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.
One major objective in geodynamics is to create models of mantle flow that provide quantitative information to other Earth science disciplines. In this respect, geologically informed fluid dynamics simulations, such as mantle circulation models (MCMs) are a key component. In addition, thermodynamic models of mantle mineralogy are essential in that they can provide detailed information on material behaviour, such as density, thermal expansivity, elastic parameters and specific heat capacity, as a function of pressure and temperature for the geodynamic simulations. They are also required in the assessment of the MCMs to link temperatures to seismic velocities and density. This way, a number of secondary predictions, such as seismic, geodetic and geologic data, can be computed, which enables the validation of our models and the testing of geodynamic hypotheses by comparison to observations.
Here, we focus specifically on the dynamic effects and seismic imprint of the mantle transition zone (TZ). The complex set of phase transformations, together with an increase in viscosity, in this depth range is expected to influence vertical mass flow between upper and lower mantle. Still, neither the associated dynamic effects nor the seismic structure of the TZ have conclusively been constrained to date. Using our highly scalable new mantle convection software TerraNeo, based on the matrix-free finite-element framework HyTeG, we present a suite of MCMs with different formulations of compressibility. Classically, compressibility is included in the mantle convection simulations in form of the truncated anelastic liquid approximation (TALA), and the effects of phase transformations are either neglected or incorporated in parametrized form at constant depth. A physically more complete treatment of compressibility has recently been introduced in the form of the ‘Projected Density Approximation’ (PDA; Gassmöller et al., 2020). The PDA is based on tabulated material properties from the thermodynamic mineralogical models, thus allowing us to self-consistently capture non-linear buoyancy effects specifically due to phase transitions in the simulation. Comparing MCMs using TALA and PDA, we will highlight effects of mineral phase transitions on the evolution of mantle flow over time, the resulting present-day temperature field, as well as its seismic signature.
How to cite: Papanagnou, I., Schuberth, B. S. A., Robl, G., Freissler, R., Ilangovan, P., D'Ascoli, E., Vilacís, B., Brown, H., Schneider, A., Burkhart, A., Kohl, N., Chen, Y.-W., Stotz, I., Mohr, M., and Bunge, H.-P.: Dynamic and seismic expressions of mineral phase transitions in mantle circulation models computed with TerraNeo, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12820, https://doi.org/10.5194/egusphere-egu25-12820, 2025.
Many geophysical studies require knowledge on the present-day temperature distribution in Earth's mantle. One example are geodynamic inverse models, which utilize data assimilation techniques to reconstruct mantle flow back in time. The thermal state of the mantle can be estimated from seismic observations with the help of thermodynamic models of mantle mineralogy. However, the temperature estimates are significantly affected by inherent limitations in both the seismic and mineralogical information, even in the case of (assumed) known chemical composition.
Using a synthetic closed-loop experiment, we quantify the theoretical ability to determine the thermal state of the mantle from tomographic models. The 'true' temperature distribution is taken from a 3-D mantle circulation model with Earth-like convective vigour. We aim to recover this reference model after: 1) mineralogical mapping from the 'true' temperatures to seismic velocities, 2) application of a tomographic filter to mimic the effect of limited seismic resolution, and 3) mapping of the 'imaged' seismic velocities back to temperatures. We test and quantify the interplay of tomographically damped and blurred seismic heterogeneity in combination with different approximations for the mineralogical 'inverse' conversion from seismic velocities to temperature. Our results highlight that, given the current limitations of seismic tomography and the incomplete knowledge of mantle mineralogy, magnitudes and spatial scales of a temperature field obtained from global seismic models will deviate significantly from the true state, with average deviations up to 200 K in the deep mantle. Large systematic errors furthermore exist in the vicinity of phase transitions due to the associated mineralogical complexities.
The inferred present-day temperatures can be used to constrain buoyancy forces in time-dependent geodynamic simulations. Initial errors in the temperature field might then 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.
How to cite: Robl, G., Schuberth, B., Papanagnou, I., and Thomas, C.: From seismic models to mantle temperatures: Uncertainties and implications for geodynamic simulations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11599, https://doi.org/10.5194/egusphere-egu25-11599, 2025.
Reconstructions of past mantle flow provide a powerful framework to sharpen our understanding of the dynamics and structure of the deep Earth. As a data-driven approach to geodynamic modelling, these reconstructions explicitly require an estimate of the present-day thermal state of the mantle, which can be derived from seismic tomography and an interpretation of observed mantle heterogeneity with mineral physics. Nonetheless, various uncertainties complicate the direct use of tomographic images. Critical issues are the spatially heterogeneous imaging quality, and the lack of definite metrics for seismic resolution and a practical quantification of model uncertainty. In many regions the patterns, but especially the amplitudes of velocity variations, are thus insufficiently constrained, making global tomography prone to drawing a dynamically inconsistent picture of the mantle’s buoyancy field. For geodynamic inferences, it is therefore vital to establish to what degree these current limitations affect our capacity to accurately reconstruct the mantle’s evolution back in time, and, where necessary, what strategies can be advised to address their impact.
We introduce a tomographic-geodynamic framework designed to tackle this issue with the aid of closed-loop experiments. Based on a reference mantle circulation model (MCM), we set up a complete, synthetic tomographic experiment with the following key components: 1) S-wave finite-frequency traveltime residuals are obtained from seismograms predicted for the MCM, recorded at ~10,000 real station locations. Therefore, we use the global wave propagation code SPECFEM3D_GLOBE to simulate in total 3,800 teleseismic earthquakes accurate down to a shortest period of ~10s. 2) We sample the complete dataset on the basis of ray turning point locations to obtain an optimal and balanced illumination of the entire mantle. 3) We perform tomographic inversions with the SOLA method and paraxial finite-frequency kernels. The explicit computation of the inverse and the corresponding resolving kernels in SOLA allow us to create tomographically filtered representations of the `true` MCM heterogeneity. Furthermore, it gives us the possibility to analyze them together with associated local resolution and uncertainty estimates. The resulting synthetic tomographic images are generally able to reproduce the patterns of major anomalies from the MCM. Yet, the amplitudes and exact shapes remain difficult to recover, even in the case of optimized data coverage and tuning of inversion parameters towards highly localized and narrow resolving kernels. This work serves as the basis for subsequent testing of the tomographic input within adjoint mantle flow reconstructions to complete the closed-loop setup.
How to cite: Freissler, R., Schuberth, B. S. A., Zaroli, C., and Bunge, H.-P.: A tomographic testbed for geodynamic reconstructions of past mantle flow, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12871, https://doi.org/10.5194/egusphere-egu25-12871, 2025.
The Lithosphere-Asthenosphere Boundary (LAB) demarcates the transition from a conductive thermal lid to a convecting asthenosphere below. The Southwestern United States presents an intriguing natural laboratory for investigating the processes at play in this critical boundary: intraplate volcanism is abundant and geochemical and geophysical analyses suggest the presence of a sub-lithospheric layer of partial melt. It has been suggested that a change in mantle strength at the top of the melt-bearing layer helps to create the LAB, indicating that melt stability is an important factor in understanding lithospheric dynamics. The mechanism, or interplay between mechanisms, that govern the LAB has implications for geodynamic modeling as well as for understanding the long-term evolution of lithosphere and volcanism. The analysis presented here is based on seismic observations of surface waves and converted body waves, which are used to determine 1-D profiles of shear wavespeed (Vs) throughout the Southwestern United States, from the surface to 300 km depth. The LAB is determined from the depth location of negative Vs gradients within the mantle. From the Vs profiles, we estimate temperature within the upper mantle, using two different geophysical interpretive toolkits. These toolkits each predict geophysical properties via forward-modeling of temperature, melt fraction, and/or compositional state, and assumptions made within the forward-modeling can yield large discrepancies in interpreted temperature. We leverage temperatures derived from geochemical thermobarometry as a constraint to guide our choice of method and attenuation parameterization. From this workflow, we report inferred temperature at and below the gradient inferred to be the LAB, and evaluate the relationship of these temperatures to the mantle adiabat and the peridotite solidus. Temperatures are near the solidus in portions of the lithospheric mantle, particularly in the Basin and Range province, suggesting that melting does play a role in defining the LAB, but not in every location. Moreover, the prevalence or absence of partial melt appears to be connected to regional variations in deformation style, surface heat flow, and topography. Finally, we note that additional constraints on hydration state and composition of the lithosphere, as well as the geometry and distribution of partial melt, will improve the workflow presented here.
How to cite: Golos, E. and Fischer, K.: Seismic constraints on temperature and melting at the Lithosphere-Asthenosphere Boundary in the Southwestern United States, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3867, https://doi.org/10.5194/egusphere-egu25-3867, 2025.
The alternation between superchrons and periods of rapid field reversals is comparable
to timescales of mantle convection, suggesting that lowermost mantle evolution impacts
the reversal frequency of the Earth’s magnetic field. By controlling the heat flow from
the outer core, the deep mantle temperature distribution can either support or hamper
the convective pattern in the outer core that generates the dipolar field component.
Due to the long timescales, the main means of testing a potential correlation between
reversal frequency rate and CMB heat flow distribution is through tectonically informed
geodynamic modelling. However, even though state-of-the-art mantle circulation models (MCMs)
typically explain statistical properties of seismological data, they do not consistently
reproduce the location of present-day mantle features. The main influence
on position is given by the assimilated absolute plate motion model, which is inherently
restricted by the lack of longitudinal constraints as well as the need to separate plate
motion and true polar wander signal in paleo-magnetic data. Geodynamic model predictions
therefore need to be compared to independent observations.
In this contribution, we investigate predictions of present-day mantle structure that
are based on differences in the absolute plate motion model. We compute synthetic seismic
data by coupling MCM predicted structure with a thermodynamic mineralogical model.
The analysis is predominantly focused on normal mode data, as they capture the longwavelength
component of structures throughout the entire mantle. In addition, the
global sensitivity of normal modes reduces the drawbacks of uneven data coverage. By
quantifying the fit to seismic data, we evaluate different realisations of mantle structure
that reflect plausible variations in the absolute plate motion history.
