Many rifted margins are thought to have formed in areas that have previously experienced subduction and orogenesis. Yet, our understanding of how structural and thermal inheritance from preceding convergence affects rifting is still incomplete. We use 2D thermo-mechanical numerical models to investigate how the size of a collisional orogen affects the style of subsequent continental rifting. Our models build an orogen through subduction and collision before the onset of rifting. We focus on the deformation style of the resulting rifted margins and the degree in which inheritance is utilized.

We find that the style of extension changes with the size of the orogen. A narrow orogen produces a narrow margin on the side of the overriding plate with core-complex-style reactivation of the subduction interface while a large amount of oceanic material is preserved in the conjugate margin. In contrast, wide orogens localize rifting away from the subduction interface: the subduction interface is temporarily reactivated, but deformation quickly shifts to the thick orogenic assembly resulting in wide rifted margins. Ductile deformation in the lower crust promotes localization of simultaneously active conjugate shear-zones in the brittle crust above. Rifting in these experiments occurs within the subducting plate.

Our results demonstrate a wide range of features that can form in the presence of inherited compressional structures and emphasise the importance of taking the deformation history into account when trying to understand the evolution of continental rifting.

The South China Sea experienced Cenozoic rifting in a region that was previously part of a Mesozoic Andean-type orogeny, which presumably had resulted in structural, compositional, and thermal inheritance. Recent studies using seismic profiles, drill cores, and geochronological analysis have revealed evidence for such heterogeneous pre-rift lithosphere in the South China Sea (Fan et al., 2017). Here, we further investigate the impact of orogenic inheritance on rift evolution using a numerical forward model that integrates both geodynamic and landscape evolution software (Neuharth et al., 2022). By varying our velocity boundary conditions over time, the model encompasses first continental collision, followed by post-orogenic collapse, continental rifting, and final lithospheric breakup. The model is constrained by observed crustal thicknesses, cooling history, and lithosphere-asthenosphere boundary depth, and successfully reproduces realistic orogenic topography, thrust fault distribution, and rifted margin of the SCS.We find that during orogeny, crustal thickening leads to the development of inherited weaknesses in the modelled crust. From orogenic collapse to continental rifting, pre-existing thrust faults are reactivated and serve as nucleation sites for normal faults, which interact with later rift-related normal faults to modify the regional stress field. The modeling results demonstrate that pre-existing thrust faults and a ductile lower crust play a crucial role in shaping the wide rifted margin of the SCS. We infer from our results that the location of crustal breakup is often influenced by these inherited structures. These regions have typically undergone thermal weakening, which further facilitates the process of crustal breakup during rifting.

Many large sediment-hosted clastic-dominated (CD) base metal deposits occur in failed continental rifts and the passive margins of successful rifts, e.g., in the MacArthur Basin, Australia, and in the Selwyn Basin in Canada. Continental rifts and their margins provide a specific mix of higher temperatures and heat flows, fault networks facilitating fluid flow, sediment input from the generated topography, and ocean water contributing pelagic sediments and sulfates. The large-scale geodynamics thus provide the necessary ingredients for metal leaching, with metal deposition then occurring on much smaller spatial and temporal scales.

To identify the specific geodynamic conditions conducive to large CD-type deposit formation, we numerically model 2D rift systems from inception to break-up with the geodynamic code ASPECT (Heister et al. 2017) coupled to the landscape evolution model FastScape (Braun and Willett 2013; Neuharth et al. 2022). With high-resolution (~300 m) simulations, we investigate how rift type (e.g., wide versus narrow), the presence of a craton, and the efficiency of erosional and depositional processes affect the formation of potential source and host rock domains. We subsequently analyse the optimal alignment of these regions where metals are leached and deposited, respectively, with faulting events providing fluid pathways between them. For these favorable co-occurrences, we estimate the potential size of metal deposits and identify those conditions that predict the largest deposits.

Braun and Willett. 2013. Geomorphology 180–181. 10.1016/j.geomorph.2012.10.008.

Heister et al. 2017. Geophys. J. Int. 210 (2): 833–51. 10.1093/gji/ggx195.

Neuharth et al. 2022. Tectonics 41 (3): e2021TC007166. 10.1029/2021TC007166.

Present spatiotemporal variations of hydrothermal fluxes in the modern and recent ocean provide an observational snapshot of the dynamic interaction between the tectonics of ocean basins and submarine hydrothermal systems. In order to support the understanding of feedbacks between tectonics and the life cycle of hydrothermal systems, we discuss the mechanical, fluid flow and heat flux patterns in a coupled ThermoHydroMechanical model at the ocean basin scale. The case study is an ultra-slow spreading basin, evolving from the initial rifting stages up to the ridge formation. Heat release by plastic deformation at fractures and faults, exothermic serpentinization reactions, sensible and latent crystallization heat from magmatic emplacement and radiogenic heat provide different energy-source signatures promoting hydrothermal activity. The large basin-scale domain allows us to navigate through the evolution of the modelled concurrent hydrothermal systems, emerging and decaying in consonance with the tectonics and the energy-sources. We discuss how the evolving permeability field in crust and sediments exerts a strong control on the hydrothermal circulation, and describe the dynamics of reorganization patterns in fluid flow in response to the mechanical strains and heat sources.

