The mixing and mingling of magmas of different compositions are important geological processes. They produce various distinctive textures and geochemical signals in both plutonic and volcanic rocks and have implications for eruption triggering. Both processes are widely studied, with prior work focusing on field and textural observations, geochemical analysis of samples, theoretical and numerical modelling, and experiments. However, despite the vast amount of existing literature, there remain numerous unresolved questions. In particular, how does the presence of crystals and exsolved volatiles control the dynamics of mixing and mingling? Furthermore, to what extent can this dependence be parameterised through the effect of crystallinity and vesicularity on bulk magma properties such as viscosity and density? In this contribution, we review the state of the art for models of mixing and mingling processes and how they have been informed by field, analytical, experimental and numerical investigations. We then show how analytical observations of mixed and mingled lavas from four volcanoes (Chaos Crags, Lassen Peak, Mt. Unzen and Soufrière Hills) have been used to infer a conceptual model for mixing and mingling dynamics in magma storage regions. Finally, we review recent advances in incorporating multi-phase effects in numerical modelling of mixing and mingling, and highlight the challenges associated with bringing together empirical conceptual models and theoretically-based numerical simulations.

Several paleomagnetic studies have been conducted on five main group pallasites: Brenham, Marjalahti, Springwater, Imilac and Esquel. These pallasites have distinct cooling histories, meaning that their paleomagnetic records may have been acquired at different times during the thermal evolution of their parent body. Here we compile new and existing data to present the most complete time-resolved paleomagnetic record for a planetesimal, which includes a period of quiescence prior to core solidification as well as dynamo activity generated by compositional convection during core solidification. We present new paleomagnetic data for the Springwater pallasite, which constrains the timing of core solidification. Our results suggest that in order to generate the observed strong paleointensities (∼ 65 - 95 μT), the pallasites must have been relatively close to the dynamo source. Our thermal and dynamo models predict that the main group pallasites originate from a planetesimal with a large core (> 200 km) and a thin mantle (< 70 km). The density of our model large-cored planetesimals is similar to the predicted density of the asteroid (16) Psyche. We therefore suggest that it is plausible that the main group pallasites originated from a Psyche-like parent body. 1

Two adjacent segments of the Chile margin exhibit significant differences in earthquake magnitude and rupture extents during the 1960 Valdivia and 2010 Maule earthquakes. We use the Discrete Element Method to simulate the upper plate as having an inner and outer wedge defined by different frictional domains along the decollement. We find that outer wedge width strongly influences coseismic slip distributions. We use the published peak slip magnitudes to pick best fit slip distributions and compare our models to geophysical constraints on outer wedge widths for the margins. We obtain reasonable fits to published slip distributions for the 2010 Maule rupture. Our best-fit slip distribution for the 1960 Valdivia earthquake suggests that peak slip occurred close to the trench, differing from published models but being supported by new seismic interpretations along this margin. Finally, we also demonstrate that frictional conditions beneath the outer wedge can affect the coseismic slip distributions.

We highlight a mechanism for the co-production of research with local communities as a means of elevating the social relevance of the geosciences, increasing the potential for broader and more diverse participation. We outline the concept of an “equitable exchange” as an ethical framework guiding these interactions. This principled research model emphasizes that “currencies”- the rewards and value from participating in research - may differ between local communities and geoscientists. For those engaged in this work, an equitable exchange emboldens boundary spanning geoscientists to bring their whole selves to the work, providing a means for inclusive climates and rewarding cultural competency.

Due to the mixed distribution of buildings and vegetation, wildland-urban interface (WUI) areas are characterized by complex fuel distributions and geographical environments. The behavior of wildfires occurring in the WUI often leads to severe hazards and significant damage to man-made structures. Therefore, WUI areas warrant more attention during the wildfire season. Due to the ever-changing dynamic nature of California’s population and housing, the update frequency and resolution of WUI maps that are currently used can no longer meet the needs and challenges of wildfire management and resource allocation for suppression and mitigation efforts. Recent developments in remote sensing technology and data analysis algorithms pose new opportunities for improving WUI mapping methods. WUI areas in California were directly mapped using building footprints extracted from remote sensing data by Microsoft along with the fuel vegetation cover from the LANDFIRE dataset in this study. To accommodate the new type of datasets, we developed a threshold criteria for mapping WUI based on statistical analysis, as opposed to using more ad-hoc criteria as used in previous mapping approaches. This method removes the reliance on census data in WUI mapping, and does not require the calculation of housing density. Moreover, this approach designates the adjacent areas of each building with large and dense parcels of vegetation as WUI, which can not only refine the scope and resolution of the WUI areas to individual buildings, but also avoids zoning issues and uncertainties in housing density calculation. Besides, the new method has the capability of updating the WUI map in real-time according to the operational needs. Therefore, this method is suitable for local governments to map local WUI areas, as well as formulating detailed wildfire emergency plans, evacuation routes, and management measures.

