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Plate tectonics is among the most important geological processes on Earth, but its emergence and evolution remain unclear. Here we extrapolate models of present-day plate tectonics to the past and propose that since about three billion years ago the rise of continents and the accumulation of sediments at continental edges and in trenches has provided lubrication for the stabilization of subduction and has been crucial in the development of plate tectonics on Earth. We conclude that the two largest surface erosion and subduction lubrication events occurred after the Palaeoproterozoic Huronian global glaciations (2.45 to 2.2 billion years ago), leading to the formation of the Columbia supercontinent, and after the Neoproterozoic ‘snowball’ Earth glaciations (0.75 to 0.63 billion years ago). The snowball Earth event followed the ‘boring billion’—a period of reduced plate tectonic activity about 1.75 to 0.75 billion years ago that was probably caused by a shortfall of sediments in trenches—and it kick-started the modern episode of active plate tectonics. The rise of continents and the accumulation of sediments in trenches since about three billion years ago has had a crucial role in the emergence and evolution of plate tectonics on Earth.

When continents break apart, continental crust and lithosphere are thinned until break-up is achieved and an oceanic basin is formed. The most remarkable and least understood structures associated with this process are up to 200 km wide areas of hyper-extended continental crust, which are partitioned between conjugate margins with pronounced asymmetry. Here we show, using high-resolution thermo-mechanical modelling, that hyper-extended crust and margin asymmetry are produced by steady state rift migration. We demonstrate that rift migration is accomplished by sequential, oceanward-younging, upper crustal faults, and is balanced through lower crustal flow. Constraining our model with a new South Atlantic plate reconstruction, we demonstrate that larger extension velocities may account for southward increasing width and asymmetry of these conjugate magma-poor margins. Our model challenges conventional ideas of rifted margin evolution, as it implies that during rift migration large amounts of material are transferred from one side of the rift zone to the other. During continental rifting, various stages and structures are observed, the least understood being hyper-extended continental crust at magma-poor margins. Here, the authors use finite-element thermomechanical models to investigate the mechanism causing observed margin asymmetry and crustal hyper-extension.

The Earth’s biggest magmatic events are believed to originate from massive melting when hot mantle plumes rising from the lowermost mantle reach the base of the lithosphere. Classical models predict large plume heads that cause kilometre-scale surface uplift, and narrow (100 km radius) plume tails that remain in the mantle after the plume head spreads below the lithosphere. However, in many cases, such uplifts and narrow plume tails are not observed. Here using numerical models, we show that the issue can be resolved if major mantle plumes contain up to 15–20% of recycled oceanic crust in a form of dense eclogite, which drastically decreases their buoyancy and makes it depth dependent. We demonstrate that, despite their low buoyancy, large enough thermochemical plumes can rise through the whole mantle causing only negligible surface uplift. Their tails are bulky (>200 km radius) and remain in the upper mantle for 100 millions of years. The classic mantle plume concept explains large igneous provinces and hotspot magmatism, but often contradicts observed surface uplift and plume morphology. Here, the authors present a plume model that better supports observations by considering low-buoyancy plumes containing up to 15% of recycled oceanic crust.

The rates of continental crust growth and recycling on early Earth remain unclear due to the lack of information resulting from the extensive alteration of ancient rocks. Melt inclusions trapped and shielded from alteration in Archean high-Mg olivine crystals offer a solution to this problem. We report an unprecedented unradiogenic Sr mantle source component ( 87 Sr/ 86 Sr = 0.69932 ± 0.00024, 95% confidence interval) of melts included in olivine from 3.27 Ga komatiitic lava flows in the Barberton Greenstone Belt, South Africa. This component indicates a model age of 4.31 ± 0.19 Ga and significant chemical fractionation (Nb/U = 36.9 ± 1.5, Ce/Pb=16.7 ± 1.1), suggesting up to 80% ± 16% of the present-day continental crust’s mass was extracted by the late Hadean from the whole mantle. Geodynamic models support this finding, explaining geochemical data by producing 40% to 70% of the present-day continental crust mass during the Hadean in a variable tectonic regime with tens of millions of years-long periods of massive impulsive subduction induced by mantle plumes. Massive subduction and continental crust production during the Earth’s first 500 million years is suggested by the composition of a 4.3 Ga old mantle source of melt included in olivine from Archean komatiites and geodynamic models.

