GeoHealth represents the critical intersection between the Earth and environmental sciences, and agricultural and health sciences. Following a specific request from the National Science Foundation (NSF) this report provides a series of recommendations aimed at empowering research, building fundamental workforce capacity, and improving communication around GeoHealth to the public and policy makers. This development is critical as a robust GeoHealth research enterprise is essential to global health, human and ecosystem well-being, and sustainability. The AGU community along with those from several allied societies provided the recommendations in this report; these were developed for a detailed survey and two workshops. The survey and other input revealed several broad challenges and needs, including highly siloed funding and support for researchers across institutions and societies, the inability to access or combine key datasets, and in particular the lack of clear career trajectories and support. The recommendations consist of: (i) six programmatic areas where significant attention to building a GeoHealth research enterprise is needed; (ii) approaches and concepts for four specific challenges in GeoHealth for which significant results could be enabled rapidly, within 2-3 years; (iii) ideas for developing an education/career path and for outreach; (iv) larger “moonshot” ideas that might yield very significant impacts over ca. 10 years. All of these have several common elements and themes: they leverage many directorates within NSF, including all within the GEO division; can build off of existing initiatives; are best developed through partnerships with other agencies and communities; and rely on open and FAIR data sets. Although the focus of these recommendations is toward and for the NSF, the suggestions are more general and hopefully will be considered by other funding agencies and other parts of the research enterprise in the U.S. and internationally.

Stable Ca isotopic composition (δ44/40Ca) of crustal carbonates are typically lighter than that of the bulk silicate Earth value (~1.05 ‰). Hence, δ44/40Ca of mantle-derived rocks can potentially trace recycled crustal carbonates into the mantle. We report the Ca isotopic compositions of globally distributed carbonatites (n = 46), which are unique igneous rocks with more than 50% modal carbonate minerals, with eruption ages ranging from Precambrian until recent. The δ44/40Ca (w.r.t. SRM915a) of these carbonatites show a large range (0.35 ‰ to 1.26 ‰), which is significantly higher than the analytical uncertainty (0.08‰) of the measurements performed using TIMS at CEaS, IISc. These samples are well-characterized in terms of their major and trace element geochemistry as well as Nd, Sr, B, C, and O isotopic compositions for selected samples. No systematic trend is observed between δ44/40Ca of the carbonatites and their eruption ages. Significant variability is observed in δ44/40Ca values in samples from individual provinces including those from the Oka complex in Canada (0.44 ‰ – 1.26 ‰, n= 8), Ambadongar (0.53 ‰ – 1.1 ‰, n= 8) and the Newania complexes (0.44 ‰ – 0.83 ‰, n= 4) in north-west India, the South Indian carbonatites (0.65 ‰ – 0.91 ‰, n= 3) and carbonatites from the Palabora complex in South Africa (0.35 ‰ – 0.84‰, n= 3). The δ44/40Ca of carbonatites from Oka, Newania and the Ambadongar show strong correlations with Ca/Mg, Ca/Fe as well as CaO and MgO contents. The δ44/40Ca of the Oka and Ambadongar carbonatites show correlated variations with their Mg# and K/Rb ratios, respectively. The large variability in δ44/40Ca of global carbonatites is explained in terms of: (1) presence of isotopically lighter ancient subducted carbonates in the mantle-source regions and carbonate metasomatism of the mantle, (2) partial melting and differentiation of the carbonatite magma and (3) heterogeneity in the source-mantle mineralogy of carbonatites.

Assessing volcanic hazard in regions of distributed volcanism is challenging because of the uncertain location of future vents. A statistical-mechanical strategy to forecast future vent locations was recently proposed. Here we further develop and test that strategy with analog models. We stress a gelatin block in controlled conditions and observe air-filled crack trajectories. We use the observed surface arrivals to sample the distributions of parameters describing the stress state of the gelatin block, combining deterministic crack trajectory simulations with a Monte Carlo approach. We find the algorithm retrieves the stress imposed on the gelatin and successfully forecasts the arrival points of subsequent cracks in the same experimental setups. We discuss how the approach may be used to gain insight on the stress state of regions of distributed volcanism.