Understanding how normal fault networks initiate and evolve is important for quantifying plate boundary deformation, assessing seismic hazard and finding natural resources. State-of-the-art numerical forward models treat faults as finite-width shear zones, not as discrete entities. To better understand fault system dynamics over geological scales, we develop workflows to isolate individual faults and their role in shaping the fault network.

We present 3D numerical rift models of moderately oblique extension using the ASPECT software. These models reproduce the thermo-mechanical behavior of Earth's lithosphere and simulate fault system dynamics from inception to breakup accounting for visco-plastic rheology, strain softening and surface processes. We extract surficial fault systems as a hierarchical, time-dependent 2D network of nodes, edges and components representing individual faults.

We find that the initial fault network forms through rapid fault growth and linkage, followed by competition between neighboring faults that leads to their coalescence into a stable network. At this point, modelled normal faults continue to accumulate displacement but do not grow any longer. As deformation localizes towards the center of the rift, the initial border faults shrink and disintegrate, being replaced by new faults in the center of the rift. The longevity of faulting is thereby controlled by crustal rheology and surface process efficiency. Quantitative analysis of fault evolution allows us to deduce fault growth and linkage as well as fault tip retreat and disintegration in unprecedented detail.

Der Braunkohleausstieg führt zu Veränderungen in allen Bereichen der Wasserwirtschaft. Im Rheinischen Revier werden sich nach dem Ende des Bergbaus einige der größten deutschen Seen bilden. Der Grundwasserspiegel steigt und die Fließrichtung des Grundwassers ändert sich. Einige Oberflächengewässer führen mehr Wasser, andere weniger. Wasser wird ein wichtiger Faktor in der gesamten Region sein, aber es wird auch einen Wettbewerb um Wasser auf lokaler Ebene geben. Die Veränderungen in der Wasserwirtschaft sind wesentliche Randbedingungen im Strukturwandel im Bergbaugebiet.

Im Rheinischen Revier verursachten die Entwässerungsmaßnahmen rund um die Tagebaue ein Defizit von mehr als 20 Milliarden Kubikmetern Wasser. Beim Ausgleich dieses Defizits spielt die Nutzung von Wasser aus dem Rhein, das durch große Wasserleitungen gepumpt wird, eine wichtige Rolle. Die Befüllung der Seen wird etwa 40 Jahre dauern. Die Auswirkungen des Klimawandels werden in diese Planung einbezogen.

Eine der Kernaufgaben im Rahmen des Braunkohleausstiegs ist die Sicherstellung der Trinkwasserversorgung. Der Zufluss von Grundwasser aus den Abraumdeponien, das aufgrund von Pyritoxidationseffekten etwa 1.500 mg/l Sulfat enthält, wird die Schließung von mindestens vier Wasserwerken erzwingen. Darüber hinaus werden ca. 12 Wasserwerke von infiltriertem Rheinwasser betroffen sein, das verschiedene organische Spurenstoffe enthält. Ein flächendeckendes Wasserversorgungskonzept wird die Trinkwasserversorgung von mehr als 2,5 Millionen Einwohnern sicherstellen.

The largest contiguous former opencast lignite mining district in the EU is located in Lusatia (Germany). Hydrochemical contaminations such as acid mine drainage from opencast mines as well as increased susceptibility to soil instabilities pose major challenges for the reclamation of the Lusatian mining district in the coming decades. Therefore, time- and cost-efficient methods investigating former opencast lignite mines are vital for a sustainable remediation and reclamation.

In Lusatia, loose Cenozoic sediments (sands, silts, clays, and glacial tills) form several tens of metres of heterogeneous lithological successions in extensive opencast dumps. However, the effects of newly formed depositional structures, spatial heterogeneities and pore water mineralisation of the opencast dumps on groundwater flow and mass transport remain largely unknown in the post-mining areas of Lusatia.

In this study, we developed a workflow that makes use of spatially variable and heterogeneous input data ranging from airborne geophysics, geological maps and drilling logs. In a first step, we created 3D-representations of an exemplary post-mining area in Lusatia by using both classical geological interpretations as well as machine learning approaches. In a second step, the 3D representations are compared to each other and are used as input data for numerical groundwater modelling in order to analyse the effect on the simulated groundwater flow. This approach allows us to optimise the 3D-modelling workflow and to refine our understanding of the flow and mass transport processes between groundwater and pit lakes in the subsurface of post-mining areas.

As a result of the rearrangement of tertiary sediments and the groundwater lowering during open pit lignite mining, the formerly stable iron sulfide compounds oxidize to iron and sulfate ions and acidity. With the end of mining operations and the resulting rise in groundwater levels, these substances are transported into surface water, causing negative effects on the ecosystem and water management.
Sulfate reduction reverses the preceding oxidation process. By adding a carbon source, sulfate-reducing bacteria are activated in the aquifer. These metabolize the added carbon, producing sulfide which combines with the iron present in the groundwater to form iron sulfide and is fixed in the subsurface.
The process has already been tested as a pilot project in the Lusatian coalfield. For the transfer to the Central German mining district, adjustments had to be made to the plant design due to the cohesive soils and higher concentrations of iron and sulfate.
The plant configuration provides for a modular structure consisting of six self-sufficient sections. In each module, 86 individually controllable lances are provided for both lifting and infiltration of the water. Infiltration takes place in one lance at a time, while water is being lifted from other lances or these are paused so that water flows in. In this way, the problem of groundwater surface drawdown caused by upstream wells or the disadvantages of using external water are avoided. The lifted water is mixed with glycerine as a carbon source and then infiltrated again.

