UPPER MANTLE (EN: upper mantle, outer mantle, peridotite shell; DE: oberer Mantel, Peridotit-Schale; FR: manteau superieur; ES: manto superior; RU: верхняя мантия) is the geosphere, which is situated between the Earth's crust and the lower mantle of the Earth. The upper mantle is separated from the Earth's crust with the Mohorovičić discontinuity, which is located at the depth of 20-80 kilometres under the mainlands, and at the depth of 11-15 kilometres under the oceans.
The lower boundary of the upper mantle is not precise, at the depth of approximately 900 kilometres (in case of the division of the mantle into the upper and lower parts), or at the depth of 400 kilometres (in case of the division of the mantle into the upper, middle, and lower parts).
The upper layer of the upper mantle is the substrate (which, together with the Earth's crust, forms the rigid lithosphere), and underneath the substrate, there lies the asthenosphere. The lower part of the upper mantle (deeper than 400 kilometres, the so-named layer of Golitsyn), is characterized by the strong increase of the speed of the seismic waves with depth, apparently on the account of the fact, that the packaging of the crystal lattice of olivine, which is the main mineral, which forms the upper mantle, is compacted with the depth under the impact of the pressure. The majority of the researchers supposes, that there proceeds within the upper mantle the thermal convection, the vertical flows of the hot substance rise into the asthenosphere, spread themselves there, and, while cooling themselves, submerge themselves. According to another hypothesis, there rise through the upper mantle into the asthenosphere and further into the Earth's crust the hot lightweight masses, which are released during the gravitational differentiation, which proceeds within the lower mantle. The upper mantle plays the important role for the tectonic, magmatic, and metamorphic processes, which are proceeding within the Earth's crust, and for the forming of the useful minerals. See also the "Earth" article.
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