Our session will provide rich opportunities for presenters and attendees from a range of disciplines, demographics, and stages of their scientific career to engage in this exciting and multidisciplinary problem in Earth science.
Orals: Mon, 4 May, 08:30–18:00 | Room K1
Slab pull has come to be widely regarded as a dominant driver of plate motions. The nature of slab–plate coupling is typically conceptualised in terms of the Orowan–Elsasser stress-guide model, in which the capacity of the slab to support a differential stress results in a tension-like force transmitted through the subduction hinge, providing an edge force on the trailing plate. Meanwhile, advances in geodynamic modelling now allow subduction to be simulated using increasingly Earth-like constitutive behaviour and, critically, permit the internal force balance to be examined explicitly. While the forces driving tectonic plates on Earth remain debated, the force balance within any given numerical model should be unambiguous. I discuss results from a vertically integrated horizontal force balance applied to a suite of numerical subduction models. I focus on a particularly useful decomposition that highlights the role of topographic (or gravitational potential energy–related) forces, including ridge push, plate tilting driven by asthenospheric pressure gradients, and—critically—the influence of non-isostatic trench topography. Each of these topographic forces can be expressed in terms of differences in the integrated vertical normal stress - a proxy for the topographic-related pressure gradients in the boundary layer. The trench topographic force, or trench pull force, is of special interest because it mediates the coupling between predominantly vertical loading imparted by the slab and a horizontal force (pressure gradient) acting on the trailing plate. Numerical models suggest that a tension-like formulation of net slab pull plays at most a secondary role. Instead, it is primarily through the trench topographic force (trench pull) that the slab induces a net horizontal force on the trailing plate. Numerical models provide a direct means to isolate, compare, and quantify the trench topographic force relative to a tension-like edge force, and to establish quantitative bounds that can guide future analytical investigation of trench topographic forces.
How to cite: Sandiford, D.: Re-examining Slab Pull: Trench Topography and Trailing Plate Force Balance in Numerical Subduction Models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2649, https://doi.org/10.5194/egusphere-egu26-2649, 2026.
Subduction is considered the primary driver of plate tectonics, which is sometimes accompanied by back-arc spreading. Back-arc deformation on Earth exhibits substantial variability, ranging from compressional regimes in the Japan Sea to rapid spreading with rates up to 15 cm/yr in the Lau Basin. Even within a single subduction zone, back-arc basins can exhibit significant spatial and temporal variability in spreading rates along the trench. The mechanisms underlying this variability remain inadequately understood. To address this issue, we compiled global back-arc deformation rates and quantified slab area penetration into the deeper mantle. Additionally, we conducted a series of numerical simulations to elucidate the factors that govern back-arc deformation rate. Our global back-arc compilation and numerical models reveals a robust negative correlation between back-arc spreading rate and slab penetration into the deeper mantle, highlighting the initial stage of subduction as the peak phase of back-arc spreading. Furthermore, numerical simulations offer insights into the underlying dynamic mechanisms, demonstrating that slab-driven poloidal flow play a dominant role in governing back-arc deformation rates.
How to cite: Jian, H.: Evolution of slab-driven poloidal flow symmetry governs back-arc deformation rates, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3957, https://doi.org/10.5194/egusphere-egu26-3957, 2026.
Some hotspot tracks, such as those formed by the Hawai’i and Galápagos mantle plumes, exhibit long-lived cross-track isotopic zonation, thought to reflect the streaking out of heterogeneous material in the plume conduit during upwelling. In lavas associated with the Galápagos mantle plume, three geochemical domains, present for at least 15 Myr, have been identified: northern, southern and central. The most extreme isotopic enrichments are observed in the northern domain of the Cocos Ridge at ~15 Ma, and in the southern domain of the Galápagos Archipelago at the present day. Owing to the northward migration of the Galápagos Spreading Center above the plume at ~5-10 Ma, this relationship suggests that geochemical enrichment in the Galápagos basalts is greatest above the region of the plume furthest from the nearby mid-ocean ridge. We examine the hypothesis that these temporal and spatial variations in geochemical enrichment reflect a ''shallow mantle control'', associated with differences in the mean depth of melting. We conducted forward melting models of a mixed peridotite-pyroxenite mantle to calculate the isotopic composition of the resulting melts formed under two different mantle flow regimes. Our results demonstrate that variations in the average pressure of melt generation, due to the influence of the nearby ridge axis, may explain the range of isotopic compositions across ~15 Ma of Galápagos plume-related volcanism. The patterns of isotopic zonation observed along the hotspot track confirm the paradigm of persistent plume striping, with variations in the degree of geochemical enrichment modulated by shallow mantle processes.
How to cite: Richards, M., Gleeson, M., Farnetani, C., Hoernle, K., and Gibson, S.: Persistent Geochemical Zonation (“Striping”) within the Galápagos Mantle Plume, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15073, https://doi.org/10.5194/egusphere-egu26-15073, 2026.
The geochemical composition of ocean island basalts (OIB) from Réunion Island has been controversially interpreted as recording either interaction between the mantle and Earth’s core [1] or the preservation of an ancient, Hadean silicate reservoir isolated since early Earth differentiation [2,3]. Resolving this debate bears directly on the nature of deep mantle heterogeneity, the longevity of early-formed reservoirs, and the efficiency of whole-mantle mixing through time. In particular, the extinct 182Hf-182W decay system provides a powerful tracer of both, core contribution due to the strong siderophile behaviour of W during core formation as well as early silicate differentiation processes because of the short half-life of 182Hf.
Here we present new high-precision radiogenic W isotope data (μ182W) for 39 basaltic lavas from Réunion Island, complemented by major and trace element compositions and long-lived radiogenic isotope ratios including 143Nd/144Nd, 87Sr/86Sr, and 206,207,208Pb/204Pb. Measured μ182W values range from 0 to –11, fully overlapping with the range reported in previous studies of Réunion and related plume products [1–3]. These results confirm that the Réunion mantle source is isotopically heterogeneous and requires the involvement of a geochemically distinct component not represented in depleted upper mantle reservoirs.
By integrating short-lived and long-lived isotope systematics with trace element constraints, we evaluate the origin of this component and its implications for deep Earth processes. In particular, we assess whether the observed μ182W anomalies are more consistent with contributions from an early-formed silicate reservoir that avoided complete mantle homogenization, or with addition of core-derived material to the mantle plume source. Our dataset is discussed in the context of isotopic findings that provide compelling evidence for ongoing or episodic core–mantle chemical exchange recorded in OIB sources [4].
The combined data of Réunion basalts indicate that core addition is the most likely process to explain the chemical and isotopic observations. Our findings allow qualitative constraints on the mass exchange between the Earth’s core and mantel and highlight the importance of integrating multiple isotope systems to disentangle the complex history of mantle plume sources and their role in recording the mass exchange from core to surface on Earth.
References:
[1] Rizo et al. (2019) Geochemical Perspectives Letters, 6–11.
[2] Peters et al. (2018) Nature, 555, 89–93.
[3] Pakulla et al. (2025) Earth and Planetary Science Letters, 653.
[4] Messling et al. (2025) Nature, 642, 376–380.
How to cite: Willbold, M., Messling, N., Huang, X., and Hoffmann, D.: The Réunion Island mantle plume – isotopic constraints on core addition or ancient silicate component?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12125, https://doi.org/10.5194/egusphere-egu26-12125, 2026.
Oceanic lithospheric plates form from hot mantle material ascending along the axis of mid-ocean ridges (MORs). As newly formed lithosphere moves away from the ridge, it cools from the surface, leading to progressive deepening of the ocean floor due to thermal contraction and to a decrease in surface heat flow. Turcotte and Oxburgh (1967) proposed a model in which the lithosphere is treated as a cooling half-space with a uniform initial temperature and purely conductive heat transport. Assuming constant thermophysical properties, this model predicts that heat flow and seafloor depth vary linearly with age⁻¹ᐟ² and age¹ᐟ², respectively. Observations of ocean floor topography and heat flow follow these trends up to ages of approximately 50–60 Myr. For older lithosphere, however, the agreement breaks down: observed heat flow is higher and seafloor depth is shallower than predicted by the half-space model.
Several models have been proposed to account for this discrepancy, but all of them are purely kinematic in nature. For example, the widely used “plate model” assumes that temperature is fixed at a certain depth within the mantle. At young ages, the solution coincides with the half-space model, whereas at greater ages it asymptotically approaches the prescribed basal temperature. Although both the basal temperature and the depth of the thermal boundary can be adjusted to fit observations, no known physical mechanism can sustain the boundary condition assumed by this model.
In contrast, we demonstrate that a rheological instability developing within the cooled upper part of the lithospheric plate explains the observations both qualitatively and quantitatively. The key point is that such an instability inevitably arises in a plate cooled from above. Our quantitative analysis is based on experimentally determined non-Newtonian rock viscosity (Hirth and Kohlstedt, 2003) and on the formulation of the Rayleigh number for Arrhenius-type rheology (Solomatov, 1995; Korenaga, 2009). We show that the characteristic Rayleigh number of the instability increases as surface heat flow decreases. Owing to the strong temperature dependence of viscosity, only the lower part of the cooled lithosphere is potentially unstable. For a given heat flow, the thickness of this deformable layer is self-consistently determined by the condition of maximum Rayleigh number. Once the Rayleigh number reaches its critical value, an instability develops that supplies heat to the oceanic lithosphere, inhibits further cooling, and results in the observed flattening of heat flow and seafloor depth records with age.
How to cite: Aryasova, O. and Khazan, Y.: Physics of the flattening of ocean floor depth and heat flow records, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2743, https://doi.org/10.5194/egusphere-egu26-2743, 2026.
Sub-plate mantle flow traction (MFT) has been considered as a major driving force for plate motion; however, the force acting on the overlying plate is difficult to constrain. One of the reasons lies in the variable rheological flow laws of mantle rocks, e.g. linear versus power-law rheology, applied in previous studies. Here, systematic numerical models are conducted to evaluate MFT under variable rheological, geometrical and kinematic conditions. The results indicate that MFT with power-law rheology is much lower than that with linear rheology under the same mantle/plate velocity contrast. In addition, existence of a lithospheric root in the overlying plate could enhance MFT, where integrated normal force acting on the vertical walls of lithospheric root is much lower than the shear force in a large-scale domain. In a regime of several thousand kilometers, MFT with power-law rheology is comparable to the ridge push of about 3×1012N/m, whereas that with linear rheology is comparable to the slab pull of about 3×1013 N/m. The roles of MFT in driving plate motion are further analyzed for the Tethyan evolution. It indicates that MFT with power-law rheology could partially support the cyclic Wilson cycles experienced in the Tethyan system, whereas that with linear rheology could easily dominate any kinds of plate tectonic evolutions. The quantitative evaluation of MFT in this study clarifies the roles of rheological flow laws on MFT and could help to better understand the contrasting results in previous numerical studies.
How to cite: Cui, F., Li, Z.-H., and Fu, H.-Y.: Quantitative evaluation of mantle flow traction on overlying tectonic plate: Linear versus power-law mantle rheology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3641, https://doi.org/10.5194/egusphere-egu26-3641, 2026.
Understanding the internal dynamics, structure, and composition of our planet is a fundamental goal of Earth science, and geodynamic modelling has been central to this effort by providing a theoretical window into mantle convection. Moreover, the asthenosphere plays a key role in linking mantle dynamics to surface observations; its channelized nature allows it to be described analytically within the framework of Couette and Poiseuille flow regimes.
Using this framework, we predict global stress fields and compare them directly with observations from the World Stress Map (WSM), a global compilation of crustal stress indicators. Our approach enables fast hypothesis testing and the development of first-order expectations for how different mantle flow states influence surface stress patterns. It also identifies three distinct basal shear traction regimes, depending on whether the asthenosphere locally moves faster than, slower than, or at the same velocity as the overlying plate. As a result, some regions experience driving tractions, others resisting tractions, while some are nearly traction-free. These results show that stress field patterns cannot be explained without realistic upper mantle flow geometries, particularly the spatial distribution and combined effects of plumes, slabs, and plate-driven flow.
How to cite: Stotz, I. L., Hayek, J. N., Bunge, H.-P., and Carena, S.: Predicting present-day Earth’s lithospheric stress using analytical upper mantle flow models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17485, https://doi.org/10.5194/egusphere-egu26-17485, 2026.
We derive global stress fields through time using an analytical asthenospheric flow estimation that involves plate motions, subduction geometry, and time-variable plume flux. Among these, the most effective way to drive rapid regional stress changes in the continents is by varying plume flux, especially when more than one plume is present, as is the case for Europe. We apply our paleostress model to the case study of western Europe, a region that experienced rapid, substantial, and large-scale lithospheric stress changes in the Late Mesozoic and Cenozoic. We find that the behaviour of pressure-driven asthenosphere flow, resulting from variations in plume flux, dominates the rapidly temporo-spatially varying stress signal. Given the potential causes of stress change in this particular region, we further interpret the tectonic changes in the context of dynamic topography as expressed by the stratigraphic record, shifts in plate motion, paleostress indicators, and past interpretations of the tectonic evolution of Europe. Through this approach we move away from the paradigm of stress changes being driven by plate-boundary or body forces in the lithosphere, and emphasize the active role of the mantle and the importance of interpreting models in relation to multiple process-linked observations.
How to cite: Bunge, H.-P., Hayek, J. N., Stotz, I. L., Kahle, B., and Vilacis, B.: Plume-driven rapid paleo stress field changes in western Europe since Mid-Cretaceous inferred from analytic upper mantle flow models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9724, https://doi.org/10.5194/egusphere-egu26-9724, 2026.