How to cite: Schneider, A., Schuberth, B., Koelemeijer, P., Shephard, G., Myhill, A., and Al-Attar, D.: Investigating deep mantle evolution by linking geodynamic modelling to seismic data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16609, https://doi.org/10.5194/egusphere-egu25-16609, 2025.
One of the surface expressions of mantle convection is dynamic topography, as the the surface is uplifted above upwellings and pulled down above downwellings. However, it is challenging to extract the topography signal from the convecting mantle, because of large isostatic topography contributions from within the crust and subcrustal lithosphere. Technically, the latter can be included as part of dynamic topography but that needs to be clearly specified to avoid confusion. Here we use two recent crustal models to subtract crustal isostasy, and show that the remaining (residual) topography signal as well as the geoid can be matched well by a model where density anomalies and temperatures in the subcrustal mantle are inferred from seismic tomography. The model uses depth-dependent viscosity, and lateral variations due to temperature dependence below depth 219 km, and the distinction between (thicker) cratons, thinner lithosphere elsewhere and weak plate boundaries above that depth. We show that the fit can be improved if, in addition to densities inferred from tomography, a negative buoyancy between zero and about -40 kg/m^3 is added in continental lithosphere, in particular in cratons. The exact amount depends on model specifics, especially which crustal and tomography models are used. In our model, this buoyancy is added in the entire lithosphere, however, in reality, chemical buoyancy may be prevalent in certain depth regions. To address that issue we follow an approach similar to Wang et al. (Nature Geoscience, 16, 637–645, 2023) and plot the difference between dynamic topography from only sub-lithospheric density anomalies, and residual topography after only subtracting crustal isostatic topography against lithosphere thickness derived from tomography. The slope of this plot gives an indication of lithospheric density anomalies. For our best-fitting combination of dynamic and residual topography, we find a break in slope from nearly zero above 150 km to a negative slope below. This indicates that chemical density anomalies that cause lithospheric buoyancy are concentrated in the upper ~150 km.
How to cite: Steinberger, B. and Cui, R.: Modeling geoid and dynamic topography from tomography-based thermo-chemical density anomalies in the lithosphere and convecting mantle beneath , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8840, https://doi.org/10.5194/egusphere-egu25-8840, 2025.
Mantle convection drives large-scale vertical motion at the surface (dynamic topography), which is linked to present-day geoid undulations and residual topography. However, this link depends crucially on the mantle viscosity profile, which remains one of the largest uncertainties in global geodynamics. While instantaneous flow models based on seismic tomography have provided classic constraints on mantle viscosity structure, here the profile acts only to map a given density structure to surface observations. This means the viscosity profile is not necessarily consistent with the density structure. Here we tackle this problem using a suite of high-resolution time-dependent mantle circulation models which assimilate plate velocities over the past 400 Myrs. This allows us to study the role of the mantle viscosity profile in altering the density structure of the mantle through the planform of convection, in tandem to its role in mapping this to the surface through kernels. We find that the changes in the spherical harmonic density spectrum of the mantle, which result from a given change in the profile, can alter surface observations with the same magnitude as the changes to the kernel. The coupled influence of the profile on the mantle density spectrum and kernels, together with observed geoid undulations and residual topography, provides a new method of constraining the mantle viscosity profile using time-dependent convection modelling.
How to cite: Brown, H., Stotz, I. L., and Bunge, H.-P.: Probing the influence of the mantle viscosity profile on the density spectrum and its effect on present-day surface observations , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12880, https://doi.org/10.5194/egusphere-egu25-12880, 2025.
Mantle convection alters Earth’s ellipsoidal shape and modifies its moment of inertia, leading to rotation-axis shifts known as true polar wander (TPW). By combining seismic tomography with the Back-and-Forth Nudging (BFN) method, we created a time-dependent convection model that reconstructs mantle density evolution and Earth’s moment of inertia over the last 70 million years. This modeling framework closely agrees with independent paleomagnetic data on Cenozoic changes in Earth’s rotation pole, notably reproducing the previously unexplained U-turn in TPW around 50 million years ago.
Our results show that TPW can exceed five degrees, despite stabilizing factors such as high viscosity in the lower mantle and Earth’s remnant rotational bulge. Verification of predicted variations in Earth’s ellipsoidal figure, based on paleomagnetic constraints, provides a robust reference point for forecasting convection-induced dynamic flattening. Over the 70-million-year interval, we document changes in flattening that range from -0.2% to +0.1% during the Paleogene. Furthermore, our predictions of Paleogene axial precession frequency align with recent independent cyclostratigraphic analyses, offering strong evidence for the accuracy of our model and reinforcing the hypothesis of diminished luni-solar tidal dissipation during that period.
How to cite: Forte, A. M., Rowley, D., Rowley, D., and Kamali Lima, S.: Resolving 70 Million Years of Earth’s True Polar Wander and Precession: Paleomagnetic Validation of a Seismic Tomography–Based Mantle Convection Model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2596, https://doi.org/10.5194/egusphere-egu25-2596, 2025.
The flux of subducting slabs into the mantle is an essential component of the Earth’s mantle convection. However, the slab flux remains poorly known for pre-Jurassic times because of the absence of preserved oceanic seafloor. Sinking of subducted slabs within the mantle perturbs Earth’s moment of inertia, which, in addition to perturbations related to upwellings, results in long-term motion of the solid Earth relative to the rotation axis, resulting in so-called True Polar Wander (TPW). This motion, which can be inferred using paleomagnetic data, should therefore yield crucial information about the large-scale subduction kinematics back in time. However, it is not yet clear how to separate the numerous contributions to TPW, since these result from the superimposition of a complex distribution of mantle mass heterogeneities that are advected through time. In this study, we developed a new approach to assess the impact of subducting slabs on TPW based on the harmonic decomposition of plate kinematics into large-scale patterns. We constructed simple plate models that yielded pure dipole and pure quadrupole and net stretching kinematics, which represent the spherical harmonic degree 1 and degree 2 components of relative plate motions, respectively. We then implemented these three patterns of large-scale plate motions, and their subduction zones, into three simple mechanistic models and computed mantle mass heterogeneities through time. We then calculated changes to Earth’s moment of inertia tensor to predict the resulting TPW. In this contribution, we will first show the results of these sensitivity experiments highlighting the evolution of inertia perturbations associated to each of these three large-scale patterns. We will then show the calculated TPW using the harmonic decomposition of full-plate models over the last 250 Myrs and discuss the influence of each of these three plate kinematic components on the observed TPW. Finally, we will discuss how the observed TPW can help better constrain the evolution of mantle mass heterogeneities and rates of subduction flux for past times.
How to cite: Robert, B., Conrad, C. P., Steinberger, B., and Domeier, M. M.: Linking Plate Kinematics and True Polar Wander over the last 250 Myrs, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11831, https://doi.org/10.5194/egusphere-egu25-11831, 2025.
Constraining the long-term evolution of geoid anomalies is essential for unraveling Earth's internal dynamics. While most studies focus on present-day geoid snapshots, we reconstruct the time-dependent evolution of Earth’s strongest geoid depression, the Antarctic Geoid Low (AGL), over the Cenozoic. Unlike geodetic reference frames that place the deepest geoid low in the Indian Ocean, a geodynamic perspective (relative to a hydrostatic ellipsoid) reveals the strongest nonhydrostatic geoid depression actually resides over Antarctica. Using a back-and-forth nudging technique for time-reversed mantle convection modeling, we leverage 3-D mantle density structures derived from seismic tomography and geodynamic constraints. Our results show that the AGL has persisted for at least ~70 Myr, undergoing a major transition in amplitude and position between 50 and 30 Ma. This coincides with abrupt lateral shifts in Earth’s rotation axis at ~50 Ma, validated through paleomagnetic constraints on True Polar Wander. Initially, stable lower mantle contributions dominated the AGL, but over the past ~40 Myr, increasing upper-mantle buoyancy, particularly above ~1300 km depth, amplified the AGL magnitude. This shift stems from the interplay between long-term deep subduction beneath the Antarctic Peninsula and a buoyant, thermally driven upwelling of hot, low-density material from the lowermost mantle. These new results contrast with earlier interpretations, clarifying the crucial role of evolving mantle buoyancy in shaping global geoid anomalies. By incorporating seismic, geodynamic, and mineral-physics data, our reconstructions provide a more comprehensive understanding of mantle flow beneath Antarctica and offer new insights into the dynamic coupling between lower and upper mantle processes that govern Earth’s long-wavelength geoid evolution.
How to cite: Glišović, P. and Forte, A.: The Cenozoic Evolution of Earth’s Strongest Geoid Low: Insights into Mantle Dynamics below Antarctica, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12626, https://doi.org/10.5194/egusphere-egu25-12626, 2025.
The Earth's lithosphere undergoes vertical motion on a range of spatial and temporal scales. In recent years it has become increasing clear that mantle related forcing and in particular mantle plumes are a significant contributor to uplift events in many regions of the world, making vertical motions a powerful probe into sublithospheric processes. Significant improvements of observational methods (e.g. satellite missions) and publicly-accessible databases (e.g. digital geological maps) make it now feasible to map vertical motions from geodetic to geologic time scales. This in turn provides invaluable constraints to inform key, yet uncertain, parameters (e.g. rheology) of geodynamic models. Here we report results of an ongoing Research Training Group (RTG) 2698, with 10 individual dissertation projects and a Post-doc project, funded by the German Research Foundation. The RTG follows an interdisciplinary approach of Geodynamics, Geodesy and Geology aiming to answer questions related to how the interaction of exo- and endogenic forcing shapes a diverse array of earth processes. From a combined interpretation of interdisciplinary observations with different spatial and temporal sensitivity, together with physical models, work in the RTG tries to disentangle different uplift mechanisms, including the plume, plate and isostatic mode, based on their specific spatial and temporal patterns. We will give an overview of key results and highlight the synergies that derive from bringing multiple constraints to bear on vertical motion processes of the lithosphere.
How to cite: Bunge, H.-P., Friedrich, A., Pail, R., and Chen, Y.-W.: Geophysical modelling of vertical motion processes constrained by geodetic and geological observations (UPLIFT), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17175, https://doi.org/10.5194/egusphere-egu25-17175, 2025.
