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The exact upper and lower boundaries of the mesosphere vary with latitude and with season (higher in winter and at the tropics, lower in summer and at the poles), but the lower boundary is usually located at altitudes from 47 to 51 km (29 to 32 mi; 154,000 to 167,000 ft) above sea level, and the upper boundary (the mesopause) is usually from 85 ...
The lower boundary of the asthenosphere, the top of the tentatively defined mesosphere or mesospheric shell, [18] is less well-defined, but has been placed at the base of the upper mantle. [19] This boundary is neither seismically sharp nor well understood [9] but is approximately coincident with the complex 670 km discontinuity. [20]
The upper boundary is defined by the sharp increase in seismic wave velocities and density at a depth of 660 kilometers (410 mi). [8] At a depth of 660 km, ringwoodite (γ-(Mg,Fe) 2 SiO 4) decomposes into Mg-Si perovskite and magnesiowüstite. [8] This reaction marks the boundary between the upper mantle and lower mantle. This measurement is ...
The lowest part of the mantle next to the core-mantle boundary is known as the D″ (D-double-prime) layer. [23] The pressure at the bottom of the mantle is ≈140 G Pa (1.4 M atm ). [ 24 ] The mantle is composed of silicate rocks richer in iron and magnesium than the overlying crust. [ 25 ]
Earth's crust and mantle, Moho discontinuity between bottom of crust and solid uppermost mantle. The Mohorovičić discontinuity (/ ˌ m oʊ h ə ˈ r oʊ v ɪ tʃ ɪ tʃ / MOH-hə-ROH-vih-chitch; Croatian: [moxorôʋiːtʃitɕ]) [1] – usually called the Moho discontinuity, Moho boundary, or just Moho – is the boundary between the crust and the mantle of Earth.
The lithosphere–asthenosphere boundary (referred to as the LAB by geophysicists) represents a mechanical difference between layers in Earth's inner structure. Earth's inner structure can be described both chemically ( crust , mantle , and core ) and mechanically.
In the mantle, temperatures range from approximately 500 K (230 °C; 440 °F) at the upper boundary with the crust to approximately 4,200 K (3,900 °C; 7,100 °F) at the core-mantle boundary. [20] The temperature of the mantle increases rapidly in the thermal boundary layers at the top and bottom of the mantle, and increases gradually through ...
The Motagua Fault, which crosses through Guatemala, is a transform boundary between the southern edge of the North American plate and the northern edge of the Caribbean plate. New Zealand's Alpine Fault is another active transform boundary. The Dead Sea Transform (DST) fault which runs through the Jordan River Valley in the Middle East.