High latitude glacierized coastal catchments of the Gulf of Alaska (GoA) are undergoing rapid hydrologic changes in response to climate change and glacial recession. These catchments deliver important nutrients in the form of both inorganic and organic matter to the nearshore marine environment, yet are relatively understudied with respect to characterization of the solute generation processes and total yields. Using multiple linear regression informed by Bayesian Information Criterion analysis we empirically demonstrate how watershed characteristics affect solute generation as represented by concentration-discharge relationships. We find that watershed mean slope and relief control solute generation and that solute yields are influenced most by glacier coverage. We contribute a new flux and concentration-discharge based conceptualization for understanding solute cycles across a hydroclimatic gradient of GoA watersheds that can be used to better understand future watershed responses to rapid hydrologic change.

The transition from the Semail ophiolite mantle to the underlying metamorphic sole was drilled at ICDP OmanDP Hole BT1B. We analyzed the bulk major, volatile and trace element compositions of the mantle-derived listvenite series and metamorphic rocks, with the aim to constrain chemical transfers associated to peridotite carbonation along the ophiolite basal thrust. The listvenite series comprise variously carbonated serpentinites and (fuchsite-bearing) listvenites. They have high CO2 (up to 43.2 wt.%) and variable H2O (0-12.1 wt.%). Yet, they have compositions close to that of the basal banded peridotites for most major and lithophile trace elements, with fuchsite-bearing listvenites overlapping in composition with amphibole-bearing basal lherzolites (e.g., Al2O3= 0.1-2.2 wt.%; Yb= 0.05-1 x CI-chondrite), The protolith of the listvenite series was likely similar in structure and composition to serpentinized banded peridotites which immediately overlie the metamorphic sole elsewhere in Oman. The listvenite series are enriched in fluid mobile elements (FME) compared to Semail peridotites (up to ~103-104 x Primitive Mantle), with concentrations similar to the underthrusted metabasalts and/or metasediments for Cs, Sr and Ca and sometimes even higher for Pb, Li, As, and Sb (e.g., Li up to 130 ppm; As up to 170 ppm). We also observe a decoupling between Sr-Ca enrichments and other FME, indicating interactions with several batches of deep CO2-rich fluids transported along the basal thrust. These results suggest that peridotite carbonation could represent one of the major trap-and-release mechanisms for carbon, water and FME along convergent margins.

Applying Phosphorus (P) to global cropland supports crop growth and helps to address the increasing global food demand. However, poor management of P application leads to nutrient loss and environmental pollution in many countries, while some countries (e.g., India and Vietnam) are also facing the depletion of national phosphate rock reserves. One critical strategy to address these challenges is to improve phosphorus use efficiency (PUE) in crop production. The success of this strategy depends on improving regional PUE with advanced technologies and effective management strategies, and an understanding of relevant socio-economic and agronomic drivers influencing regional and global PUE. However, low-efficiency regions and the key drivers remain unclear, and no studies have quantified the impacts of PUE improvement on addressing P challenges. This study developed a unique database of P budget and PUE by country and crop type over 50 years, and examines the temporal and spatial patterns, and makes projection of future P budget under three scenarios with different PUE improvement levels. By studying the historical data, we found that PUE has been significantly affected by a country’s development stage, crop portfolios, nitrogen use efficiency (NUE), fertilizer to crop price ratio, and average farm size. By improving the global PUE in crop production from the current 60% to around 69-82% by 2050, we could decrease the global P surplus from 8.8 in 2010 to about 4.5-9 Tg P yr-1 by 2050. Improvement of some countries (e.g., China and India) and some crop types (e.g., fruit and vegetable) should be prioritized, as they currently have relatively lower PUE.

Connectivity provides a framework for analyzing coastal sediment transport pathways, building on conceptual advances in graph theory from other scientific disciplines. Connectivity schematizes sediment pathways as a directed graph (i.e., a set of nodes and links). Existing techniques in graph theory and network analysis provide a low barrier to entry for using connectivity to quantify complex coastal systems, exemplified here using Ameland Inlet in the Netherlands. We divide the study site into geomorphic cells (i.e., nodes), and then quantify sediment transport between these cells (i.e., links) using a numerical model. The system of cells and fluxes between them are then schematized in a network described by an adjacency matrix. Network metrics like link density, asymmetry, and modularity quantify system-wide connectivity. The degree, strength, and centrality of individual nodes identify key locations and pathways through the system. These metrics allow us to address fundamental questions about sediment bypassing of Ameland Inlet and the optimal placement of sand nourishments. Connectivity thus provides a novel and valuable technique for predicting the response of our coasts to climate change and the human adaptations it provokes.