The Chilean central Andes are known for its variety of cryospheric landforms, which have included almost every kind of glacier since their first exploration back in the XIX century. However, there has been a severe reduction of the glacierized area since the 1950s, driven by climate change and enhanced due to the megadrought, which has endured for over a decade in the region. Such decline in glacier volume combined with temperature increasing and precipitation reduction can lead to different types of instabilities. In mountainous regions of high public affluence, glacial instabilities are considered as potential hazards leading to the loss of lives and infrastructure. Here we analyze the Rio Volcan basin (-32.82/-70.00), located 40 km east of Santiago city in the international border with Argentina. The region is known for its closeness to the capital, which favors outdoor activities and hydroelectric power development. Elevation ranges from 3380 to over 6000 m a.s.l. at the San José Volcanic Complex, allowing conditions for coexistence of mountain glaciers, valley glaciers, rock glaciers and glaciarets. According to the public Chilean Glacier Inventory, there are more than 140 mapped cryoforms occupying an area of 57 km2 . Beside snow avalanches, there are multiple factor that provide ideal conditions for cryospheric hazards involving glaciers. Some of those factors are pointed out on the following: The presence of an active volcanic complex sets up the triggering agent for lahars and mixed snow/ice avalanche occurrence. There are three moraine-dammed glacial lakes with a cumulated area of up to 24 hectares in front of the El Morado glacier and two innominates. The lakes are still enlarging along with the glacier shrinkage, conforming three potential glofs in the region. Several debris-free glaciers have a very steep front, steeper than 30 degrees, favoring the occurrence of ice falls and ice avalanches. There is a reported surge event in the Nieves Negras glacier, located at the south face of the San Jose; volcano. The latter would have happened in the late 1940s according to literature. In addition, at least four glaciers showed abnormal advance rates in the early 1990s of up to 100 m/yr, along with the surge-like behavior of the Loma Larga glacier. Providing further knowledge of this complex region is key in order to enhance understanding and hazard management on a day to day basis.

Three dimensional dunes of crescentic shape, called barchans, are commonly found on Earth and other planetary environments. In the great majority of cases, barchans are organized in large fields in which corridors of size-selected barchans are observed, and where barchan-barchan interactions play an important role in size regulation. Previous studies shed light on the interactions between barchans by making use of monodisperse particles, but dunes in nature consist, however, of polydisperse grains. In this paper, we investigate the binary interactions of barchans consisting of (i) bidisperse mixtures of grains and (ii) different monodisperse grains (one type for each barchan). We performed experiments in a water channel where grains of different sizes were poured inside forming two barchans that interacted with each other while filmed by a camera, and we obtained their morphology from image processing. We observed that a transient stripe appears over the dunes in cases of bidisperse mixtures, that interaction patterns vary with concentrations, and that different interactions exist when each barchan consists of different monodisperse grains. Interestingly, we found the conditions for a collision in which the upstream barchan is larger than the downstream one, and we propose a timescale for the interactions of both monodisperse and bidisperse barchans. Our results represent a new step toward understanding complex barchanoid structures found on Earth, Mars and other celestial bodies.