Dynamic uplift may be expressed in the geologic record by the presence of unconformities, which represent periods of erosion and/or halted sedimentation. One distinct example, the early Miocene unconformity (EMU), formed shortly before the impingement of the Yellowstone plume in the northern Rocky Mountains. The most complete geologic record around this event is preserved in southwest Montana. There, we sampled eight sedimentary sections crossing the EMU. Our magnetostratigraphic study in combination with published radiometrically-dated ash layers determines the EMU ended at ~20.1 Ma and lasted up to 1.5 Myr. We found that the EMU is marked by an abrupt increase in magnetite concentration coincident with a shift in detrital zircon age spectra. These data indicate a rapid reorganization in sediment source likely caused by the emplacement of the Columbia River flood basalt synchronous with a shift in the North American drainage divide. The passage of the Yellowstone plume and/or the onset of Basin and Range extension likely provided the tectonic stimulus for the widespread unconformity and changes in sediment source.
How to cite: Gerritsen, D., Gilder, S., Chen, Y.-W., Wack, M., and Ludat, A.: Magnetic tracing of lost time in Cenozoic sediments: Testing dynamic topography of the Yellowstone plume, USA, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3202, https://doi.org/10.5194/egusphere-egu25-3202, 2025.
How to cite: Kahle, B., Kübler, S., Purohit, C., Junginger, A., Sloan, A., Friedrich, A., Rieger, S., and Zebari, M.: Fault evolution in the Kenya Dome: an area of highly elevated topography within the East African Rift System, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16517, https://doi.org/10.5194/egusphere-egu25-16517, 2025.
Viscosity and thickness of Earth’s asthenosphere are typically inferred from observations of postglacial rebound of the lithosphere. Parameter values deduced from studies of these observations serve a wide range of geodynamic models that simulate processes evolving over time periods of hundred Myr - much longer than the duration of the rebound process itself. The question remains whether inferences derived from the kyr-long rebound process hold over Myr-long periods. The record of past motions of non-subducting plates may help address such a question, because these motions are necessarily driven by asthenospheric Poiseuille-type flow, which is sensitive to viscosity and thickness of the asthenosphere. Here I show how a simple model for the dynamics of non-subducting plates may be used to address the question whether parameter values derived from the kyr-long rebound hold over the longer time-scales of plate motions. By interrogating the reconstructed records of past motions of three non-subducting plates, I find that indeed this is the case. Furthermore, including also constraints on the asthenosphere thickness from seismic tomography narrows down the range of plausible values of asthenosphere viscosity to [1, 3]*10^19 Pa*s.
How to cite: Iaffaldano, G.: Viscosity and thickness of Earth’s asthenosphere: inferred from Kyr-long processes, applicable to Myr-long dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16470, https://doi.org/10.5194/egusphere-egu25-16470, 2025.
Mantle plumes are hot upwellings that transport heat from the core to the base of the lithosphere, and sample lowermost-mantle chemical structure. Plume buoyancy flux is a crucial parameter measuring the mass and heat mantle upwellings bring to the surface. However, the calculation of the global plume buoyancy fluxes is still in contention. Hotspot swells (topographically high regions with elevations of up to 2~3 km and widths of up to ~1500 km) are diagnostic surface expressions of mantle plumes.
Traditional approaches to calculate the swell buoyancy flux are based on two assumptions: (1) the asthenosphere moves at the same speed as the overriding plate; (2) hotspot swells are fully isostatically compensated, in other words, the seafloor is uplifted due to the isostatic effect of replacing ”normal” asthenosphere with hot plume material. However, at least some plumes (e.g., Iceland) can move faster than the corresponding plate motion. Also, hotspot swells are partly dynamically compensated as plume material is injected into the upper mantle. With increasingly accurate observational constraints for dynamic seafloor topography, it is time to update plume buoyancy fluxes globally and build a scaling law between the surface dynamic topography and plume buoyancy flux.
Here, we conduct thermomechanical models to study plume-lithosphere interaction and hotspot swell support. We use the finite-element code ASPECT in a high-resolution, regional, 3D Cartesian framework. We consider composite diffusion-dislocation creep rheology and a free-surface boundary at the top. We systematically investigate the effects of plume excess temperature, plume radius, plate velocity and age, and mantle rheological parameters. From these results for plume spreading beneath moving plates, the buoyancy fluxes of individual plumes, as well as the relevant plume temperatures and radii are quantitatively constrained. We find that: (1) for a fixed plume radius, higher plume excess temperature results in higher but not necessarily wider swell; (2) plume buoyancy flux is linearly proportional to swell height × width2; (3) both faster plate velocities and older plates result in a lower swell height; (4) Lower upper mantle viscosity results in a wider but lower swell provided at a fixed plume buoyancy flux.
We demonstrate that previous swell-geometry-based estimates underscore the true buoyancy fluxes of the underlying plume upwelling. We update the plume-flux catalogue by building a scaling law for buoyancy flux as a function of swell geometry in order to estimate global heat and material fluxes carried by plumes.
How to cite: Ma, Z., Ballmer, M., and Manjón-Cabeza Córdoba, A.: New Insights into Plume Buoyancy Fluxes and Dynamic Topography from Numerical Modelling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10765, https://doi.org/10.5194/egusphere-egu25-10765, 2025.
The anomalous seismic structure of the upper mantle at the Hawaiian hotspot, including the X-discontinuity at 310 km depth and a perturbed 410, has been ascribed to large quantities (>40%) of recycled eclogite in the Hawaiian mantle plume. These estimates far exceed the classical geodynamic constraints of 15-20%, suggesting the existence of additional mechanisms driving eclogite accumulations.
We tackle this discrepancy by superimposing discrete heterogeneities of recycled eclogite to a plume featuring a realistic mechanical mixture composition. This approach allows us to entrain higher amounts of denser material and quantify its segregation in the 310-410 km depth range. To reproduce the ample spectrum of buoyancy fluxes reported for the Hawaiian hotspot, we test plume radii of 80-100 km, excess plume temperatures of 200-300 K, and recycled heterogeneity fractions between 5 and 20%.
Our 8 best-fit cases yield average eclogite accumulations of 19.5% at 310 km and 21-25% at 410 km, with peaks of 21-24% and 26-32%, respectively. This uniformity indicates that higher eclogite entrainments do not substantially increase material segregation in the mid-upper mantle.
We demonstrate that, while the Hawaiian plume has the potential of recycling more than 18% denser material, high segregations are unsustainable over geological timescales, and excess entrainments above 20% would require unrealistic buoyancy fluxes. Our findings provide the first quantitative constraint of the dynamic relationship between the Hawaiian mantle plume and the X-discontinuity, critically advancing our understanding of the influence of recycled eclogite on mantle discontinuities.
How to cite: Monaco, M., Russo, R., and Brown, H.: The thermochemical Hawaiian plume and its dynamic influence on upper mantle discontinuities , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18199, https://doi.org/10.5194/egusphere-egu25-18199, 2025.
Mantle slabs imaged by seismic tomography provide complementary subsurface information that could improve global plate reconstructions because they are indications of ancient tectonic plates. Linking mantle slabs to the surface plates requires approaches that follow geodynamic principles in a highly vigorous mantle. Here, we propose a new workflow that couples a slab unfolding approach and a mantle circulation model through which tomotectonic reconstructions can be performed, evaluated, and improved in a closed-loop experiment. We found that intra-oceanic subductions are crucial for understanding the evolution of the mantle and surface tectonics in the Pacific realm. Our closed-loop experiment allows us to reinterpret published tomotectonic reconstructions based on the vertical sinking slabs hypothesis. We conclude that highly vigorous mantle flow that allows lateral slab transport up to 4,000 km and non-constant sinking rates that deviate by up to 10 mm yr-1 locally within a 1,000 km area must be accounted for in tomotectonic reconstructions.
How to cite: Chen, Y.-W., Wu, J., Bunge, H.-P., Stotz, I., Robl, G., and Schuberth, B. S. A.: Tomotectonic reconstructions validated via mantle circulation models in a closed-loop experiment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10156, https://doi.org/10.5194/egusphere-egu25-10156, 2025.
Surface features in oceanic basins, such as mid-oceanic ridges, hotspots, seafloor subsidence, and fracture zones, result from geodynamic processes in the uppermost mantle. Insight into these processes are obtained from tomographic imaging using surface waves. However, the poor distribution of earthquakes and seismic stations, as well as noise in seismic data, give rise to spatial resolution artefacts and errors in tomography models, complicating their interpretation.
We constructed SS3DPacific, a model of the vertically-polarised shear-wave velocity structure of the Pacific uppermost mantle and surrounding regions. The model derives from Rayleigh-wave phase delays, that we measured along with an estimation of their uncertainty. SS3DPacific is accompanied by 3D resolution and uncertainty. To obtain this information, we combined the SOLA inverse method to control and produce resolution and uncertainty with finite-frequency theory for Rayleigh waves, leading to a 3D model.
In this talk, I will present SS3DPacific, its 3D resolution, and uncertainty. The model shows well-known large-scale features such as cratons, ridges, and the increase of seismic velocity with distance from mid-oceanic ridges. Detailed analysis of the 3D resolution reveals strong spatial artefacts, particularly vertically, which manifest themselves in the form of structural depth leakages. This effect, expected for this type of surface-wave tomography, will ultimately bias the analysis of the lithosphere cooling process if not accounted for. Additionally, SS3DPacific shows an intriguing pattern of bands of velocity variations aligned with fracture zones.
Given the availability of 3D resolution and uncertainty quantification, SS3DPacific can be utilised in studies aimed to assess mantle circulation models, and thus dynamic processes in the Earth.
How to cite: Latallerie, F., Zaroli, C., Lambotte, S., Maggi, A., Walker, A., and Koelemeijer, P.: SS3DPacific: Structure of the Pacific uppermost mantle with 3D resolution and uncertainty, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1081, https://doi.org/10.5194/egusphere-egu25-1081, 2025.