The oceanic phosphorus cycle describes how phosphorus moves through the ocean, accumulates with the sediments on the sea floor, and participates in biogeochemical reactions. We propose a new two-reservoir scenario of the glacial-interglacial phosphorus cycle. It relies on diagenesis in methane hydrate-bearing sediments to mobilize sedimentary phosphorus and transfer it to the ocean during times when falling sea level lowers the hydrostatic pressure on the sea floor and destabilizes methane hydrate. Throughout the cycle, primary production assimilates phosphorus and inorganic carbon into biomass which, upon settling and burial, returns phosphorus to the sedimentary reservoir. The impact of the two processes is not balanced: the former increases the oceanic phosphorus inventory whereas the latter decreases it. Primary production also lowers the partial pressure of COin the surface ocean, potentially drawing down COfrom the atmosphere. Concurrent with this slow ‘biological pump’, but operating in the opposite direction, a ‘physical pump’ brings metabolic COenriched waters from deep-ocean basins to the upper ocean. The two pumps compete, but the direction of the COflux at the air-sea interface depends on the nutrient content of the deep waters. Because of the transfer of reactive phosphorus to the sediment throughout a glaciation cycle, low phosphorus/ high COdeep waters reign in the beginning of the deglaciation, resulting in rapid transfer of COto the atmosphere. The new scenario provides another element to the suite of processes that may have contributed to the rapid glacial-interglacial climate transitions documented in paleo records.

We use fast synchrotron X-ray imaging to understand three-phase flow in mixed-wet porous media to design either enhanced permeability or capillary trapping. The dynamics of these phenomena are of key importance in subsurface hydrology, carbon dioxide storage, oil recovery, food and drug manufacturing, and chemical reactors. We study the dynamics of a water-gas-water injection sequence in a mixed-wet carbonate rock. During the initial waterflooding, water displaced oil from pores of all size, indicating a mixed-wet system with local contact angles both above and below 90 •. When gas was injected, gas displaced oil preferentially with negligible displacement of water. This behaviour is explained in terms of the gas pressure needed for invasion. Overall, gas behaved as the most non-wetting phase with oil the most wetting phase; however pores of all size were occupied by oil, water and gas, as a signature of mixed-wet media. Thick oil wetting layers were observed, which increased oil connectivity and facilitated its flow during gas injection. A chase waterflooding resulted in additional oil flow, while gas was trapped by oil and water. Furthermore, we quantified the evolution of the surface areas and both Gaussian and the total curvature, from which capillary pressure could be estimated. These quantities are related to the Minkowski functionals which quantify the degree of connectivity and trapping. The combination of water and gas injection, under mixed-wet immiscible conditions leads to both favourable oil flow, but also to significant trapping of gas, which is advantageous for storage applications.

The retroarc of the North American Cordilleran orogen in Nevada and Utah has been divided into the frontal Sevier fold-thrust belt in Utah, which accommodated shortening between ~145 and ~50 Ma, and a broad region of Nevada referred to as the ‘Sevier hinterland’. The hinterland is hypothesized to have developed into a high-elevation orogenic plateau (or ‘Nevadaplano’) at some point between the Late Jurassic and the Paleogene. Recent paleoaltimetry utilizing clumped isotope temperature estimates suggests that at least some basins on the Nevadaplano were at an elevation of 2.2-3.1 km by the latest Cretaceous. However, it remains uncertain precisely when the Nevadaplano attained these high elevations and if surface uplift developed steadily along with protracted shortening in the Sevier fold-thrust belt or occurred rapidly and was decoupled from the shortening record. In order to extend the surface elevation history of the Nevadaplano further back in time, we have investigated the type-exposure of the mid-Cretaceous (~113-98 Ma) Newark Canyon Formation (Knc) in central Nevada. The Knc records synorogenic sedimentation in the Sevier hinterland during the early to middle stages of shortening in the Sevier thrust belt. We will present terrestrial surface temperature estimates from clumped isotope analyses derived from palustrine, lacustrine, and pedogenic carbonate-bearing facies. Contextualized by structural evidence and corrected for secular climate change, these data suggest that the studied Knc basin had not developed substantial surface elevation by the mid-Cretaceous. However, there was likely some considerable surface relief in this region associated with active fold-thrust structures in the upper crust. Preliminary temperature estimates range between 22 and 70°C. These temperatures reflect a range of facies-specific differences in primary carbonate formation, as well as, diagenetic overprinting of some samples. Consistently warm temperatures throughout the stratigraphic section suggest that there was no significant cooling due to elevation gain between ~113 and ~98 Ma. We will discuss the implications of these results for the style and timing of deformation and surface uplift within the Nevadaplano.