We use Distributed Strain Sensing (DSS) through Brillouin scattering measurements to characterize the reactivation of a fault zone in shale (Opalinus clay), caused by the excavation of a gallery at ∼400 m depth in the Mont Terri Underground Laboratory (Switzerland). DSS fibers are cemented behind casing in six boreholes cross-cutting the fault zone. We compare the DSS data with co-located measurements of displacement from a chain potentiometer and a three-dimensional displacement sensor (SIMFIP). DSS proves to be able to detect in- and off-fault strain variations induced by the gallery excavated 30-50 m away. The total permanent displacement of the fault is ∼200 microns at rates up to 1.5 nm/sec. DSS is sensitive to longitudinal and shear strain with measurements showing that fault shear is concentrated at the top and bottom interfaces of the fault zone with little deformation within the fault zone itself. Such a localized pattern of strain relates to the architecture of the fault that is characterized by a thick, weak layer, slipping at the edges, with no surrounding damage zone. Overall, DSS shows that slow slip may activate everywhere there is a weak fault within a shale series. Thus, our work demonstrates the importance of shear strain on faults caused by remote loading, highlighting the utility of DSS systems to detect and quantify these effects at large reservoir scales.

Large igneous provinces (LIPs) represent some of the largest volcanic events in Earth history with significant impacts on the ecosystem, including mass extinctions. However, there are some fundamental questions related to the eruption rate, eruption style, and vent locations for LIP lava flows that remain unanswered. In this review, we use the Cretaceous-Paleogene Deccan Traps as an archetype to address these questions since it is one of the best-preserved large continental flood basalt provinces. We describe the volcanological features of the Deccan flows and their potential temporal and regional variations as well as the spatial characteristics of potential feeder dikes. Along with estimates of eruption rates for Deccan lavas from paleomagnetism and Hg proxy records, the Deccan volcanic characteristics suggest a unified conceptual model for the eruption of voluminous (> 1000 km$^3$) LIP lavas with large spatial extent (> 40,000 km$^2$). We conclude the review by highlighting a few key open questions and challenges that can help improve our understanding of how Deccan, as well as LIP flows in general, erupt and flow over long distances.

Recent experiments systematically explore rock friction under crustal earthquake conditions revealing that faults undergo abrupt dynamic weakening. Processes related to heating and weakening of fault surface have been invoked to explain pronounced velocity weakening. Both contact asperity temperature $T_a$ and background temperature $T$ of the slip zone evolve significantly during high velocity slip due to heat sources (frictional work), heat sinks (e.g. latent heat of decomposition processes) and diffusion. Using carefully calibrated High Velocity Rotary Friction experiments, we test the compatibility of thermal weakening models: (1) a model of friction based only on $T$ in an extremely simplified, Arrhenius-like thermal dependence; (2) a flash heating model which accounts for evolution of both $V$ and $T$; (3) same but including heat sinks in the thermal balance; (4) same but including the thermal dependence of diffusivity and heat capacity. All models reflect the experimental results but model (1) results in unrealistically low temperatures and models (2) reproduces the restrengthening phase only by modifying the parameters for each experimental condition. The presence of dissipative heat sinks in (3) significantly affects $T$ and reflects on the friction, allowing a better joint fit of the initial weakening and final strength recovery across a range of experiments. Temperature is significantly altered by thermal dependence of (4). However, similar results can be obtained by (3) and (4) by adjusting the energy sinks. To compute temperature in this type of problem we compare the efficiency of three different numerical solutions (Finite differences, wavenumber summation, and discrete integral).

Excess nitrogen (N) from anthropogenic sources deteriorates freshwater resources. Actions taken to reduce N inputs to the biosphere often show no or only delayed effects in receiving surface waters hinting at large legacy N stores built up in the catchments soils and groundwater. Here, we quantify transport and retention of N in 238 Western European catchments by analyzing a unique data set of long-term N input and output time series. We find that half of the catchments exhibited peak transport times larger than five years with longer times being evident in catchments with high potential evapotranspiration and low precipitation seasonality. On average the catchments retained 72% of the N from diffuse sources with retention efficiency being specifically high in catchments with low discharge and thick, unconsolidated aquifers. The estimated transport time scales do not explain the observed N retention, suggesting a dominant role of biogeochemical legacy in the catchments’ soils rather than a legacy store in the groundwater. Future water quality management should account for the accumulated biogeochemical N legacy to avoid long-term leaching and water quality deteriorations for decades to come.

