Compare and contrast the lithosphere and asthenosphere. The layer under the lithosphere is known as the asthenosphere. The lithosphereasthenosphere boundary lab represents the base of the. Low viscosity of the asthenosphere is used to explain the mechanical decoupling between the plates in the plate tectonic theory and the underlying mantle. Hard, rigid, brittle, and solid, except for the ocean. The asthenosphere is where the convection currents drive the plates apart and consist of upper mantle flowing. Crust under the oceans is only about 5 km thick while continental crust can be up to 65 km thick. The asthenosphere is not quite liquid but it does contain some melted rock there. Lithosphere, asthenosphere, and perisphere request pdf. Under the lithosphere there is the asthenosphere, the weaker, hotter, and deeper part of the upper mantle. The lithosphere is made of the brittle crust and uppermost mantle and lies on the plastic asthenosphere.
Asthenosphere plastic layer, solid rock that flows very slowly. Structure and composition of lithosphere rock geology. Apr 15, 2017 the lithosphere and the asthenosphere duration. That means the crust and the upper part of the mantle which is joined to the crust see picture on the right. It is conjectured that there is a slow overflow of masses in a horizontal direction within the asthenosphere because of the low yield point. A clue to this may be found in the other name for tectonic plate, which is lithospheric plate. Lithosphere, asthenosphere, and perisphere anderson. Ocean crust about 7 km thick forms the ocean floors. Heat from deep within earth is thought to keep the. The crust is the outermost solid layer of the earth. Composition of the earths mantle the earths mantle is a layer with a thickness of 2,900 km or 1800 miles 46% of the earths average radius of 6371 km or 3,960 miles and extends from the outer core of the earth at 3500 km radius from the center of the earth, to the lithosphere that is only less than 200 km 124 miles thick, so it. Lithosphere and asthenosphere are divisions based on mechanical properties. Plate tecton ics 187 lithosphere and asthenosphere the asthenosphere is a hotter, softer layer of rock on which the lithosphere rests. The lithosphere is generally assumed to have viscosities 2 or 3 orders of magnitude higher.
The lithosphereasthenosphere boundary is usually referred to as lab. Asthenospheric viscosities are of the order of 1021 to 10 tm pa s. The asthenosphere is part of the upper mantle, the lithosphere is the uppermost mantle and the crust is above it. The lithosphere is underlain by the asthenosphere, the weaker, hotter, and deeper part of the upper mantle. The asthenosphere extends from 100 km depth to 660 km beneath the earths surface. The lithosphere consists of the heavy oceanic and lighter continental crusts, and the. The asthenosphere consists of many varieties of rock mostly in a semimolten condition. Institute of environment and sustainable development course. The asthenosphere is hotter, and the convective processes are believed to become important. Pdf diamonds from the asthenosphere and the transition zone. The boundary between the lithosphere and the underlying asthenosphere is defined by a difference in response to stress. Unfortunately, the term has also been applied to the surface thermal boundary layer tbl and a shallow enriched geoch. The lithosphere is the tectonic plate we talk about in plate tectonics. Only if the toothpaste is ultramafic in composition, and then it would only be able to flow if it were really, really hot.
In this lesson, you will learn more about this important part of our planet. The asthenosphere is part of the upper mantle located below the crust of the earth. In fact, if the upper part of the asthenosphere cools down it becomes part of the lithosphere. Lithosphere is a mechanical concept implying strength and relative permanence. Facts about asthenosphere talk about the region located at the upper mantle of earth. Composition, structure and dynamics of the lithosphere. Earths crust, lithosphere and asthenosphere windows to. The asthenosphere boundary is primarily defined by temperature, and it starts when the crust heats up to 0 c. The lithosphere asthenosphere boundary lab represents the base of the. Earths layers are made of different mixtures of elements. Lithosphere, asthenosphere, and mesosphere we usually dont discuss this last layer represent changes in the mechanical properties of the earth. The crust overlying the lithospheric mantle is either of oceanic type which is mainly composed of gabbroic and basaltic rocks resulting in a mean density of 3. The asthenosphere is solid even though it is at very hot temperatures of about 1600 c due to the high pressures from above. It consists of hot, weak material that can be deformed like silly putty.