Reconstructing the thermo-chemical evolution of Earth’s mantle and its diverse surface manifestations is a grand challenge in the geosciences. Achieving this requires the development of a digital twin -- a dynamic digital representation of Earth’s mantle across space and time, constrained by observational data on the mantle’s structure, dynamics, and evolution. To this end, geodynamicists are increasingly exploring adjoint-based approaches, which reformulate mantle convection modelling as an inverse problem. In this framework, unknown model parameters are optimized to fit available observational data.
Traditionally, inverse geodynamic models have primarily focused on observations that constrain either the initial (inverse sense) or final (forward modelling sense) state of the system, such as seismic tomography and geodesy. However, additional observational constraints are needed to rigorously reconstruct the mantle’s evolution over geological time. Surface plate velocities, their time-dependent behaviour, and plate boundary characteristics provide critical constraints. Another untapped dataset is the geochemistry of intra-plate volcanic lavas, which reflects the depth and temperature of mantle melting at the time of eruption. This geochemical signature provides insights into lithospheric thickness (the ‘lid’) and underlying thermal structure, extending our ability to constrain mantle evolution into the past.
Here, we present early efforts to incorporate mantle geochemistry into adjoint models of mantle convection using the Geoscientific ADjoint Optimisation PlaTform (G-ADOPT -- https://gadopt.org/). Our synthetic experiments demonstrate that geochemical constraints on temperature and pressure enhance the accuracy of reconstructed mantle flow trajectories, unlocking insights into dynamic processes and interactions previously obscured in mantle retrodiction models. This integration offers the potential for a transformative leap in resolving mantle evolution, illuminating the interplay between deep Earth dynamics and surface processes that shape our planet’s geological history.
How to cite: Davies, R., Ghelichkhan, S., and Turner, R.: Enhancing Adjoint Reconstructions of Earth’s Mantle with Geochemical Data from Intra-Plate Lavas, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8681, https://doi.org/10.5194/egusphere-egu25-8681, 2025.
Mantle convection is the principal driver of Earth's long-wavelength surface structure, manifesting as dynamic topography—surface undulations induced by convective currents within the mantle. Unveiling the temporal evolution of dynamic topography remains a central challenge in predictive geodynamics. Adjoint methods have recently gained prominence for reconstructing mantle convection history and correlating it with key geological phenomena, including the cessation of marine inundation in North America, the uplift of Africa, and the tilting of Australia.
In this study, we introduce a new generation of retrodiction models developed using the Geoscientific ADjoint Optimisation PlaTform (G-ADOPT). These models incorporate Earth-like rheological parameters and leverage state-of-the-art Global Full‐Waveform seismic tomography to achieve unparalleled resolution of mantle structures. The models are refined through integration with the latest plate reconstruction models, yielding regularised solutions that reconcile tectonic and seismic observations.
For the first time, we unveil the evolution of dynamic topography during the late Cenozoic, as derived from these advanced models. These results provide novel insights into the interplay between mantle convection and surface processes, refining constraints on dynamic topography and illuminating the forces that have governed Earth’s geological evolution.
How to cite: Ghelichkhan, S., Davies, D. R., Gibson, A., and Roberts, D.: Unveiling Late Cenozoic Dynamic Topography Evolution Using Non-Linear Adjoint Models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13762, https://doi.org/10.5194/egusphere-egu25-13762, 2025.
The tectonic evolution of the Tibetan Plateau has been influenced by continental collision and post-collisional convergence of Indian and Eurasian plates, both of which have undoubtedly imposed their imprints on the lithosphere and upper-mantle structures beneath the collision zone. However, the mode by which the Indian Plate has subducted beneath Tibet, and its driving forces, have been highly uncertain. Here, we present seismic evidence from a full-waveform tomographic model that reveals flat subduction of the Indian Plate beneath nearly the entire plateau at ~300 km depth, implying that the slab may have transitioned to positive/neutral buoyancy and is no longer capable of supporting steep-angle deep subduction. The horizontal distance over which the flat slab slides northward increases from west (where it collides with the Tarim lithospheric keel) to east (where it has resided approximately north of the Songpan-Ganzi Fold Belt beyond the Qiangtang Block). The Asian lithosphere is subducting beneath northeastern Tibet without colliding with the Indian slab. The low-velocity zone, with a thickness of 50-110 km, sandwiched between the Tibetan crust and Indian slab, is positively correlated with the high-elevation, low-relief topography of Tibet, suggesting partial melting of the uppermost mantle that has facilitated the growth and flatness of the plateau by adding buoyant material to its base. We propose that deep mantle convective currents, traced to the Réunion plume and imaged as large-scale low-velocity anomalies from the upper mantle under the Indian Plate downward towards the uppermost lower mantle under the Baikal-Mongolia Plateau, are the primary force driving the ongoing India-Asia post-collisional convergence.
How to cite: Ma, J., Song, X., Bunge, H.-P., Fichtner, A., and Tian, Y.: Wholesale flat subduction of Indian slab and northward mantle convective flow: Plateau growth and driving force of India-Asia collision, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7772, https://doi.org/10.5194/egusphere-egu25-7772, 2025.
Complex interactions between plate subduction, mantle flow, and the overriding plate govern the dynamics of subduction zones. Numerous studies have highlighted the critical role of subduction processes in redistributing thermo-chemical domains within the mantle, significantly influencing mantle dynamics and plate tectonics. However, debates persist regarding the thermal conditions and dynamic models of the mantle affected by stagnant slabs. The physical state and long-term dynamics of the mantle surrounding stagnant slabs in the mantle transition zone (MTZ) remain poorly understood, partly due to the lack of detailed reconstructions of subduction history and robust constraints on mantle temperatures.
The northwestern Pacific region, with its extensive subduction history spanning over 40 million years and involving multiple oceanic plates with episodic plate boundary modifications, provides an ideal setting for studying subducting slab structures and their associated tectonic and dynamic processes. High-resolution seismic tomography of the MTZ beneath the coastal margins of northeast Asia has revealed a narrow channel of low-velocity anomalies surrounded by high-velocity regions, indicating the presence of segmented western Pacific stagnant slabs. The geometric features of these imaged structures likely reflect rapid plate boundary reorganization during the Cenozoic in the western Pacific, driven by continuous lateral extension and tearing of the retreating Pacific slab. This process has led to the formation of a laterally extended MTZ gap characterized by moderate mantle temperatures (Tp ~1350–1450°C), as determined through joint analyses of seismic velocities and mantle phase transition thicknesses.
We propose that the current MTZ gap in the western Pacific exhibits minimal thermal anomalies capable of inducing focused mantle upwellings. Our observations suggest that mantle dynamics around the stagnant slabs would be largely passive, unless thermochemical sources capable of driving active convection are present. This further implies that active mantle upwellings, if they existed, were spatially and temporally constrained during past slab segmentation processes.
How to cite: Song, J.-H., Rhie, J., Kim, S., and Tauzin, B.: Cold Mantle Transition Zone Gap Formed by Progressive Tearing of the Segmented Western Pacific Slab, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14576, https://doi.org/10.5194/egusphere-egu25-14576, 2025.
Mantle convection is a crucial component for providing driving and resisting forces for horizontal motion of tectonic plates, as well as for generating non-isostatic vertical motion commonly termed “dynamic topography”. These two kinds of surface motion are often investigated in isolation. However, the existence of a thin, mechanically weak asthenosphere allows us to study mantle convection in the context of Couette/Poiseuille flow, which links mantle flow properties to temporal changes in both horizontal and vertical motions. In this study, we utilize publicly available finite rotations and stage-resolution stratigraphic dataset in the North Atlantic region to investigate its surface-motion history in early Paleogene, which coincides with the peak Icelandic plume activity deduced from independent geologic constraints. We find that our inferred horizontal and vertical motion changes are temporally correlated. We examine this correlation through a quantitative torque analysis, which incorporates an analytic Couette/Poiseuille flow model. We parameterize this flow model in terms of observed kinematics coupled with flow-flux estimates of Icelandic plume and/or Farallon slab activity. Our analysis indicates (1) that torque-variation tied to the Icelandic plume flux closely resembles our kinematic inferences, and (2) that the inclusion of slab flux does not modify such a scenario significantly. In light of these inferences, our efforts shed light on the role of asthenospheric channelized flow flux in influencing the North Atlantic surface expressions in early Paleogene.
How to cite: Wang, Z. R., Iaffaldano, G., and Hopper, J.: North Atlantic surface-motion changes in early Paleogene: Observations and geodynamic interpretations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3336, https://doi.org/10.5194/egusphere-egu25-3336, 2025.
Postseismic deformation in the far field following large earthquakes is increasingly recognised as a key factor contributing to regional land height and relative sea-level (RSL) changes. The Sumatran subduction zone provides a unique setting to study this deformation owing to the availability of far-field (600 – 1000 km from the trench) and long-term (>20 years) Global Navigation Satellite System (GNSS) observations. In this study, we model the GNSS-constrained postseismic deformation of multiple great (Mw ≥ 8.0) regional earthquakes using a layered and self-gravitating spherical Earth model. Our results reveal a weak asthenosphere beneath the continental lithosphere in explaining the far-field GNSS observations. We estimated an asthenosphere Maxwell viscosity as low as 𝜂m = 1.5 – 3e18 Pa s. Even assuming the presence of a weaker lithosphere-asthenosphere boundary layer (𝜂m = 1.3 – 2.8e17 Pa s) of 5-10 km thickness, the asthenospheric Maxwell viscosity remains less than 1e19 Pa s. Using these mantle viscosities, we estimated horizontal and vertical postseismic viscoelastic surface deformation over a broader region beyond where GNSS observations are available. We show that a weak backarc asthenosphere leads to relatively large, fast, and extensive postseismic deformation, a conclusion that likely applies to many other subduction zones. The great Sumatran megathrust earthquakes, namely the 2004 Sumatra-Andaman, 2005 Nias-Simeulue, and 2007 Bengkulu events, caused continuous far-field postseismic land subsidence over two decades. The 2012 Mw 8.6 and Mw 8.2 Wharton Basin strike-slip earthquake sequences in the Indian Ocean produced postseismic uplift in the far field, slowing down but not offsetting the ongoing subsidence caused by the great megathrust earthquakes. Our results highlight a critical concern for Southeast Asia’s coastal population, as the regional VLM and RSL rise due to large earthquakes compounds the impacts of climate-driven sea-level changes.