Empirical trophic models (Vollenweider-type) are one of the basic "tools of the trade" in management of natural and artificial lakes. They are not applicable to open-cast mining lakes (PML) because they underestimate their resilience to phosphorus (P) inputs. The high iron availability causes an efficient binding for phosphorus (P) in water and sediment of PML. The main objective was use hydrogeochemical modelling to assess the risks of eutrophication in the following way:

i) to develop conceptual (empirical) models (Vollenweider type) that can be used to more accurately estimate tolerable P loading to PMLs

ii) to represent the transition range from conditions with Fe excess to natural conditions in a model structure

iii) to identify specific indicators and tipping points for different P retention.

We analysed hydrological data, loads, and sediment properties to derive a closed P balance for 29 neutral mining lakes. The latter cover a range of water retention times and external P inputs. We distinguished three phases of PML development or maturation and the relevance of P-binding processes or binding forms. The Fe:P ratio in sediment was found to be the most important predictor of P retention. By integrating this ratio into conceptual models it is now possible to predict in-lake P-concentration from P inputs for PMLs and even for lakes with decreasing Fe import at the transition to “natural lake” conditions. We conclude that processes such as Fe~P adsorption and vivianite formation under anoxic conditions most likely ensure high P retention in the long term.

Lake Runstedt (near Merseburg, Germany; area 2.3 km², volume 53x10⁶ m³, max. depth 32.8 m) is an artificial lake resulting from lignite mining. The lower part of the former mine void was filled by industrial wastes consisting mainly of ashes but also containing waste from nitrogen fertilizer production rich in ammonium. Ammonium concentrations exceed 300 mgL^-1 in the pore water in the deposited wastes and constitute a threat for the regional groundwater resources. For protecting the groundwater, Lake Runstedt was created by filling the remaining space of the mine void above the waste with water from Saale River. The neighbouring pit lakes are managed in a way that groundwater flows into Lake Runstedt from all directions and that there is no outflow except evaporation. Hypolimnetic aerators provide the hypolimnion with oxygen needed for nitrification and reed was established in the littoral as habitat for denitrification. Since completion of the filling in 2003, the system has worked well as documented by monitoring. Usually, limnologists look at lakes as valuable ecosystems that have to be protected. In case of Lake Runstedt, the lake is used as a reactor. This unusual approach should not be a common preference but considered as exceptional option in applied limnology. The presentation will report on the creation of Lake Runstedt, the results of monitoring and research, and discuss the use of lakes as reactors protecting other compartments of the environment.

The climax of the 2021-2022 eruption of Hunga Volcano (also called Hunga Tonga – Hunga Ha’apai) on the 15^th January 2022 was the most explosive volcanic eruption this century. The eruption generated pressure waves that travelled around the planet multiple times, ash clouds that reached the mesosphere, tsunamis with run-ups over 10 m and severed the subsea telecommunication cables that connected the Kingdom of Tonga to the rest of the world.

Hunga Volcano, 70 km offshore from Tongatapu, is an almost entirely submerged caldera volcano. The 2023 eruption was the most explosive in recent history, and resulted in substantial modification to the seafloor. By comparing bathymetric datasets from before the eruption with datasets acquired by this team and autonomous vehicles in the months immediately after the event, we are able to identify the impacts of the eruption on the seafloor and the processes that caused the damage to the cables and, by combining this with auxiliary datasets, provide new constraints on the speed and dynamics of volcanic triggered submarine flows.

The eruption deepened the caldera floor by 800 m, with a loss of > 6 km³ of material, while high energy submarine density flows, focussed into gullies, caused upwards of 90 m of erosion higher up the flanks and deposited large lobes of material at the bases of them. These flows travelled hundreds of kilometres from the volcano at some of the fastest speeds ever measured for submarine density flows and were responsible for the damage to the subsea cables.

During expedition MSM109 in July 2022, a new hydrothermal vent field was discovered, which is the first active field found along the 500-km-long ultra-slow spreading Knipovich Ridge. The so-called Jøtul hydrothermal field is not located on an axial volcanic ridge (AVR) but is associated with the eastern bounding fault of the rift valley. A hydrothermal plume with methane concentrations between 100-1000 nmol/L emits hot fluids into the water column above the hydrothermal field, and is being drifted north with the bottom current. These high methane emissions are likely related to interactions between magmatic intrusions and sediments of the Svalbard continental slope produce unusually high release of thermogenic methane. Further investigations during MSM109 using ROV Quest show a wide variety of fluid escape sites such as diffusive venting from sediments, as well as seepage from joints and cracks within igneous rocks. Additionally, new inactive and active mounds with abundant hydrothermal precipitates and chemosynthetic organisms were discovered. Fluids were sampled from an active black smoker emitting fluids with temperatures > 316°C, and from three other sites with venting temperatures between 8°C and 272°C. The fluids are characterized by high methane, carbon dioxide, and ammonium concentrations, as well as high ⁸⁷Sr/⁸⁶Sr isotope ratios, indicating a strong interaction of the fluids with sediments from the continental margin of Svalbard. Locations with such intense magma/sediment interactions are of particular importance for the carbon cycle, and a focus of the Bremen Cluster of Excellence "The Ocean Floor – Earth’s Uncharted Interface".