Shear-wave tomography models of the upper mantle below Western and Central Europe are indicative of a thermally very heterogeneous lithosphere-asthenosphere system. High shear-wave velocities indicate a deep 1300 °C isotherm and thus a thick (ca. 200 km) lithosphere in the southwestern North Sea and the Paris Basin. This contrasts with a shallower (< 120 km) lithosphere-asthenosphere boundary across the European Cenozoic Rift System and much of the British Isles. These major, long-wavelength thickness fluctuations of the thermal boundary layer are locally superposed by a number of smaller-scale thermal anomalies reaching into the lithospheric mantle (such as the Eifel mantle thermal anomaly). Previous work indicates that the distribution of earthquakes in this region is related to density and strength variations inside the mantle lithosphere that affect the localization of present-day crustal deformation. With this contribution, we explore and discuss the potential ages of the imaged upper mantle thermal anomalies in an attempt to delineate their roles in the geological past. Thereby we make use of the multiphase tectonic evolution recorded in the overlying sedimentary systems and crystalline crust. To evaluate if and where the upper mantle structure may have controlled Paleozoic to Cenozoic crustal deformation phases, we investigate spatial correlations between upper mantle temperature variations as derived from shear-wave tomography models with major crustal structures of known geological age and tectonic setting. Our new findings provide important observational constraints for geodynamic models of Western and Central Europe – a region affected by glacial isostatic adjustment, foreland orogenic processes as well as extensional and passive margin tectonics.
How to cite: Bott, J., Scheck-Wenderoth, M., May, T., and Cacace, M.: Upper Mantle Controls on the Phanerozoic Evolution of Western and Central Europe , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9286, https://doi.org/10.5194/egusphere-egu26-9286, 2026.
I present the results of a series of numerical experiments, based on a visco-elasto-plastic rheological model of the lithosphere, aimed at studying the interplay between mantle convection and tectonic processes at continental margins. In these experiments, the reference thermal states of the oceanic and continental lithospheres are described by a plate cooling model and by the solutions of the steady heat equation, respectively, while a small non-adiabatic temperature gradient is assumed for the asthenosphere and transition zone. The resulting thermo-mechanical model incorporates both vertical (Rayleigh-Benard) and horizontal (small-scale) convection and allows to predict the state of stress across continental margins, as well as some tectonic processes that are observed in these regions. Small-scale convection arises from lateral temperature gradients. It always develops along passive margins, where the thermal regime of the oceanic lithosphere meets the downward-dipping isotherms of the continental lithosphere. This form of horizontal convection has the potential to deform the lower part of the continental lithosphere, generate Rayleigh-Taylor instabilities, and produce up to ~50 MPa of compressional stress across continental margins. The formation of Rayleigh-Taylor instabilities is accompanied by lithospheric thinning, which in turn induces negative thermal anomalies that contribute to the maintenance of isostatic equilibrium by increasing the density of the residual lithosphere. These anomalies propagate towards the interior of the continental lithosphere, until the increased rheological strength associated with lower temperatures is sufficient to prevent further delamination. Therefore, the lower continental lithosphere is always colder than predicted by steady-state solutions of the heat equation. Basal landward traction along passive margins, resulting from small-scale convection, is further enhanced when the oceanic lithosphere adjacent to the continental margin is bounded by a spreading ridge. In this instance, numerical experiments consistently show the existence of an active spreading component, up to 5 mm/yr, which generates additional traction below the continental margins and contributes to a compressive stress regime in these regions. Consequently, a net horizontal landward push develops along the continental margins of a tectonic plate, which combines with other driving forces to determine the plate kinematics. Finally, numerical experiments show that non-adiabatic vertical temperature gradients drive the formation of Rayleigh-Benard convective cells with a wavelength of 600-700 km and a height 500-600 km.
How to cite: Schettino, A.: Sea-floor spreading, small-scale convection, and passive margins: Interplay and effect on the driving forces of Plate Tectonics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4362, https://doi.org/10.5194/egusphere-egu26-4362, 2026.
In this presentation, I will review some of our recent global tomography results, that provide constraints on the Earth mantle structure and mantle convection.
In the upper mantle, we have recently constructed global tomographic models of SV wave velocity, 𝑉𝑠𝑣, and radial anisotropy, 𝜉, using the same tomographic approach, with similar regularization and smoothing for the Rayleigh and Love wave data. We also use Rayleigh waves to constrain the azimuthal anisotropy, the quality factor 𝑄 and the melt content. We find that a 1-D model of radial anisotropy, close to PREM, but including a 3D crustal structure, explains the Love/Rayleigh differences almost everywhere, except in oldest parts of the continents and youngest parts of the Pacific ridge. No age dependence of the radial anisotropy 𝜉 in the oceanic upper mantle is required, while age is the main parameter controlling 𝑉𝑠𝑣, melt content and azimuthal anisotropy. In the asthenosphere, azimuthal anisotropy aligns on a large scale with present plate motion only for fast plates (> ∼4 cmyr−1), suggesting that only fast-moving plates produce sufficient shearing at their base, to organize the flow on the scale of the entire tectonic plates. Part of the azimuthal anisotropy is also frozen in the shallow oceanic lithosphere. The presence of a small amount of partial melt, by reducing mantle viscosity, facilitates plate motion and large-scale crystal alignment in the asthenosphere.
We have also built global shear tomographic models of the whole mantle for the shear velocity (SEISGLOB2) and attenuation (QL3D). In the lower mantle, SEISGLOB2 has revealed a change in the shear velocity spectrum at around 1000 km depth. The spectrum is the flattest (i.e. richest in "short" wavelengths corresponding to spherical harmonic degrees greater than 10) around 1000 km depth and this flattening occurs between 670 and 1500 km depth. QL3D combines various S-phase measurements, including surface waves, direct (S, SS, SSS, SSSS), core-reflected (ScS, ScSScS, ScSScSScS), diffracted (S𝑑𝑖𝑓𝑓) and their depth phases (e.g., sS, sScS, sS𝑑𝑖𝑓𝑓), providing extensive depth and spatial coverage. A high attenuation zone highlights the peculiar nature of the mantle around 1000 km depth. This may indicate the presence of a global low-viscosity layer, in a region that roughly corresponds to the upper boundary of the Large Low Shear Velocity Provinces (LLSVPs), and where various changes in the continuity of slabs and mantle plumes have been observed. Our 3D shear quality factor model also confirms that the LLSVPs are attenuating, at least for body waves with periods near 35 s. The correlation between strong attenuation and low shear velocities within these regions suggests that the shear quality factor mostly captures the thermal signature of the LLSVP.
How to cite: Debayle, E., Stéphanie, D., Sun, S., and Ricard, Y.: Insights on mantle convection from global tomography, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11226, https://doi.org/10.5194/egusphere-egu26-11226, 2026.
Tomographic images play a crucial role in estimating the thermodynamic state of Earth's mantle, yet reliable quantification of their uncertainties is essential for drawing robust conclusions in geodynamics. In particular, reconstructions of past mantle flow that rely on tomographic inputs require a practical handling of the difference in spatial scales between predictions from fluid dynamics and the heterogeneities observable through seismology. This scale discrepancy can indeed already be addressed through so-called tomographic filtering as a post-processing step applied to standard forward models of mantle circulation. However, integrating such approaches technically into adjoint or inverse modeling frameworks—used in data-driven mantle flow reconstructions—remains to be thoroughly explored.
Here, we perform a fully synthetic experiment to highlight the difficulties in quantitatively linking tomographic images with geodynamic models. Specifically, we employ the Subtractive Optimally Localized Averages (SOLA) method—a linear Backus–Gilbert-type inversion technique—to image a reference mantle circulation model. The SOLA inversions are based on finite-frequency traveltime residuals derived from full-waveform numerical seismograms computed for the geodynamic reference model.
Drawing on the insights provided by this synthetic experiment, we propose a workflow for adjoint-based mantle flow reconstructions that aims to leverage the tools provided by the SOLA approach. For the tomographic component, this involves generating spatially optimized averaging kernels that characterize local resolution (i.e. the specific tomographic filter), along with rigorous uncertainty estimates for parameter averages obtained by the propagation of data errors (both being built-in features of SOLA). On the geodynamic side, one should first aim to incorporate measures of tomographic resolution directly into the misfit/cost function of the adjoint method. This step is critical because the adjoint model validation compares observed surface dynamic topography in time with its prediction from the reconstructed flow history, which is highly sensitive to the tomographic input. Once resolution-related biases are factored in, small model ensembles should make it possible to practically account for stochastic uncertainties, eventually yielding more robust constraints on mantle flow history. We suggest that the success of a specific misfit function and the realization of model ensembles can be assessed with dedicated synthetic closed-loop experiments, prior to their actual application.
Overall, our results offer practical guidance towards a strategy that integrates the complete tomographic information, including resolution and uncertainty, into fully operational reconstructions of past mantle flow.
How to cite: Freissler, R., Schuberth, B. S. A., Stotz, I. L., Zaroli, C., and Bunge, H.-P.: On the role of tomographic resolution and uncertainty in reconstructing past mantle flow, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12227, https://doi.org/10.5194/egusphere-egu26-12227, 2026.
Dynamic topography, the transient deflection of Earth's surface driven by mantle convection, exerts a first-order control on continental flooding, sedimentary basin subsidence, and long-term eustatic sea level. Changes in dynamic topography have been invoked to explain the widespread Cretaceous marine transgression, the subsequent retreat of epicontinental seas, and regional patterns of uplift and subsidence that cannot be attributed to tectonics alone.
Here I present global, high-resolution retrodictions of dynamic topography evolution over the Cenozoic, constrained by seismic tomography, plate kinematic reconstructions, and geological proxies of past surface elevation. These models reveal how migrating mantle upwellings and downwellings have driven substantial changes in surface elevation across multiple continents throughout the Cenozoic. The retrodicted patterns of dynamic topography change provide estimates of mantle-driven sea level contributions, offering new constraints on interpreting the stratigraphic and palaeogeographic record in terms of deep Earth processes.
How to cite: Ghelichkhan, S. and Davies, R.: Reconstructing Cenozoic Dynamic Topography, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20350, https://doi.org/10.5194/egusphere-egu26-20350, 2026.
Reconstructing the thermo-chemical evolution of Earth’s mantle across geological time is a central challenge in the geosciences. Addressing this problem increasingly relies on adjoint-based approaches, which cast mantle convection modelling as an inverse problem and enable the systematic assimilation of observational data into time-dependent simulations. Such methods underpin emerging efforts to build a digital twin of Earth’s mantle: a dynamic, physics-based representation constrained by diverse geological and geophysical observations.
To date, adjoint geodynamic inversions have primarily relied on constraints that act at the beginning or end of model evolution, or at Earth’s surface only, such as plate motions, geodesy, or seismic tomography. However, these datasets provide limited leverage on the evolving thermal and chemical structure of the mantle through time. Intra-plate volcanic lavas offer an underexploited observational constraint, as their major- and trace-element geochemistry records the pressure, temperature, and composition of mantle melting at the time of eruption, providing direct insight into past lithospheric thickness, plume excess temperature, and mantle source heterogeneity.
Here, we present an integrated framework for assimilating geochemical information from ocean island basalts into adjoint models of mantle convection using the Geoscientific ADjoint Optimisation PlaTform (G-ADOPT). Using simulation-informed inversions of rare earth element concentrations, we demonstrate the power of geochemical data to recover the thermal structure of plume melting regions, including lithospheric thickness and plume excess temperature. We then use synthetic experiments to show how these geochemically derived constraints on melting conditions can be incorporated into adjoint reconstructions, substantially improving recovery of mantle temperature fields and flow trajectories relative to inversions based on surface or boundary constraints alone.
By explicitly linking geochemical observables to mantle thermal structure and flow, this approach reduces non-uniqueness in time-dependent inversions and strengthens the ability of adjoint models to retrodict mantle evolution. More broadly, it highlights the transformative potential of integrating geochemistry into data-assimilative geodynamic frameworks and represents a key step toward a fully constrained digital twin of Earth’s interior.
How to cite: Davies, R. and Ghelichkhan, S.: Assimilating Intra-Plate Lava Geochemistry into Adjoint Reconstructions of Earth’s Mantle Evolution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19074, https://doi.org/10.5194/egusphere-egu26-19074, 2026.
With the plans of the MAGIC/NGGM mission approved, there will be several decades of satellite gravity data available. Both periodic and secular mass changes can be studied with this data, mostly surface mass changes like hydrology, ice melt, glacial isostatic adjustment, and large earthquakes. With the increasing time period of the gravity data set, smaller processes in the signal can be detected. Therefore, we conduct sensitivity analysis on small temporal gravity signals which can be related to mass change due to mantle convection.
We perform various sensitivity analysis studies to understand the added benefit of detecting mantle flow with satellite gravity change observations. A fast stoke solver (FLAPS) is developed that is based on an axisymmetric half annulus geometry. The model evolves over 50 years after which the difference between the initial and final state to compute the rate of change. Realistic Earth models (PREM) as well as synthetic models are tested to better understand the sensitivity of the gravity change data. To understand 3D variations in structure and viscosity, we use the open-source mantle flow software ASPECT and incorporate interior models related to ESA's 4D Dynamic Earth project. For the upper mantle the WINTERC-G model incorporates multi data types information in a joint inversion. New analysis show data sensitivity down to the transition zone. For the lower mantle, we use available global tomography models.
