Influence of the asthenosphere on earth dynamics and evolution

Abstract

The existence of a thin, weak asthenospheric layer beneath Earth’s lithospheric plates is consistent with existing geological and geophysical constraints, including Pleistocene glacio-isostatic adjustment, modeling of gravity anomalies, studies of seismic anisotropy, and post-seismic rebound. Mantle convection models suggest that a pronounced weak zone beneath the upper thermal boundary layer (lithosphere) may be essential to the plate tectonic style of convection found on Earth. The asthenosphere is likely related to partial melting and the presence of water in the sub-lithospheric mantle, further implying that the long-term evolution of the Earth may be controlled by thermal regulation and volatile recycling that maintain a geotherm that approaches the wet mantle solidus at asthenospheric depths.

Coupled fates of Earth’s mantle and core: Early sluggish-lid tectonics and a long-lived geodynamo

“…Last, as well as large plate dissipation, synonymous to early sluggish-lid tectonics is the existence of an early asthenosphere. While we do not explore specific mechanisms to produce this crucial weak layer, our work shows the importance of further exploring asthenospheric evolution (e.g., its expansion or reduction in thickness; section S4), its source (e.g., partial melt and water content), and its dynamics ( 16 ). This is an important direction for future studies of tectonic evolution.…”

“…The history of cooling, degassing, atmospheric and oceanic evolution, magnetic field generation, as well as crustal generation and orogenesis are all shaped by the forces that drive plate motion ( 1 ). Hence, this calls for rigorous and systematic exploration into the cause of transitions between tectonics regimes ( 16 ).…”

A novel approach for studying lithospheric deformation driven by asthenospheric flow

“…As discussed above, the velocities of asthenospheric flow in the model can be scaled to nature, but the model requires an approximation of a homogenous viscous asthenosphere with Newtonian behaviour, without taking into account potential viscosity variations and heterogeneities or non-Newtonian behaviour (Becker 2006;Karato 2010;Garel et al, 2020;Cerpa et al, 2022;Cathles et al, 2023). Uncertainties related to asthenosphere viscosities of natural systems (e.g., Fjeldskaar 1994; James et al, 2009;Conrad and Behn, 2010;Karato 2010;Garel et al, 2020;Cathles et al, 2023) provide relatively high flexibility when scaling model viscosities. However, the choice of viscosities for the asthenosphere and lithospheric mantle directly affects the lithosphere-asthenosphere coupling/decoupling in models.…”