structure of the Earth. New York: Prentice-Hall.
- Jordan, T. H. 1978 Composition and development of the continental tectosphere. Nature 274, 544-548.
- Stanley Chernicoff and Donna Whitney. Geology. An Introduction to Physical Geology, 4th ed. , Pearson 2007
See also
- Biosphere
- Cryosphere
- Earth's atmosphere
- Hydrosphere
- Kola Superdeep Borehole
- Pedosphere
- Plate tectonics
- Table of Global Climate System Components
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