What Controls Effective Elastic Thickness of the Lithosphere in the Pacific Ocean?

Abstract

The effective elastic thickness (Te) of the lithosphere is a proxy for mechanical strength and can be used to constrain lithospheric rheology and understand how surface deformation relates to deep Earth processes. Here, we map Te variations over the Pacific Ocean from the inversion of the admittance between free‐air gravity anomaly and bathymetry data calculated using a continuous wavelet transform, taking both surface and subsurface loads into account. The Pacific lithosphere show Te ranging between 0 and 80 km with a mean of 13.5 km and a standard deviation of 12.3 km. We find that Te is generally poorly correlated with plate loading age, crustal age, heat flow and Curie point depth, except for relatively young (<60 Ma) and warm lithospheres. Most oceanic plateaus and seamounts show Te≤10 km, with the lowest values (<5 km) around active spreading centers. The highest Te estimates (>30 km) are found along subduction zones and around the Hawaiian‐Emperor Seamount Chain (HESC). Taken together, these results support a temperature control on Te for small loads and warm lithosphere through steady‐state creep processes, but strain hardening operating at large plastic strain and low temperature could explain high Te associated with large‐amplitude and long‐wavelength loads (subduction zones and the HESC) and should be incorporated in yield strength models of oceanic Te.

Constraining the Crustal and Mantle Conductivity Structures Beneath Islands by a Joint Inversion of Multi‐Source Magnetic Transfer Functions

“…There is a consensus that the oceanic lithosphere thickens with age. This thickening occurs by conductive cooling, which converts the hot asthenosphere into the lithospheric mantle and causes the oceanic lithosphere to become increasingly thick and dense with age (Lu et al., 2021; Turcotte & Schubert, 2002). Specifically, the age of the lithosphere can be converted into the thickness of the oceanic lithosphere by exploiting the following formula (Ranalli, 1995): $$${D}_{\mathit{lit}}(\theta ,\phi )=2.32\sqrt{\kappa \,a(\theta ,\phi )},$$$ where κ is the average thermal diffusivity for the silicate rocks—taken as 10 −6 m 2 s −1 , cf.…”

Lithosphere Weakening During Arctic Ocean Opening: Evidence From Effective Elastic Thickness

“…In the North Chukchi Sea Basin, the thinned crust (Figure 2a) with low coincides with several rifting phases in the Aptian‐Albian (125–100 Ma) and in the Cenozoic (45–37 Ma) (Nikishin et al., 2020). Interestingly, the western Gakkel Ridge is characterized by a thin crust (∼5 km) but a much higher (10–15 km) than other mid‐ocean ridges in the world (e.g., Lu et al., 2021). Cannat (1996) proposed that the melts of slow‐spreading ridges extracted from the asthenosphere crystallize in the mantle before they reach the crust.…”

“… corresponds to the thickness of an idealized elastic plate that would produce equivalent flexure under observed geological loading (Watts, 2001). In oceanic domains, has been shown to reflect the plate age at the time of loading, and to some degree crustal age and thermal structure (Lu et al., 2021; Kalnins & Watts, 2009; Watts, 1978; Watts & Burov, 2003).…”

“…equivalent flexure under observed geological loading (Watts, 2001). In oceanic domains, e T has been shown to reflect the plate age at the time of loading, and to some degree crustal age and thermal structure (Lu et al, 2021;Kalnins & Watts, 2009;Watts, 1978;Watts & Burov, 2003). e T can be modeled using lithospheric strength profiles calculated using empirical constitutive flow laws constrained by lithospheric temperature estimates (e.g., Burov & Diament, 1995;Brown & Phillips, 2000;).…”

Constraining the crustal and mantle conductivity structures beneath islands by a joint inversion of multi-source magnetic transfer functions

“…There is a consensus that the oceanic lithosphere thickens with age. This thickening occurs by conductive cooling, which converts the hot asthenosphere into the lithospheric mantle and causes the oceanic lithosphere to become increasingly thick and dense with age (Lu et al, 2021;Turcotte & Schubert, 2002). Specifically, the age of the lithosphere can be converted into the thickness of the oceanic lithosphere by exploiting the following formula (Ranalli, 1995):…”