摘要：AbstractIs the westerly rotation of the lithosphere an ephemeral accidental recent phenomenon or is it a stable process of Earth's geodynamics? The reason why the tidal drag has been questioned as the mechanism determining the lithospheric shift relative to the underlying mantle is the apparent too high viscosity of the asthenosphere. However, plate boundaries asymmetries are a robust indication of the ‘westerly’ decoupling of the entire Earth's outer lithospheric shell and new studies support lower viscosities in the low-velocity layer (LVZ) atop the asthenosphere. Since the solid Earth tide oscillation is longer in one side relative to the other due to the contemporaneous Moon's revolution, we demonstrate that a non-linear rheological behavior is expected in the lithosphere mantle interplay. This may provide a sort of ratchet favoring lowering of the LVZ viscosity under shear, allowing decoupling in the LVZ and triggering the westerly motion of the lithosphere relative to the mantle.Graphical abstractDisplay OmittedHighlights•The westward drift of the lithosphere is observed in any mantle reference frame.•The mechanism of the westward drift of the lithosphere is still unconstrained.•The tidal drag exerted by the Moon on the solid Earth could explain the W-drift.•The tidal drag acts as a ratchet and non-linear mantle rheology is expected.•Lithosphere-asthenosphere decoupling may occur with the known LVZ viscosity.
关键词：KeywordsenWestward drift of the lithosphereTectonic equatorLow-velocity layerAsthenosphere viscosityNon-linear rheologyTidal ratchet
