California’s Central Valley is responsible for $17 billion of annual agricultural output, producing 1/4 of the nation’s food. However, land in the Central Valley is sinking at a rapid rate (as much as 20 cm per year) due to continued groundwater pumping. Land subsidence has a significant impact on infrastructure resilience and groundwater sustainability. It is important to understand subsidence and groundwater depletion in a consistent framework using improved models capable of simulating in-situ well observations and observed subsidence. Currently, groundwater well data is sparse and sampled irregularly, compromising our understanding of groundwater changes. Moreover, groundwater pumping data is a major missing piece of the puzzle. Limited data availability and spatial/temporal uncertainty in the available data have hampered understanding the complex dynamics of groundwater and subsidence. To address this limitation, we first integrated multimodal data including InSAR, groundwater, precipitation, and soil composition by interpolating data with the same spatial and temporal resolutions. We then identified regions with different temporal dynamics of land displacement, groundwater depth, and precipitation. Some areas (e.g., Helm) with coarser grain soil compositions exhibited potentially reversible land transformations (elastic land compaction). Finally, we fed the integrated data into the deep neural network of a gated recurrent unit-based sequence-to-sequence generation model. We found that the combination of InSAR, groundwater depth, and precipitation data had predictive power for soil composition using deep neural networks (correlation coefficient R=0.83, normalized Nash-Sutcliffe model efficiency NNSE=0.84). A random forest model was tested as baseline (R=0.65, NNSE=0.69). We also achieved significant accuracy with only 40% of the training data (NNSE=0.8), suggesting that the model can be generalized to other regions for indirect estimation of soil composition. Our results indicate that soil composition can be estimated using InSAR, groundwater depth and precipitation data. In-situ measurements of soil composition can be expensive and time consuming and may be impractical in some areas. The generalizability of the model sheds light on high spatial resolution soil composition estimation utilizing existing measurements.

Microplastic (MP) contamination of freshwaters and soils has become one of the major challenges within the Anthropocene. MP is transported in large quantities through river systems from land to sea. However, the question is whether there is transport only or also deposition within the system? Floodplains and their soils as part of the river system are known for their sink function for sediments, nutrients, and pollutants. The present case study analyzes the spatial distribution of large (L-MP, 2,000–1,000 μm) and medium (M-MP, 1,000–500 μm) MP particles in floodplain soils of the Lahn River (Germany). Based on a geospatial sampling concept, the MP contents in floodplain soils are investigated down to a depth of 2 meters through a holistic method approach. The analysis of the plastic particles is carried out by density separation, visual fluorescence identification, and additional ATR-FTIR analysis. In addition, grain size analyses and 210Pb/137Cs dating was performed to reconstruct the MP deposition conditions in floodplains. The results prove a spatial frequent accumulation of MP in upper floodplain soils (0–50 cm) deposited by flood dynamics since the 1960s. MP detection over the entire soil column to a depth of 2 meters and below recent (>1960) sediment accumulation indicates MP relocation and in-situ vertical transfer of mobile MP particles through natural processes (e.g., preferential flow, bioturbation). Furthermore, the role of MP as a potential marker of the Anthropocene is assessed based on the findings. This study advances our understanding of the deposition and relocation of MP at the aquatic-terrestrial interface.

Distributed Acoustic Sensing (DAS) was originally intended to measure oscillatory strain at frequencies of 1 Hertz or more on a fiber optic cable. Recently, measurements at much lower frequencies have opened the possibility of using DAS as a dynamic strain sensor in boreholes. A fiber optic cable mechanically coupled to a geologic formation will strain in response to hydraulic stresses in pores and fractures. A DAS interrogator can measure dynamic strain in the borehole which can be related to fluid pressure through the mechanical compliance properties of the formation. Because DAS makes distributed measurements, it is capable of both locating hydraulically active features and quantifying the fluid pressure in the formation. We present field experiments in which a fiber optic cable was mechanically coupled to two crystalline rock boreholes. The formation was stressed hydraulically at another well using alternating injection and pumping. The DAS instrument measured oscillating strain at the location of a fracture zone known to be hydraulically active. Rock displacements of less than one nanometer were measured. Laboratory experiments confirm that displacement is measured correctly. These results suggest that fiber optic cable embedded in geologic formations may be used to map hydraulic connections in three dimensional fracture networks. A great advantage of this approach is that strain, an indirect measure of hydraulic stress, can be measured without beforehand knowledge of flowing fractures that intersect boreholes. The technology has obvious applications in water resources, geothermal energy, CO sequestration, and remediation of groundwater in fractured bedrock.