The active volcanic arcs of the Scotia- and Caribbean Plate are two prominent features along the otherwise passive margins of the Atlantic Ocean, where subduction of oceanic crust is verifiable. Both arcs have been important oceanic gateways during their formation. Trapped between the large continental plates of North- and South America, as well as Antarctica, the significantly smaller oceanic plates show striking similarities in size, shape, plate margins and morphology, although formed at different times and locations during Earth’s history.

Structural analyses of the seafloor are based on bathymetric datasets by multibeam-echosounders, including data of GMRT, AWI, BAS, MARUM/Uni-Bremen, Geomar/Uni-Kiel and Uni-Hamburg. Bathymetric data were processed to create maps of ocean floor morphology with resolution of 150-250 meters in accuracy. The Benthic Terrain Modeler 3.0, amongst other GIS based tools, was utilized to analyse the geomorphometry of both plates. Furthermore, we used bathymetric datasets for three-dimensional modelling of the seafloor to examine large-scale-structures in more detail. The modelling of ship-based bathymetric datasets, in combination with the GEBCO 2014 global 30 arc-second grid, included in the GMRT bathymetric database, delivered detailed bathymetric maps of both areas.

With the help of the fine- and broad-scale bathymetric position index, we present the first detailed interpretation of combined bathymetric datasets of the entire Caribbean, the Scotia Sea and adjacent areas, such as the South Sandwich Plate. We identified typical morphological features of the abyss, based on determination of steep and broad slopes, ridges, boulders, flat plains, flat ridge tops and depressions in various scales.

Natural marine gas hydrate deposits are one of the largest solid carbon-sequestrated reservoirs on Earth. Here we show that, remarkably, over 80 percent of all natural hydrate-bearing systems exhibit stable periodicity (i.e. periodic growth and dissolution of massive gas hydrate layers) without any external forcing such as the bottom water warming or sea level fluctuations. This stable periodicity is the manifest of the intrinsic gas hydrate system dynamics related to a complex, kinetically controlled interplay between three phases, e.g. the free gas, solid gas hydrate, and methane-saturated pore fluids. Our results state that, globally, periodic (cyclic) states are present for wide range of marine sediment type and sedimentation regimes and the length of each cycle can last from tens to hundreds of thousands of years with cyclic variations in gas hydrate concentration from 20 vol. % to 60 vol. %. Each cycle is also associated with periodic release of the free methane gas in large quantities without the presence of any external forcing. The apparent existence of the periodic states has profound implications setting hard limits on hydrate predictability and implies a systematic source of uncertainty embedded within hydrate dynamics. Moreover, the anthropogenic climate perturbations may overprint the natural gas hydrate cycle and push formerly stable hydrate reservoirs to new periodic states with large p-T-s fluctuations, thereby significantly increasing the risks of uncontrolled gas escape and geomechanical failures, or formerly periodic states towards chaotic states, making long-term predictions extremely challenging.

The discovery and characterization of Earth-sized planets that are in, or near, a tidally-locked state are of crucial importance to understanding terrestrial planet evolution, and for which Venus is a clear analog. Exoplanetary science lies at the threshold of characterizing hundreds of terrestrial planetary atmospheres, thereby providing a statistical sample far greater than the limited inventory of terrestrial planetary atmospheres within the Solar System. However, the model-based approach for characterizing exoplanet atmospheres relies on Solar System data, resulting in our limited inventory being both foundational and critical atmospheric laboratories. Present terrestrial exoplanet demographics are heavily biased toward short-period planets, many of which are expected to be tidally locked, and also potentially runaway greenhouse candidates, similar to Venus. Here we describe the rise in the terrestrial exoplanet population and the study of tidal locking on climate simulations. These exoplanet studies are placed within the context of Venus, a local example of an Earth-sized, asynchronous rotator that is near the tidal locking limit. We describe the recent lessons learned regarding the dynamics of the Venusian atmosphere and how those lessons pertain to the evolution of our sibling planet. We discuss the implications of these lessons for exoplanet atmospheres and their detection with observations using JWST and other future facilities. We outline the need for a full characterization of the Venusian climate in order to achieve a full and robust interpretation of terrestrial planetary atmospheres.

We conducted the first study on Ga-Al systematics in Archaean and Palaeoproterozoic banded iron formations (BIFs). Adjacent Fe oxide, metachert and mixed-type bands were analysed comparatively with solution-based SF-ICP-MS and ICP-MS/MS and laser-ablation SF-ICP-MS on nano-particulate pressed powder tablets and polished sections. Furthermore, we conducted a matrix-matched two-component mixing experiment with the BIF reference material IF-G and pure synthetic quartz sand. Results of the three comparative analytical procedures and the two-component mixing experiment assure a high quality of our analytical data even in the trace metal-poorest (meta)chert samples. Furthermore, the results suggest that finely dispersed Fe oxide particles dominate the Ga and Al content in BIF (meta)chert bands. Regardless of the samples' mineralogy, the Ga/Al ratios of BIFs range between 2×10^-4 and 1×10^-3. A compilation of Ga/Al ratios in the investigated samples throughout time shows that during Precambrian global marine Ga/Al ratios were most likely rather constant. The BIF Ga/Al ratios are above those of potential detritus but below those of modern seawater. Two conclusions are conceivable: (i) Precambrian seawaters had lower Ga/Al ratios than modern seawater, possibly due to the reduced importance of organisms and organic compounds during weathering, riverine and estuarine processes. (ii) Ga and Al were fractionated during BIF formation, and BIFs did not preserve the original seawater Ga/Al ratios.

