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Regional geodynamic modeling has shown that oceanic plateau subduction can modify the slab behavior. However, few studies have explored these interactions beyond 100 Myr in 3‐D spherical models. Using 3‐D spherical mantle convection models with self‐consistent plate‐like behavior, we investigate how the geometry and rheological properties of oceanic plateaus influence trench evolution and mantle flow across regional to global scales. Our models show that plateau width and thickness exert the strongest control on trench retreat, while buoyancy alone plays a secondary role. A mechanically strong plateau produces a transient arcuate trench morphology that gradually heals once the plateau is fully subducted, leaving only a delay in retreat. The pronounced curvature of the northern Mariana Trench suggests that the Ogasawara Plateau is mechanically strong. Although plateau subduction leaves no long‐term geological scar unless slab break‐off occurs, it substantially slows trench migration and can influence global tectonic evolution for over 200 Myr.

The slow gravitational collapse of early continents could have kick-started transient episodes of plate tectonics until, as the Earth’s interior cooled and oceanic lithosphere became heavier, plate tectonics became self-sustaining. Spreading continents primed plate tectonics Patrice Rey and co-authors present a numerical model showing that, because Earth's early oceanic crust was probably thick and buoyant, early continents would have produced intra-lithospheric gravitational stresses large enough to drive their gravitational spreading. They find that this spreading could initiate episodes of subduction at continental margins. Their model predicts the enigmatic multimodal volcanism and tectonic record of Archaean cratons, as well as the petrological stratification and tectonic structure of the sub-continental lithospheric mantle. They conclude that the slow gravitational collapse of early continents could have kick-started transient episodes of plate tectonics until, as the Earth's interior cooled and oceanic lithosphere became heavier, plate tectonics became self-sustaining. Stresses acting on cold, thick and negatively buoyant oceanic lithosphere are thought to be crucial to the initiation of subduction and the operation of plate tectonics 1 , 2 , which characterizes the present-day geodynamics of the Earth. Because the Earth’s interior was hotter in the Archaean eon, the oceanic crust may have been thicker, thereby making the oceanic lithosphere more buoyant than at present 3 , and whether subduction and plate tectonics occurred during this time is ambiguous, both in the geological record and in geodynamic models 4 . Here we show that because the oceanic crust was thick and buoyant 5 , early continents may have produced intra-lithospheric gravitational stresses large enough to drive their gravitational spreading, to initiate subduction at their margins and to trigger episodes of subduction. Our model predicts the co-occurrence of deep to progressively shallower mafic volcanics and arc magmatism within continents in a self-consistent geodynamic framework, explaining the enigmatic multimodal volcanism and tectonic record of Archaean cratons 6 . Moreover, our model predicts a petrological stratification and tectonic structure of the sub-continental lithospheric mantle, two predictions that are consistent with xenolith 5 and seismic studies, respectively, and consistent with the existence of a mid-lithospheric seismic discontinuity 7 . The slow gravitational collapse of early continents could have kick-started transient episodes of plate tectonics until, as the Earth’s interior cooled and oceanic lithosphere became heavier, plate tectonics became self-sustaining.

Computer models of mantle convection with plate-like behaviour are used to demonstrate that the size–frequency distribution of tectonic plates on Earth is controlled by subduction geometry—the spacing between subducting slabs controls the layout of large plates, and the stresses caused by the bending of trenches break plates into smaller fragments. Mallard The subsurface layers of Earth appear as an interlocking network of tectonic or lithospheric plates of various sizes and shapes. The nature of the link between mantle flow and tectonics, and the origin of the layout of the plates remain largely unknown. Claire Mallard et al . have developed computer models of mantle convection with plate-like behaviour and use them to produce a series of 'virtual Earths' that project the network of plate boundaries through time. The models suggest that the layout of large plates is controlled by the spacing between subducting slabs, and that stresses caused by the bending of trenches break plates into smaller fragments, explaining why rapid evolution in small back-arc plates reflects the dramatic changes in plate motions during times of major plate-tectonic reorganizations. The theory of plate tectonics describes how the surface of Earth is split into an organized jigsaw of seven large plates 1 of similar sizes and a population of smaller plates whose areas follow a fractal distribution 2 , 3 . The reconstruction of global tectonics during the past 200 million years 4 suggests that this layout is probably a long-term feature of Earth, but the forces governing it are unknown. Previous studies 3 , 5 , 6 , primarily based on the statistical properties of plate distributions, were unable to resolve how the size of the plates is determined by the properties of the lithosphere and the underlying mantle convection. Here we demonstrate that the plate layout of Earth is produced by a dynamic feedback between mantle convection and the strength of the lithosphere. Using three-dimensional spherical models of mantle convection that self-consistently produce the plate size–frequency distribution observed for Earth, we show that subduction geometry drives the tectonic fragmentation that generates plates. The spacing between the slabs controls the layout of large plates, and the stresses caused by the bending of trenches break plates into smaller fragments. Our results explain why the fast evolution in small back-arc plates 7 , 8 reflects the marked changes in plate motions during times of major reorganizations. Our study opens the way to using convection simulations with plate-like behaviour to unravel how global tectonics and mantle convection are dynamically connected.