Bedload movement is fundamentally probabilistic. Our quantitative understanding of gravel transport is particularly limited when flow conditions just exceed thresholds of motion, in part because of difficulties in measuring transport statistics during floods. We used accelerometer-embedded tracer clasts to precisely measure the timing of grain motions and rests during snowmelt floods in Halfmoon Creek, a gravel-bed mountain stream in Colorado, USA. These new data let us explore how probabilities of tracer movement vary with snowmelt discharge. Bedload hysteresis occurred over both daily and seasonal timescales, and included clockwise, counter-clockwise, and figure-eight patterns. We quantitatively explain these observations in terms of how thresholds of motion progressively evolved over 22 days during a seasonal snowmelt flood. Our results suggest that thresholds of motion are functions of both (a) cumulative shear stress and (b) temporal changes in shear stress during floods.

Subglacial models represent moulins as cylinders or cones, but field observations suggest the upper part of moulins in the Greenland Ice Sheet have more complex shapes. These more complex shapes should cause englacial water storage within moulins to vary as a function of depth, a relationship not currently accounted for in models. Here, we use a coupled englacial--subglacial conduit model to explore how moulin shape affects depth-dependent moulin water storage and water pressure dynamics within a subglacial channel. We simulate seven different moulin shapes across a range of moulin sizes. We find that the englacial storage capacity at the water level is the main control over the daily water level oscillation range and that depth-varying changes in englacial water storage control the temporal shape of this oscillation. Further, the cross-sectional area of the moulin within the daily oscillation range, but not above or below this range, controls pressures within the connected subglacial channel. Specifically, large cross-sectional areas can dampen daily to weekly oscillations that occur in the surface meltwater supply. Our findings suggest that further knowledge of the shape of moulins around the equilibrium water level would improve englacial storage parameterization in subglacial hydrological models and aid predictions of hydro-dynamic coupling.

Continued global warming is expected to result in drying of Central America, with projections suggesting a decrease in precipitation. Poor hindcasting of precipitation, however, due in part to spatial and temporal limitations in instrumental data, subjects these projections to considerable uncertainty. Paleoclimate proxy data are therefore critical for understanding regional climate responses during times of global climate reorganization. Here we present two lake-sediment based records of precipitation variability in Guatemala along with a synthesis of Central American hydroclimate records spanning the last millennium (800-2000 CE). The synthesis reveals that regional climate responses have been strikingly heterogeneous, even over relatively short distances. Our analysis further suggests that shifts in the mean position of the Intertropical Convergence Zone, which have been invoked by numerous studies to explain variability in Central American and circum-Caribbean proxy records, cannot alone explain the observed pattern of hydroclimate variability. Instead, interactions between several ocean-atmosphere processes and their disparate influences across variable topography have resulted in complex precipitation responses. These complexities highlight the difficulty of reconstructing past precipitation changes across Central America and point to the need for additional paleo-record development and analysis before the relationships between external forcing and hydroclimate change can be robustly determined. Such efforts should help anchor model-based predictions of future responses to continued global warming.