More than 50 per cent of the Earth's upper mantle consists of olivine and it is generally thought that mantle-derived melts are generated in equilibrium with this mineral. Here, however, we show that the unusually high nickel and silicon contents of most parental Hawaiian magmas are inconsistent with a deep olivine-bearing source, because this mineral together with pyroxene buffers both nickel and silicon at lower levels. This can be resolved if the olivine of the mantle peridotite is consumed by reaction with melts derived from recycled oceanic crust, to form a secondary pyroxenitic source. Our modelling shows that more than half of Hawaiian magmas formed during the past 1 Myr came from this source. In addition, we estimate that the proportion of recycled (oceanic) crust varies from 30 per cent near the plume centre to insignificant levels at the plume edge. These results are also consistent with volcano volumes, magma volume flux and seismological observations.

The magnitude of earthquakes on continental normal faults rarely exceeds 7.0 Mw. However, because of their vicinity to large population centers they can be highly destructive. Long recurrence time, relatively small deformations, and limited observations hinder our understanding of the deformation patterns and mechanisms controlling the magnitude of events. Here, this problem is addressed with 2D thermomechanical modeling of normal fault seismic cycles. The 2020 Samos, Greece Mw7.0 earthquake is used as an example as it is one of the largest and most studied continental normal fault earthquakes. The modeling approach employs visco‐elasto‐plastic rheology, compressibility, free surface, and a rate‐and‐state friction law for the fault. Modeling of the Samos earthquake suggests the pore fluid pressure ratio on the fault ranges from 0 to 0.7. The model demonstrates that most of the deformation during interseismic and coseismic periods, besides on the fault, occurs in the hanging wall and footwall below the seismogenic part of the fault. The largest vertical surface displacement during the earthquake is the subsidence of the hanging wall in the vicinity of the fault, while the uplift of the footwall and remote part of the hanging wall is significantly smaller. Modeling of the seismic cycles on normal faults with different setups shows the dependency of the magnitude on the thermal profile and dipping angle of the fault; low heat flow and low dipping angle are favorable conditions for the largest events, while steep normal faults in the areas of high heat flow tend to have the smallest magnitudes. Key Points We use numerical modeling to investigate continental normal fault earthquakes, using the 2020 Samos Mw7.0 earthquake as an example Most of the deformation during the seismic cycle, besides on the fault, occurs in the crust below the seismogenic part of the fault Low dipping angle and low heat flow favor larger magnitudes of normal fault earthquakes

The commonly used rheological model for the Earth's mantle when considering geological time scales (mantle convection) is the viscoelastic Maxwell model, which assumes a steady state creep process. However, application of this model to phenomena on shorter time scales, such as postglacial rebound or postseismic relaxation, leads to difficulties in finding a consistent interpretation of obtained viscosities. Using standard Maxwell viscosity of 1e19 Pa s to analyze postseismic near‐field GPS time series from the 2004 Sumatra‐Andaman earthquake requires large time‐dependent afterslip with a relaxation time of about 1 year. We show that using linear biviscous Burgers rheology for the asthenosphere, together with a refined coseismic slip model, we can drastically reduce the amount of apparent afterslip. Comparison of predicted geoid change to observations by the GRACE satellite mission shows that a univiscous Maxwell model with afterslip is not compatible with observations, since even large afterslip has a more localized effect than transient relaxation due to the main earthquake, which in turn is in agreement with observations. Thus, a combination of ground‐ and space‐based geodetic observations is very useful in differentiating between rheological models. An additional independent discrimination between afterslip and biviscous relaxation could be obtained by installing ocean bottom pressure gauges close to the trench. Key Points Postseismic GPS data can be interpreted by Maxwell rheology and large afterslip Biviscous Burgers rheology reduces the amount of required slip Gravity data from GRACE favors the biviscous model