Lake Magadi is a saline soda lake in East African Rift Valley (Kenya). It is fed by perennial warm and hot saline springs. Na+-HCO3- type dilute inflows evolve into Lake Magadi brines rich in Na+, CO3 (2-), Cl-, HCO3- and SO4 (2-) and depleted in Ca2+ and Mg2+. The pH, CO3 (2-), and SiO2 content of these brines reach 11.5, 109000 ppm, and 1440 ppm respectively. Evaporative concentration coupled with mineral precipitation and fractional dissolution is thought to be the main process responsible for the stepwise evolution between dilute inflows and brines. In order to understand the details of the precipitation kinetics, we have performed simulations of mineral precipitation sequences and the resulting hydrochemical evolution during evaporation under different partial pressure of CO2 (pCO2) and temperature by using EQL-EVP program. In addition, we have performed laboratory precipitation experiments. The crystallization sequence was monitored by using in situ video microscopy and in situ and ex situ X-ray diffraction and Raman spectroscopy. The precipitation sequence was also monitored by scanning electron microscopy coupled with energy dispersive x-ray analysis. Trace amounts of magnesite, calcite, and pirssonite precipitate at the beginning. Magnesium silicate precipitate at low pCO2 (<-2.5) by redissolution of magnesite. Pirssonite forms from calcite dissolution at low pCO2. The rise in temperature highly delayed amorphous silica precipitation. Trona was the second precipitate. At low temperature-high pCO2, nahcolite precipitates at the second place whereas at high temperature-low pCO2, thermonatrite forms instead of trona. Halite is the third in the precipitation sequence. Burkeite (pCO2 of -3 to -4.5) and thenardite (pCO2 of -2 to -2.5) are the fourth in the sequence, which upon redissolution form glaserite. Sylvite, kalicinite, and villiaumite form at the end. Evaporation linearly raises the solute concentration until saturation of Na-CO3-HCO3 minerals and halite, which upon precipitation deplete solute content. Glaserite is a minor phase depleting K+ and SO4 (2-). The combination of modeling based on a kinetic approach and in situ mineralogical analysis is a powerful tool to understand mineral assemblages and kinetic precipitation pathways in soda lakes.

River deltas commonly have a heterogeneous substratum of alternating peat, clay and sand deposits. This has important consequences for the river bed development and in particular for scour hole formation. When the substratum consists of an erosion resistant top layer, erosion is retarded. Upon breaking through a resistant top layer and reaching an underlying layer with higher erodibilty, deep scour holes may form within a short amount of time. The unpredictability and fast development of these scour holes makes them difficult to manage, particularly where the stability of dikes and infrastructure is at stake. In this paper we determine how subsurface lithology controls the bed elevation in net incising river branches, particularly focusing on scour hole initiation, growth rate, and direction. For this, the Rhine-Meuse Estuary forms an ideal study site, as over 100 scour holes have been identified in this area, and over 40 years of bed level data and thousands of core descriptions are available. It is shown that the subsurface lithology plays a crucial role in the emergence, shape, and evolution of scour holes. Although most scour holes follow the characteristic exponential development of fast initial growth and slower final growth, strong temporal variations are observed, with sudden growth rates of several meters per year in depth and tens of meters in extent. In addition, we relate the characteristic build-up of the subsurface lithology to specific geometric characteristics of scour holes, like large elongated expanding scour holes or confined scour holes with steep slopes. As river deltas commonly have a heterogeneous substratum and often face channel bed erosion, the observations likely apply to many delta rivers. These findings call for thorough knowledge of the subsurface lithology, as without it, scour hole development is hard to predict and can lead to sudden failures of nearby infrastructure and flood defence works.

Landslide susceptibility models are fundamental components of landslide risk management strategies. These models typically assume that landslide occurrence is time-independent, even though processes including earthquake preconditioning and landslide path dependency transiently impact landslide occurrence. Understanding the temporal characteristics of landslide occurrence remains limited by a lack of systematic investigation into how landslide distributions vary through time, and how this impacts landslide susceptibility. Here, we apply Kolmogorov-Smirnoff and Chi-2 statistics to a 30-year inventory of monsoon-triggered landslides from Nepal to systematically quantify how landslide spatial distributions vary through time in ‘normal’ years and years impacted by extreme events. We then develop Binary Logistic Regression (BLR) susceptibility models for 12 years in our inventory with > 400 landslides and use Area Under Receiver Operator Curve (AUROC) validation to assess how well these models can hindcast landslide occurrence in other years. Landslide distributions are found to vary through time, particularly in years impacted by storms (1993 and 2002), earthquakes (2015) and floods (2017). Notably, Gorkha earthquake landscape preconditioning shifted 2015 monsoon-triggered landslides to higher slopes, reliefs and excess topographies. These variations significantly impact BLR susceptibility modelling, with models trained on extreme years unable to consistently hindcast landslide occurrence in other years. However, developing BLR models using increasingly long historical inventories shows that susceptibility models developed using > 6 - 8 years of landslide data provide consistently good hindcasting accuracy. Overall, our results challenge time-independent assumptions of landslide susceptibility approaches, highlighting the need for time-dependent modelling techniques or historical inventories for landslide susceptibility modelling.