Mechanism for fault segmentation in thrust belt is a key to understanding the orogenic process and seismic risks. A ~50 km long aftershock gap emerged between the ruptures of the 2008 Wenchuan and the 2013 Lushan earthquakes along the eastern margin of the Tibetan Plateau. Previous studies suggested that weak materials under ductile deformation cause the gap. Here we propose an alternative explanation: differential erosion drives the along-strike variation in fault activity. To testify the two competing models, we conducted low-temperature thermochronology and fluvial shear stress analyses to depict the spatial distributions of erosion. We obtained eight apatite fission track dates (6-44 Ma) in the gap and deduced erosion rates of 0.5-0.6 mm/yr and 0.3-0.4 mm/yr since ~8 Ma in the hanging -wall and footwall of the Shuangshi-Dachuan fault, respectively. We carried out linear fitting based on an empirical relationship between thermochronology-derived erosion rate and fluvial shear stress, and then calculated the erosion rate for each survey point of fluvial shear stress. Our new data reveal that in the hinterland, the erosion rate at the gap is lower than that of adjacent areas along strike, whereas in the range front, the erosion rate at the gap is greater. This spatial pattern supports the “differential erosion” hypothesis and is at odds with the “weak material” model. This study illustrates that heterogeneous erosion regulates fault segmentation in this thrust belt. Moreover, the aftershock gap acts as a barrier for the past major earthquakes, which poses substantial seismic potential to this region.

Submarine slope failures and the tsunamis they generate pose risks to coastal communities and infrastructure. While slope failures on passive margins represent some of the largest mass failures on Earth, little is known about their dynamics. The recurrence interval of submarine slope failures on passive margins is longer than on active margins, which facilitates thick sediment accumulation before failure, yields larger failures, and may be associated with higher potential for tsunami generation. While numerous studies model failure likelihood based on temporal distribution, overpressure, or earthquake proximity, there is limited insight linking initial conditions, preconditioning, slope failure initiation, and failure evolution. We observed dynamic submarine slope failure processes via physical experiments in a benchtop flume. Submarine slope failures were induced under controlled pore pressure with varied sand-clay mixtures (0%, 2%, 4%, and 5%, clay, by weight) constrained to a constant pre-failure slope geometry. Commercially obtained fine-grained sand (subangular quartz; 87% SiO2; D50 = 195 µm) and clay (dioctahedral smectite; 63% SiO2 and 21% Al2O3; D90 = 44 µm) were used. Pore pressure required to induce slope failure, slope-failure initiation and evolution, and post-failure morphology were recorded and analysed via photogrammetry. Numerical models were developed to quantify the physical processes observed in flume experiments. Increased clay content corresponded to increased cohesion and pore pressure required for failure. Subsurface fractures and tensile cracks were only generated in experiments containing clay. Falling head tests showed a log-linear relation between hydraulic conductivity and clay content which we used in our numerical models. Models of our experiments effectively simulate overpressure (pressure in excess of hydrostatic) and failure potential for (non)cohesive sediment mixtures. Overall our work shows the importance of clay in reducing permeability and increasing cohesion to create different failure modes due to overpressure. Ongoing work is investigating the effects of higher clay content and the role of seismic energy in slope failure morphology.