How to cite: Ng, G., Feng, L., Zhou, X., Luo, H., Wang, K., Sun, T., Yong, C. Z., and Hill, E. M.: Geodetic Evidence for Weak Mantle Beneath the Sumatran Backarc and Its Influence on Regional Sea-Level, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19600, https://doi.org/10.5194/egusphere-egu25-19600, 2025.
The transport of heat from the interior of the Earth drives convection in the mantle, which involves the deformation of solid rocks over billions of years. Significant advancements have been made over recent years to study lower mantle assemblages under relevant pressure and temperature conditions, which have confirmed the usual view that ferropericlase is weaker than bridgmanite. However, natural strain rates are 8 to 10 orders of magnitude lower than those observed in the laboratory, and remain inaccessible to us. Once the physical mechanisms of the deformation of rocks and their constituent minerals have been identified, it is possible to overcome this limitation thanks to multiscale numerical modeling, which allows for the determination of rheological properties for inaccessible strain rates. This presentation will demonstrate how this theoretical approach can be used to describe the elementary deformation mechanisms of bridgmanite and periclase. These descriptions are compared with available experimental results in order to validate the theoretical approach. In a subsequent phase, the impact of very slow strain rates on the activation of the aforementioned mechanisms is evaluated. Our findings indicate that significant alterations in deformation mechanisms can occur in response to changes in strain rate.
How to cite: Carrez, P., Cordier, P., Gouriet, K., Weidner, T., Van Orman, J., Castelnau, O., and Jackson, J.: On the effect of strain rates on the deformation creep mechanisms in deep Earth mantle, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8576, https://doi.org/10.5194/egusphere-egu25-8576, 2025.
The development of the Dead Sea Transform (DST) coincided with a vertical uplift of the transform margins, forming the main N-S mountain ridge of Israel, as well as a subsidence of Dead Sea pull-apart basin. So far only minor parts of these events have been accurately dated. Karst processes that started after marine regression, led to the formation of karst aquifers in the carbonate lithologies of Cenomanian to Eocene age. The vertical tectonics (mountain uplift and Dead Sea Valley subsidence) caused the caves to be gradually uplifted above the regional groundwater level. In the current study, we used Laser Ablation (LA) U-Pb chronology of phreatic and vadose cave calcite to determine the timing of vertical tectonic stages: the marine regression, onset of karst processes, and transition of the caves from the groundwater up to the vadose zone. U-Th chronology was used for dating the youngest calcites. Phreatic and vadose calcite samples were collected from sites with similar altitudes and a spatial extent of ~150 kilometers on N-S transect along the western DST margin. In-situ LA U-Pb chronology of calcite, along with calcite 18O values ranging between -16‰ and -9‰ (VPDB), fluid inclusion (FI) 18O-D analyses and associated d-excess values of 9‰ to 29‰ (VSMOW) indicates that meteoric waters infiltrated into the aquifer since Late Eocene – Early Oligocene (35.1±0.3 Ma to 29.17±0.4 Ma), marking the timing of sea regression and onset of meteoric water infiltration into the aquifer. The onset of vertical tectonics in the region during the early Miocene, caused an initial uplift of the caves above water table and deposition of first vadose speleothems around 20 Ma. The average uplift rate of the western margin of DST was approximately 26 m per million years, which increased to 120 m per million years from 6 Ma to the present. This change appears to correspond with a few degrees shift in previously parallel sinistral strike slip movement of the Dead Sea Transform, introducing an extensional component and leading to the development of the pull apart basin.
How to cite: Langford, B., Vaks, A., Golan, T., Levy, E., Zilberman, T., Yasur, G., Weiss-Sarusi, K., and Frumkin, A.: Morphotectonic Chronology of the Dead Sea Rift's Western Margin: Insights from U-Pb Dating of Speleothems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19898, https://doi.org/10.5194/egusphere-egu25-19898, 2025.
Recent studies suggest that the secular variation dynamics of the geomagnetic field exhibits periodic patterns that indicate underlying wave processes in the Earth’s core. However, as long as the analytical core field models are based on geographically sparse and noisy observatory data, they have apparent limitations for studying fine structure of its spatiotemporal variations. The advent of satellite measurements of the full geomagnetic field vector in 1999 removed this limitation and made it possible to produce reliable and highly accurate models of the secular variation, allowing downward continuation to the core-mantle boundary. These models have revealed rapid core field variations on a time scale of the order of 10 years. In particular, the 6-year quasi-periodicity in the second time core feld derivative has been established. In our recent research, we expand our previously successful efforts to extract the secular variation and secular acceleration signal from the magnetic observatory data over 90-year period (1932-2022), i.e. far before the advent of the space era. As a result, our approach to data analysis for the first time has made it possible to confirm the existence of a 3-year quasi-periodicity of secular acceleration pulses of alternating polarity over the mentioned period. The proposed methodology does not imply an intermediate production of a core field model, as done according to classical approaches.
How to cite: Sidorov, R., Soloviev, A., and Bogoutdinov, S.: A 6-year quasi-periodicity in the Earth's core magnetic field dynamics from 1932 to 2022, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16588, https://doi.org/10.5194/egusphere-egu25-16588, 2025.
The Earth's palaeomagnetic record reveals the existence of a global magnetic field persisting for at least 3.4 billion years. This geomagnetic field is generated by thermochemical convection, driven by the cooling of the Earth's core. Efficient cooling of the core is crucial to sustaining the magnetic field. The solid mantle plays thus a critical role in regulating the core's long-term evolution. Notably, efficient mantle cooling resulting from plate tectonics is important for sustaining the magnetic field observed in the geological record up to the present day.
However, the timing of the onset of modern-style plate tectonics remains an open question. It may have been active since the Earth's formation (~4.5 billion years ago), or since the Archean (4 – 3 billion years ago), or emerged much more recently (<1 billion years ago). When and how plate tectonics began are major scientific questions in Earth science because of their profound implications for Earth's thermal and magnetic history. The convection regime that preceded plate tectonics remains unclear. Observations of other planetary bodies in the solar system such as Mars, Mercury, and the Moon suggest that a stagnant lid regime—characterized by a single and immobile plate—is the norm. This raises the possibility that early Earth operated under a stagnant lid regime, which is significantly less efficient at dissipating heat. Such inefficient cooling would limit the capacity to sustain a long-lived magnetic field, unlike the plate tectonics regime.
Our study aims to constrain the mantle-core co-evolution by investigating the impact of these two convection regimes—stagnant lid and plate tectonics (i.e. mobile lid)—and their transition during Earth's geological evolution. To achieve this, we developed a coupled model that integrates two one-dimensional evolution frameworks. One model describes the core's thermochemical evolution, including inner core crystallization and the potential formation of a thermally stratified layer. The other describes mantle dynamics, allowing for either stagnant lid or mobile lid behaviour.
We systematically explored a wide range of mantle parameters such as mantle viscosity, the relative efficiency of stagnant - versus mobile-lid regimes, the timing of plate tectonics onset, and the mantle's and core initial temperatures. For the core, we focused on two end-member scenarios to account for the low and high thermal conductivity of iron whose precise determination remains controversial. We compared the resulting model predictions with key constraints, including the present-day inner core size, the palaeomagnetic record, the evolution of the mantle potential temperature, and the present-day thickness of a thermally stratified stable layer at the top of the liquid core. This integrated approach sheds light on the interplay between mantle dynamics and core processes since the time of Earth’s formation.
How to cite: Bonnet Gibet, V. and Tosi, N.: The effect of different mantle convection regimes on the long-term thermochemical evolution of the Earth’s core., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11498, https://doi.org/10.5194/egusphere-egu25-11498, 2025.
As a consequence of the evolution of the water-bearing basal magma ocean, water-induced mantle overturn can well account for many puzzling observations in the early Earth, such as the formation of the Archean continents and the boundary of the Archean and Proterozoic. The upwelling of the hot basal magma ocean during the mantle overturn also significantly affects the thermal state of the core-mantle boundary and the geomagnetic field. This study models the thermal evolution of the core-mantle boundary to investigate the effects of mantle overturn on the geomagnetic field. Our results demonstrate that mantle overturn substantially accelerates the cooling of the core and increases the heat flow across the core-mantle boundary. This enhanced heat flow strengthens the geomagnetic field, which well explains the high virtual dipole moments at ~3.5-2.5 Ga. The palaeomagnetic records and the formation of the Archean continents generate a concordant picture on the evolution of the water-induced mantle overturn. Additionally, the Earth's mass redistribution driven by the mantle overturn provides a novel mechanism for triggering true polar wander in the Archean. Therefore, the recorded apparent polar wander at 3.34-3.18 Ga may not result from plate tectonics.
How to cite: Wang, D. and Wu, Z.: Water-Induced Mantle Overturn Provides a Unifying Explanation for Palaeomagnetic Records and Formation of Archean Continents, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14806, https://doi.org/10.5194/egusphere-egu25-14806, 2025.
Seismological observations suggested that Earth’s inner core presents complex heterogeneity and anisotropic structure. The key to understand the structure of Earth’s inner core is to study the mineralogical composition and dynamic mechanism of the anisotropic structure of Earth’s inner core. Hexagonal close-packed (hcp) and body centered cubic (bcc) Fe alloys both have seismically anisotropic features under temperature and pressure conditions of the Earth’s inner core. When the fast axis can be oriented along the Earth’s rotation axis, the anisotropic characteristics of the Earth’s inner core, which is fast in the north-south direction and slow in the equatorial direction, can be explained. The input of light elements into Fe alloys significantly changed the anisotropy of Fe alloys. Particularly, the fast axis orientation of superionic Fe-H alloys changes with the increase of H contents in those alloys. Interestingly, superionic Fe alloys present both ionic diffusion and seismic velocity anisotropy, which establish a potential connection between the lattice preferred orientation (LPO) anisotropic structure and dipole geomagnetic field. If the Earth’s inner core is under the superionic condition, the directional diffusion of light elements driven by the geomagnetic field could result in the presence of the lattice internal stress which would then result in the LPO. The anisotropic superionic fibers explain the anisotropic seismic velocities in the IC, suggesting a strong coupling between the IC structure and geomagnetic field.