The gravity change observations are sensitive to the absolute viscosity state of the mantle. This is contrary to dynamic topography and geoid data, which do not have this sensitivity and studies using these data always have an ambiguity wrt. viscosity state. Moreover, it seems that the gravity change data is more sensitive to the lower mantle of the Earth. 3D calculations need HPC resources and we show that the mesh resolution needs high computational demands to consistently account for the temporal gravity due to mantle flow. Nevertheless, the modelled magnitude of the gravity change linked to global mantle convection seems to be larger than the formal error estimates of the GRACE and GRACE-FO instrumentation. A longer acquisition period will reduce the secular errors in the ocean, atmosphere and tidal correction models, such that eventually mantle convection can be studied directly by satellite gravimetry.
How to cite: Root, B. and Thieulot, C.: Global simulations of temporal gravity due to mantle flow and their sensitivity to the mantle rheology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16730, https://doi.org/10.5194/egusphere-egu26-16730, 2026.
The geological evolution of the Barents Sea Basin in the Arctic region during the Cretaceous reflects a complex interplay between subsidence and uplift processes. In this study, we analyse well lithostratigraphic data to identify hiatuses, unconformities and depositional periods, assess their spatial distribution, and quantify subsidence using the backstripping technique. Our results reveal episodic deposition and hiatuses across all wells during the Early Cretaceous, followed by a dominant basin-wide hiatus in the Late Cretaceous. Early Cretaceous subsidence was spatially variable, the southeastern parts of the Barents Sea Basin experienced more intensive subsidence compared to other areas. These observations could be linked to the influence of mantle-driven dynamic topography on basin evolution in relation with the High Arctic Large Igneous Province. The results indicate the importance of geodynamic processes in controlling basin architecture and stratigraphic development, with implications for understanding sedimentary evolution and hydrocarbon prospectivity in the Barents Sea.
How to cite: Babina, E., Vilacís, B., Makuluni, P., and Clark, S.: Vertical motions and Cretaceous basin evolution of the Barents Sea Basin in relation to mantle-induced dynamic topography, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16736, https://doi.org/10.5194/egusphere-egu26-16736, 2026.
Stratigraphic evidence shows the presence of an unconformity starting at 68 Ma (Maastrichtian) in the Canadian archipelago, on- and off-shore west and north Greenland, in Svalbard, on the Lomonosov Ridge, in East Greenland, on- and off-shore Norway and the Faroe Basin (Japsen et al., 2023). These observations are consistent with interpretation of apatite fission track data in the same areas. We suggest that this unconformity reflects doming above the rising head of the Iceland Plume in the upper mantle and prior to its impact at the base of the lithosphere at 62 Ma, 6 Myr later. These observations are consistent with the predictions of Campbell (2007) who showed evidence that pre-impact doming can become evident 3 to 10 Myr before plume impact, and that the diameter of the dome can be of the order of 1000 to 2000 km.
References.
Campbell, 2007. Testing the plume theory. Chem. Geol. 241, 153–1117. https://doi.org/10.1016/j.chemgeo.2007.01.024
Japsen, Green, Chalmers, 2023. Synchronous exhumation episodes across Arctic Canada, North Greenland and Svalbard in relation to the Eurekan Orogeny. Gondwana Research, 117, 207-229. https://doi.org/10.1016/j.gr.2023.01.011
How to cite: Chalmers, J., Japsen, P., and Green, P.: Stratigraphic and fission track evidence for the rising Iceland Plume in the Maastrichtian , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9778, https://doi.org/10.5194/egusphere-egu26-9778, 2026.
Cratons such as the Guiana Shield are often considered as stable regions, undergoing long-term emergence and denudation due to buoyancy. However, by integrating geological and geomorphological observations with apatite fission-track analysis, we define a history involving repeated episodes of burial and exhumation over the last 500 Myr.
Over much of the shield, the thermal history is dominated by the effects of earliest Jurassic magmatism, followed by Early Cretaceous exhumation coincident with the onset of seafloor spreading in the southern South Atlantic when South America was driven westward by mantle flow from the hot, upwelling upper mantle in the southeast toward the downwelling, pre-Andean subduction zone in the west.
Further episodes of regional exhumation occurred in Aptian-Albian time coincident with a global-scale plate reorganization and in Eocene times coincident with a slowdown in the movement of the South American plate. Results from the Amazon Basin also define these four episodes.
Thermal data from a deep well in the Amazon Basin show that the Early Cretaceous and Eocene exhumation episodes were preceded by burial by kilometre-scale thicknesses of cover, subsequently removed. Continuity of data from basin to shield suggests that burial extended across the shield. Early Cretaceous exhumation led to formation of a base-Cretaceous peneplain across the entire continent, from the Andes (during post-orogenic collapse) to the Amazon Basin and the Guiana Shield. This peneplain was then buried beneath Cretaceous–Paleogene sediments prior to the onset of Eocene exhumation, which also extended into in the offshore. The Eocene episode also correlates with post-orogenic collapse of the Andes.
Miocene exhumation correlates with a regional, late Miocene unconformity, onshore and offshore, coincident with a slowdown in the movement of the South American plate. This episode resulted in the formation of a vast coastal planation surface, along the Guyanas Atlantic margin and in the incision of the present-day valley along the Amazon River, leading to the reversal of the Amazon River.
The history of repeated burial and exhumation defined for the Guiana Shield appears to be a common property of supposedly stable cratons. The correlation between Andean tectonics, episodes of exhumation and changes in the motion of the South American plate, shows that sub-lithospheric forces and intra-plate stress governed the vertical movements across the continent.
References
Baby et al., 2025. The Northern Central Andes and Andean tectonic evolution revisited: an integrated stratigraphic and structural model of three superimposed orogens. Earth Sci. Rev. https://doi.org/10.1016/j. earscirev.2024.104998
Japsen et al., 2025. Ups and downs of the Guiana Shield and Amazon Basin over the last 500 Myr. Gondw. Res. https://doi.org/10.1016/j.gr.2025.06.020
Stotz et al., 2023. Plume driven plate motion changes: New insights from the South Atlantic realm. J. S. Am. Earth Sci. https://doi.org/10.1016/j.jsames.2023.104257
Szatmari & Milani, 2016. Tectonic control of the oil-rich large igneous-carbonate- salt province of the South Atlantic rift. Mar. Pet. Geol. https://doi.org/ 10.1016/j.marpetgeo.2016.06.004
How to cite: Japsen, P., Green, P. F., and Bonow, J. M.: Ups and downs of the Guiana Shield and Amazon Basin driven by sub-lithospheric forces and intra-plate stress, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8912, https://doi.org/10.5194/egusphere-egu26-8912, 2026.
Histories of vertical lithospheric motion preserved in sedimentary basins provide constraints on evolving mantle buoyancy and convection histories. We present a quantitative analysis of subsidence, exhumation and stratigraphic hiatuses to constrain mantle dynamics during the Cretaceous–Cenozoic, illustrated by case studies from northwestern Australia. Basin analysis across multiple basins from this region calculates the continental-scale vertical response to evolving geodynamic forces, from Jurassic–Cretaceous subsidence during sub-basin development associated with rifting and Gondwana breakup to the recent northeastward tilting of Australia driven by dynamic topography linked to slab subduction beneath the Indonesian margin.
In particular, our kinematic reconstructions of the Northern Carnarvon Basin quantify Jurassic–Cretaceous nearshore intraplate rift-extension rates (~8 mm/yr), with rift cessations at ~155 and ~120 Ma coinciding with major Gondwana breakup events. This temporal correspondence demonstrates strong coupling between far-field plate reorganisations and regional vertical and lateral motions and constrains lithospheric controls on strain localisation during Gondwana breakup events.
Integration of compaction and paleothermal data identifies two significant Mesozoic exhumation episodes that correlate spatially with mapped magmatic bodies, implying that thermal perturbations from sub-lithospheric sources drove regional uplift. Jurassic–Early Cretaceous NE–SW gradients in uplift and exhumation shoe dynamically evolving magmatic systems, associated with the Kerguelen and Exmouth plumes. In addition, we present uncertainty propagation analysis. This analysis indicates that robust coverage and high-quality data on the Northwest Shelf reduces uncertainty in subsidence and exhumation estimates, thereby increasing our confidence in the results and conclusions from this study.
How to cite: Clark, S., Makuluni, P., and Hauser, J.: Dynamic Reconstructions of Basins in Australia: Stratigraphic Constraints on Cretaceous to Cenozoic Mantle Convection, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10561, https://doi.org/10.5194/egusphere-egu26-10561, 2026.
The Galápagos Islands’ unique endemic flora and fauna originated mainly from colonization from South and Central America, including the famous Galápagos iguanas. Genetic analysis suggests that these iguanas arrived from Central America ~5-12 Ma million years ago (Late Miocene) or even earlier, yet the oldest of the present-day islands were formed at ~3.5 Ma. Recent geophysical analysis shows that now-submerged islands along the Cocos Ridge (Galápagos hotspot track) provided terrestrial habitat for colonization and differentiation during the time frame ~6-18 Ma. Remarkably, this was also a time window during which ocean currents and winds were much more favorable for transport from mainland Central America to these ancient islands, prior to the closing of the Isthmus of Panama at ~3-5 Ma due to regional plate tectonic forces. Thus, we can explain both the colonization timing and provenance of Galápagos iguanas in a framework that shows much promise for understanding the origins of other unique Galápagos species.
How to cite: Richards, M., Gentile, G., Karnauskas, K., and Orellana-Rovirosa, F.: Geophysically Determined Island Habitat History and Colonization of the Galápagos Islands by Central American Iguanas, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15113, https://doi.org/10.5194/egusphere-egu26-15113, 2026.
True polar wander (TPW) records displacements of Earth’s rotation axis induced by mantle convective redistribution of internal mass anomalies. A TPW reversal near ~50 Ma inferred from paleomagnetic data remains debated, particularly its cause and its robustness across reference frames. We present 70-million-year, tomography-assimilative mantle-convection reconstructions that evolve present-day seismic structure backwards in time, with an energy-consistent flow formulation, yielding time-dependent density, inertia tensor, and TPW. Three independent diagnostics converge on a single, time-localized driver: (i) maps of the long-wavelength geoid-rate (∂N/∂t) show a focused Aleutian–Kamchatka lobe at 50 Ma; (ii) off-diagonal inertia-tensor time derivatives peak contemporaneously at this time; and (iii) cap-blanking experiments that zero anomalies within a 30–40° North-Pacific cap erase the U-turn, whereas comparable caps elsewhere do not. We interpret the causative structure as a coherent North-Pacific (“Kula–Izanagi” sensu lato) slab-flux pulse entering the lower mantle.
Predicted TPW paths quantitatively match palaeomagnetic trajectories across multiple mantle frames (reduced χ² ≈ 0.6; mean path-averaged angular misfit ≈ 1.7°) and reproduce the observed ~50 Ma U-turn bracketed by twin maxima in TPW speed. Present-day mantle-driven TPW rates of 0.2–0.4° Ma-1 imply ~20–40% of the 20th-century geodetic rate. In head-to-head tests, slab-history reconstructions (with or without hotspot-fixed “domes”) differ markedly in azimuth and TPW-speed evolution, tend to distribute path reorientation over 60–45 Ma, and yield substantially larger misfits to the same data.
These results (i) isolate a geographically localized, time-specific mantle driver of the ~50 Ma TPW reversal, (ii) demonstrate reference-frame robustness using explicit misfit metrics, and (iii) provide a transferable workflow – geoid-rate mapping, inertia-tensor derivatives, and cap-blanking – for attributing TPW events to concrete mantle processes.
How to cite: Forte, A., Glišović, P., Greff-Lefftz, M., Rowley (Deceased), D., and Kamali Lima, S.: A North-Pacific slab-flux pulse drove the ~50 Ma TPW reversal, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15742, https://doi.org/10.5194/egusphere-egu26-15742, 2026.
The emergence of plate-like surface motion in self-consistent mantle convection models is a key behaviour requiring detection in numerical experiment results featuring terrestrial characteristics. However, the identification and verification of candidate plates is a challenging task, in practice. On Earth, narrow divergent, convergent, and strike-slip plate boundaries as well as regions exhibiting widespread diffuse deformation, comprise roughly 10 to 20% of the lithosphere that does not adhere to rigid body motion. Accordingly, the detection of candidate plates must be performed in light of the existence of diffuse deformation occurring regularly as a tectonic characteristic. To address this challenge, we have recently developed a new plate detection tool, `platerecipy`, that utilizes the Random Walker (RW) segmentation algorithm to identify candidate plates in both mantle convection model output as well as global geophysical data sets and terrestrial measurements. We describe how the discrete probability solution arising from RW can be used to both assess confidence in the association of each location with a distinct rigid plate, and to identify diffuse surface regions. Furthermore, we show how utilizing the RW probabilities can significantly improve Euler vector inversion for fitting the plate motion as a probability field allows for a systematic means of incorporating uncertainties inherent to the plate detection process. We demonstrate the effectiveness of our method by applying it to the surface of a mantle convection model and a terrestrial strain-rate dataset. We show how our findings can be used for an Euler vector inversion that allows plate rigidity analysis.
How to cite: Javaheri, P. and Lowman, J.: Implementing Platerecipy: an open access tool utilizing a graph theory method for detecting tectonic plate boundaries in geophysical data sets and numerical model output, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8360, https://doi.org/10.5194/egusphere-egu26-8360, 2026.
The origin of the two large low-velocity provinces (LLVPs) remains debated today. The debate has often focused on their density, which can provide us insight into their origin. For example, if LLVPs were long-lived features, they would require a higher intrinsic density (the difference in density to the background mantle under the same temperature and pressure) than their surroundings to negate their positive thermal buoyancy and to remain physically stable at the base of the mantle for billions of years. Better constraints on the origin of LLVPs would provide further insight into dynamic processes at the lower boundary of the mantle. This has implications for how the deep mantle impacts Earth’s surface.