In younger continental regions the lithosphereasthenosphere boundary is shallower commonly at about 80100 km. Earths layers and plate tectonics study guide part 2 1. Its density is lesser than that of the lithosphere. If you were showing a scale for the asthenosphere to be liquid or solid it would be weighing in moe onto the solid side. If you continue browsing the site, you agree to the use of cookies on this website.
In terms of chemical composition, there is no difference between the upper part of the asthenosphere and the lower part of the lithosphere. This article throws light upon the three distinctive spheres of the earth. In a nutshell, the asthenosphere is part of the earth, the mesosphere is part of the atmosphere. The lithosphere is the outermost mechanical layer, which behaves as a brittle, rigid solid. The lithosphere, asthenosphere, and the mesosphere lithosphere the asthenosphere is a soft layer of the mantle on which pieces of the lithosphere move. Crust and mantle refer to changes in the chemical composition of the earth. Lithosphere and asthenosphere read earth science ck.
The asthenosphere is the highly viscous, mechanically weak and ductile region of the upper mantle of the earth. However, at this temperature, minerals are almost ready to melt and they become ductile and can be pushed and deformed like silly putty in response to the warmth. The earths crust, lithosphere and asthenosphere crust, the upper layer of the earth, is not always the same. Still the toothpaste analogy gives you a good image of how the asthenosphere might behave if you squeezed it. The earths crust, lithosphere and asthenosphere crust.
The viscosity of the substance of the asthenosphere is 10 19 to 10 23 poises, whereas below and above the boundaries of the asthenosphere it is at least 10 23 poises. Hope this article helps you get a better understanding about this layer of the earth. Compare and contrast lithosphere and asthenosphere enotes. Mechanical properties lithosphere and asthenosphere. The composition and structure of earth physical geography. Asthenosphere, zone of earths mantle lying beneath the lithosphere and believed to be much hotter and more fluid than the lithosphere. Note that the crust is a thinner layer inside the lithosphere. Get an answer for compare and contrast the lithosphere and the asthenosphere. A presentation on the structure and composition of lithosphere. Structure and composition of lithosphere free download as powerpoint presentation. The lithosphere is broken up into rigid plates that ride on top of the flowing asthenosphere. Compare and contrast the lithosphere and asthenosphere the lithosphere is the tectonic plate and consists of crust continental and oceanic, moho line, upper mantle rigid. It comprises the crust and the upper portion of the mantle which is stiff and rigid and behaves elastically over millions of years. The basis of the three layers in composition make up of the layers while the basis of the five layers is physical properties.
In fact, if the upper part of the asthenosphere cools down it. Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. The strong lithosphere is about one half the thickness of the tbl. Pdf to text batch convert multiple files software please purchase personal license. The temperatures reach levels high enough for most of the rock to turn soft and almost plasticlike. Layers of differing chemical composition tankonyvtar.
Differences in their physical properties establish the fundamental mechanism behind plate tectonics. The lithosphere is made up of the crust and very top of the mantle. The gaseous canopy that envelops the lithosphere and the hydrosphere is known as the atmosphere. It is composed of different types of rocks which, as a whole, has the density and composition of granite. This volume is devoted to recent advances in investigating the earths crustal and mantle structure, its composition and dynamics. Why, then, is the asthenosphere soft and the lithosphere rigid. Composition of the earths mantle the earths mantle is a layer with a thickness of 2,900 km or 1800 miles 46% of the earths average radius of 6371 km or 3,960 miles and extends from the outer. The continental lithosphereasthenosphere boundary mantle plumes.
The asthenosphere extends from about 100 km 60 miles to about 700 km 450 miles below earths surface. Feb 26, 2014 a brief desciption about the structure and composition of earths lithosphere. The nature and composition of igneous rocks originating in the asthenosphere strongly depend on carbon and hydrogen abundance and cycling throughout the earths history dasgupta, 20. The lithosphere is composed of both the crust and the portion of the upper mantle that behaves as a brittle, rigid solid. The lithosphere is the tectonic plate and consists of crust continental and oceanic, moho line, upper mantle rigid. It lies below the lithosphere, at depths between approximately 80 and 200 km 50 and 120 miles below the surface. Diamonds from the asthenosphere and the transition zone article pdf available in european journal of mineralogy 5. Broken into tectonic plates that float on the asthenosphere. The asthenosphere and lithosphere form the outermost layers of the earth.