How to cite: He, Y.: Superionic inner core and anisotropic structure driven by geomagnetic field, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4922, https://doi.org/10.5194/egusphere-egu25-4922, 2025.
Posters on site: Thu, 1 May, 14:00–15:45 | Hall X1
Global topography plays a fundamental role in shaping climate, influencing atmospheric circulation and precipitation patterns through orographic effects. While much of Earth's topography arises from isostatic support due to variations in crustal and lithospheric thickness and density, a significant portion of up to 1-2km results from dynamic forces driven by slow yet vigorous mantle convection. Despite decades of research on the spatial and temporal evolution of such ‘dynamic topography’, its impact on global climate remains largely unexplored. In this study, we address this gap by quantifying the influence of mantle-induced dynamic topography on present-day atmospheric circulation and precipitation patterns. Using an Earth Model of Intermediate Complexity forced with different models of global dynamic topography, we isolate the mantle’s contribution to climate patterns. Our findings reveal prominent climatic effects linked to mantle dynamics, particularly along the American Cordillera, the East African Rift System, and other regions across latitudes which are critical to biodiversity and the evolution of life. These results uncover a hitherto unknown connection between Earth's deep interior and surface environments, with the mantle dynamics as active driver of climate processes, enhancing our understanding of the Earth System. By linking mantle dynamics to global climate, our study offers new opportunities for paleoclimate investigations and insights into how geodiversity and biodiversity have co-evolved throughout Earth's history.
How to cite: Sternai, P., Meroni, A., Vaes, B., and Pasquero, C.: Dynamic Topography and The Mantle Forcing on Climate: A Missing Link in Earth System Science, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5805, https://doi.org/10.5194/egusphere-egu25-5805, 2025.
The lateral and vertical thermochemical heterogeneity in the mantle is a long-standing question in geodynamics. The forces that control mantle flow and therefore Plate Tectonics arise from the density and viscosity lateral and vertical variations. Satellite gravity data are a unique source of information on the density structure of the Earth due to its global and relatively uniform coverage, which complements gravimetric terrestrial measurements. Gravity data (geoid, gravity, gravity gradients) sense subsurface mass anomalies have proven to be helpful in determining the Earth’s thermochemical field in virtue of density’s relatively stronger dependence on rock composition compared to seismic velocities. However, the inversion of gravity data alone for the density distribution within the Earth is an ill-posed problem with a highly non-unique solution that requires regularization and smoothing, implying additional and independent constraints. A common approach to estimate the density field for geodynamical purposes is to simply convert seismic tomography anomalies sometimes assuming constraints from mineral physics. Such converted density field does not match in general with the observed gravity field, typically predicting anomalies the amplitudes of which are too large. Furthermore, a complete description of the Earth’s gravity field must include the internal density distribution and must satisfy the requirement of mechanical equilibrium as well. Therefore, the deformation of the density contrast interfaces (surface of the Earth and Core Mantle Boundary-CMB, primarily) must be consistent with the 3D mass distribution for a given rheological structure of the Earth. With the current resolution of modern tomography models and integrated geophysical-petrological modelling it is possible to consistently predict the topography of the mineral phase transitions across the transition zone (i.e., olivine à wadsleyite, and ringwoodite+majorite à perovskite+ ferropericlase) based on a temperature and chemical description of the Earth. However, for a consistent representation of the gravity field such thermochemical (i.e., density) 3D models must be compatible with the mantle flow arising from the equilibrium equations that explains both the surface topography (dynamic + isostatic-lithospheric components) and the CMB topography. Here we present a new inversion scheme to image the global thermochemical structure of the whole mantle constrained by state-of-the-art seismic waveform inversion, satellite gravity (geoid and gravity anomalies and gradiometric measurements from ESA's GOCE mission) and surface heat flow data, plus surface and CMB dynamic topography (Stokes flow). The model is based upon an integrated geophysical-petrological approach where mantle seismic velocities and density are computed within a thermodynamically self-consistent framework, allowing for a direct parameterization in terms of the temperature and composition variables.
How to cite: Fullea, J., Ortega-Gelabert, O., Lebedev, S., Martinec, Z., Afonso, J. C., and Root, B.: Geodynamic modelling the thermochemical structure of the Earth's mantle using integrated geophysical and petrological inversion of surface wave and satellite gravity data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3690, https://doi.org/10.5194/egusphere-egu25-3690, 2025.
The planform is a defining feature of mantle convection and it can be gleaned from the stratigraphic record by mapping the continent-scale sediment distribution. Positive and negative surface deflections induced by mantle convection (dynamic topography) imprint the stratigraphic record at inter-regional scales. Dynamically uplifted continental regions create erosional/non-depositional environments which lead to gaps in the stratigraphic record, known as sedimentary hiatuses. Contrarily, subsided regions result in continuous sedimentation.
We use continental- and country-scale digital geological maps, regional geological maps, online geological databases, correlation charts, drill logs and regional stratigraphic studies, at a temporal resolution of geological series (ten to tens of millions of years) to map these events through geological time. This results in the hiatus maps---a proxy for the interregional patterns of uplift and subsidence associated with dynamic topography.
We carry this out for all continents apart from Antarctica for eight geological series since the Upper Jurassic and obtain a proxy for dynamic topography for each geological series. We study the temporal and spatial changes of the hiatus surfaces, their correlation with flood basalts eruptions, and the effects of sea-level variation in the resulting maps. Moreover, we also study the manual and digital approaches employed in the mapping of these hiatus surfaces.
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How to cite: Vilacís, B., Brown, H., Carena, S., Hayek, J. N., Stotz, I. L., Bunge, H.-P., and Friedrich, A. M.: Tracking dynamic topography through hiatus surfaces, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11583, https://doi.org/10.5194/egusphere-egu25-11583, 2025.
Density variations within the Earth’s mantle drive convective Stokes flow and shape key geophysical observables, one of which is dynamic topography, defined as the surface deflection due to normal stresses exerted on the base of the crust. For decades, predicted dynamic topography has differed from observations in two regards. First, the predictions contain too much power at long wavelengths i.e > 10,000 km). Secondly, there is insufficient power at shorter wavelengths (i.e. < 1,000 km). Here, the propagator method is utilised to solve for the Stokes equation and self-gravitation within a spherically symmetric viscosity regime. To solve these equations, kernels (i.e. Green’s functions) are obtained, which represent the sensitivity of observables like surface and core-mantle boundary topographies to density anomalies at varying depths and wavelengths within the mantle. These kernels are strongly sensitive to viscosity structure. In exploring the parameter space within the forward problem, predicted dynamic topography must match the observational dataset of dynamic topography, containing over 14,000 measurements. The geoid is sensitive to the Earth’s (relative) viscosity structure, and therefore provides an excellent primary constraint. In constructing predicted dynamic topography, a whole-mantle density model is required, usually acquired from a global shear-wave velocity model and using a constant scaling factor from mineral physics. A large range of tomographic models (n = 17) are utilised to undertake a more comprehensive search for the most appropriate mantle structure. In isolation, the lower mantle is found to produce several hundred metres of surface dynamic topography and match the long-wavelength features remarkably well. Current whole-mantle tomographic models result in predictions with insufficient short-wavelength features, as compared to residual topography studies. Hybrid density models are therefore constructed by smoothly blending high-resolution upper-mantle models, such as SL2013, with the previous suite of whole-mantle models, resulting in a predicted dynamic topography signal which better matches observed dynamic topography on shorter length scales. An improved velocity-to-density conversion is explored, by introducing a depth-dependence on the conversion and focussing on the anelastic effects within the upper mantle. Reconciling predicted and observed dynamic topography strengthens the integration of dynamic topography with other observable fields, such as the geoid, and offers a more comprehensive framework to study Earth’s interior processes.
How to cite: Jacob, I., White, N., and Al-Attar, D.: Probing Mantle Structure to Reconcile Predicted and Observed Dynamic Topography, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-908, https://doi.org/10.5194/egusphere-egu25-908, 2025.
We begin with a simple mantle dynamics model that integrates subducted lithosphere and large-scale upwelling plumes over the last 300 million years (Ma). Our calculations are performed using several plate models and mantle reference frame models, which are constructed based on various surface indicators, including geological data, thermal data from boreholes, a compilation of global surface volcanism, a reassessment of hotspot classifications, and paleomagnetic data.
A Monte Carlo approach identifies the optimal mantle viscosity and density contrasts that explain present-day geoid, gravity, and gravity gradients. Results highlight a consistent degree-2/order-2 mantle mass anomaly over 300 Ma, linked to the stable subduction girdle around the Pacific Ocean and two equatorial, quasi-antipodal mantle domes.
Time-dependent calculations of the Principal Inertia Axis (PIA) and True Polar Wander (TPW) reveal significant shifts in Earth's rotation axis, including cusps caused by the cessation of Paleo-Tethys and Tethys subduction and notable polar wander events .
Dynamic topography is computed and compared with geological and current observations, providing further insight into mantle dynamics and Earth's surface evolution.
How to cite: Greff-Lefftz, M., Robert, B., and Besse, J.: 300 Million Years of Mantle Dynamics: Subduction, True Polar Wander, and Earth's Surface Evolution, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3805, https://doi.org/10.5194/egusphere-egu25-3805, 2025.
Over the past decade, advances in data assimilation techniques combined with a rapid increase in computational power have allowed for increasingly realistic dynamo simulations. One of the key parameters controlling the dynamics of the magnetic field is the amount of heat loss through the core-mantle boundary (CMB), highlighting the crucial role of the lower mantle in the dynamo processes. Previous studies (Kutzner and Christensen, 2004) suggest that heat flux variations at the lower mantle may explain the observed changes in reversal frequency on time scales of some 10 million years.