Long-wavelength observations of the geoid and core-mantle boundary (CMB) topography are particularly sensitive to the lowermost mantle. These observables have therefore been used to infer the density of LLVPs, often attributing a higher intrinsic density, if any, to chemical heterogeneity. Yet, many of these studies have not jointly considered the effects of chemical composition with the transition from bridgmanite to post-perovskite on lowermost mantle density. This phase transition is associated with a 1-2% increase in density, but occurs primarily in cold regions, thus impacting the amplitude and spatial patterns of the geoid and CMB topography. Therefore, the presence of post-perovskite can affect inferences of LLVP chemical composition and density from geodetic observables. It is therefore important to take the presence of post-perovskite into account when inferring LLVP density and chemical composition from geoid and CMB topography observations.
Here, we investigate the geodetic signatures expected from a range of scenarios related to the distribution of post-perovskite within different models of lowermost mantle temperature and composition. We calculate synthetic density fields from existing temperature and compositional fields as predicted by geodynamic simulations and a recent thermodynamic database. These density fields are then convolved with kernels derived from models of instantaneous mantle flow to obtain synthetic geodetic observables. We show that the effect of a higher post-perovskite density alone produces a comparable effect to chemical heterogeneity on the geoid and CMB topography. This implies that the effects of post-perovskite need to be taken into account when modelling dynamic processes and inferring physical properties in the deep mantle.
How to cite: Leung, J., Walker, A. M., Koelemeijer, P., and Davies, D. R.: Implications of post-perovskite on the density of lowermost mantle structures based on geoid and core-mantle boundary topography observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5779, https://doi.org/10.5194/egusphere-egu26-5779, 2026.
Iron content in the lower mantle significantly influences mineral density and mantle convection dynamics. Electrical conductivity, an important physical property of minerals and rocks, is highly sensitive to iron content. Ground-based and satellite geomagnetic observations reveal radial and lateral variations in electrical conductivity in the lower mantle, where some conductive anomalies are up to one order of magnitude higher than the ambient mantle. However, the poorly understood quantitative correlation between iron content and electrical conductivity hinders our ability to decipher the composition of the lower mantle. We systematically measured the electrical conductivity of Al-bearing bridgmanite, the most abundant mineral in the lower mantle, as a function of iron content (XFe= 0.1–0.37) at 27 GPa and temperatures up to 2000 K, corresponding to conditions in the uppermost lower mantle. Our results demonstrate that bridgmanite conductivity increases substantially with iron content while exhibiting minimal temperature dependence. This remarkable sensitivity of bridgmanite conductivity to iron content enables us to constrain the iron content of the lower mantle through geomagnetic observations.
How to cite: Han, K., Özaydın, S., Fei, H., Man, L., Wang, F., Chanyshev, A., Withers, A., Grayver, A., and Katsura, T.: Constraining iron content in the lower mantle through electrical conductivity of bridgmanite, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6558, https://doi.org/10.5194/egusphere-egu26-6558, 2026.
Heat flux at the Earth’s core-mantle boundary (CMB) partially controls the outer core dynamics and its associated geodynamo. On the mantle side, lateral variations in temperature above the CMB trigger lateral variations in heat flux with low temperature (typically, in and around subducted slabs) and high temperatures (at plumes roots and beneath hot thermo-chemical piles) areas being associated with high and low heat flux regions, respectively. Spatial and temporal variations in temperature are, in turn, controlled by details of mantle convection and mantle material properties. Here, we investigate the influence on CMB heat flux of two key parameters: the excess internal heating within piles of hot, dense material (also referred to as primordial material) modelling the large low shear-wave velocity provinces (LLSVPs) observed by global seismic tomography maps; and the temperature-dependence of thermal conductivity. For this, we perform a series of high-resolution numerical simulations of thermo-chemical convection in spherical annulus geometry using the code StagYY. Importantly, the total heating rate within the mantle is fixed, meaning that an excess heating within piles is balanced by a reduced heat released elsewhere. The initial condition on composition consists in a thin basal layer of chemically denser material, which subsequently evolves into piles of hot, primordial material on the top of which plumes are being generated. Our simulations show that the CMB heat flux is lower than the core adiabatic heat flux throughout the base of primordial material piles, and that it can be locally negative, i.e., heat flows from the mantle to the core. We further investigated the conditions needed for such patches to appear. As one would expect, a larger internal heating excess and a stronger temperature dependence of thermal conductivity both favor the development of negative heat flux patches. However, patches disappear if the piles excess heating gets too large. In this case, heat released in the regular mantle is strongly reduced, allowing plumes generated at the top of piles to extract more heat from these piles. Finally, our simulations predict relatively large CMB heat flux spatial heterogeneity, together with substantial temporal variations in this heterogeneity. Our findings have strong implications for core dynamics. In particular, they support the hypothesis that partial stratification at the top of the core can occur beneath LLSVPs, reconciling geomagnetic and seismic observations. In addition, and based on core dynamics studies, the CMB heat flux heterogeneity and temporal variations predicted by our simulations may play a key role in the occurrence of geomagnetic superchrons.
How to cite: Deschamps, F., Guerrero, J., Amit, H., Terra-nova, F., and Hsieh, W.-P.: Patches of negative core-mantle boundary heat flux: simulations of mantle convection and implications for core dynamics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2141, https://doi.org/10.5194/egusphere-egu26-2141, 2026.
Constraining the transport of mass in the Earth’s mantle over a broad range of timescales is a key step in order to understand the mantle convection and its dynamic interactions with tectonic plates and core flows. Mapped with high accuracy all over the globe from GRACE and GRACE Follow-On satellite missions, the temporal variations of the gravity field can provide unique information on potential rapid mass redistributions within the Earth’s deep interior, even if their separation with the signals from the Earth’s fluid enveloppe is challenging. In the present study, we focus on the base of the mantle and the boundary with the core (CMB). Applying dedicated methods of space-time patterns recognition in the gravity field, we identify a rapid, anomalous north-south oriented gravity signal at large spatial scales across the Eastern Atlantic ocean in January 2007, which evolves over months to years. We show that this signal likely originates, at least partly, from the solid Earth ; it appears concomittant, both spatially and temporally, with the 2007 geomagnetic jerk. We hypothesize that it may be induced by vertical displacements of the perovskite to post-perovskite phase transition, caused by moving thermal anomalies near the base of the African Large Low Shear Velocity Province. This may result in the creation of a decimetric dynamic CMB topography over a timespan of a few years. To assess a potential link with the 2007 geomagnetic jerk, we finally investigate the impact of these changes in core-mantle boundary topography on the flow and the geomagnetic field in a thin layer at the top of the core. These results stress the interest of satellite gravimetry for providing novel insights into the dynamical interactions between the mantle and the core.
How to cite: Gaugne Gouranton, C., Panet, I., Mandea, M., Greff-Lefftz, M., and Rosat, S.: Rapid mass redistributions in the deep mantle from satellite gravity and interactions with core flows, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12420, https://doi.org/10.5194/egusphere-egu26-12420, 2026.
During the last 7 years several groups have reported paleomagnetic data documenting an unprecedented interval during the Ediacaran Period when the global geomagnetic field strength was only 10 to 3 percent of the present-day value, defining an ultra-low time-averaged field interval (UL-TAFI) from 591 to 565 Ma. Moreover, the EMANATE hypothesis suggests that atmospheric H loss to space through the UL-TAFI weak magnetosphere led to increased oxygenation, assisting the Avalon explosion of animal life (Tarduno et al., 2025). A relatively rapid increase in field strengths after the UL-TAFI has been suggested to record the onset of inner core nucleation; the return of magnetic shielding may have assisted subsequent Cambrian evolution. Herein, we present new data that suggest: 1. the UL-TAFI was at least 90 million years long, beginning in the Cryogenian Period and, 2. the field may have completely collapsed to zero during events as long as 200 kyr within the UL-TAFI. While the existence of the UL-TAFI does not comment on the need for core supercooling for inner core nucleation, the extended duration defined here is compatible with some models for such a process. Variations of the field strength and dipolarity within the UL-TAFI may record bistability between the weak and strong field branches of the geodynamo as seen in some numerical simulations. This bistability, proposed to characterize the very start of the geodynamo, may have also been the underlying nature of the field during late Neoproterozoic times, explaining seemingly anomalous magnetic directions from global sites. The extended duration of the UL-TAFI, and the episodic complete collapse of the dynamo, support the hypothesis that H loss and increased oxygenation of the atmosphere and ocean, enabled the radiation of macroscopic Ediacaran animal life.
How to cite: Tarduno, J., Blackman, E., Schneider, J., and Cottrell, R.: A fibrillating Cryogenian-Ediacaran magnetic field: Implications for the nature of the dynamo, inner core nucleation, and the Avalon explosion of life, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15540, https://doi.org/10.5194/egusphere-egu26-15540, 2026.
The Earth has possessed a magnetic field for at least ~4.3 Ga, as indicated by paleomagnetic data. To constrain Earth’s thermal and magnetic evolution, parameterized core models have traditionally relied on a parameterized mantle assumed to be vigorously convecting due to plate tectonics. By neglecting spatial variations in mantle temperature and viscosity, these models typically predict an inner core nucleation (ICN) age of 0.5–0.8 Ga, which requires a thermally driven dynamo prior to that time. Recent experimental constraints indicating higher core thermal conductivities have therefore led to the “new core paradox,” in which sub-adiabatic conditions can result in gigayear-long interruptions of the modeled geodynamo.
Alternatively, studies that couple higher-dimensional mantle convection models with parameterized core evolution have found that hot initial core temperatures and an insulating primordial lid above the core–mantle boundary (CMB) are required to reproduce the present-day inner core size, with minimal influence from the surface tectonic regime. However, these studies did not predict magnetic field strengths and showed that the available magnetic dissipation overestimates Earth’s magnetic field in the early evolution and underestimates it at later times.
Here, we present a new two-dimensional mantle convection model coupled to a core evolution model that incorporates state-of-the-art mineral physics data and magnetic field strength scaling laws. Our results require a ~200 km thick primordial dense layer and the presence of the post-perovskite phase at the base of the mantle, forming a CMB thermal lid that inhibits strong early core-cooling. By varying surface plasticity and the maximum density contrast of the lower mantle relative to the ambient mantle, we identify best-fit models that reproduce both inner core growth and the secular variation of the magnetic field.
Assuming a bulk silicate Earth (BSE) composition, 12 wt.% light elements in the core, a core thermal conductivity of 125 W m⁻¹ K⁻¹, an initial CMB temperature of 4564 K, and a CMB lid that is 7% denser than peridotite, ICN occurs at ~1.3 Ga, while the thermal dynamo ceases after ~3 Ga. Future constraints on the presence and evolution of a thermally stable layer in the core will further refine models of Earth’s magnetic field evolution.
How to cite: Müller, L., Kislyakova, K., Noack, L., Macdonald, E., Van Looveren, G., and Raorane, A.: Core–mantle coupling: New insights into the magnetic and thermal evolution of Earth, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12612, https://doi.org/10.5194/egusphere-egu26-12612, 2026.
The Earth has sustained a magnetic field for at least 3.4 billion years, generated by convective motions of liquid iron within the outer core. Maintaining such a long-lived geodynamo requires efficient cooling of the core. However, a high core thermal conductivity as suggested by experiments and theoretical calculations reduces the convective power available prior to inner-core nucleation, making the continuous persistence of the magnetic field more difficult. This apparent incompatibility between high thermal conductivity estimates and evidence for a ~3.4 Ga-long geodynamo is known as the “New Core Paradox”. Because core cooling is primarily controlled by heat transfer through the overlying solid mantle, an accurate quantification of the heat extracted from the core via mantle convection is therefore essential to resolving this paradox.
Today, the mantle cools efficiently mainly through plate tectonics, via subduction of cold large plates. But when plate tectonics actually began is still debated. Did it start soon after Earth formed, around 4.5 billion years ago? Did it appear later, between 4 and 3 billion years ago? Or is it a more recent process, less than a billion years old?
We explored how different styles of mantle cooling would have influenced Earth’s thermal and magnetic history. We explored either a mobile surface like modern plate tectonics (i.e. mobile lid) or a less efficient, stagnant-lid-like regime (where the surface doesn’t move), or a transition from stagnant- to mobile-lid regime at a given time and with a given duration. This is important because how Earth’s mantle cooled over time is closely tied to its ability to keep generating a magnetic field.
We built a global model for the Earth coupling a core model including inner core formation and the possibility to form stably stratified layers, with a mantle model simulating different convective (hence cooling) regimes.
We performed a Markov Chain-Monte Carlo inversion using as constraints the present-day size of the inner core, the continuous 3.4 billion years old magnetic record, and the mantle potential temperature record. We inverted the viscosity parameters, tectonic transition parameters and core thermal conductivity. Our models successfully reproduce all the constraints for an onset between 4.0 Ga and 2.5 Ga, with a bimodal distribution characterized by a relatively early onset of mobile-lid convection with a long-duration transition, or a later onset with a more rapid transition to a mobile-lid regime. Our result show that the late and rapid transition case allows for a core thermal conductivity up to 110 W/m/K, providing a possible solution to the New Core Paradox.
How to cite: Bonnet Gibet, V. and Tosi, N.: A late onset of plate tectonics as a solution of the New Core Paradox., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13060, https://doi.org/10.5194/egusphere-egu26-13060, 2026.
The structure of the Earth's deep mantle is a result of complex processes that are influenced by surface tectonics through the subduction of oceanic lithosphere and by core dynamics through the heat flow across the core-mantle-boundary. The other way around the structures in the deep mantle affect the Earth's surface by feeding mantle plumes that sustain volcanism. By modulating the heat flow at the CMB the mantle also affects the dynamics of the core and the magnetic field.