The magmato-tectonic environment(s) of origin for Earth’s earliest crust are enigmatic and fiercely debated. Revealing the composition of the melts from which Hadean (>4.02 Ga) zircons crystallized might clarify conditions of initial crust construction. We calculate model melts using Ti-calibrated zircon/melt partition coefficients (KdZrc(Ti)) and published trace element data for Hadean and Archean zircons. The same treatment is applied to zircons from possible analogue environments (MORB, Iceland, arcs, lunar), to constrain potential petrogenetic similarities and distinctions between the early and modern world. Model melts from oceanic environments (MORB, oceanic arc, Iceland) have higher heavy rare earth element (HREE) contents and shallower middle REE (MREE) to HREE/chondrite (ch) slopes than those from continental arcs and tonalite-trondhjemite-granodiorite suites (TTGs). Hadean and Archean model melts are nearly indistinguishable from one another, both resembling TTGs and continental arcs, with pronounced depletion of HREE and slope reversal in heaviest REE. A limited number of samples > 4.25 Ga yield model melts with broadly similar characteristics to those from younger Hadean and Archean zircons, but with relatively elevated REE (~half order of magnitude) and higher LREE and MREE relative to HREE. Rare earth element patterns of early Earth model melts suggest a common petrogenetic history in the Hadean and Archean, involving garnet +/-amphibole in relatively low-temperature, high-pressure, environments.

Dislocation recovery experiments were conducted on predeformed olivine single crystals at temperatures of 1,450 to 1,760 K, room pressure, and oxygen partial pressures near the Ni-NiO buffer to determine the annihilation rate constants for [001](010) edge dislocations. The obtained rate constants were found to be comparable to those of previously determined [001] screw dislocations. The activation energies for the motion of both dislocations are identical. This result suggests that the motion of screw dislocations in olivine is not controlled by cross-slip but by the same rate-limiting process of the motion of edge dislocations, i.e., climb, under low-stress, high-temperature conditions. The diffusivity derived from dislocation climb indicates that dislocation recovery is controlled by pipe diffusion. The conventional climb-controlled model for olivine can be applied to the motions of not only edge but also screw dislocations. The softness of the asthenosphere cannot be explained by cross-slip controlled olivine dislocation creep.

After three foreshocks the day before (M5.0, M4.7 and M4.1, respectively), a strong M6.4 Petrinja earthquake occurred on December 29, 2020, followed by thousands of aftershocks (the strongest was a January 6 M5.0 earthquake). This paper presents a unique multihazard sequence of complex events resulting in numerous cover-collapse sinkhole failures. Although the area heavily impacted by the earthquake was larger than 1,000 km2, all 91 sinkholes appeared within a 4 km2 area surrounding Mečenčani and Borojevići villages located 20–25 km SE of the epicentral area, during the three months following the main earthquake. That area was also previously prone to seldom sinkhole appearances, as evidenced by 45 documented fossil sinkholes. All 91 sinkholes opened as post-seismic events; the first one (the second biggest, 10.8x9.8 m in diameter and 3.6 m deep) started to open six hours after the strongest earthquake. The biggest sinkhole, 25x23 m in diameter and 11.7 m deep, opened seven days after the main earthquake and one day before the strongest aftershock; its total volume is larger than volume of all other 90 new sinkholes combined. The Mečenčani and Borojevići villages surroundings is the only area where a 4–15 m thick sequence of Holocene soil built of unsaturated low plasticity clays with gravel and sand interlayers and lenses covers the heavily karstified carbonate bedrock composed of alternating highly porous Miocene limestones and calcarenites. The unconfined aquifer within a soil is underlain by a well-permeable confined karst aquifer in which the water pressure during wet periods becomes subartesian to artesian, enabling significant erosion and formation of numerous caverns at the soil–limestone contact. Continuous removal of eroded sediment by groundwater flow through karstified systems in carbonates gradually expands cavernous space until a final cover-collapse. The 2020–2021 Petrinja earthquake sequence significantly accelerated these processes, resulting in 91 cover-collapse sinkholes opened during a three-months period, instead of usually one sinkhole opened every few years as reported by local people. It is interesting to note that during the strongest earthquake the water level in the unconfined aquifer was very close to the surface, and in the underlying karst aquifer artesian conditions prevailed.