Characterizing the interior structure of exoplanets is an essential part in understanding the diversity of observed exoplanets, their formation processes and their evolution. As the interior of an exoplanet is inaccessible to observations, an inverse problem must be solved, where numerical structure models need to conform to observed parameters such as mass and radius. Since the relative proportions of iron, silicates, water ice, and volatile elements are not known, this is a highly degenerate problem whose solution often relies on computationally-expensive and time-consuming inference methods such as Markov Chain Monte Carlo.

We present here ExoMDN, a new machine-learning-based approach to the interior characterization of observed exoplanets using Mixture Density Networks that improves upon our previous work (Baumeister et al., ApJ, 2020). This improved model, trained on a large database of 5.6 million synthetic interior structures, can make a complete probabilistic inference about possible planetary interior structures within a fraction of a second, without the need for extensive modeling of each exoplanet's interior. We can demonstrate how the model, trained on different sets of (potentially) observable parameters including the received irradiation at the planet’s orbit and the fluid Love number, can help to further constrain the interior of a large number of exoplanets. In particular, we can show how precisely these parameters need to be measured to well constrain the interior.

Inside the upper mantle, incompatible trace elements are redistributed from solid mantle rocks into partial melt. The melt that accumulated the trace elements and that is less dense than the surrounding material rises towards the surface and as a result enriches the crust and depletes the upper mantle. In the case of heat producing elements, this process can affect the thermal evolution and crust production of a planet, whereas in the case of volatiles, the outgassing and atmosphere evolution can be influenced. With mineral/melt partition coefficients, we can quantify the amount of redistributed elements. Due to a lack of high-pressure models and experimental results, partition coefficients were generally taken as constant in mantel evolution models, however, they dependent heavily on pressure, temperature and composition.

In this study, we inserted a P,T,X-dependent clinopyroxene/melt partition coefficient model that is applicable for higher pressure [1] into a mantle evolution code and investigated the effects. Due to their implications for the thermal and atmosphere evolution, we focused both on heat producing elements (Uranium, Thorium, Potassium) and volatiles (H₂O). As a result, we found that the planet size influences partitioning behavior due to differences in depth and temperature inside the melt zones in the upper mantle. With these results, we can infer the impact on various planetary processes, such as the outgassing of water, crust production, and thermal evolution.

[1] Schmidt, J.M. and Noack, L. (2021): Clinopyroxene/Melt Partitioning: Models for Higher Upper Mantle Pressures Applied to Sodium and Potassium, SysMea, 13(3&4), 125-136.

For rocky planets it is typically assumed that they are able to differentiate into a silicate mantle and a metal core, due to the fact that metals are denser than silicates and should sink towards the gravitational center, i.e. the core of the planet.

However, more massive planets experience a higher pressure and compressibility in their interior, which can strongly impact the differentiation of the planet, potentially leading to inefficient core formation and even to coreless planets (Elkins-Tanton and Seager, 2008; Lichtenberg, 2021). By using a mantle convection code, we show that even over geological timescales, and depending on the size and distribution of iron droplets forming during the magma ocean crystallisation or later on due to phase transition disproportionation in the silicate mantle, the iron may indeed never be able to sink to the centre of the planet to form a metal core. Since the ability to form a (large) core should decrease with increasing planetary mass, this study suggests that the mantle of super-Earths may be more iron-rich and therefore more reducing than for Earth, which would be reflected in their atmospheric composition and could potentially be confirmed by future observations of exoplanetary atmospheres.

References:
Elkins-Tanton and Seager, 2008, Coreless Terrestrial Exoplanets, ApJ 688, 628-635
Lichtenberg, 2021, Redox Hysteresis of Super-Earth Exoplanets from Magma Ocean Circulation, ApJL 914:L4

Planetary surfaces hold evidence of past geological processes through the geomorphological record of landforms. Fast erosion rates, active tectonics, and a thick atmosphere contribute to partial or total loss of the terrestrial record, therefore leading to the misinterpretation and underestimation of the geological processes that formed it. Well-preserved extraterrestrial landforms, coupled with high resolution imagery, can compensate for the terrestrial missing geomorphological information. On the other hand, on Earth, we have direct access to landforms. Field observations are vital to gain insights into the mechanisms involved and into the environmental and climatic conditions in which landforms form. Therefore, the combination of terrestrial and planetary observations can be very effective in better understanding geological processes across the Solar System.

This talk will focus on long runout landslides and impact craters. I will discuss: a) the importance of comparative planetary geology in studying long runout landslides on Mars and Earth, in the attempt to understand their emplacement mechanisms and the link with climatic conditions; b) present day impact events on the Moon and the implications for Solar System chronology and impact flux rate.

Polygonal networks occur on various terrestrial and extraterrestrial surfaces holding valuable information on the pedological and climatological conditions under which they develop. However, in contrast to their periglacial counterparts, the information that polygons in the hyper-arid Atacama Desert can provide is little understood. To gain insights into their geometrical and geochemical build-up, we performed a morphometric terrain characterization in combination with geochemical and sedimentological analysis on four polygonal networks in the Yungay area of the Atacama Desert. The polygons are composed of siliciclastic sediment that is mainly cemented by sulfates in ~0–50 cm depth and by nitrates and chlorides in ~50–100 cm depth while being separated by about 1 m deep, salt-poor and V-shaped sand wedges. The high salt content (>60 wt%) and high surface temperature variations make a thermal contraction origin likely. The low clay content (~2 wt%) makes an exclusive desiccation origin less relevant but a formation based on dehydration of sulfates remains conceivable. Morphometric data indicate a link between topography and polygon geometry, as the flat-centered polygons (mean size ~4 m) are aligned either in slope direction or perpendicular to it, while being more elongated on steeper slopes. Erosion of these networks is mainly eolian-driven, but we also find signs for aqueous resurfacing of microtopography by fog and minimal rainwater infiltration. Our findings provide a basis for future polygon research in hyper-arid environments, such as Mars, while allowing for the use of polygons as environmental proxies in the Atacama Desert that indicating saline soils and hyper-arid conditions.