Few of the large Southern peri-alpine lakes have been studied with a sedimentological approach in their deep basin to understand the dynamics of their long-term sedimentation due, among other factors, to the high complexity of the coring in such deep lakes. In 2018, a 15.5 m-long sediment section was retrieved from the deep basin of Lake Iseo (Italy) at 251 m of water depth. Seismic survey associated to a multi-proxy approach with sedimentological and geochemical analyses, reveals a high number of event layers that corresponds to 61.4 % of the total sedimentation during the last 2000 years. The great heterogeneity of textures, colours, and grain-size distribution between the different types of event layers can be explained by the high number of potential sources of sediment inputs in this large lake system. By combining proxies for sediment source with transport processes, we were able to distinguish: i) flood events, and ii) destabilisations of slopes and deltas due to an increase of the sediment load and/or to seismic shaking. From a thorough comparison with both, the regional climatic fluctuations, and the human activity in the watershed, it appears that periods of high sediment remobilization can be linked to a previous increase in Critical Zone erosion in the watershed mainly under human forcing. Hence, even in large catchments, human activities play a key role on erosion processes and on sediment availability, disrupting the recording of the Critical Zone functioning in such lacustrine archive.

Benthic oxygen fluxes consist of advective and diffusive terms. Both terms in the south-eastern North Sea exhibit a prominent annual cycle but with opposite variation patterns. To understand the driving mechanisms quantitatively, a novel 3-D benthic-pelagic coupled model resolving interactions among macrobenthos, bioturbation, oxygen consumption and carbon early diagenesis was applied to reconstruct the benthic states. Simulation results show a satisfactory agreement with field data and reveal that the benthic oxygen flux is determined by not only pelagic drivers but also by internal dynamics associated with the interaction between organic carbon and macrobenthos, and bedform morphodynamics. Variation of advective flux, characterized by summer-low and winter-high, is mainly driven by hydrodynamics and bedform morphodynamics, while variation of diffusive flux, featured by summer-high and winter-low, is a compound effect of pelagic and benthic drivers with a dominant control by macrobenthos through bioturbation. The role of bioturbation in benthic oxygen consumption is twofold: (i) on the one hand, it alters the particulate organic carbon (POC) distribution in surface sediments, thereby changing the availability of POC to oxygen consumption; (ii) on the other hand, it mixes oxygen down into sediments, thereby facilitating oxygen consumption. Our results indicate that the first role prevails in sandy seafloor characterized by energetic hydrodynamics, while the second role becomes increasingly important along with a weakening of bottom currents. We found that bioturbation-induced oxygen consumption contributes to more than 85% and 52% of the total benthic oxygen fluxes in muddy seabed and at a regional scale, respectively.

Since 1973 micro-erosion meters (MEM) have been used at Kaikōura Peninsula to determine lowering rates on inter-tidal shore platforms. Rates measured over two, two year periods (1973-1975 and 1994-1996) and at decadal scales (20-30 years) demonstrate that platform surface lowering is on average 1.1 mm/yr. The 14 November 2016 Kaikōura magnitude 7.8 (Mw) earthquake caused an instantaneous uplift of 0.8-1.0 m of the peninsula. The uplift offers the rare opportunity to examine how such an event alters processes and rates of erosion on these shore platforms, since these are now partially marine terraces as the inner margins of some platforms are now above high tidal levels (but perhaps not storm surge). Since the earthquake, 42 MEM sites have been measured seven times at 3 monthly intervals. Most recently in September 2018. MEM sites show widely varying responses to the uplift. Erosion rates are at some MEM sites three times the previous annual rate while other sites show significant amounts of rock swelling (3-4 mm in 6 months), or aggradation as weathered rock fragments are no longer removed by wave action. The coseismic uplift has fundamentally changed the process regime operating on these platforms. Zones of maximum wetting and drying have migrated seaward causing previously slow eroding (< 1 mm/yr) MEM sites to accelerate to twice the pre-earthquake rates. Erosion rates demonstrate rapid adjustment of the platform surface to this disturbance and illustrate how uplifted marine terraces can be rapidly eroded despite being above sea level. The preservation of the new marine terrace is probably dependent on further uplift within the next 300-400 years, otherwise erosion by lowering and backwear will likely remove the new surface. This scenario has significant implications for marine terrace preservation and the recording of coseismic events in the landscape.