These processes focus in the D'' layer that marks the mysterious few hundred kilometers directly above the core-mantle-boundary which contain dominant features like the Large Low Shear Velocity Provinces and features with rather extreme properties like the Ultra Low Velocity Zones. Knowledge of the structural features in the D'' layer is of importance for the understanding of long- and short-term processes in our direct environment at the surface of the Earth.
The remoteness of D'' layer more than 2,500 kilometers below the surface poses challenges for geophysical investigations and limits the resolution of seismological imaging. Seismic tomography with surface waves and normal modes therefor locate the large scale features, only. Detailed wavefield analysis and modeling of particular seismic phases, often based on array observations provide more detailed information about locally dominating structures and their contrasts. For the characterization of distributed small scale structures that can be referred to as heterogeneity even wavefield analysis fails due to the superposition of waves scattered at different locations of the heterogeneous material. Such heterogeneity can for instance represent remnants of oceanic crust that has been subducted down to the CMB.
Despite the complexity of signals generated by distributed heterogeneity the analysis of high frequency scattered waves provides constraints on the presence structures at short length scales of a few kilometers in the deep mantle. I review the theoretical basics of scattering theory and the observational evidence for deep Earth distributed heterogeneity. I discuss new observations of high frequency seismic waves scattered in the deep mantle together with limitations in the interpretation imposed by the nature of the scattered wavefield.
How to cite: Sens-Schönfelder, C.: Investigating small-scale deep-mantle structure, the stories told by high frequency scattered waves, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14881, https://doi.org/10.5194/egusphere-egu26-14881, 2026.
The structure of Earth's crust, mantle, and core holds clues to its thermal state and chemical composition, and, in turn, its origin and evolution. Geophysical techniques, and seismology in particular, have proved successful at probing Earth's deep interior and have done much to advance our understanding of its inner workings from mantle convection to crystallization and solidification of Earth’s liquid core. As the outer core cools and solidifies, light elements, such as Si, S, C, O and H, preferentially partition in the fluid outer core. However, the exact composition and thermal state of the outer core remains unknown. Traditionally, the composition of the core has been determined by performing theoretical ab initio calculations on candidate compositions and comparing the results for Vp, Vs and density to seismic reference models (e.g., PREM). Instead, we determine structure, composition and thermal state of Earth's outer core by inverting a plethora of short- and long-period seismic and astronomic-geodetic data in combination with new density functional theory calculations that are fit to a novel Gaussian Process Regression (GPR) equation of state (EoS). The GPR-EoS allows us to self-consistently compute thermo-elastic properties of liquid multi-component mixing models in the Fe-Ni-Si-S-C-O-H system along outer-core adiabats and across its entire pressure and temperature range. By mapping out the thermo-chemical model space of Earth’s outer core that match the seismic and geophysical data within uncertainties, we find two families of solutions characterised by: 1) Si (~4 wt%) and negligible amounts of H and C and 2) C and H (both 0.5 wt%) and smaller amounts of Si (<1 wt%). A correlation between H content and outer-core thermal structure is apparent, such that solutions with little-to-no H correspond to relatively high CMB and ICB temperatures (4100--4400~K and 5750–6000 K, respectively), whereas models with large amounts of H are characterised by lower CMB and ICB temperatures (~3600 K and 4750 K).
How to cite: Munch, F. D., van Driel, J., Khan, A., Brodholt, J., and Vocadlo, L.: Unraveling the composition and structure of the Earth's outer core, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17208, https://doi.org/10.5194/egusphere-egu26-17208, 2026.
Recent advances in geodynamo modelling have been very successful in explaining many features of the geo-
magnetic field, including the field reversals and excursions. Previous studies have shown that the dynamics
of these features depend on spatial variation in the core-mantle boundary (CMB) heat flux pattern. Contrary to
previous studies, an up-to-date mantle reconstruction for the last 200 Myr provides patterns with a higher degree
of complexity, featuring a network of interconnected regions with subadiabatic heat flow. We use these patterns
as outer boundary conditions for dynamo simulation in order to explore whether its evolution can explain the
observed variation in reversal rate. While the impact of large-scale structures at the core-mantle boundary has
been thoroughly explored by Frasson et al. (2025), the contribution of smaller scales remains poorly constrained,
which we aim to cover within the scope of these studies.
For our study, we apply the codensity approach which combines the effects of thermal and compositional density
to represent both thermally driven convection and the enrichment of the outer core with light elements due to
the inner core solidification. We first investigate the relative impact of thermal and compositional convection
a for patterns with various degrees of complexity, defined by the spherical harmonics degree truncation lmax.
Our models indicate that the field dynamics, including the reversal rate, depends on the truncation lmax, with
solutions for lmax = 8 and lmax = 16 exhibiting more reversals than higher truncation degrees. This effect is
present in models with mixed convection (a = 0.33 and a = 0.66). However, when compositional convection
clearly dominates (a = 0.99), the pattern has no impact on the reversal behaviour, and the model evolves
similarly to the homogeneous case. We also observe the emergence of subsurface low-radial-velocity regions,
reminiscent of the stably-stratified lenses discussed by Mound et al. (2019). Our models also show strong
zonal flows comparable to those discussed in Frasson et al. (2025). Our ongoing work focuses on comparing
simulations for the CMB heat flux pattern at the present-day time and during the CNS.
How to cite: Lohay, I. and Wicht, J.: Influence of Small-Scale Core-Mantle Boundary Structures on the Dynamics of the Earth’s Outer Core, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20825, https://doi.org/10.5194/egusphere-egu26-20825, 2026.
The geomagnetic field has undergone hundreds of polarity reversals over Earth's history, at a variable pace. In numerical models of Earth's core dynamics, reversals occur with increasing frequency when the convective forcing is increased past a critical level. This transition has previously been related to the influence of inertia in the force balance. Because this force is subdominant in Earth's core, concerns have been raised regarding the geophysical applicability of this paradigm. Reproducing the reversal rate of the past million years also requires forcing conditions that do not guarantee that the rest of the geomagnetic variation spectrum is reproduced. These issues motivate the search for alternative reversal mechanisms. Using a suite of numerical models where buoyancy is provided at the bottom of the core by inner-core freezing, we show that the magnetic dipole amplitude is controlled by the relative strength of subsurface upwellings and horizontal circulation at the core surface. A relative weakening of upwellings brings the system from a stable to a reversing dipole state. This mechanism is purely kinematic because it operates irrespectively of the interior force balance. It is therefore expected to apply at the physical conditions of Earth's core. Subsurface upwellings may be impeded by stable stratification in the outermost core. We show that with weak stratification levels corresponding to a nearly adiabatic core surface heat flow, a single model reproduces the observed geomagnetic variations ranging from decades to millions of years. In contrast with the existing paradigm, reversals caused by this stable top core mechanism become more frequent when the level of stratification increases i.e. when the core heat flow decreases. This suggests that the link between mantle dynamics and magnetic reversal frequency needs to be reexamined.
How to cite: Aubert, J., Landeau, M., Fournier, A., and Gastine, T.: Core-surface kinematic control of polarity reversals in advanced geodynamo simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3465, https://doi.org/10.5194/egusphere-egu26-3465, 2026.
Geomagnetic jerks are the fastest variations we observe in secular variation (SV) of the internal geomagnetic field. They have been deemed spatiotemporally unpredictable, and thus make it difficult to forecast magnetic field changes. Recent core surface flow-inversions of satellite SV data show that pulses in modelled azimuthal flow acceleration are contemporaneous with localised low latitude jerks observed in the Atlantic and Pacific from 2000—2024.
In order to explore to what extent such pulses might be responsible for observed geomagnetic jerks, we simulate them with synthetic flow models. We use a Fisher–Von Mises probability distribution to spatially define the pulse, which ensures that its spherical harmonic expansion in terms of poloidal and toroidal spherical harmonic coefficients converges. To recover a dynamic flow, we add uncorrelated noise to these toroidal and poloidal acceleration coefficients. After this, we obtain SV from flow acceleration using the diffusionless induction equation, investigating a variety of background flows and core-surface magnetic field structures with our flow-acceleration pulse. Finally, we plot the expected SV at the Earth’s surface.
We successfully generate geomagnetic jerks, similar to those observed by CHAMP in the Atlantic in 2003.5 and 2007, and Swarm in the Pacific in 2017 and 2020. This pulse-like simulator for low-latitude jerks is in agreement with results from numerical dynamo simulations, which suggest that jerks originate from Alfvén wave packets emitted from the inner-outer core boundary. Our results further suggest that there is no need for waves longitudinally propagating along the outer core surface for jerks to occur.
How to cite: Madsen, F., Whaler, K., Brown, W., Beggan, C., and Holme, R.: Geomagnetic jerks as core surface flow acceleration pulses – observations and simulations., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-255, https://doi.org/10.5194/egusphere-egu26-255, 2026.
In data assimilation, smoothers improve estimates of the system state by incorporating future observations. However, in geomagnetic data assimilation, the application of smoothers requires solving complex adjoint operators associated with the full nonlinear MHD equations, and the computation of gradients of the objective function is computationally expensive. Here, we employ the ensemble Kalman smoother (EnKS), which exploits ensemble-based statistical correlations across different times and thereby avoids the explicit construction of adjoint operators. We evaluate the performance of EnKS using synthetic observation experiments in moderately nonlinear models and compare it with Ensemble Kalman Filter (EnKF). The results show that both methods recover similar velocity field structures. EnKS exhibits velocity intensities closer to the reference model and performs better in the recovery of the surface flows. However, EnKS is more sensitive to sampling errors, which lead to filter divergence in the magnetic field. We further examine the impact of model error on EnKS, where the model error only arises from variations in viscous effects. The results show that model error causes the loss recovery of some dominant velocity field modes in the recovered solution and ultimately leads to filter divergence. Overall, our results indicate that EnKS can further improve recovery quality in regimes where EnKF already achieves reasonable performance, but may perform worse in regions strongly affected by sampling errors.
How to cite: Zhipeng, Z. and Yufeng, L.: Geomagnetic data assimilation utilizing the ensemble Kalman smoother, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2437, https://doi.org/10.5194/egusphere-egu26-2437, 2026.
Dynamo action in Earth's liquid-iron core has generated a magnetic field for at least 3.4 billion years. Prior the onset of solidification that formed the inner core at about 1 Ga, the energy source driving the geodynamo is unknown. Contemporaneously, the bottom of the mantle may have been fully molten, forming a basal magma ocean. We propose that the boundary between this silicate magma and the immiscible, liquid core was susceptible to tides driven by the Moon’s gravity. We present theoretical predictions for the laminar component of this tidal flow. Our results indicate that a tidal resonance provided enough energy to sustain dynamo action for ~3.5 Gyr by turbulent magnetic induction. Lunar tides may thus have played a key role in generating Earth's ancient magnetic field, which shielded early life from solar radiation.
How to cite: Katz, R. F., Kiernan, M. B. C., Hay, H. C. F. C., Rees Jones, D. W., and Bryson, J. F. J.: Ancient geodynamo driven by lunar tides beneath a basal magma ocean, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2575, https://doi.org/10.5194/egusphere-egu26-2575, 2026.
Understanding the stable phase of iron under Earth's inner core conditions is fundamental to interpreting its composition, evolution, and dynamics. Despite its importance, the stability of candidate phases (e.g., bcc, fcc, hcp) remains contentious due to the extreme pressure-temperature conditions and the meagre free energy differences (~10 meV/atom) between them. This has resulted in conflicting predictions from ab initio, force field, and machine learning approaches. To resolve this discrepancy, we introduce a Bain-path thermodynamic integration (BP-TI) method that directly computes free energy differences from the work performed by internal stress along a transformation path. This approach eliminates the need for an external reference system and avoids the uncertainties associated with conventional entropy calculations. Applying this rigorous benchmark with strict convergence criteria, we find that hcp Fe is the thermodynamically stable phase with the highest melting temperature under inner core conditions. In contrast, bcc Fe is consistently shown to be metastable across all tested interatomic potentials and computational methods. This metastability is intrinsic, persisting independent of simulation cell size and thus is not a finite-size artifact. Our findings reconcile previous disparities and provide a robust thermodynamic foundation for future studies of inner-core properties and dynamics.
How to cite: Yang, H., Wan, L., Li, Y., Vočadlo, L., and Brodholt, J.: Resolving the Iron Phase Stability Debate in Earth's Inner Core: A Consistent Thermodynamic Benchmark, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6077, https://doi.org/10.5194/egusphere-egu26-6077, 2026.
Light elements are thought to be essential components of liquid cores in terrestrial planets and play a key role in core formation, chemical evolution, and the generation of planetary magnetic fields. In multicomponent iron–light element (Fe–LE) systems, when multiple light elements coexist in liquid iron, their solubilities are mutually constrained, forming an anti-correlated solubility relationship, referred to here as simultaneous solubility.
Here we investigate the simultaneous solubility and exsolution behavior of light elements in the Fe–Si–C–(H) system using a combination of high-pressure and high-temperature experiments and machine-learning force field accelerated molecular dynamics (MLFF-MD) simulations. Multi-anvil experiments conducted at pressures of 9–21 GPa and temperatures of 1400–2200 °C reveal that these light elements can dissolve simultaneously in liquid iron and exhibit simultaneous solubility limits, with exsolution of Si, C, and H observed during melting and quenching. Complementary MLFF-MD simulations of the Fe–Si–C system provide atomic-scale insights into light element interactions in metallic melts and reproduce the experimentally observed anti-correlated solubility trends under core-relevant conditions.