One of the limits of planetary habitability of Earth and other water-rich planets relates to the instability with respect to global glaciation, a fundamental property of the climate system caused by the positive ice-albedo feedback. Due to the steady increase in solar luminosity, the atmospheric concentration of carbon dioxide (CO₂) at which this Snowball bifurcation occurs evolves over time. Earlier studies on the limit of global glaciation are based on investigations with very simple climate models for Earth’s entire history or studies of individual time slices carried out with a variety of more complex models and for different boundary conditions, making comparisons difficult. Here we use a relatively fast coupled climate model of intermediate complexity to trace the Snowball bifurcation of an aquaplanet through Earth’s history in one consistent modelling framework. We find that the critical CO₂ concentration decreases more or less logarithmically with increasing solar luminosity until about 1 billion years ago, but drops faster in more recent times. Furthermore, there is a fundamental shift in the dynamics of the critical state about 1.8 billion years ago, driven by the interplay of wind-driven sea-ice dynamics and the surface energy balance. These results highlight once again the importance of climate dynamics for investigations of planetary habitability.

The Earth’s magnetic field shields our planet against highly energetic particles from the Sun and outer space. Over geological times, the time-varying geomagnetic field exhibited periods of dramatic changes, both in intensity and direction. Recent data compilations of paleomagnetic records enable us to model the long-term, global evolution of the geomagnetic field and better understand the internal dynamics and underlying phenomena. On the other hand, the spatial and temporal changes influence the shielding and cosmogenic nuclide production rates. In general, the higher the field intensity, the larger the shielding and the fewer cosmogenic nuclides are produced in the atmosphere.

We cover the evolution of the geomagnetic field over the past 100 000 years by presenting characteristics found to be robust in available global models. The period includes a few geomagnetic excursions, including the Laschamps excursion 41 000 years ago – when the intensity was globally very low, and the field had a complex, multipolar structure. Several properties of and estimates based on the models will be discussed, including the field morphology at the core-mantle boundary and Earth’s surface, global cutoff rigidity variations, impact area, global cosmic ray flux, and production rates of different cosmogenic nuclides. The latter results from the models are validated through comparison with actual measurements from ice and marine cores.

AlpArray is changing notions of lithospheric subduction along the Alps and its effects on orogeninc lithosphere. Teleseismic V_p tomography reveals a slab of European lithosphere that is largely detached at and below 150 km in the Western Alps. Only in part of the Central Alps is the slab still attached, possibly reaching down to the mantle transition zone, where it appears connected to subducted remains of Alpine Tethys. SKS directions beneath the Alps suggest that asthenosphere not only flowed passively around the sinking slab, but may have induced the anomalous northward dip of the detached slab segment beneath the Eastern Alps.

The structure of the orogenic lithosphere differs profoundly along strike of the Alps, as revealed by local earthquake tomography, ambient-noise studies, as well as S-to-P receiver-functions and gravity studies: In the Central Alps where the slab is still attached, the exhumed retro-wedge of the orogen overrides a wedge of Adriatic lower crust. In the Eastern Alps where the slab has detached, exhumation is focused in the orogenic core (Tauern Window) north of and above bulged lower crust of presumed Adriatic origin. This indicates decoupling at the base of qtz-rich, presumably hydrous intermediate crust to accommodate coeval Miocene N-S shortening, orogen-parallel thinning and eastward extrusion of orogenic lithosphere.

We propose a new model for Alpine orogenesis that invokes changing wedge stability and migrating subduction singularities above the delaminating and detaching Alpine slab in the east to explain east-west differences in Oligo-Miocene structure, magmatism, erosion and sedimentation in peripheral Alpine basins.

Orogens in the Alpine-Himalayan collision zone (AHCZ) exhibit characteristic diffused seismicity compared to the stable continental interiors. Interestingly, they also have a thicker-than-average silica-rich upper crust and total crustal thickness, while their lithosphere thickness is similar to that of stable continental interiors (e.g., Tibet, Zagros). These observations provide a metric for the lithospheric-scale geological inheritance, the role of which we aim to understand in continental lithosphere dynamics over seismic and geologic timescales. To achieve this understanding, we use data-driven modelling to compute the present-day thermomechanical state of the AHCZ lithosphere.

Our results indicate the existence of a critical crustal thickness, which is thermodynamically controlled by the internal energy and chemical composition of the crust and is similar to the global average of continental crust thickness. Orogenic lithospheres with thicknesses above this critical value possess higher potential energy and are weakened by the internal energy from heat-producing elements, whereas continental interior lithospheres with thicknesses close to the critical crustal thickness are stronger. Weaker orogenic lithospheres respond via dissipating this energy in a diffused deformation mode, leading to zones of deformation in contrast to focused deformation at the plate-boundaries. The observed crustal differentiation in the AHCZ could be understood as perturbations to the critical crustal thickness caused by plate-boundary forces. The dynamic evolution of these perturbations indicates that the critical crustal thickness is a stable fixed-point attractor in the evolutionary phase-space.