Mantle plume fixity has long been a cornerstone assumption to reconstruct past tectonic plate motions. However, precise geochronological and paleomagnetic data along Pacific continuous hotspot tracks have revealed substantial drift of the Hawaiian plume. The question remains for evidence of drift for other mantle plumes. Here, we use plume-derived basalts from the Mid-Atlantic ridge to confirm that the upper-mantle thermal anomaly associated with the Azores plume is asymmetric, spreading over ~2,000 km southwards and ~600 km northwards. Using for the first time a 3D-spherical mantle convection where plumes, ridges and plates interact in a fully dynamic way, we suggest that the extent, shape and asymmetry of this anomaly is a consequence of the Azores plume moving northwards by 1–2 cm/yr during the past 85 Ma, independently from other Atlantic plumes. Our findings suggest redefining the Azores hotspot track and open the way for identifying how plumes drift within the mantle. Tectonic plate motions are often reconstructed based on the assumption that mantle plumes are fixed within the mantle. Here, the authors provide geochemical and geodynamic evidence to suggest that the asymmetry of the Azores thermal anomaly can be explained by northward motion of the Azores plume.

It has long been recognised that spreading ridges are kept in place by competing subduction forces that drive plate motions. Asymmetric strain rates pull spreading ridges in the direction of the strongest slab pull force, which partially explains why spreading ridges can migrate vast distances. However, the interaction between mantle plumes and spreading ridges plays a relatively unknown role on the evolution of plate boundaries. Using a numerical model of mantle convection, we show that plumes with high buoyancy flux (>3000 kg/s) can capture spreading ridges within a 1000 km radius and anchor them in place. Exceptionally high buoyancy fluxes may fragment the overriding plate into smaller plates to accommodate more efficient plate motion. If the plume buoyancy flux wanes below 1000 kg/s the ridge may be de-anchored, leading to rapid ridge migration rates when combined with asymmetric plate boundary forces. Our results show that plume-ridge de-anchoring may have contributed to the rapid migration of the SE Indian Ridge from 43 million years ago (Ma) due to waning buoyancy flux from the Kerguelen plume, supported by magma flux estimates and radiogenic isotope geochemistry of eruption products. The plume-ridge de-anchoring mechanism we have identified has global implications for the evolution of plate boundaries near mantle plumes. When mantle plumes are coupled to spreading ridges, they can act as an anchor and impede spreading ridge migration but if the plume weakens, it can de-anchor from the ridge and facilitate rapid ridge migration.

Geodynamic modeling studies have demonstrated that mantle global warming can occur in response to continental aggregation, possibly leading to large‐scale melting and associated continental breakup. Such feedback calls for a recipe describing how continents help to regulate the thermal evolution of the mantle. Here we use spherical mantle convection models with continents to quantify variations in subcontinental temperature as a function of continent size and distribution and convective wavelength. Through comparison to a simple analytical boundary layer model, we show that larger continents beget warming of the underlying mantle, with heating sometimes compounded by the formation of broader convection cells associated with the biggest continents. Our results hold well for purely internally heated and partially core heated models with Rayleigh numbers of 105 to 107 containing continents with sizes ranging from that of Antarctica to Pangea. Results from a time‐dependent model with three mobile continents of various sizes suggests that the tendency for temperatures to rise with continent size persists on average over timescales of billions of years.

The Earth has changed dramatically in its 4.5-billion-year life span. But only within the past century have we started to appreciate the ways that geophysics on Earth's surface and deep below are constantly shaping the planet. Here, Coltice discusses how geophysical forces shape the Earth.

If a stable layer of dense melt formed at the base of the mantle early in Earth's history, it would have undergone slow fractional crystallization and could provide an unsampled geochemical reservoir hosting a variety of incompatible geochemical species (most notably the missing budget of heat producing elements). The distribution of geochemical species in the Earth’s interior is largely controlled by fractional melting and crystallization processes that are intimately linked to the thermal state and evolution of the mantle. The existence of patches of dense partial melt at the base of the Earth’s mantle 1 , together with estimates of melting temperatures for deep mantle phases 2 and the amount of cooling of the underlying core required to maintain a geodynamo throughout much of the Earth’s history 3 , suggest that more extensive deep melting occurred in the past. Here we show that a stable layer of dense melt formed at the base of the mantle early in the Earth’s history would have undergone slow fractional crystallization, and would be an ideal candidate for an unsampled geochemical reservoir hosting a variety of incompatible species (most notably the missing budget of heat-producing elements) for an initial basal magma ocean thickness of about 1,000 km. Differences in 142 Nd/ 144 Nd ratios between chondrites and terrestrial rocks 4 can be explained by fractional crystallization with a decay timescale of the order of 1 Gyr. These combined constraints yield thermal evolution models in which radiogenic heat production and latent heat exchange prevent early cooling of the core and possibly delay the onset of the geodynamo to 3.4–4 Gyr ago 5 .

We simulate landscape evolution using a diffusion-advection equation with a source term, where the advection velocity is derived from the classical parametrization of the Stream Power Law. This formulation allows for forward modeling of uplift, hillslope and fluvial erosion within a finite-element framework, and enables the use of adjoint methods for sensitivity analysis and parameter inversion. When considered individually, model parameters such as the diffusion coefficient, fluvial erodibility, initial topography, and time-dependent uplift can be inverted using constraints from final topography, sediment flux, or cumulative denudation at specific locations. Sensitivity analysis on a real landscape reveals that sensitivity to erosion parameters is higher in steep, high-relief areas and that hillslope diffusion and fluvial incision affect the model differently. After a series of tests on synthetic topographies, we apply the adjoint model to two natural cases: (1) reconstructing the pre-incision topography of the southeastern French Massif Central, which appears as a smooth, flat footwall bounded by a linear escarpment along a major lithological boundary; and (2) estimating the Quaternary uplift rate along the Wasatch Range, USA, where our model suggests a significant increase in uplift from 0.2 to 1 mm yr−1 over the last ∼ 2 million years.