To study the effect of the mantle on reversals, we use the numerical code MagIC, simulating the dynamo process over geological timescales. The long required simulation time forces us to use a relatively large Ekman number of E = 3 · 10-4. Following Frasson et al. (2024), we first explore the impact of several fundamental heat-flux patterns (spherical harmonic degree Y10, Y20, Y22, ...) and amplitudes imposed at the outer boundary. Secondly, we use a codensity approach to explore whether a higher degree of compositional driving reduces the impact of the core-mantle boundary heat flux pattern. Finally, we investigate the impact of the stably stratified layer at the top of the outer core (Buffett et al., 2016) on the geodynamo process and the stability of the magnetic field.
How to cite: Lohay, I. and Wicht, J.: Utilizing Codensity Approach to Assess How Core-Mantle Boundary Properties Influence Geomagnetic Reversal Frequency, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19113, https://doi.org/10.5194/egusphere-egu25-19113, 2025.
The Hawaiian-Emperor Chain in the North Pacific features a conspicuous 60° bend that has been the subject of multiple interpretations, including an abrupt change in Pacific plate motion in the Eocene (~47 Ma), a rapid southward drift of the Hawaiian hotspot before the formation of the bend, or a combination of the two factors. The latest geodynamic model has proposed that 30-35° of the Hawaiian-Emperor Bend (HEB) was caused by the sudden westward movement of the Pacific Plate at the latitude of Hawaii around 50 Ma, which occurred as a result of the cessation of the slab pull force generated by intraoceanic subduction in the northern Pacific. The remaining 25-30° of the bend is attributed to the southward movement of the Hawaiian hotspot. But according to geometric analysis and back extrapolation of plate reconstructions, a stronger westward component in the motion of the Hawaiian hotspot is required to achieve a better fit of the HEB. However, there is no geodynamic justification for a significant westward component in the drift of the hotspot.
Here, using geometric analysis with constraints from plate kinematics, we show a significant longitudinal hotspot motion is required to fit the Hawaiian-Emperor Chain. Further application of global mantle convection models reveals a westward (by ~6°) and then an eastward (by ~2°) hotspot drift in addition to the southward motion before and after the bend, with the westward motion primarily controlled by the intraoceanic subduction in Northeast Pacific. While both the westward and southward motion are required to fit the seamount chain, the former contributes ~20 degrees to the bend angle, larger than the later, challenging traditional views. Combining geodynamically-predicted Pacific Plate motion change at 47 Ma, our model provides a nearly perfect fit to the seamount chain, suggesting plate-mantle reorientation as the ultimate cause. It also suggests that the Hawaiian plume conduit is tilted towards the southwest, solving the long-lasting debate on the source of the Hawaiian plume among seismological studies.
How to cite: Zhang, J. and Hu, J.: Dynamics of longitudinal Hawaiian hotspot motion and the formation of the Hawaiian-Emperor Bend, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1975, https://doi.org/10.5194/egusphere-egu25-1975, 2025.
This study introduces a time-domain methodology for analyzing the response of solid Earth tides, focusing on their phase delay relative to maximum vertical gravitational attraction. Unlike traditional frequency-domain approaches, which primarily decompose tidal signals into harmonic components, the proposed method emphasizes temporal dynamics, offering higher resolution and fewer assumptions about signal periodicity.
Solid Earth tides, driven by gravitational forces from the Moon and Sun, induce periodic deformations of the Earth's surface, known as tidal bulges. These bulges are expected to coincide with maximum gravitational attraction, but a measurable phase delay often occurs due to the Earth's internal rheological and viscoelastic properties. Understanding this delay is crucial for deciphering the complex interplay between tidal forces and tectonic processes, including stress evolution, crustal deformation, and even earthquake triggering mechanisms.
To achieve this, the study analyzed high-precision gravity data from 14 permanent gravity stations in Europe, alongside GNSS-derived measurements of vertical surface displacement. Corrections were applied to isolate the gravitational effects of solid Earth tides, accounting for factors such as atmospheric pressure variations, ocean tidal loading, and direct gravitational attraction. The residual gravity signal, reflecting the solid Earth tidal bulge, was then examined for phase delay using time-domain algorithms.
Key findings revealed significant variability in the phase delay across geographic and tectonic settings, suggesting localized geological factors influence the Earth’s response to tidal forcing. This delay, although small, was found to redistribute stresses within the crust and mantle, potentially affecting fault reactivation and long-term tectonic plate dynamics. The integration of GNSS data allowed a comprehensive view of vertical deformation, further validating the gravity-based findings.
This time-domain approach provides a complementary perspective to frequency-domain analyses, capturing nonlinear and time-dependent effects often overlooked in traditional studies. By enhancing our understanding of tidal lag phenomena, the research contributes to refining models of lithospheric and asthenospheric dynamics. The methodology holds promise for broader applications in geophysical monitoring, offering insights into stress and strain evolution in tectonically active regions.
These advancements pave the way for improved interpretations of solid Earth processes and their implications for natural hazards, resource management, and planetary dynamics. This study underscores the potential of integrating gravity and GNSS data for high-resolution analyses of Earth’s dynamic behavior.
How to cite: Capponi, M., Sampietro, D., and Greco, F.: Time-Domain Analysis of Solid Earth Tides: A Pathway to Understanding Tectonic Dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16300, https://doi.org/10.5194/egusphere-egu25-16300, 2025.
The StruCtiv project, funded by and in collaboration with the Geological Survey of Bavaria (Bayerisches Landesamt für Umwelt, Hof), focuses on the structural geological characterization of active fault zones in the Frontal Bavarian Forest and explores their implications for large-scale cause-effect relationships of tectonic activity within the crystalline basement of the Bavarian Forest. Our findings provide new insights into the tectonic, petrological, structural, and geomorphological processes shaping the region while highlighting the need for further investigations to refine our understanding of these complex systems. Preliminary U–Pb and K–Ar dating of minor faults exposed in granite quarries reveal a multiphase tectonic evolution spanning the Eocene to the Pleistocene, with possible indications of recent activity. U–Pb dating of calcite has proven especially promising, though additional sampling and structural characterization are required to address variability in ages within quarry outcrops. Complementary geomorphological analyses and cosmogenic nuclide measurements of river sediments show regional differences in erosion rates (21–40 m/Myr) and topographic variations, reflecting differential uplift rates. We used high-resolution TanDEM-X data and cosmogenic nuclide dating of older fluvial terraces to explore the long-term interactions between tectonics, climate, and erosion. Deliverables from the first project phase include ten high-resolution 3D models of quarries in the Bavarian Forest, structural measurements, dating of fault surfaces, and geomorphological analyses. These results have identified episodic fault reactivation from the post-Variscan to late Cenozoic periods. Landscape analyses based on chi-index and knickpoint studies and cosmogenic nuclide dating provide a consistent picture of the region's landscape evolution. Together, these findings suggest differential tectonic uplift across the Bavarian Forest. The ongoing project aims to build on these results through expanded structural and geochronological studies, the development of 3D models in additional quarries, and further digital mapping of structural inventories. The outcomes will deepen our understanding of fault-system evolution in continental intraplate settings and their role in understanding the long-wavelength vertical motion of the Earth's surface.
How to cite: Friedrich, A., Ludat, A., Zebari, M., Carena, S., Hildebrandt, D., Kahle, B., Assbichler, D., and Dusingizimana, M.: Structural Geological Characterization of Active Fault Zones in the Frontal Bavarian Forest and Implications for Large-Scale Cause-Effect Relationships of Tectonic Activity in the Bavarian Crystalline Basement (StruCtiv), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11593, https://doi.org/10.5194/egusphere-egu25-11593, 2025.
The Afar Depression, a key tectonic and volcanic region in East Africa, is characterized by complex interactions between rifting processes and mantle dynamics, particularly the influence of the rising Afar plume. This study offers a detailed investigation of uplift patterns in the Afar Depression over a decade (from 2014 to 2024) using Interferometric Synthetic Aperture Radar (InSAR) time-series analysis. The objective of this study is to generate critical insights and key observations as a foundational resource for advancing and refining future geological research. Resolving subtle, spatially distributed uplift patterns linked to tectonic activity has historically been challenged by methodological limitations. To address this, we analyzed three ascending (14, 87, 116) and four descending (6, 35, 79, 108) Sentinel-1A paths, applying the Small Baseline Subset (SBAS) method, complemented by decomposition techniques to achieve precise deformation measurements. We categorized the Afar area according to regions with the highest uplift rates, aiming to identify zones exhibiting significant tectonic activity. Our analysis reveals significant spatial and temporal variations in uplift rates, providing new insights into the region’s tectonic complexity and the role of the Afar plume. These findings highlight the intricate interplay between plume-driven uplift and tectonic structures, advancing our understanding of the Afar Depression’s geological evolution and the broader dynamics of continental rifting and lithospheric deformation.
How to cite: Milczarek, W. and Namdarsehat, P.: Investigating Uplift in the Afar Depression: Tectonic Complexity and Afar Plume through InSAR Time Series (2014–2024), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19803, https://doi.org/10.5194/egusphere-egu25-19803, 2025.
Within the 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 at magnetic high-latitude flux lobes (HLFLs). The focus is on four target regions on the Northern Hemisphere: Siberia, Canada, the North Atlantic, and Indonesia. While Siberia and Canada show the HLFLs, the North Atlantic should be the location of a third postulated HLFL, but this area does not show an intense-flux signal in the magnetic field. The region beneath Indonesia and the Indian Ocean is characterized by an area of intense magnetic flux that changes direction and moves westwards over time. Our aim is to understand whether mineralogy and seismic structure (i.e., thermal constraints) could be responsible for the different magnetic signatures at the core mantle boundary (CMB). This is done by combining two approaches: seismic anisotropy (KIT) and seismic reflections (University of Münster) near the CMB (https://www.geo.lmu.de/deepdyn/en/projects/ritter-joachim-und-thomas-christine-understanding-the-influence-of-deep/).
To study anisotropy, we measure 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), e.g., between SKS and SKKS phases, as they are a clear indication for a lowermost mantle contribution to the splitting signal. For the target region underneath Siberia, SWS measurements are obtained using earthquakes with epicenters in Southeast Asia recorded at stations in the North of Scandinavia and Svalbard as well as earthquakes with epicenters in Central America recorded at the station ULN in Mongolia. These SWS measurements indicate that for the discrepant pairs the phases with piercing points closer to the center of the HLFL beneath Siberia show splitting while the phases more distant to the HLFL do not show anisotropy. Furthermore, we present first results for the target region North Atlantic. Based on our SWS measurements, we will derive structural and mineralogical anisotropy models using the MATLAB Seismic Anisotropy Toolbox (Walker and Wookey 2012). To test these models, we then simulate synthetic seismograms using AxiSEM3D (Leng et al. 2016, 2019).