To relate Intraplate volcanism to upper mantle structure, we investigate small-scale structural-variations of the lithosphere-asthenosphere beneath the Circum-Mediterranean using regional high-resolution 3-D surface-wave tomography. The imaged low shear-wave velocities (Vs<4.2 km/s) between depths of ~70-300 km indicate the presence of nine shallow asthenospheric volumes (SAVs) across the Circum-Mediterranean upper mantle forming a partly interconnected belt and separated only by high velocity slabs and thickened lithosphere. Integrated geophysical-petrological modelling for 14 representative locations, yields estimates of the lithospheric thickness and the upper mantle geotherm and confirms the presence of thin lithosphere (<80 km) above areas of anomalously warm SAVs (>1300°C).

We distinguish between Intraplate, Mixed-origin and Subduction-related volcanism in the Circum-Mediterranean during the last 70 Ma and find a remarkable colocation between the SAVs and Cenozoic Intraplate and Mixed-origin volcanic provinces (IMVPs). Moreover, the lateral distance from any shallow asthenosphere to the closest neighboring volcanic province is, on average, as low as 100 km, with a maximum distance of 350 km, indicating a dense network of IMVPs above SAVs. By contrast, IMVPs are completely absent in areas of thick mantle lithosphere.

We relate origin of the SAVs either to asthenospheric upwelling caused by slab-rollback and back-arc extension (Aegean-Anatolian, Pannonian, Moesian, Western Mediterranean SAVs) or to thermal erosion of the lithosphere partly coupled with continental rifting (Adriatic, Central European, North African, Middle East SAVs), respectively. The oldest ages of the IMVPs in the Circum-Mediterranean indicate that the development of the current SAVs started at about ~60-70 Ma ago and accelerated in Neogene.

Imaging the deep Earth structures is conventionally carried out using earthquake recordings. However, the resolving capability of such techniques (e.g., SS precursors and receiver function analysis) is often limited by the uneven spatial distribution of earthquake events and the high complexity of earthquake rupture processes. Recent advances in passive noise interferometry demonstrated the possibilities of recovering body waves from noise correlations, opening up new prospects for imaging the deep earth.

In this study, we map the mantle transition zone (MTZ) discontinuities beneath South- Central Europe using P-wave reflection phases recovered from noise correlations. We analyze up to four years of seismic noise recordings from 900 broadband stations in the study area. By stacking noise correlations in selected summer months, we significantly improved the retrieval of typically low-amplitude body-wave reflection phases in the light of a quiet surface-wave environment and sufficient noise body-wave illumination from deep paths. We obtain reliable P-wave reflections associated with the 410-km and 660-km discontinuities in the period band of 4-10 s. These short-period reflections reveal clear lateral depth variations of the two discontinuities, indicating a complex MTZ arrangement in the greater Alpine region that is related to both present and past tectonic regimes. Our imaging method shows its potential for general applications in studying deep-earth discontinuities.

The tectonic structure of the Eastern Alps is heavily debated with successive geophysical studies that are unable to resolve areas of ambiguity (e.g., the presence of a switch in subduction polarity and differing crustal models). In order to better understand this area, we produce a high resolution Moho map of the Eastern Alps based on a dense seismic broadband array deployment. Moho depths were derived from joint analysis of receiver function images of direct conversions and multiple reflections for both the SV (radial) and SH (transverse) components, which enables us to map overlapping and inclined discontinuities. We observe the European Moho to be underlying the Adriatic Moho from the west up to the eastern edge of the Tauern Window. East of the Tauern Window, a sharp transition from underthrusting European to a flat and thinned crust associated with Pannonian extension tectonics occurs, which is underthrust by both European crust in the north and by Adriatic crust in the south. The Adriatic lithosphere underthrusts northward below the Southern Alps and becomes steeper and deeper towards the Dinarides where it dips towards the north-east. Our results suggest that the steep high velocity region in the mantle below the Eastern Alps, observed in tomographic studies, is likely to be of European origin.

The Late Cretaceous collision of the Adriatic microplate with Eurasia resulted in an overall SW-vergent and in-sequence structural architecture of the Dinarides. In the Paleogene the deformation propagated from the Internal towards the External Dinarides, associated with ca. 130 km of crustal shortening. Fault kinematic data and balanced cross-sections across the External Dinarides suggest contrasting styles along-strike the orogen, separated by a ca. 250 km long dextral transpressive fault. This fault delimits the southern, SW-vergent nappe stack segment from a northern, NE-vergent backthrust-dominated Velebit segment. Based on the distribution of the flexural foreland basin sediments, it is known that these two domains deformed contemporaneously, which marked the end of the Paleogene Dinaric orogeny.

Within these Eo- to early Oligocene syntectonic and older Mesozoic carbonate platform rocks horizontal marine terraces are preserved at elevations of up to 600 m. We extracted terrace surfaces along the entire Adriatic coast from DEMs. All these flat surfaces are degradational, not related to bedding or faults, and they are located on the western side of the main drainage divide facing the Adriatic Sea. Their spatial correlation is in agreement with the position of a reported negative P-wave tomography anomaly, which in turn correlates with the thinned part of the Adriatic lithosphere. Our findings suggest an orogen-wide surface uplift affecting the Dinarides in the Neogene due to mantle delamination.