By combining experimental and computational results, we derive simultaneous solubility relationships in the Fe–Si–C–(H) system and show how they vary with temperature and pressure. These results suggest that in reduced planetary cores, such as those of Mercury and Earth, Si, C, and H may coexist as simultaneously dissolved light elements. As the liquid core cools, the progressive decrease in simultaneous solubility drives continuous exsolution of light elements, providing an additional potential energy source for core dynamics and offering a potential explanation for chemical heterogeneity at the core–mantle boundary (CMB).
How to cite: Li, Y. and Zhu, F.: Light Elements Exsolution in the Fe–Si–C–(H) System of Terrestrial Planet Liquid Cores, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13280, https://doi.org/10.5194/egusphere-egu26-13280, 2026.
Earth’s magnetosphere is generated by convective dynamo action within its liquid metallic outer core. This same core-driven dynamo process has been inferred for other terrestrial planetary bodies which either presently possess a magnetosphere, or may have in the past. These bodies include Ganymede, Mercury, the Moon, and Asteroid 4 Vesta. However, understanding these core processes requires that the core composition be known. By experimentally determining the solid-liquid phase transitions of core-relevant alloys, the likely compositions of these terrestrial cores may be constrained.
Experiments were conducted on 8 Fe-Si alloys in the range of Fe-5 wt% Si to Fe-33 wt% Si (FeSi) using a 1000-ton cubic anvil press, at pressures of 3-5 GPa and temperatures into the liquid state. A central 5-hole BN cylinder held 5 different Fe-Si sample compositions simultaneously with a thermocouple located at the base of the BN cylinder, and was surrounded by a graphite furnace within a pyrophyllite cubic pressure cell. Following quenching of each experiment, the samples were analysed by electron microprobe for composition and texture. From these analyses, the solidus and liquidus boundaries were mapped across the aforementioned compositional range at of 3, 4, and 5 GPa.
It was determined that the melting boundary for 3-5 GPa was roughly 50-150 K higher than that of 1 atm, with a eutectic composition of Fe-20 wt% Si. Across the 3-5 GPa range, there was an increase in the melting boundary of roughly 50-75 K. Using pressure and temperature estimates from previous core modelling studies, a range of approximately 10-15 wt% Si was suggested for the core of the Moon.
How to cite: Kalman, B., Yong, W., and Secco, R.: High pressure melting of Fe-Si alloys with applications to the lunar core composition and dynamo processes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13514, https://doi.org/10.5194/egusphere-egu26-13514, 2026.
Posters on site: Tue, 5 May, 14:00–15:45 | Hall X2
Seismic data from the InSight mission reveal that Mars possesses a structure comprising a crust, mantle, and core, with recent studies indicating the existence of a solid inner core. While the composition of the inner core of Mars remains unclear, but some scholars argue that it might be FeO and/or Fe3C. Here, the thermoelastic properties of high‑spin antiferromagnetic B1‑phase FeO was derived from first‑principles calculations, and the composition of the core was inverted by combining with the previous experimental data. Additionally, the possible light element components in the Martian outer core have also been restricted. These results provide a new starting point for the composition of the Martian core and might have implications for understanding the chemical composition and magnetic evolution of the Mars.
How to cite: Pan, Z., Wang, W., and Wu, Z.: High‑Spin Antiferromagnetic B1‑Phase FeO: Implications for the Martian Inner core, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6533, https://doi.org/10.5194/egusphere-egu26-6533, 2026.
The majority of metallic materials exhibit viscoelastic or anelastic behavior when subjected to elastic cyclic loading under specific temperature and frequency conditions. This anelastic nature is commonly characterized by the dissipation or loss of mechanical energy, manifested as a hysteresis loop between stress-strain signals. The energy loss is quantified by the loss tangent (tanδ) or the inverse of quality factor (Q-1). The origin of this dissipation is associated with internal variables, particularly the microstructure, and this phenomenon is referred to as internal friction. The microstructures are inherently complex, and their overall response is governed by multiple factors such as solute type and content, crystallographic texture, dislocation density, residual stresses, and grain boundary characteristics. Consequently, any modification in microstructure directly influences the internal friction behavior. Additionally, the operating temperature and imposed frequency strongly affect the magnitude of tanδ. This work provides a comprehensive summary of the role of microstructural parameters on the viscoelastic behavior of various metals over a wide range of length and time scales and over an extensive temperature range.
Subsequently, the understanding of internal friction in metallic materials is extended to the earth’s inner core. It is well established that inner core exists under extreme conditions, with very high temperatures (~5700 K) and extremely high pressures (~330 GPa). Under such conditions, reliable estimates of seismic wave dissipation or attenuation are not readily available. At same time, the underlying mechanisms governing seismic wave propagation remain unclear. This study provides a summary and proposes plausible attenuation mechanisms in the earth’s inner core over a range of testing conditions. These are supported by dynamic mechanical analysis (DMA) experiments and atomistic simulations.
How to cite: Manda, S., Carin, L., Kolesnikov, E., Chantel, J., Hilairet, N., and Merkel, S.: Understanding Relaxation Mechanisms in Metals: Application to Earth’s Inner Core , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5754, https://doi.org/10.5194/egusphere-egu26-5754, 2026.
The nature and properties of the inner core has been a topic of keen interest since its discovery as a solid body by Lehmann in 1936. Since then, there have been numerous studies into its (isotropic and anisotropic) velocity and attenuation structure. These models typically feature strong hemispherical and layered structures, which dominate the interpretations of these models.
In this study, we focus on the attenuation structure of the inner core: energy that is lost inelastically, i.e. not through elastic scattering or redistribution. Here, we will demonstrate the progress we have made in creating a data set of new measurements of attenuation in the inner core from a variety of seismic phases (but especially PKPdf-PKPbc) with a focus on improving the spatial distribution of observations from previous studies using earthquakes from 2018--2025. We go on to benchmark our results against those of Pejic et al (2017), who used 400 high quality dt* measurements to invert for attenuation structure in the uppermost 400 km of the inner core.
How to cite: Martin, C. and Tkalčić, H.: New measurements of inner core attenuation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15485, https://doi.org/10.5194/egusphere-egu26-15485, 2026.
The Earth’s inner core is made of a solid iron alloy. Seismic observations suggest a structure and an anisotropy which leads to variations in both the velocity and the attenuation of the seismic waves. Attenuation is the loss of energy during the propagation of the seismic waves. Whether this attenuation arises from intrinsic properties of the iron alloys or extrinsic origins remains an open question. In this context, studying attenuation in metallic alloys could help improving our knowledge about the physical properties and the geodynamic of the inner core.
Extrinsic attenuation is linked to external environment that impact the wave propagation, such as scattering or heterogeneities. Intrinsic sources are related to the properties of the material itself such as its viscoelastic behavior. This work focuses on the latter and particularly on the anelastic relaxation, which is one of the sources of internal friction.
In this work, we seek to understand attenuation mechanisms in metals at high temperature. The experiments are conducted on a dynamic mechanical analysis (DMA) instrument with control of temperature and oxygen fugacity albeit at ambient pressure. We use a Mg alloy as analogous material to that of the inner core, which presents similar crystallographic structure and is expected to behave the same way.
Here, we will present some results and hypotheses derived from temperature, frequency, and strain sweeps realized with DMA. These analyses allow us to investigate viscoelastic values like internal friction, storage and loss modulus at different conditions. Results show a temperature-dependent behavior that can be related to the underlying mechanisms. Scanning electron microscopy analyses (electron back scattered diffraction) were performed to further assess the attenuation mechanisms involved in our experiments. Grain size, texture or grain boundaries were analyzed to understand our analogous material. These experiments are led in conditions which could allow us to discuss attenuation in the inner core.
How to cite: Carin, L., Manda, S., Kolesnikov, E., Chantel, J., Hilairet, N., and Merkel, S.: First results for experiments on inner core attenuation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5753, https://doi.org/10.5194/egusphere-egu26-5753, 2026.
The thermal conductivity of iron and iron alloys play a key role in determining how telluric planetary cores cool over time. The thermal conductivity of core-forming alloys is needed to establish the heat budget for core and mantle processes. This budget in turn controls the characteristics of core and mantle dynamics, as well as the geologic timescales over which they are active. However, there is little consensus on the effect of composition on the thermal conductivity of iron at conditions relevant to planetary interiors. Here I present the results of recent experimental investigations to understand how the thermal conductivity varies for iron and iron alloys varies at extreme pressures and temperatures, providing quantitative insight into the transport properties of core-forming alloys.
How to cite: Edmund, E.: Thermal Conductivity of Iron and Iron Alloys at Planetary Core Conditions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3504, https://doi.org/10.5194/egusphere-egu26-3504, 2026.
The geomagnetic field undergoes both long-term and short-term deviations from its predominantly dipolar configuration, expressed as polarity reversals and geomagnetic excursions. These episodes are characterized by significant drops in field intensity and an increase in the paleosecular variation index (PSV index), reflecting changes in the underlying geodynamo. This work focuses on analysing the temporal evolution of the field during these events in order to better constrain the dynamics of the geodynamo.
We utilized some of the most reliable paleomagnetic data-based models such as LSMOD.2, GGFSS70, GGFMB and PADM2M, encompassing different time periods to analyse the rate of change in the dipole moment and the PSV index. A sawtooth pattern of gradual dipole decay followed by rapid recovery during reversals, as proposed by past studies, has been observed in our study on the Matuyama Brunhes reversal. But, in contrast, we observed an opposite behavior of fast decay and slow recovery during most of the excursions. Accordingly, the PSV index exhibited a slow growth–fast recovery pattern during the reversal and a fast decay–slow recovery pattern during many excursions, although the PSV index results vary more than the dipole moment results. In this study, we test whether similar or distinct asymmetries characterize the Gauss–Matuyama reversal. The preliminary outputs from the newly developing Gauss–Matuyama field model were made use for that. Here, we will report the results of this ongoing work.
How to cite: Shinu, S., Nasser Mahgoub Ahmed, A., and Korte, M.: Geomagnetic Field Dynamics During Excursions and Reversals, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17051, https://doi.org/10.5194/egusphere-egu26-17051, 2026.
The investigation of geomagnetic variations has revealed the presence in Earth's core of a planetary-scale, axially columnar and eccentric gyre flow. Together with the magnetic anomaly of low intensity presently seen beneath the South Atlantic, these structures show that longitudinal hemisphericity is a common feature of the geodynamo. Here, we propose that these hemispherical features result from the onset properties of spherical shell rotating convection in presence of an imposed axial magnetic field, with spatially homogeneous fixed-flux thermal boundary conditions. For an Earth-like range of background magnetic field amplitudes, we find hemispherical critical convection modes that are largely supported by a magneto-Archimedes-Coriolis (MAC) balance and where viscosity plays a secondary role. Pursuing this analysis with fully developed, turbulent self-sustained dynamo simulations, we find that hemispherical modes inherited from convection onset can be maintained if the MAC balance is not perturbed by inertia, the force coming at the next order in the force balance. The presence of the eccentric gyre is therefore conditioned to the magnetic energy matching or exceeding the kinetic energy in the system, the so-called strong-field dynamo regime. The simulations also feature low magnetic intensity anomalies that rotate westward together with the gyre flow. We highlight a strong correlation between the gyre longitudinal position, the low intensity focus of magnetic intensity, and the eccentricity of the dynamo-generated dipole, showing that these hemispherical structures are indeed linked by the properties of magnetic induction.
How to cite: Grasset, L.: Longitudinally hemispheric structures in the geodynamo : from their physical origin to their geomagnetic consequences, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21834, https://doi.org/10.5194/egusphere-egu26-21834, 2026.
Small-scale lateral heterogeneities at the lowermost mantle are fundamental to understanding mantle convection dynamics and core-mantle interactions. PKP precursors, generated by seismic scattering from fine-scale structures near the core-mantle boundary (CMB), provide a powerful yet underutilized probe for imaging deep Earth heterogeneities. However, the manual identification of these weak signals is inefficient, subjective, and inadequate for the vast volumes of modern seismic data.
We present a comprehensive analysis of global PKP precursor observations using a supervised deep learning framework combined with iterative human-guided optimization. Processing over 2 million vertical-component waveforms from earthquakes (Mw ≥ 6.0) recorded between 1990 and 2024, we automatically identified 227,770 high-quality PKP precursor signals—an order of magnitude increase compared to previous global compilations. This unprecedented dataset, termed DeepScatter-PKP, provides the densest and most spatially complete observational foundation for characterizing CMB scattering structures to date.
To systematically evaluate the stability and spatial distribution of scattering signals, we developed a dual-probability framework integrating precursor occurrence probability (Pocc) and scatterer location probability (Pscat). This approach enables simultaneous assessment of broad-area scattering stability and precise localization of strong scatterers. Our significantly enhanced sampling density and coverage connect previously isolated scattering patches into continuous anomaly belts, notably beneath the Pan-American region and the western Pacific margin.
Cross-validation with independent seismic phases confirms the robust embedding of multiple ultra-low velocity zones (ULVZs) within diverse velocity heterogeneity backgrounds, suggesting thermochemical origins involving remnants of multi-episode subducted slabs, partial melting, and interactions with large low-velocity provinces (LLVPs). Extension to undersampled regions reveals six previously unidentified high-potential strong scattering zones, including beneath the South Atlantic, high-latitude Eurasia, and circum-Antarctic domains.
Our results demonstrate that small-scale scatterers occur in both high-velocity and low-velocity domains, highlighting the diversity and independence of their origins beyond LLSVP boundaries. The DeepScatter-PKP dataset and dual-probability framework establish priority targets for future multi-phase joint inversions and high-resolution CMB imaging, offering new constraints on the thermochemical state and dynamic evolution of Earth's deep interior.