How to cite: Fröhlich, Y., Dorn, F., Dillah, M. I. F., and Ritter, J. R. R.: Investigation of seismic anisotropy in the D’’ layer and at the CMB underneath Siberia and the North Atlantic, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6615, https://doi.org/10.5194/egusphere-egu25-6615, 2025.
Ferropericlase (Mg,Fe)O, is the second most abundant mineral in the Earth’s lower mantle, and it’s structural and electronic properties are critical for understanding the formation processes and evolutionary history of the Earth's core.
This study focuses on the behavior of ferropericlase under extreme conditions that simulate the environment near the core-mantle boundary (CMB) and within the outer core, at pressures around 130 GPa and temperatures of about 3500 K related to a depth of approximately 2800 km by using shock compression experiments. It is well-documented that FeO exhibits varying structural configurations under high pressure and temperature [1] and iron electron spin changes [2]. This study aims at deepening understanding of ferropericlase's role in geophysical processes occurring at extreme conditions within Earth’s interior, ultimately contributing valuable insights into core formation theories and mantle dynamics. To investigate these properties, we synthesized ferropericlase (Fe0.14Mg0.86O) samples resembling pyrolytic mantle composition suitable for dynamic compression experiments. The experiments were conducted at the High Energy Density Scientific instrument at European XFEL within the scope of the DiPOLE community proposal 6656, utilizing time-resolved diagnostics to capture changes in the material's structure and electronic state. Two X-rays pulses were synchronized with a target impact, one before and another after the drive laser pulse of the DiPOLE 100-X laser, which allow us to probe the sample in a cold state and under pressure and temperature. The setup enabled us to acquire multiple datasets, including Velocity Interferometry for Any Reflector (VISAR) images, X-ray emission spectroscopy (XES), and X-ray diffraction (XRD). Data processing involved several steps: XES, spectra of Fe Kβ1,3 lines were analyzed for both pulses separately ensuring accurate timing of X-ray arrivals. XRD data underwent flat fielding correction followed by summation of diffraction patterns to calculate unit cell parameters for ferropericlase.
The XES data reveal a clear transition from high-spin to low-spin states as a function of laser energy and delay relative to the ambient conditions. Concurrently, XRD analysis shows a notable shift to larger momentum transfer in the main Bragg peak compared to cold runs, allowing for precise calculation of unit cell dimensions under varying pressure conditions. By integrating our initial findings with established equations of state (EoS) [3] we can estimate the pressure conditions at each experimental shot, indicating the variation of pressures up to ~130 GPa, i.e. conditions at the CMB. This analysis facilitates the construction of a volume-pressure curve that elucidates spin transitions relevant to Earth's depths. Next step consists in analyze VISAR data and get the Hugoniot for this composition. Furthermore, we aim to understand the electronic structure of the melts.
[1] Ozawa et al. Spin crossover, structural change, and metallization in NiAs-type FeO at high pressure. Phys. Rev. B 84, 134417 (2011)
[2] Greenberg et al. Phase transitions and spin state of iron in FeO under the conditions of Earth's deep interior. Phys. Rev. B 107, L241103 (2023)
[3] Fei et al. Spin transition and equations of state of (Mg, Fe)O solid solutions. Geophys. Res. Lett., 34, L17307 (2007)
How to cite: Camarda, C., Appel, K., Buakor, K., Amouretti, A., Crepisson, C., Harmand, M., Pennacchioni, L., Sieber, M., and Sternemann, C.: Characterization of ferropericlase under extreme condition using shock wave experiments carried at European XFEL utilizing DiPOLE 100-X drive laser, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13580, https://doi.org/10.5194/egusphere-egu25-13580, 2025.
Through almost the entire mantle column, oceanic crust is denser than ambient mantle. In a ca. 100 kilometers thick channel below the lower-upper-mantle boundary, however, this relation is reversed. Hence, this channel constitutes a trap for oceanic crust and several recent studies have indeed proposed large ponds of crust at this depth. Accumulation of crust would be expected to be continuous, while sequestration into the lower mantle should be episodic due to the metastable nature of the gravitational trap. Non-steady-state concentration of crust in the channel would be associated with variations in Earths volume in the order of several millions of cubic kilometers. While transfer of crust from the upper mantle into the channel causes volume increase, the collapse of crust into the lower mantle would be associated with net volume decrease. We propose that collapse events could be associated with rising mantle plumes, hence, a net volume decrease of Earth would precede the eruption of large igneous provinces (LIP). A dramatic volume loss in 650 kilometers depth might be able to pull down the surface for a brief time. Such an event might be expressed in an outstanding sea-level-drop before the eruption of LIP. This hypothesis is confirmed by a review of eustatic sea-level changes accompanying late Paleozoic – Cenozoic LIPs activity showing that a majority of LIP emplacement are shortly (< 500 kyr) preceded by an episode of up to 50 meters (average of 25 meters) eustatic sea-level fall, with return to pre-perturbation levels at the onset of LIP eruption.
How to cite: Nagel, T. and Bodin, S.: Variations of Earth's volume driven by intermittend mantle stratification, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18671, https://doi.org/10.5194/egusphere-egu25-18671, 2025.
In their seminal work, Munk and MacDonald (1960) showed that considering only the crustal contribution to the Earth’s moment of inertia (MOI) would predict a rotation axis passing through a location near Hawaii – clearly inconsistent with the present-day geographic pole. This finding implied there must be additional mass anomalies, which the authors speculated to be in the convecting mantle, that realign the rotation axis with the observed North Pole.
Modern geodynamic studies confirm that isostatic compensation of crustal thickness and density variations explains much of Earth’s observed topography, yet the crust’s gravitational contribution is often overlooked because it is relatively small compared to that generated by density anomalies in the mantle. As a result, residual topography (the difference between observed and isostatic topography) remains a prominent global constraint on the amplitude and spatial distribution of mantle density anomalies, while residual geoid (the difference between observed and crustal isostatic geoid) is utilized far less frequently. Crucially, this omission disregards the crust’s influence on Earth’s moment of inertia (MOI) and, by extension, its impact on the location of the rotational axis. Overlooking crustal mass heterogeneities can therefore lead to unrealistic (non-Earth-like) inferences of mantle density anomalies that do not correctly predict the location of the present-day rotational axis.
By analyzing satellite-derived non-hydrostatic geoid data and comparing modeled and observed moments of inertia, we find that preserving the present-day location of the rotational axis requires systematically accounting for crustal contributions. We implement a second order-accurate isostasy model – which integrates crustal buoyancy variations in a deformable crust – to more accurately capture the interplay between surface topography, the geoid, and the convective mantle. Neglecting this refinement not only fails to preserve the present-day rotational axis position but also compromises True Polar Wander (TPW) predicted by time-dependent mantle convection simulations.
Our findings suggest that integrating a second-order accurate isostasy framework into global mantle convection models is essential for producing consistent TPW trajectories, ensuring alignment between the modeled rotational axes and Earth’s observed pole positions.
How to cite: Kamali Lima, S., Forte, A. M., Greff, M., and Glišović, P.: Crustal Contributions to Moment of Inertia as Key Constraints for Earth-Like Mantle Convection Models: “Munk & MacDonald (1960)” Revisited, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7454, https://doi.org/10.5194/egusphere-egu25-7454, 2025.
Posters virtual: Tue, 29 Apr, 14:00–15:45 | vPoster spot 1
EGU25-14815 | ECS | Posters virtual | VPS22
Playing with Edges: The Influence of Arbitrary Definitions on Hotspot–LLSVP CorrelationsTue, 29 Apr, 14:00–15:45 (CEST) | vP1.12
Correlating surface hotspot volcanism with sharply defined edges of Large Low Shear Velocity Provinces (LLSVPs) is a common yet potentially oversimplified approach in mantle geodynamics. Such direct radial projections ignore the lateral displacement of plume conduits observed in seismic tomographic imaging, which suggests that purely vertical transport through the mantle is not guaranteed. Furthermore, many studies merge the African and Pacific LLSVPs, despite evidence that their correlation with hotspots differs significantly. These oversimplifications can lead to misinterpretations of plume-lithosphere interactions, the interaction between mantle plumes and the ambient ”mantle wind”, and mantle flow dynamics in general. Here, we systematically investigate how varied criteria can alter the inferred hotspot– LLSVP edge relationship. We separately analyze African and Pacific LLSVPs using: multiple tomography models, horizontal-gradient based definitions of edges, different vote-map methodologies, and distinct plume geometry assumptions–from perfectly vertical “spokes” to randomly deflected trajectories. We also apply the 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), to provide a geodynamically consistent assessment of the relationship between present-day hotspot locations and their source regions in the deep lower mantle. This independent geodynamic assessment clarifies how arbitrary choices concerning the interpretation of hotspots and LLSVP edges may lead to biased or skewed deep-plume reconstructions. Our results reveal that adjustments in hotspot catalogs, or the decision to combine the two main LLSVPs rather than regard each as dynamically distinct, can yield important differences in the significance attributed to sharply defined LLSVP edges. These findings underscore that commonly cited correlations between hotspot locations and LLSVP boundaries hinge on assumptions that vary considerably across the literature. Recognizing and rigorously defining input parameters–particularly the separate treatment of the African and Pacific LLSVPs and the inclusion of realistic lateral plume deflection–proves essential for robust interpretations of deep Earth structure. This highlights the need for standardized methodologies and careful parameter choices to avoid overstating the importance of LLSVP edges in shaping plume pathways.
How to cite: Johnston, G., Liu, S., Forte, A., and Glisovic, P.: Playing with Edges: The Influence of Arbitrary Definitions on Hotspot–LLSVP Correlations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14815, https://doi.org/10.5194/egusphere-egu25-14815, 2025.