Our overarching results show that the Paleogene Dinaric orogeny was related to high crustal shorten- and thickening, whereas the Neogene was related mainly to surface uplift.

Current tectonic activity in the eastern Southern Alps is driven by the ongoing collision of Adria with Europe at a rate of ca. 2-3 mm/yr. While the South Alpine Front is well-studied, the deformation in the hinterland of the orogenic front is still not well-understood. Structurally, this area is characterised by dominantly E-W-trending, south-vergent thrusts and dextral strike-slip faults of the eastern Periadriatic fault system and the Dinaric system in Slovenia. Here we present new data on active faulting from tectonic geomorphology studies, field mapping, paleoseismology, and Quaternary dating techniques. We show that in Slovenia, crustal deformation is accommodated by a system of NW-SE striking right-lateral strike slip faults in a more than 60 km-wide zone. While the largest of those faults might be capable of magnitude M≥7 earthquakes, there is no historical or geological record for such large events. Several shorter faults with lengths of less than 15 km also show postglacial activity, but very little is known about their earthquake history. In Italy, most of the deformation is accommodated by thrusting at the South Alpine orogenic front and in the Friulian Plain. However, historical reports and our geomorphological observations indicate that strong earthquakes (M>6) occurred in the interior of the mountain chain, but these events are probably very rare. In Austria, the geological record of active faulting is sparse, although damaging historical quakes are known. New dating results from undisturbed geomorphic markers allow us to place constraints on the maximum amount of deformation that is accommodated here.

The eastern Southern Alps are a seismically active region. Research has been conducted to identify seismically active faults, with the sources of several catastrophic earthquakes still unknown.

In this study, we conducted a paleoseismological investigation around the Fella-Sava Fault in the trijunction of Austria, Italy, and Slovenia, within the epicentral area of the destructive 1348 earthquake (M_W 6.6-7.0). The Fella-Sava Fault is a ca. 100 km long, E-W- to WNW-ESE trending dextrally transpressive fault related to the Periadriatic fault system. Using digital elevation models (DEMs), we tried to identify direct evidence for surface rupturing earthquakes like fault scarps or offset geomorphic markers. Additionally, we put a special emphasis on sackungen. Sackungen are created by the gravitational collapse of mountain flanks, both aseismically and coseismically. Hillshades and aspect-maps derived from the DEMs proved suitable for mapping sackungen on a regional scale covering an area of ca. 1500 km².

A systematic remote sensing-based mapping of sackungen (of which several were subsequently ground-proven) in an area 15 km to both sides of the western segment of the Fella-Sava Fault revealed their clustering within 5 km on either side of the fault. The sackungen correlate neither with lithology nor valley depth. A directional analysis shows that the preferred trend of the sackungen is parallel to the Fella-Sava Fault and doesn’t correlate with the distribution of regional slope orientations. Thus, we suspect that the higher number sackungen in proximity of the Fella-Sava-Fault provides geomorphological evidence for its postglacial seismic activity, including the 1348 earthquake.

The Periadriatic Fault System (PAF) is among the largest post-collisional structures of the Alps. Recent studies using GPS velocities suggest that Adria-Europe convergence is still being accommodated in the Eastern Alps. However, according to instrumental and historical seismicity records, earthquake activity is mostly concentrated along structures in the adjacent Southern Alps. This is also the case for the PAF, which except for ambiguous historical events presents little to no earthquake record. Electron spin resonance (ESR) and Optically Stimulated Luminescence (OSL) are ultra-low temperature thermochronometers (closing temperature below 100 °C), with a Quaternary dating range (a few decades up to ~2 Ma). Both have the potential to date shear heating episodes. In this contribution, we present a first approach to narrow down earthquake activity during the Quaternary in the Eastern Alps by combining the application of ESR and OSL. Specifically, we aim to show which segments of the PAF system accommodated seismotectonic deformation by directly dating quartz and feldspar from fault gouges. For ESR, we measure the signals from the Al center in quartz following the single aliquot additive (SAAD) and single aliquot regenerative (SAR) protocols, focusing on the 4-11 µm and 100-150 µm grain size fractions. For OSL, we measure the IR₅₀ and pIRIR₂₂₅ signals on K-feldspar aliquots of the 100-150 µm grain size fraction. Our ESR results indicate the PAF accommodated seismic slip during the Quaternary with a maximum age ranging from 1-0.5 Ma, and OSL minimum ages of around 0.3 Ma.

The 2019, Mw 6.4 earthquake struck Albania at the Adriatic port city of Durres, 30 km away from the capital Tirana. It caused significant destruction and more than 50 deaths. The mainshock had thrust mechanism typical for the western Balkan margin along which the Adriatic micro plate collides with Europe. A dense temporary network of 30 seismic stations was deployed for 9 months to record the aftershock sequence. We applied a fully automated, machine learning-based detection and phase-picking routine to analyse the seismic data. This way more than 19,000 events were detected and located. Deriving cross-correlation-based differential travel times and relocating the entire catalogue of events with the HypoDD algorithm and a newly derived 1D velocity model reveals the fine-scale structure of the thrust fault. The rupture occurred on a ~30° NE dipping fault between approx. 10 and 20 km depth. The aftershocks collapse to several additional synthetic and antithetic structures highlighting a complex fault network.