Asthenosphere

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Yird cutaway frae core tae crust, the asthenosphere lyin atween the upper mantle an the lithospheric mantle (detail nae tae scale)

The asthenosphere (frae Greek asthenēs 'weak' + sphere) is the heichly viscous, mechanically weak[1] an ductilely-defurmin region o the upper mantle o the Yird. It lies belaw the lithosphere, at depths atween ~80 an ~200 km (~ 50 an 124 miles) belaw the surface. The lithosphere-asthenosphere boondary is uisually referred tae as LAB. Asthenosphere is generally solid altho some its regions could be meltit (e.g. belaw mid-ocean ridge). The lawer boondary o the asthenophere is nae well defined. The thickness o the asthenosphere depends mainly on the temperatur. For some regions asthenosphere could extend as deep as 700 km (430 mi). It is considered the soorce region o mid-ocean ridge basalt (MORB).[2]

References[eedit | eedit soorce]

  1. Barrel, J. The strength of the crust, Part VI. Relations of isostatic movements to a sphere of weakness - the astenosphere. J. Geol. 22, 655-683, 1914.
  2. Hofmann, A.W., 1997. Mantle geochemistry: the message from oceanic volcanism. Nature 385, 219-228.