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The asthenosphere (from Ancient Greek ἀσθενός (asthenós) 'without strength') is the mechanically weak [1] and ductile region of the upper mantle of Earth. It lies below the lithosphere, at a depth between ~80 and 200 km (50 and 120 mi) below the surface, and extends as deep as 700 km (430 mi). However, the lower boundary of the ...
Beneath oceanic crust, the LAB ranges anywhere from 50 to 140 km in depth, except close to mid-ocean ridges where the LAB is no deeper than the depth of the new crust being created. [10] Seismic evidence shows that oceanic plates do thicken with age. This suggests that the LAB underneath oceanic lithosphere also deepens with plate age.
Only beneath mid-ocean ridges does it define the lithosphere–asthenosphere boundary (the depth at which the mantle becomes significantly ductile). The Mohorovičić discontinuity is 5 to 10 kilometres (3–6 mi) below the ocean floor , and 20 to 90 kilometres (10–60 mi) beneath typical continental crusts, with an average of 35 kilometres ...
Earth's inner core is the innermost geologic layer of the planet Earth. It is primarily a solid ball with a radius of about 1,220 km (760 mi), which is about 19% of Earth's radius [0.7% of volume] or 70% of the Moon 's radius. [32][33] The inner core was discovered in 1936 by Inge Lehmann and is generally composed primarily of iron and some nickel.
Geothermal gradient is the rate of change in temperature with respect to increasing depth in Earth 's interior. As a general rule, the crust temperature rises with depth due to the heat flow from the much hotter mantle; away from tectonic plate boundaries, temperature rises in about 25–30 °C/km (72–87 °F/mi) of depth near the surface in ...
core–mantle boundary. outer core–inner core boundary. The core–mantle boundary (CMB) of Earth lies between the planet's silicate mantle and its liquid iron–nickel outer core, at a depth of 2,891 km (1,796 mi) below Earth's surface. The boundary is observed via the discontinuity in seismic wave velocities at that depth due to the ...
The transition zone is the part of Earth's mantle that is located between the lower and the upper mantle, most strictly between the seismic-discontinuity depths of about 410 to 660 kilometres (250 to 410 mi), but more broadly defined as the zone encompassing those discontinuities, i.e., between about 300 and 850 kilometres (190 and 530 mi) depth. [1]
This releases water into the hotter asthenosphere, which leads to partial melting of the asthenosphere and volcanism. Both dehydration and partial melting occur along the 1,000 °C (1,830 °F) isotherm, generally at depths of 65 to 130 km (40 to 81 mi). [4] [5] Some lithospheric plates consist of both continental and oceanic lithosphere. In ...