How can i distinguish the mafic magma derived from asthenosphere. Differences between the earths lithosphere and asthenosphere. Asthenosphere mesosphere beneath the asthenosphere is the strong, lower part of the mantle called the mesosphere. A lithosphere is the rigid, outermost shell of a terrestrialtype planet, or natural satellite, that is. The asthenosphere derives its name from the greek word asthenis, meaning weak, because its strength is much lower than that of the overlying lithosphere. Lithosphere, asthenosphere, and perisphere anderson 1995. The asthenosphere at the soft layer of the mantle on which the lithospheric plates move. The asthenosphere is the ductile part of the earth just below the lithosphere, including the upper mantle. The flowing asthenosphere carries the lithosphere of the earth, including the continents, on its back. The asthenosphere is the highly viscous, mechanically weak and ductile region of the upper. The lithosphere from the greek words lithos meaning rocky and sphaira meaning sphere is defined as the outermost rigid shell of the earth skinner et al. The semi fluid areas of the asthenosphere allow for movement of the tectonic plates in the lithosphere. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Mantle convection and the thermal structure of the plates pdf.
Earth layers fact cards lithosphere 0100 km deep the outermost layer of the earth, including the crust and the upper mantle. At geochemical aspect, the mafic magma from the asthenospheric mantle have. Magmatic activity at depths exceeding 100200 km is probably almost impossible without the involvement of volatile species, which can be described mostly in the coh system. The chemical composition of the asthenosphere is about the same as the chemical composition of the overlying lithospheric mantle.
Asthenosphere article about asthenosphere by the free. The asthenosphere will flow readily at much lower stress levels. Magma genesis and mantle dynamics at the harrat ash. If you want to know the lower boundary of asthenosphere, it is not easy since it cannot be defined by the scientists since the thickness is influenced by the temperature. The asthenosphere is just below the lithosphere, and it is also hot which is making it able to become deformed like clay or silly putty. Get an answer for how are the lithosphere and asthenosphere alike. The lithosphere is composed of both the crust and the portion of the upper mantle. Zircon survival in shallow asthenosphere and deep lithosphere arxiv. Unfortu nately, the term has also been applied to the surface thermal boundary layer tbl and a shallow enriched. Anderson seismological laboratory california institute of technology pasadena abstract. Temperature, density, and viscosity ability to flow.
Unfortunately, the term has also been applied to the surface thermal boundary layer tbl and a shallow enriched geochemical reservoir, features having nothing to do with strength. Our only deeper samples are rare diamond inclusions and some xenoliths inverted from majoritic garnet, which are unlikely to represent the bulk composition of the asthenosphere. The composition of earth the earth is divided into several layers with different composition and physical properties. Hot materials that make up the mesosphere heat up the asthenosphere, causing melting of rocks semifluid in asthenosphere, provided temperatures are high enough. The asthenosphere may extend to a depth of 700km below the earths surface. The lithosphere and asthenosphere are defined on the basis of their mechanical properties, whereas the crust and mantle are defined on the basis of their chemical composition. The lithosphere is the solid shell of a rocky planet called earth. From the earths surface to an altitude of about 80 km the chemical composition of the atmosphere remains highly uniform throughout, in terms of the proportions of its constituent gases. It is because at the depth of the asthenosphere, temperatures are very close to the melting point of the rock, weakening the rock. The differences are due to plate tectonics which then refers to plates and the movement of the plates above the asthenosphere, driving. Mechanical properties lithosphere and asthenosphere we may think we know what we mean by the earths tectonic plates, but there is more to a tectonic plate than just crust. The asthenosphere is closer to the surface of the earth in oceans and is within a few kilometers below the surface in ridges on the ocean floor. The temperature is very important to define the thickness of asthenosphere. Be able to compare and contrast the lithosphere and asthenosphere, including thickness, composition, temperature, and density.
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