We present deformation measurements of the Kirishima volcanic complex from ALOS and ALOS-2 Interferometric Synthetic Aperture Radar (InSAR) time-series during 2006-2019. Shinmoe-dake deflated ~6 cm during the 2008-2010 phreatic eruptions and inflated ~5 cm prior to the 2017 magmatic eruption. Iwo-yama inflated ~19 cm within the crater since January 2015 and ~7 cm around the southern and western vents since four months before the 2018 eruption. These deformations can be modeled as ellipsoids at ~700 m depth beneath Shinmoe-dake and as a sphere on top of an ellipsoid at ~130 and ~340 m depths beneath Iwo-yama. Combining geodetic, geoelectric, geochemical and petrological analysis, we interpret the hydrothermal origin of the deflation at Shinmoe-dake and inflation at Iwo-yama; the hydrothermal-magmatic transition during the 2011 Shinmoe-dake eruption; water-boiling and bottom-up pressurization as driving mechanisms of the inflation at Iwo-yama. The study highlights the imaging potential of InSAR time-series on complex hydrothermal systems.

This article provides a commentary about the state of integrated, coordinated, open, and networked (ICON) principles in Earth and Planetary Science Processes (EPSP) and discussion on the opportunities and challenges of adopting them. This commentary focuses on the challenges with current inclusive, equitable, and accessible science and highlights how research undertaken in the earth and planetary surface processes community currently benefit from and would be able to grow as a discipline with more directed implementation of ICON principles.

Improved understanding of the impact of crystal mush rheology on the response of magma chambers to magmatic events is critical for better understanding crustal igneous systems with abundant crystals. In this study, we extend an earlier model by (Liao et al, 2018) which considers the mechanical response of a magma chamber with poroelastic crystal mush, by including poroviscoelastic rheology of crystal mush. We find that the coexistence of the two mechanisms of poroelastic diffusion and viscoelastic relaxation causes the magma chamber to react to a magma injection event with more complex time-dependent behaviors. Specifically, we find that the system’s short-term evolution is dominated by the poroelastic diffusion process, while its long-term evolution is dominated by the viscoelastic relaxation process. We identify two post-injection timescales that represent these two stages and examine their relation to the material properties of the system. We find that better constraints on the poroelastic diffusion time are more important for the potential interpretation of surface deformation using the model. We also find that the combination of the two mechanisms causes magma transport to reverse direction in the system, which would successively expose crystals to magma with different chemical compositions.

Nowadays, geology has a big “social” problem. Starting in the field of education where the science of geology is less well taught, so that society knows less about geology and its important role in daily life. For example, we can see on the news lots of people suffering because of natural phenomenon such as volcanic eruptions (e.g. Fuego in Guatemala, Kilauea in Hawaii), landslides or building collapses (e.g. Morandi Bridge in Genova, Italy), which could have been minimised or even prevented if society were better aware of the pivotal role that the geosciences can provide for such problems. However, we still cannot solve this problem, until we have not solved our “internal problems”. First of all, Geology has further to evolve, in the manner that Physics did from Classical Physics of Newton to Quantum Physics. Modern geology has only started using Plate Tectonics theory, but needs more time to evolve and find its “quantum theory”. Our science has been “distracted” by the rest of “earth sciences” which is less interested in pure geological research to improve learning. Consequently our community understands our science very well, but we have not been able to improve key factors, such as predictability or more precise modelling. The more we are specialised, the less we know about the other geological disciplines. If we want to contribute to this evolution, all disciplines must work together. As many say “the best geologists have seen the most rocks”. Secondly, geology is suffering from the subtle degradation of science education, allowing poor science to be accepted as true by the media. No-one wants to see the policing of science but it is a daily occurrence that emotional issues take precedence over data-driven facts. We have a role to ensure that our own scientific opinions are clear and not subject to the whims of fashionable though Once this has been solved, we should be able to transmit more effectively the key role of geosciences in daily life. An obvious start is transmitting geology to those that love the countryside such as artists, walkers, mountain climbers or landscapers, those who appreciate nature and already have wide perspectives on their environment. Geology can help to improve those qualities. If we also use our research to help the economic and social development of an area, we will have advanced our role in optimising the tasks. Combining geological knowledge with other disciplines of science, e.g. the International Medical Geology Association (IMGA), a good example of applying our expertise to enhance mutually beneficial solutions. During our cooperation, we had the opportunity to get to know about H2020, an EU Programme destined to improve scientific research and share knowledge between scientists. This project, as well as IMGA, are examples of structures in which geosciences are applicable in sustainable development. Attending Geoscience and Society Summit will allow us to explain in detail all these ideas.