Pore pressure in aquifers confined below a cryosphere will increase as Mars cools and the cryosphere thickens. The increase in pore pressure decreases the effective stress and hence will promote seismicity. We calculate the rate of pore pressure change from cooling of the Martian interior and the modulation of pore pressure from solar and Phobos tides and barometric loading. Using the time-varying pressure and tidal stresses, we compute Coulomb stress changes and the expected seismicity rate from a rate-and-state friction model. Seismicity rate will vary by several 10s of percent to two orders of magnitude if the mean pore pressure is within 0.2 MPa and 0.01 MPa of lithostatic, respectively. Seismic events promoted by high pore pressure may be tremor-like. Documenting (or not) tidally-modulated shallow seismicity would provide evidence for (or against) water-filled confined aquifers, that pore pressure is high, and that the state of stress is close to failure — with implications for processes that can deliver of water to the Martian surface.

In this research, GRACE satellite data have been used in order to investigate the possibility of estimating the amount of groundwater used in agriculture. The level-2 data of the GRACE satellites have been used to estimate the monthly groundwater level changes in central plateau catchment in Iran during the period of 2003 to 2013. One degree grid is used along with corrections of soil moisture, canopy, rainfall and snowfall from GRACE satellite data with the CLM4 hydrology model. The results revealed the amount of current groundwater in Iran and agricultural usage from groundwater have been determined (the largest consumer of groundwaters). verification of the results has been done by comparing the GRACE satellite data and piezometric wells data. Furthermore, ArcMap (ArcGIS) software were used for data analysis.

Social scientists have a long history of documenting disasters and natural extreme events’ behavioural response through the collection of perishable post-event data (Gruntfest 1977; Quarantelli and Dynes, 1977; Stalling, 1987; Quarantelli, 1997, 2003; Drabeck, 1999). Such empirical and theoretical foundations constitute a strong background to understand crisis responses and advance our knowledge of the drivers of human behavioural responses to fast evolving weather-related events. Outputs from this field of research show that public warning and behavioural response is a social process that takes several phases before a protective action is put in place (Mileti, 1995; Trainor et al., 2008, Parker et al., 2009, Lindell et al., 2004). These authors identified factors related to the characteristics of the hazard, the warning information characteristics, the situational and personal characteristics of the receiver and the socio-cultural context as strong determinants of the public behavioural response. In fast-moving events like flash-floods, the amount of time available to detect the threat and respond to it is so limited that protective actions often consist in dealing with contingent situations triggered by the irruption of dangerous circumstances in the middle of daily life activities and routines (Ruin et al., 2008, 2009; Terti et al., 2015). Understanding how people actually detect potentially dangerous circumstances and manage to timely adapt their routine to cope with the speed of the hazard evolution remains a challenge. Based on insights from post-event interviews, online surveys were used to quantitatively document behavioural responses associated with 3 catastrophic flash flood events that happened in southern France in 2014 and 2015. The coupled analysis of responses to these surveys with hydrometeorological parameters allows to better understand the link between the event magnitude and self-protective behaviours in the context of short-fuse weather events as flash floods. Knowledge gained from such an integrated approach is necessary for drawing lessons for the development of coupled human-natural system modeling and the prediction of the human vulnerability dynamics in short-fuse weather events.

Changes in the quantity and quality of groundwater and water in the hydrological cycle in general have important implications for the evolution of water resources, the built environment, and terrestrial and aquatic ecosystems, globally. Exploitation of groundwater and other subsurface resources may lead to e.g. land subsidence, salt water intrusion, loss of important terrestrial and aquatic ecosystems and hence biodiversity. Together with biogeochemical flows of nitrogen and phosphorus and changes in the land-system and climate, these are currently considered the main environmental problems of the planet, which are breaching or close to breaching planetary boundaries. Changes in the hydrological cycle including groundwater is closely related to and affecting these changes. It is the ambition of the four GeoERA groundwater projects studying aspects of groundwater quantity and quality issues related to natural processes and human activities to further develop the European Geological Data Infrastructure as a leading information platform for groundwater data in Europe and one of the leading platforms, globally. Here we briefly present the contents and objectives of the four groundwater projects: HOVER - Hydrogeological processes and geological settings over Europe controlling dissolved geogenic and anthropogenic elements in groundwater of relevance to human health and the status of dependent ecosystems; RESOURCE - Resources of groundwater, harmonized at cross-border and Pan-European Scale; TACTIC – Tools for assessment of climate change impact on groundwater and adaptation strategies and VoGERA - Vulnerability of shallow groundwater resources to deep sub-surface energy-related activities. The four projects will deliver “FAIR” (Findable, Accesssible, Interoperable and Reusable) data and information via the European Geological Data Infrastructure easily accessible for all relevant endusers. This will improve our understanding of the subsurface and support common efforts for developing geoethical uses of the subsurface.