Ash-producing volcanic eruptions are a major natural hazard and the magnitude of the explosivity of these eruptions have been indicated for decades by a semi-quantitative “Volcanic Explosivity Index (VEI)” based on a number of interdependent factors, (eruption duration, volume of ejected material, eruptive column height, tropospheric and stratospheric injection, and qualitative descriptors). We present a simple empirical formulation for a fully quantitative VEI (𝑉𝐸𝐼Hc), based solely on eruption column height. This method directly translates the height of the eruption column into VEI, a useful formulation for immediate understanding of the explosivity of eruptions as they are taking place. This new scale is calibrated for convenience and familiarity to span the same range of values as the existing, semi-quantitative, VEI scale. In addition to being a simple and quantitative approach, this new method, translating column height directly into VEI, has the advantage of being calculated in real time during an eruption. This will improve immediate response by aviation, hazard management, and others to mitigate societal impact of hazardous eruptions.

We live in an “Ice House” world that has extensive ice cover at both poles. However, it has not always been this way. During the last 540 million years there have been only 4 other time intervals characterized by extensive polar ice caps (latest Ordovician, latest Devonian, Permo-Carboniferous, and late Cenozoic). The combined duration of these frigid intervals was approximately 160 million years, or ~30% of Phanerozoic history. During the remaining 380 million years the Earth lacked permanent polar ice caps, though some winter snow and ice may have accumulated at high latitudes during cool, greenhouse intervals (Silurian-early Devonian, late Jurassic – early Cretaceous). The modern ice house world is probably the most severe of all ice house worlds because it is the only time in Earth history when the North and South polar regions were concurrently glaciated. Using the compilation of lithologic indicators of glacial conditions (tillites, dropstone, & glendonites) compiled by Boucot et al. (2013), I have mapped the areal extent of polar ice caps (millions of km2) for the time periods when ice house conditions prevailed. Using a simple algorithm that estimates the thickness of the ice based on the total area of the ice cap, I have calculated the corresponding volume of continental ice (millions of km3) for each of these time intervals. Converting solid ice to liquid water, the equivalent volume of evaporated ocean water was calculated. Expressed as a percentage of the present-day volume of ocean water (1.35 billion km3), I estimated the amount of water removed from the oceans during each of these ice house intervals. Preliminary results, indicate that the five largest ice volume events were the Hirnantian (444.5 Ma) – 2%, Modern World – 2%, Pliocene (3 Ma) – 2%, early Permian (280 Ma) – 1.5%, and late Miocene (10-15 Ma) – 1.4%. Since the water removed from the oceans by evaporation is preferential enriched in 16O, it is possible to calculate the resulting δ18O of the remaining oceanic reservoir. These calculations may be useful when estimating paleotemperatures from the δ18O record of fossil organisms.

The Global Learning and Observations to Benefit the Environment (GLOBE) Program is an international science and education program that connects a network of communities around the world and gives them the opportunity to participate in data collection and the scientific process, and contribute meaningfully to our understanding of the Earth system and global environment. GLOBE hosts the GLOBE International STEM Network (GISN), which is an international network of STEM professionals that work with GLOBE students, teachers, and other STEM professionals around the world. Members of the GISN may mentor students and teachers, collaborate on scientific research, use GLOBE data in their research, judge student research projects, and write blogs for the GLOBE website, among other things. In January 2018, the GISN, which was previously only open to graduate students and seasoned STEM professionals, was expanded to include “Early Career STEM Professionals” which includes upper-level undergraduates or master’s students pursuing a degree in a STEM field or recent graduates working in STEM fields but have less than five years’ experience. Goals for expanding the the GISN include granting early career professionals a chance to establish ties with the next generation of STEM professionals, connecting early career professionals and students with potential mentors and collaborators, and allowing early career professionals and students to explore what a career in a STEM field can look like. All GISN members will benefit from an increase in the number of members as well as an increase in the numbers of members who have more flexibility in terms of time and finances. As well, it is another opportunity for GLOBE to engage with alumni of the program who have continued a career in STEM. Unlike other ECS networks, the GISN does not separate the ECS’ out from the other members so all members have equal access to resources and each other. Since opening up the GISN in January, 17 Early Career STEM Professionals representing 5 of our 6 regions (Africa, Asia and the Pacific, Europe and Eurasia, Latin America and the Caribbean, and North America, but not Near East and North Africa) have joined the network bringing total membership to 421 members.