How to cite: Guan, Y., Li, J., Xiao, Z., Wang, W., and Xu, T.: Global Mapping of Small-Scale Heterogeneities at the Core-Mantle Boundary: Insights from Deep Learning Analysis of PKP Precursors, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4040, https://doi.org/10.5194/egusphere-egu26-4040, 2026.
High-frequency seismic scattered waves provide unique sensitivity to small-scale heterogeneity in the lowermost mantle and at the core mantle boundary (CMB), but their interpretation is challenged by wavefront healing and the huge cost of full-waveform simulations at frequencies above about 1 Hz. We evaluate the precision of radiative transfer equation (RTE) modelling compared with wave equation (WE) modelling to establish a basis for future coupled RTE-WE approaches to high-frequency seismic scattering at the CMB.
We have used the RTE based on the Monte Carlo method to efficiently simulate the global transport of seismic energy with a 1D spherical symmetrical model and reproduced scattered waves, such as PKP precursors and Pdiff coda. Now, WE simulations are employed in localised CMB domains to resolve deterministic wave structure interactions, including scattering, interference, and diffraction. Forward models are constructed from the CMB and D” layer, including layered structures, CMB topography, ultra-low velocity zones, and distributed volumetric heterogeneity. We analyse full waveform simulations in terms of their associated energy distributions and envelopes, and explore how these waveform-derived quantities can be related to seismic intensities modelled by RTE under different structural cases. This framework provides a way toward coupling RTE simulations with WE modelling in further studies, enabling detailed investigation of CMB structure using localised wave equation modelling while substantially reducing the computational cost of global high-frequency simulations.
How to cite: Zhang, T. and Sens-Schönfelder, C.: High-Frequency Seismic Scattering at the Core Mantle Boundary: Insights from Radiative Transfer Equation and Wave Equation Modelling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7762, https://doi.org/10.5194/egusphere-egu26-7762, 2026.
Within the DFG Priority Program 2404 'Reconstructing the Deep Dynamics of Planet Earth over Geologic Time' (DeepDyn, https://www.geo.lmu.de/deepdyn/en/) we investigate possible seismic signatures related to deep Earth processes. Specifically, we investigate seismic anisotropy, by measuring shear wave splitting (SWS) of SKS, SKKS, and PKS phases. Thereby, we determine the splitting parameters, the fast polarization direction Φ and the delay time δt, using both the energy-minimization and the rotation-correlation methods. Especially, we search for phase pair discrepancies based on the observation type (null vs. split) between SKS and SKKS phases. Such discrepancies are indications for a lowermost mantle contribution to the splitting signal because these phases propagate along different paths after leaving the core. Besides using own measurements, we complement our database with measurements from Wolf et al., GJI, 2025. In two regions, beneath Siberia and North America, we find laterally varying values for Φ, in the D’’ layer just above the core-mantle boundary. The preferred directions of Φ are thought to be due to the alignment of minerals resulting from shear in a material flow. In the centers of the study regions, where high seismic velocity is present in global seismic tomography models, mainly null measurements are retrieved whereas systematic variations of Φ seem to dominate at the edges of the high seismic velocity anomalies which are often interpreted as remnants of slabs. A preliminary interpretation for our observations may be that the sinking slab material pushes local mantle material aside, inducing a flow pattern which causes an alignment of minerals and thereby seismic anisotropy.
How to cite: Ritter, J. and Dresler-Dorn, F.: Mantle flow pattern from seismic anisotropy above the core-mantle boundary underneath Siberia and North America, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17168, https://doi.org/10.5194/egusphere-egu26-17168, 2026.
The frequency of geomagnetic field reversals varies on time scales of tens of millions of years, reflecting mantle-controlled changes in outer core flow that sustains the geodynamo. Accurate knowledge of lateral heat flow variations across the core–mantle boundary (CMB) and their evolution over geologic time is therefore fundamental to understanding the long-term geodynamo behaviour.
Here, we aim at generating robust predictions of lower mantle thermal evolution based on compressible high-resolution mantle circulation models (MCM). By assimilating 410 million years of plate motion history, which coincides roughly with two mantle overturns, the time span of geologically-informed structure above the CMB covers the Cretaceous normal superchron and beyond. To estimate uncertainties in lower mantle thermal evolution, we will employ systematic variations of model parameters, with a focus on uncertainties in the underlying absolute plate motion reference frame. Appraisal of the MCMs will be performed by predicting seismic data that can be compared to observations. Long-period normal mode data are particularly suited in this context, as they provide global constraints. In addition, splitting functions show high sensitivity to variations in the absolute reference frame. The realistic histories of mantle thermal evolution and CMB heat flux that we aim for in this project can in future be linked to geodynamo models and thus be used to predict time-series of Earth's magnetic field behaviour.
How to cite: Schneider, A., Schuberth, B., Koelemeijer, P., Myhill, A., and Al-Attar, D.: Constraining deep mantle thermal evolution by linking geodynamic modelling, absolute plate motions and normal mode seismology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17109, https://doi.org/10.5194/egusphere-egu26-17109, 2026.
Many geophysical studies require knowledge on the present-day temperature distribution in Earth’s mantle, which can be estimated from seismic velocity perturbations imaged by tomography in combination with thermodynamic models of mantle mineralogy. However, even in the case of (assumed) known chemical composition, both the seismic and the mineralogical information are significantly affected by inherent limitations and different sources of uncertainty. We investigate the theoretical ability to estimate the thermal state of the mantle from tomographic models in a synthetic closed-loop experiment and quantify the interplay of tomographically damped and blurred seismic heterogeneity in combination with different approximations for the mineralogical conversion from seismic velocities to temperature. Our results highlight that, given the limitations of tomography and the incomplete knowledge of mantle mineralogy, magnitudes and spatial scales of a temperature field obtained from global seismic models deviate significantly from the true state. The average deviations from the reference model are on the order of 50–100 K in the upper mantle and can increase with depth to values of up to 200 K, depending on the resolving capabilities of the respective tomography. Furthermore, large systematic errors exist in the vicinity of phase transitions due to the associated mineralogical complexities. When used to constrain buoyancy forces in time-dependent geodynamic simulations, errors in the temperature field might grow non-linearly due to the chaotic nature of mantle flow. This could be particularly problematic in combination with advanced implementations of compressibility, in which densities are extracted from thermodynamic mineralogical models with temperature-dependent phase assemblages. Erroneous temperatures in this case might activate ‘wrong’ phase transitions and potentially flip the sign of the associated Clapeyron slopes, thereby considerably altering the model evolution. Overall, the strategy to estimate the present-day thermodynamic state of the mantle must be selected carefully to minimize the influence of the collective set of uncertainties.
How to cite: Robl, G., Schuberth, B. S. A., Papanagnou, I., and Thomas, C.: Mantle temperatures from global seismic models: Uncertainties and limitations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18500, https://doi.org/10.5194/egusphere-egu26-18500, 2026.
Properties of the mantle are difficult to constrain and critical for controlling mantle evolution and dynamics. We attempt to constrain these properties by comparing the outputs from mantle circulation models (MCMs) to 9 disparate observations. Over 250 MCMs driven at the surface by 1 Ga of plate motion history are considered. A metric is developed to quantify the fit/misfit between each observation and MCM prediction. The observations include, global seismic tomography, SOLA seismic inference of the Pacific upper mantle, global surface wave phase velocity data set, gradients of seismic velocity in the deep mantle, dynamic topography, geoid, geomagnetic reversals, temperature difference between MORB and OIB source regions, and the difference in amount of recycled oceanic crust in MORB versus OIB source regions. The comparisons are done with (i) heatmaps of each metric for each MCM, (ii) correlation between the metrics and input parameters, (iii) analyses of sub-sets where only a single MCM parameter is changed, (iv) random forest analysis where the importance and partial dependence plot of MCM parameters are produced for each metric. From this analysis we find that parameters can be constrained, including for example the temperature at the core mantle boundary, the preferred equation of state, the preferred plate motion history model, the presence of a basal layer, the buoyancy number of the recycled basalt, viscosity profile. For example the MCMs prefer a cooler core-mantle boundary, a mantle reference frame-based plate motion history, a Murnaghan EoS and a basalt buoyancy number in the lower mantle of around 0.4-0.5. Methods, analyses and further results will be presented.
How to cite: Davies, J. H., Panton, J., Plimmer, A., Beguelin, P., Andersen, M., Nowacki, A., Mason, S., Davies, C., Myhill, B., Elliott, T., Wookey, J., Roberts, G., O'Malley, C., Ferreira, A., Sturgeon, W., Shorttle, O., Andrew, W., Koelemeijer, P., Latallerie, F., and Biggin, A.: Constraining properties of mantle circulation models using disparate observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10775, https://doi.org/10.5194/egusphere-egu26-10775, 2026.
Mantle convection models are of utmost importance in understanding the physics governing major geological processes of our planet such as earthquakes, mountain building, etc. The TerraNeo framework is focussed on creating extreme-scale high-resolution geodynamic models which it achieves
with the massively parallel matrix-free finite element package HyTeG. To handle the Stokes system which arises from the conservation of mass and
momentum equations, a multigrid preconditioned Krylov subspace solver is used, whereas to handle the advection term in the conservation of energy
equation, an operator splitting approach based on the modified method of characteristics (particles) is used.
We first present standard numerical benchmark experiments for geodynamic validation of the framework against other community codes. In addition, we verify order of convergence of error in velocity and pressure against highly accurate solutions for the Stokes system computed with the propagator matrix method for radially varying viscosity and density cases. Next, a mantle circulation model with spatially varying physical parameters (viscosity and density) and assimilated plate velocities is simulated from a past physical state to present day and assessed for geodynamic correctness. Finally, we present scalability studies performed on the supercomputer SuperMUC-NG Phase 1 at LRZ (91st in TOP500, Nov’ 25). In these experiments, we were able to scale the framework to a global model resolution of ≃ 7.5 km on > 300, 000 MPI processes. These results combined with the numerical benchmarking of the framework clearly show that TerraNeo is well suited for creating large-scale geodynamic models.
How to cite: Ilangovan, P., Robl, G., Rezaei, F., Vilacis, B., Burkhart, A., Kohl, N., Mohr, M., and Bunge, H.-P.: Geodynamic Validation and Scalability of TerraNeo: Matrix-Free Mantle Convection Framework, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8727, https://doi.org/10.5194/egusphere-egu26-8727, 2026.
A key characteristic of plate tectonics is strain localization along narrow, weak boundaries between otherwise rigid tectonic plates. This localization enables efficient deformation, subduction, and plate motion, and plays a central role in the dynamic evolution of Earth. However, in mantle circulation models, plate velocities are often assimilated as surface boundary conditions without accounting for the rheological weakness of plate boundaries, relative to the surrounding lithosphere.
Weak plate boundaries can be reproduced via sophisticated strain weakening rheologies. While effective, this strategy makes the Stokes system nonlinear and incurs substantial computational cost.
Here, we exploit the fact that data assimilation implies that the locations of plate boundaries are known a priori and introduce specifically prescribed weak zones along plate boundaries in the models. These low-viscosity zones allow us to mimic the natural strain localization of Earth’s lithosphere, allowing deformation to focus at plate margins. We show that this approach can provide a computationally efficient and robust framework for bridging the gap between simplified convection models and the complex tectonic behavior of the real Earth.
How to cite: Rezaei, F., Bunge, H.-P., Ponkumar Ilango, P. I., Vilacís, B., Robl, G., Kohl, N., and Mohr, M.: Assessing the effect of weak tectonic plate boundaries in 3D global mantle circulation models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17266, https://doi.org/10.5194/egusphere-egu26-17266, 2026.
The Hawaiian–Emperor Seamount Chain (HESC) is the longest volcanic island chain in the world, which is formed by the thermal erosion of the Pacific Plate by a hot mantle plume. The HESC has two major characteristics. First, it features an approximately 60° bend formed around 47 million years ago (Ma), giving rise to its distinctive geometry. Second, over the past ~2 million years (Myr), the HESC has developed into two sub-parallel Loa-Kea trends that exhibit markedly different incompatible element and isotopic signatures, resulting in its distinctive geochemical characteristics. The causes of the two features remain vigorously debated. Here, we use global-scale geodynamic models to investigate their formation mechanisms. We find that intra-oceanic subduction systems existed in the North Pacific from the Jurassic to the Eocene, exerting significant influences on Pacific Plate motion and the thermo-chemical evolution of the Hawaiian plume from its generation at the Large Low–Velocity Provinces (LLVPs), to its drift beneath the plate, and finally its structural evolution throughout the mantle.
We quantitatively resolve the relative contributions of Pacific Plate rotation and Hawaiian hotspot drift to the formation of the Hawaiian-Emperor Bend (HEB). We propose that the demise of the Kronotsky intra-oceanic subduction system was the primary driver of a major rotational reorganization of the Pacific Plate at ~47 Ma, which our numerical simulations quantify as a ~30° rotation. Using global mantle convection models, we successfully reproduce the slab structures, the basal thermochemical anomalies including the LLVPs and an intermediate-scale anomaly (the Kamchatka anomaly) beneath the northwestern Pacific, and more importantly the present-day location of the Hawaiian hotspot. Our model predicts a predominantly southwestward migration of hotspot over the past ~80 Myr. This hotspot trajectory is consistent with plate kinematic constraints, but differs substantially from those of earlier geodynamic models that predict a predominantly southward or southeastward hotspot motion. We find the westward component of the hotspot motion is crucial for the formation of HEB. Further analysis suggests that an Late Jurassic-Cretaceous intra-oceanic subduction system in the northeast Pacific provided the forcing necessary to drive this westward hotspot migration. Combined with modeled Pacific Plate motion, we have fully reproduced the observed ~60° HEB. Furthermore, subduction activity in the North Pacific influenced the structural evolution of the Hawaiian plume, triggering a bottom-up splitting of the plume conduit. This splitting generated internal material zoning, which is expressed at the surface as parallel Loa–Kea geochemical trends. These findings not only explain the geometry and geochemistry of the HESC, but also provide insights on the tectonic evolution of the North Pacific.