The Ethiopian sector of the East African Rift system (the Main Ethiopian Rift, MER) and Afar rift showcase advanced stages of continental breakup. Here the interplay between active continental rifting and rift-induced volcanism poses key questions regarding the mantle geodynamics of late-stage rift development. A particular subject of interest is the presence of hot mantle upwellings in the sub-rift mantle, which are inferred from geophysical imaging. Magma generation in the sub-rift asthenosphere depends on the temperature, lithology, and composition of the upwelling mantle material. Geophysical observations of the sub-rift mantle must therefore be supported by petrological studies aimed at understanding the physico-chemical conditions of melt production. In this study we investigate melt generation beneath the MER and Afar using a mantle melting model constrained by olivine crystallization temperatures and rare-earth element (REE) concentrations, both observed in rift zone lavas. Olivine crystallization, a proxy for magma liquidus temperature, is directly related to the thermodynamic and geochemical conditions of the melting mantle. Through application of an olivine-spinel aluminium exchange thermometer, we provide the first petrological olivine crystallization temperatures for MER and Afar basalts (1177±16°C and 1263±43°C respectively). A multi-lithology mantle melting model subsequently allows for inversion of our olivine crystallization temperatures and observed REE concentrations of rift magmas to estimate the temperature, lithology, and composition of the Ethiopian mantle. Our results suggest that the crystallization temperatures and REE distributions measured at the MER and Afar necessitate elevated mantle temperatures (Tp ≥ 1450 °C) relative to ambient mid-ocean ridge mantle. A thick mantle lithosphere (~60 km) is also required to provide deep garnet-field mantle melting inferred from REE distributions. We additionally conclude that an enriched and fusible pyroxenitic mantle component is necessary to match crustal melt thicknesses and observed REE concentrations. The composition of this pyroxenitic lithology is further explored through our inversions, and the contributions of enriched pyroxenitic melts to rift volcanism in the MER and Afar are subsequently compared.

Maar-diatremes are inverted conical structures formed by subterranean excavation and remobilization of country rocks during explosive volcanism and common in mafic volcanic fields. We focus on impacts of excavation and filling of maar-diatremes on the local state of stress, and its subsequent influence on underlying feeder dikes, which are critical for understanding the development of intrusive networks that feed surface eruptions. We address this issue using finite element models in COMSOL Multiphysics®. Inverted conical structures of varying sizes are excavated in a gravitationally loaded elastic half-space, and then progressively filled with volcaniclastic material, resulting in changes in the orientations and magnitudes of stresses generated within surrounding rocks and within the filling portion of the maar-diatreme. Our results show that rapid unloading during maar-diatreme excavation generates a horizontal compressive stress state beneath diatremes. These stresses allow magma to divert laterally as saucer-shaped sills and circumferential dikes at varying depths in the shallow feeder system, and produce intrusion geometries consistent with both field observations from exhumed volcanic fields and conceptual models of diatreme growth. Stresses generated in these models also provide an explanation for the evolving locations of fragmentation zones over the course of diatreme’s filling. In particular, results from this study suggest that: (1) extensional stresses at the base of the diatreme fill favor magma ascent in the lower half of the structure, and possibly promote volatile exsolution and magma fragmentation; and (2) increased filling of diatremes creates a shallow compressive stress state that can inhibit magma ascent to the surface, promoting widespread intra-diatreme explosions, efficient mixing of host rock, and upward widening of the diatreme structure.