The Indus Fan, located in the Arabian Sea, contains the bulk of the sediment eroded from the Western Himalaya and Karakoram. Scientific drilling in the Laxmi Basin by the International Ocean Discovery Program (IODP) provides an erosional record from the Indus River drainage dating back to 10.8 Ma, and with a single sample from 15.5 Ma. We dated detrital zircon grains by U-Pb geochronology to reconstruct how erosion patterns changed through time. Long-term increases in detrital zircon U-Pb components of 750–1200 Ma and 1500–2300 Ma show increasing preferential erosion of the Himalaya relative to the Karakoram at 7.99–7.78 Ma and more consistently starting by 5.87 Ma. An increase in the contribution of 1500–2300 Ma zircons starting by 1.56 Ma indicates significant unroofing of the Inner Lesser Himalaya (ILH) by that time. The trend in zircon U-Pb age populations is consistent with bulk sediment Nd isotope data implies greater zircon fertility in Himalayan bedrock compared to the Karakoram and Transhimalaya. The initial change in spatial erosion patterns at 7.0–5.87 Ma occurred during a time of drying climate in the Indus foreland. The increase in ILH erosion postdates the onset of dry-wet glacial-interglacial cycles suggesting some role for climate control. However, erosion driven by rising topography in response to formation of the Lesser Himalayan thrust duplex, especially during the Pliocene may also be important. The influence of the Nanga Parbat Massif to the bulk sediment flux is modest, in contrast to the situation in the eastern Himalaya syntaxis.

Quantitative evaluations of hydrological processes that induce changes in the geohydrologic parameters of groundwater systems are of great significance in subsurface hydrology. In this study, the tidal response of the water level in Lijiang well was considered as an indicator of the hydrological parameters, and the seasonal changes of the tidal response were investigated. The results suggested that the seasonal change of tidal response should be attributed to the seasonal changes in the geohydrologic parameters, which are caused by the opening/closing of pre-existing fractures or fracture aperture changes in the groundwater system, owing to regional precipitation recharge that produces a poroelastic response in the groundwater system. This suggests that the groundwater system in the shallow crust can be viewed as a natural positive feedback poroelastic-hydraulic coupled system during the hydrological processes. These findings may have far-reaching implications for the safety of the subsurface environment, ecosystem, and groundwater resources.

Two submarine earthquakes (Mw 5.8) occurred near volcanic islands, Curtis and Cheeseman, in the Kermadec Arc in 2009 and 2017. Following both earthquakes, similar tsunamis with wave heights of about a meter, larger than expected from their moderate seismic magnitudes, were observed by coastal tide gauges. We investigate the source mechanism for both earthquakes by analyzing tsunami and seismic data of the 2017 event. Tsunami waveform analysis indicates that the earthquake uplifted a submerged caldera around the islands. Combined analysis of tsunami and seismic data suggests that trapdoor faulting, or sudden intra-caldera fault slip interacted with magma reservoir deformation, occurred due to magma overpressure, possibly in association with caldera resurgence. The earthquake scaling relationship for trapdoor faulting events at three calderas deviates from that for regular earthquakes, possibly due to the fault-reservoir interaction in calderas.