Rocks around the InSight lander were measured in lander orthoimages of the near field (<10 m), in panoramas of the far field (<40 m), and in a high-resolution orbital image around the lander (1 km2). The cumulative fractional area versus diameter size-frequency distributions for four areas in the near field fall on exponential model curves used for estimating hazards for landing spacecraft. The rock abundance varies in the near field from 0.6% for the sand and pebble rich area to the east within Homestead hollow, to ~3-5% for the progressively rockier areas to the south, north and west. The rock abundance of the entire near field is just over 3%, which falls between that at the Phoenix (2%) and Spirit (5%) landing sites. Rocks in the far field (<40 m) that could be identified in both the surface panorama and a high-resolution orbital image fall on the same exponential model curve as the average near field rocks. Rocks measured in a high-resolution orbital image (27.5 cm/pixel) within ~500 m of the lander that includes several rocky ejecta craters fall on 4-5% exponential model curves, similar to the northern and western near field areas. As a result, the rock abundances observed from orbit falls on the same exponential model rock abundance curves as those viewed from the surface. These rock abundance measurements around the lander are consistent with thermal imaging estimates over larger pixel areas as well as expectations from fragmentation theory of an impacted Amazonian/Hesperian lava flow.

On January 15, 2022, Tonga’s Hunga Tonga-Hunga Ha’apai (HTHH) volcano violently erupted, generating a tsunami that killed three people. Acoustic-gravity waves propagated by the eruption and tsunami caused global complex ionospheric disturbances. In this paper, we study the nature of these perturbations from Global Navigation Satellite System observables over the southwestern Pacific. After processing data from 818 ground stations, we detect supersonic acoustic waves, Lamb waves, and tsunamis, with filtered magnitudes between 1 and 7 Total Electron Content units. Phase arrivals appear superpositioned up to ~1000 km from HTHH and are distinct by ~2200 km. Within ~2200 km, signals have an initial low-frequency pulse that transitions to higher frequencies. We note the presence of a faster perturbation generated one hour post-eruption which crosses the tsunami disturbance ~3000 km from HTHH, potentially contributing to premature land arrivals. Lastly, the arrival of tsunami-generated disturbances coincides with deep-ocean observations.

The crustal seismogenic thickness (CST) has direct implications on the magnitude and occurrence of crustal earthquakes, and therefore, on the seismic hazard of high-populated regions. Amongst other factors, the seismogenesis of rocks is affected by in-situ conditions (temperature and state of stress) and by their heterogeneous composition. Diverse laboratory experiments have explored the frictional behavior of the most common materials forming the crust and upper most mantle, which are limited to the scale of the investigated sample. However, a workflow to up-scale and validate these experiments to natural geological conditions of crustal and upper mantle rocks is lacking. We used NW South America as a case-study to explore the spatial variation of the CST and the potential temperatures at which crustal earthquakes occur, computing the 3D steady-state thermal field taking into account lithology-constrained thermal parameters. Modelled hypocentral temperatures show a general agreement with the seismogenic windows of rocks and mineral assemblies expected in the continental crust. A few outliers in the hypocentral temperatures showcase nucleation conditions consistent with the seismogenic window of olivine-rich rocks, and are intepreted in terms of uncertainties in the Moho depths and/or in the earthquake hypocenters, or due to the presence of ultramafic rocks within the allochthonous crustal terranes accreted to this complex margin. Our results suggest that the two largest earthquakes recorded in the region (Murindo sequence, in 1992) nucleated at the lower boundary of the seismogenic crust, highlighting the importance of considering this transition into account when characterizing seismogenic sources for hazard assessments.