The geology of large-scale volcanism The Siberian Traps, a large region of volcanic rock produced more than 200 million years ago by a massive volcanic event, is a prime example of a large igneous province (LIP). Stephan Sobolev and colleagues present petrological evidence for a large amount of dense recycled oceanic crust in the head of the plume that was responsible for forming the Siberian Traps. Using this, they develop a thermomechanical model that predicts the observed lack of pre-magmatic uplift or lithospheric extension in the region. The model also indicates that massive degassing of carbon dioxide and hydrogen chloride from the plume could alone trigger a mass extinction, and predicts it happening before the main volcanic phase, in agreement with stratigraphic and geochronological data for the Siberian Traps and other LIPs. Large igneous provinces (LIPs) are known for their rapid production of enormous volumes of magma (up to several million cubic kilometres in less than a million years) 1 , for marked thinning of the lithosphere 2 , 3 , often ending with a continental break-up, and for their links to global environmental catastrophes 4 , 5 . Despite the importance of LIPs, controversy surrounds even the basic idea that they form through melting in the heads of thermal mantle plumes 2 , 3 , 6 , 7 , 8 , 9 , 10 . The Permo-Triassic Siberian Traps 11 —the type example and the largest continental LIP 1 , 12 —is located on thick cratonic lithosphere 1 , 12 and was synchronous with the largest known mass-extinction event 1 . However, there is no evidence of pre-magmatic uplift or of a large lithospheric stretching 7 , as predicted above a plume head 2 , 6 , 9 . Moreover, estimates of magmatic CO 2 degassing from the Siberian Traps are considered insufficient to trigger climatic crises 13 , 14 , 15 , leading to the hypothesis that the release of thermogenic gases from the sediment pile caused the mass extinction 15 , 16 . Here we present petrological evidence for a large amount (15 wt%) of dense recycled oceanic crust in the head of the plume and develop a thermomechanical model that predicts no pre-magmatic uplift and requires no lithospheric extension. The model implies extensive plume melting and heterogeneous erosion of the thick cratonic lithosphere over the course of a few hundred thousand years. The model suggests that massive degassing of CO 2 and HCl, mostly from the recycled crust in the plume head, could alone trigger a mass extinction and predicts it happening before the main volcanic phase, in agreement with stratigraphic and geochronological data for the Siberian Traps and other LIPs 5 .

We present a three‐dimensional finite element thermomechanical model idealizing the complex deformation processes associated with evolution of the San Andreas Fault system (SAFS) in northern and central California over the past 20 Myr. More specifically, we investigate the mechanisms responsible for the eastward (landward) migration of the San Andreas plate boundary over time, a process that has largely determined the evolution and present structure of SAFS. Two possible mechanisms had been previously suggested. One mechanism suggests that the Pacific plate first cools and captures uprising mantle in the slab window, subsequently causing accretion of the continental crustal blocks. An alternative scenario attributes accretion to the capture of plate fragments (microplates) stalled in the ceased Farallon‐North America subduction zone. Here we test both these scenarios numerically using a recently developed lithospheric‐scale code, SLIM3D, that employs free surface, nonlinear temperature‐ and stress‐dependent elastoviscoplastic rheology and allows for self‐generation of faults. Modeling suggests that microplate capture is the primary driving mechanism for the eastward migration of the plate boundary, while the slab window cooling mechanism alone is incapable of explaining this phenomenon. We also show that the system evolves to the present day structure of SAFS only if the coefficient of friction at mature faults is low (0.08 for the best fit model). Thus, our model provides an independent constraint supporting the “weak fault in a strong crust” hypothesis for SAFS. Key Points Modeling suggests that microplate capture drives eastward migration of the SAF Slab window cooling alone is incapable to explain eastward migration of the SAF Modeling supports the \"weak fault in a strong crust\" hypothesis for SAFS

In many cases the initial stage of continental break‐up was and is associated with oblique rifting. That includes break‐up in the Southern and Equatorial Atlantic, separation from eastern and western Gondwana as well as many recent rift systems, like Gulf of California, Ethiopia Rift and Dead Sea fault. Using a simple analytic mechanical model and advanced numerical, thermomechanical modeling techniques we investigate the influence of oblique extension on the required tectonic force in a three‐dimensional setting. While magmatic processes have been already suggested to affect rift evolution, we show that additional mechanisms emerge due to the three‐dimensionality of an extensional system. Focusing on non‐magmatic rift settings, we find that oblique extension significantly facilitates the rift process. This is due to the fact that oblique deformation requires less force in order to reach the plastic yield limit than rift‐perpendicular extension. The model shows that in the case of two competing non‐magmatic rifts, with one perpendicular and one oblique to the direction of extension but otherwise having identical properties, the oblique rift zone is mechanically preferred and thus attracts more strain. Key Points Oblique extension facilitates the rift process in non‐magmatic settings Shearing a continent requires up to two times less force than rifting it An oblique rift zone attracts more strain than a competitive normal rift