How to cite: Zhang, J. and Hu, J.: Geometry and Geochemistry of the Hawaiian–Emperor Seamount Chain reproduced by global plate-mantle coupling geodynamic models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9615, https://doi.org/10.5194/egusphere-egu26-9615, 2026.
Subducting slabs play a fundamental role in controlling mantle circulation, plate motions, and surface tectonics. Global slab geometry models such as Slab2 provide an essential community reference by integrating seismicity to describe the geometry of subduction zones worldwide. In many regions, however, slabs are inferred to extend beyond the depth range of seismicity, motivating the incorporation of complementary constraints from seismic tomography.
Here we introduce 3DSlabs, a new global three-dimensional upper mantle slab geometry model constructed from seismic tomography. Following the workflow of Wu et al. (2016), fast tomographic velocity anomalies are interpreted and mapped into continuous three-dimensional slab surfaces using GOCAD. Unlike automated iso-surfacing, this approach allows complex variations in slab dip and curvature to be represented with high fidelity. Furthermore, by mapping seismic velocity directly onto the slab surfaces, 3DSlabs facilitates the identification and tracking of subducted buoyancy anomalies, such as aseismic ridges, plateaus, and hotspot tracks.
To maximize utility for the community, 3DSlabs is integrated with the Geodynamic World Builder (GWB), ensuring direct compatibility with geodynamic codes such as ASPECT. The resulting high-fidelity model is well suited for instantaneous mantle flow modeling and investigations of slab–mantle interaction. The inferred subducted features mapped onto these surfaces further provide new opportunities to investigate how along-slab heterogeneities influence subduction dynamics.
How to cite: Chen, Y.-W. and Wang, J.-L.: 3DSlabs – a global tomography-based upper mantle slab geometry model, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10169, https://doi.org/10.5194/egusphere-egu26-10169, 2026.
Seismic tomography provides critical insights into Earth’s evolution, yet the origin of deep-mantle seismic velocity anomalies—particularly slow anomalies—remains debated. Here we constrain the nature of the slow anomalies within the mantle transition zone (MTZ) beneath eastern North America by quantifying their dynamic impact on continental-scale drainage evolution and offshore sedimentation since the Miocene using coupled mantle–surface process modeling. We show that reproducing the observed stability of the Mississippi River basin, the long-term subsidence of the eastern North American margin, and the sedimentary record of the Gulf of Mexico requires a dynamic-topography scenario consistent with neutral net buoyancy of these slow anomalies. Independent geophysical observations further support this interpretation: the MTZ slow anomalies spatially correlate with the remnant Farallon slab within the lower mantle, and coincide with regions of elevated electrical conductivity. This implies that the slow seismic anomalies beneath eastern North America are best explained by hydratedcompositional heterogeneity associated with long-lived Farallon subduction, rather than by a purely thermal origin. Our results further support regional buoyancy compensation, in which dense melts above the MTZ are offset by buoyant hydrous and/or thermal contributions, yielding neutral buoyancy at long wavelengths despite strong seismic velocity reduction. Finally, the predicted trajectories of subducted slabs and mantle flow from data assimilation models indicate that the MTZ slow anomalies mostly likely represent dehydration of the Mesozoic Farallon slab within the lower mantle, providing a long-lived source ofmantle volatile circulation.
How to cite: Jin, X., Liu, L., Cao, Z., Dong, H., Yang, R., Anders, A. M., and Gao, C.: Stable continental-scale drainage of North America reveals hydrated upper mantle anomaly due to long-lived oceanic subduction , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4320, https://doi.org/10.5194/egusphere-egu26-4320, 2026.
Dynamic topography is a crucial geodynamic observable that emerges as a consequence of flow in the mantle. Buoyancies associated with mantle convection induce vertical deflections at the Earth's surface. Negative surface deflections create depositional environments and allow sedimentation to occur, while positive surface deflections create erosional/non-depositional environments, that induce gaps (hiatuses) in the geological record. The temporal and spatial extent of these gaps can be mapped using geological maps and regional studies, thus providing a means of tracking mantle processes through geological time.
Here, we compare a manual and digital extraction of hiatus distributions in China. We utilise a manually compiled dataset of un/conformable contacts and compare it to a digital contact extraction using the recently published digital geological map of China. The digital approach is limited to surface data, whereas the manual approach allows the utilisation of subsurface information. We find that the digital approach is substantially faster than the manual extraction. Our results indicate that the optimal methodology combines digital processing with refinement of manual subsurface information. Furthermore, we observe that mapping the absence and presence of a geological series shows very similar results when processed using either approach. The current limitation to a wider application of this approach is the limited availability of digital geological maps. A standardised digital database of geological maps enhanced with subsurface information (i.e., covered geological maps) is necessary to promote the use of geological data within the wider Earth science community, and would increase the opportunities for interdisciplinary collaboration.
How to cite: Vilacís, B., Carena, S., Hayek, J. N., Robl, G., Bunge, H.-P., and Ma, J.: Mapping geological hiatus using a manual and a digital approach: A case study from China, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4939, https://doi.org/10.5194/egusphere-egu26-4939, 2026.
Lithospheric uplift, once attributed mainly to plate tectonic and isostatic processes, is now recognized to be strongly influenced by convective processes in the Earth's mantle. Advances in satellite observations and data analysis have strengthened geodetic constraints on geodynamic models, specifically through satellite gravimetry. However, the superposition of mass change signals driven by different Earth processes requires robust signal separation to quantify the contributions of individual processes in the data.
Signal separation is a fundamental challenge in geodetic datasets, which commonly represent the superposition of multiple physical signals. Previous studies have explored isolating solid-Earth signals due to glacial isostatic adjustment (GIA) [1] applying a neural network–based signal separation method to simulated temporal gravity data. The neural network (NN) was trained to recognize and separate individual signal components by exploiting prior knowledge about their characteristic spatiotemporal behavior, derived from forward-modeled time-variable gravity data and additional constraints.
The employed NN architecture is a multi-channel U-Net designed to separate superimposed temporal gravity signals arising from mass redistribution in the atmosphere and oceans, continental hydrosphere, cryosphere, and solid Earth. The network separates these combined inputs into their constituent sub-components. The framework is generally applicable to signal separation in any three-axis dataset (e.g., latitude, longitude, and time), using a sampling strategy in which the data are partitioned along one axis to determine the optimal two-axis combination for training [2].
This work presents progress towards extracting signals originating from deep-Earth processes, particularly mantle convection signals, from time-variable gravity data such as observed by the Gravity Recovery and Climate Experiment (GRACE) and GRACE-Follow on (GRACE-FO) satellite missions. In this context, NN-based signal separation has been demonstrated primarily for signals with comparably large amplitudes. In contrast, time-variable gravity signals caused by processes in the Earth's mantle are approximately three orders of magnitude weaker than signals related to surface processes, rendering their detection and separation particularly challenging. The current study therefore focuses on enhancing sensitivity to low-amplitude mantle signals by leveraging the ability of machine learning methodologies to learn subtle spatiotemporal patterns.
For application to real data from the GRACE/-FO missions or the upcoming Mass-Change and Geosciences International Constellation (MAGIC), we propose training the framework on representative forward-modeled signals and simulated noise and subsequently applying the trained separation model to observational time-variable gravity data.
References:
- Heller-Kaikov B, Karimi H, Lekshmy Raj D, Pail R, Hugentobler U, Werner M. 2025 Signal separation in geodetic observations: satellite gravimetry. Proc. R. Soc. A 481: 20240820.
- Heller-Kaikov B, Pail R, Werner M. 2025, Neural network-based framework for signal separation in spatio-temporal gravity data Computers & Geosciences, Volume 207, 2026, 106057, ISSN 0098-3004.
How to cite: Lekshmy Raj, D., Pail, R., and Heller-Kaikov, B.: Signal separation of temporal gravity signals for low-amplitude signal detection, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4065, https://doi.org/10.5194/egusphere-egu26-4065, 2026.
On January 23, 2024, an Ms7.1 earthquake struck Wushi County, Aksu Prefecture, Xinjiang. While resulting in relatively limited casualties and economic losses, the event posed a certain threat to the geological safety of the Tianshan region. The Tianshan seismic belt has a history of intense seismic activity, with 17 recorded earthquakes of magnitude 7 or greater since 1716, including four exceeding magnitude 8. Notably, the Wushi earthquake is the largest event in this belt since the 1992 Ms7.3 Suusamyr earthquake in Kyrgyzstan. The 1992 Suusamyr earthquake was the first in the Tianshan region recorded by broadband digital seismographs, whereas the recent Wushi earthquake presents a valuable opportunity for a detailed case study using modern high-precision geodetic techniques. Occurring at the junction of the South Tianshan and the Wushi Basin, this event provides a crucial chance to investigate the deformation characteristics of strong earthquakes within the Tianshan seismic belt and to reveal the associated seismogenic structures and mechanisms. This research carries significant implications for understanding fault activity absorption mechanisms within the Tianshan Mountains and the characteristics of active deformation along the boundary between the Tianshan orogen and its foreland basin.
For the Wushi earthquake area, we acquired Sentinel-1 satellite data and GNSS data covering the region. Pre-seismic data collection included 200 frames from Sentinel-1 ascending track (T56) and 208 frames from descending track (T136). For co-seismic deformation analysis, data from tracks T56, T136, and T34 were utilized. Post-seismic data comprised 44 frames from track T56 and 36 frames from track T136. Time-series InSAR and D-InSAR methods were employed to derive regional deformation. The co-seismic results show significant line-of-sight surface deformation in both ascending and descending tracks, with a maximum displacement of approximately 75 cm. Fault slip distribution inversion indicates that the earthquake occurred on a northwest-dipping, left-lateral strike-slip fault with a variable strike and a thrust component. Co-seismic slip was primarily concentrated at depths between 4 and 25 km. Post-seismic deformation results suggest that short-term deformation was mainly induced by an Ms5.7 aftershock. Pre-seismic GNSS deformation results reveal differential crustal activity between the eastern and western sections of the Maidan Fault Zone within the study area, with higher activity observed in the eastern segment where the Wushi earthquake occurred.
Future work will involve analyzing pre-seismic InSAR deformation results to obtain long-term, large-scale seismic cycle deformation fields for the Tianshan earthquake region. The co-seismic slip motion consistency model will be applied to analyze the seismogenic structure and mechanism of the Wushi earthquake. Furthermore, numerical simulations will be employed to elucidate the coupling mechanisms of various post-seismic deformation effects, such as afterslip, viscoelastic relaxation, and pore rebound, following the Wushi earthquake. This integrated approach aims to establish a more systematic understanding of the earthquake's seismogenic mechanism and its post-seismic deformation processes.
How to cite: qingyun, Z., quancai, X., and shuang, Z.: Analysis of Seismic Cycle Deformation for the Ms7.1 Wushi Earthquake in Xinjiang Based on Geodetic Data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10499, https://doi.org/10.5194/egusphere-egu26-10499, 2026.
Posters virtual: Thu, 7 May, 14:00–18:00 | vPoster spot 3
EGU26-15990 | ECS | Posters virtual | VPS25
How Well Is the Mantle Sampled? A Global Voxel-Based Analysis of Residence Time and Flux from Forward- and Reverse-Time Mantle ConvectionThu, 07 May, 14:18–14:21 (CEST) vPoster spot 3
How well mixed is Earth's mantle? Are there primordial reservoirs? What fraction of the mantle feeds surface volcanism? We attempt to address these questions using large-scale Lagrangian particle tracking in time-reversed and forward convection models. We track particles backward in time using a Back-and-Forth Nudging (BFN) method applied to time-reversed thermal convection, initialized with a present-day seismic–geodynamic–mineral physics model (Glisovic & Forte, 2016, 2025). We likewise carried out long-term (multi-hundred-million-year) forward-in-time mantle convection simulations initialized with present-day mantle structure inferred from tomography. In all cases, we employ mantle viscosity structure that has been independently constrained and verified against a wide suite of present-day geodynamic observables that include free-air gravity anomalies, dynamic surface topography, horizontal divergence of plate velocities, excess core-mantle boundary ellipticity, and glacial isostatic adjustment data. A voxel-based analysis quantifies sampling density, residence time, and flux throughout the mantle.
We use different particle starting conditions, each designed to address a specific aspect of mantle mixing. To identify long-lived isolated regions, we track uniformly distributed particles both forward and backward in time, calculating residence times to locate candidate reservoirs. To estimate the sampling of lower mantle material in the upper mantle, we initialize particles in the D" layer and track them forward to determine what fraction reaches the upper mantle. To address plume dynamics and sampling, we place cylindrical arrays of particles beneath present-day hotspots and track them backward, using the statistical evolution of their standard deviation to quantify mixing along transport pathways, with transit time, and voxel analysis. To measure upper-to-lower mantle exchange, we initialize particles uniformly in the upper mantle. By combining these approaches, we systematically identify regions of low flux and high residence time, candidates for reservoirs. We further take a statistical approach based on voxel density sampling to quantify mixing across the volume of the mantle.
How to cite: Johnston, G., Anderson, M., Forte, A., and Glišović, P.: How Well Is the Mantle Sampled? A Global Voxel-Based Analysis of Residence Time and Flux from Forward- and Reverse-Time Mantle Convection, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15990, https://doi.org/10.5194/egusphere-egu26-15990, 2026.