The American Geophysical Union (AGU) is committed to inspiring and educating present and future generations of diverse, innovative, and creative Earth and space scientists. To meet our commitment, AGU provides career and educational resources, webinars, mentoring, and support for students and professionals at each level of development to reduce barriers to achievement and to promote professional advancement. AGU is also working with other organizations and educational institutions to collaborate on projects benefiting the greater geoscience community. The presentation will include an overview of current Pathfinder efforts, collaborative efforts, and an appeal for additional partnerships.

Post-wildfire mudflows have intensified in recent years due to extreme wildfire occurrence, causing significant damage and infrastructure threats. However, despite recent advancements, across-scale geotechnical characterization of mudflow onset and flow behavior remains a challenge. We present a novel experimental and theoretical understanding of the sand type and rain intensity roles on mudflow onset and composition, integrating micromechanics and laboratory experiments. The analysis shows that hydrophobic fine sand, a consequence of wildfires, significantly enhances raindrops’ downhill velocity and splash due to Cassie-Baxter-type surface, as opposed to medium or coarse sand, which affects raindrops as Wenzel surface wettability model. We use micromechanical and single-drop interactions with sand particles to explain erosion on the intermediate scale laboratory tests. Raining experiments on hydrophobic sloped flumes evaluate different slope failure mechanisms in fine, medium, and coarse hydrophobic sand as erosion patterns and seepage induced infinite slope failure in the case of embedded hydrophobic layers. The sand type also affects the spatio-temporal dynamic of erosion onset and distribution of eroded material and overflown rainwater. Surprisingly, we detected a possible equilibrium state where the eroded surface roughness changes affect water overflow and lead to an equilibrium state with very little subsequent erosion under constant rain intensity. On the other hand, erosion gradually increases after the rain starts, reaches a peak, and then subsides very quickly in coarse sand. In contrast, fine sand erosion continues for a longer time but decreases as the surface roughness increases. Furthermore, micromechanical investigation of mixtures of hydrophobic sands, water, and air gives an insight into air entrapment during flow and transport of mudflows. Hydrophobic sand particles attach to air bubbles and form agglomerates, contributing to the mixture heterogeneity and affecting flow and transport properties. Sand particle size, due to gravity, also plays a role in the amount and size of resulting agglomerates. Covering air bubbles with attached sand particles decreases the post-wildfire mudflow density up to 33% in laboratory conditions.

Tropical cyclones dominate the disturbance regime experienced by forest ecosystems in many parts of the world. Interactions between cyclone disturbance regimes and nutrient availability strongly influence forest ecosystem dynamics. However, uncertainty exists over the importance of soil fertility properties (i.e., total soil phosphorus-P concentration) in mediating forest resistance and recovery from cyclone disturbance. We hypothesized that forests on soils with low total P (e.g., developed on limited-P parent material) have a higher resistance to but a slower recovery from cyclone disturbance than forests on high P soils. We investigated cyclone impacts on litterfall, an essential conduit for nutrient recycling in forest ecosystems. We compiled site-level forest litterfall data from 53 studies and datasets associated with 15 naturally-occurring one simulated tropical cyclone in 23 sites within five regions (Taiwan, Australia, Mexico, Hawaii, and the Caribbean)and four cyclone basins. We calculated the effect sizes of cyclone disturbance on the litterfall mass and nutrient (P and nitrogen-N) concentrations and fluxes during the first (< five) years post-disturbance across a total soil P gradient. We also assessed the effect of 20 covariates on the degree of cyclone impact on litterfall. Total litterfall mass flux increased by 4820%following cyclone disturbance. Such an initial increase in litterfall mass reflects the magnitude of cyclone-derived plant material input to the forest floor, which was highest in the Caribbean and lowest in Taiwan. Among 20 covariates, soil P and region were the best predictors of cyclone effects on total litterfall mass, explaining 80% of the variance. The effect sizes increased linearly with soil P and region, from significantly lower in Taiwan (low-P) to largest in the Caribbean (high-P). Total litterfall P and N fluxes increased significantly post-cyclone, whereas the increase in leaf P flux was twice as that in Nflux. Results highlight the importance of understanding the interactions between disturbance and nutrient gradients in forest ecosystems to understand forest responses to altered cyclone regimes expected under climate change.