asthenosphere
/əsˈθɛnəsfɪə
/noun Geology
The upper layer of the earth’s mantle, below the lithosphere, in which there is relatively low resistance to plastic flow and convection is thought to occur.Because the downgoing slab of lithosphere is heavier than the plastic asthenosphere below, it tends to sink passively; and the older the lithosphere, the steeper the dip....
- The models consist of a two-layered brittle-ductile system representing the overriding continental lithosphere, overlying a low-viscosity layer simulating the asthenosphere to provide isostatic support.
- Scientists believe that below the lithosphere is a relatively narrow, mobile zone in the mantle called the asthenosphere.
Derivatives
asthenospheric
- They are interpreted to have been derived from subduction modified lithospheric and asthenospheric mantle sources.
- We attribute the rapid return to subsidence in the basin to the confinement of abnormally hot asthenospheric mantle in the zone of continental break-up to the NW as sea-floor spreading commenced.
- Given the lack of evidence for significant magmatism in the area, the likely heat sources are either radiogenic, or elevated heat flux from asthenospheric mantle emplaced at a relatively shallow level beneath the orogen.
Origin
Early 20th century: from Greek asthenēs 'weak' + sphere.
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