The water adsorption into pore spaces in brittle rocks affects wave velocity and transmitted amplitude of elastic waves. Experimental and theoretical studies have been performed to characterize moisture-induced elastodynamic variations due to macroporous effects; however, little attention has been paid to the manner in which wetting of nanopores affect elastic wave transmission. In this work, we extend our understanding of moisture-induced elastic changes in a microcracked nanopore-dominated medium (80 \% of the surface area exhibits pore diameters below 10 nm). We studied acousto-mechanical response resulting from a gradual wetting on a freestanding intact Herrnholz granite specimen over 98 hours using time-lapse ultrasonic and digital imaging techniques. Linkages between ultrasonic attributes and adsorption-induced stress/strain are established during the approach of wetting front. We found that Gassmann theory, previously validated in channel-like nanoporous media, breaks down in predicting P-wave velocity increase of microcracked nanopore-dominated media. However, squirt flow – a theory recognized to characterize wave velocity increase and attenuation in microcracked macropore-dominated media at pore scale – also accounts for the observed increase of P-wave velocity in microcracked nanopore-dominated media. The transmitted amplitude change in direct P waves are explained and predicted by the elastic wave propagation within P-wave first Fresnel zone and reflection/refraction on the wetting front.

Volcanic eruptions could be disastrous. Understanding how magma accumulates, migrates, and erupts to the surface has both scientific and societal implications. However, the variation of the scale of volcanoes, the co-occurrence of earthquakes, and the duration of eruptions make it difficult to understand and, eventually, to predict volcanic eruptions, particularly for those without surface deformation. With a method based on ambient noise interferometry, this study characterizes the subsurface response, in terms of the variation of seismic velocities, to different stages of the eruption process at the Great Sitkin Volcano in Central Aleutian Islands. This volcano erupted in May and July of 2021, with elevated seismicity, gas release, and the formation of a new lava dome. It had an increase in seismicity in February 2020 but without any eruption. We measured the variation of seismic velocities from August 2019 to March 2022. We observe a velocity decrease up to one month before the eruption, followed by velocity increases after the eruption. The seismic velocities would restore to the normal level within about one month after the eruption started. We don’t observe a velocity increase before the increase in seismicity rate in February 2020. The observations from seismicity, dv/v, and shear-wave velocity model suggest a four-stage eruption cycle. Despite its remote location and relatively small scale, the findings of this study at the Great Sitkin volcano have significant implications for understanding vocalism and the development and prediction of volcanic eruptions in general.

Chemical data acquired by Curiosity’s Alpha Particle X-ray Spectrometer (APXS) during examination of the contact between the upper Mount Sharp group and overlying Stimson formation sandstones at the Greenheugh pediment reveal compositional similarities to rocks encountered earlier in the mission. Mount Sharp group strata encountered below the Basal Siccar Point group unconformity at the base and top of the section, separated by >300 m in elevation, have distinct and related compositions. This indicates enhanced post-depositional fluid flow and alteration focused along this contact. Sandstone targets exposed immediately above the unconformity have basaltic compositions consistent with previously encountered eolian Stimson formation sandstones, except at the contact, where they show the addition of S. Resistant sandstone outcrops above the contact have higher K, Mn and Na and lower Ni concentrations that primarily reflect changes in provenance. They are compositionally related to cap rock float blocks encountered as Curiosity climbed through the Mount Sharp group, and Bradbury group sandstone outcrops. The higher K, pediment sandstones are interpreted to have a similar provenance to some Bradbury group sandstones, further evidence for widespread, alkaline source rock within and/or in the vicinity of Gale crater. The Bradbury and Siccar Point groups may both be younger than the Mount Sharp group. Alternatively, an alkaline source area in and around Gale crater has been eroded by both water and wind at different times (both before and after deposition of the Mount Sharp group), during the evolution of the crater and its infill.