In this study, the role of fluids in a slow slip events (SSEs) regime was examined by investigating the rheological properties of the solid-liquid two-phase system on a laboratory scale. We specifically investigated how the rheological properties change with the shear rate when the granular layer is fluid-rich. We used a velocity-controlled rheometer to apply shear to a liquid-saturated granular layer. The results show that the liquid-saturated granular layer’s shear viscosity depended on the liquid viscosity and exhibited pseudoplastic behavior. Additionally, the saturated granular layered exhibited hysteresis, which increased as the viscosity of the liquid decreased. After a quantitative discussion through Bagnold (1954) framework, we propose a fault model that includes a fluid-rich granular layer.

Apatite – Ca5(PO4)3(OH,F,Cl) – is a common accessory mineral in many terrestrial rocks and has a low (~75˚C) closure temperature for He retention[1]. As such the (U-Th-Sm)/He thermochronometer has become one of the most used dating techniques to constrain low temperature cooling histories of terrestrial samples. Apatite has been documented in many meteoritic, lunar, and martian samples, and is a particularly common accessory phase in many martian lithologies[2]. In meteoritic samples, (U-Th-Sm)/He dating of apatites provides some methodological challenges in that grains are frequently anhedral making it complicated to do a FT correction[2]. Results are commonly interpreted to represent the timing of shock metamorphism related to impacts onto the (planetary) surface which often correlates with cosmic-ray exposure ages[2]. NWA 7034, and its pairings, represents a piece of martian regolith that documents events on the martian surface that span approximately 4 Ga[3]. NWA 7034 is known to contain upwards of 4 wt.% apatite as detrital mineral fragments and as accessory phases in many lithic and impact-derived clasts[4]. These apatites have been previously analyzed geochronologically via U-Pb apatite and isotopically via δD, δ37Cl, and H2O using microbeam techniques[5,6]. At present, (U-Th)/He dating of NWA 7034 and its pairings has been restricted to bulk rock analyses[4,7,8,9]. This whole-rock approach relies on assumptions that the He, and its parent isotopes, are evenly distributed throughout the sample and that resetting of the WR-He thermochronometer is universal throughout the sample in response to the thermal pulse associated with the impact. These studies have yielded widely dispersed datasets that range from 50 Ma to 200 Ma, putting some of those assumptions into question[4,7,8,9]. In this contribution, we utilize the laser ablation double-dating (LADD) technique on individual apatites present within several polished slabs of NWA 7034. This targeted approach allows us to acquire (U-Th-Sm)/He ages, U-Pb ages, and trace element information within a petrological framework. The (U-Th-Sm)/He ages will provide additional constraints on the low temperature history of NWA7034 and help test the veracity of WR-He retention ages. References: [1] Zeitler et al. 1987 GCA, [2] Min 2005 Rev. Mineral Geochem; [3] Cassata et al. 2018, SciAdv; [4] Agee et al. 2013 Sci; [5] Hu et al. 2019 MAPS; [6] Davidson et al. 2020 EPSL; [7] Cartwright et al. 2014 EPSL; [8] Lindsay et al. 2021 MAPS; [9] Stephenson et al. 2017 MAPS

China’s first Mars Exploration Mission Tianwen-1 achieved full success. The loaded Zhurong Rover landed south of the Utopia Planita. The Tianwen-1 orbiter also sending back high-resolution images. We utilized the High-Resolution Imaging Camera (HiRIC) of Tianwen-1 and Context Camera loaded on the Mars Reconnaissance Orbiter to collect the image data and construct a 3D strata model of the Zhurong landing site. Using this model, we analyzed the material loss of ghost craters. Judging from the morphological characteristics of pitted cones at the Zhurong landing site, we confirmed their classification as mud volcanoes. We also analyzed the possible cause of formation by combining the gravity field and magnetic field data. The experimental results indicate that (1) the Zhurong landing site can be divided into the dry sedimentary, moisture sedimentary, and Vastitas boreal (VB) members as three strata and another ejecta blocks. The three strata are categorized into VB formations with an integral width of 1.2 km. (2) The cones at the Zhurong landing site are mud volcanoes formed by groundwater thermal activity, and the heat source originate from a southern underground magma chamber. The density of mud volcanoes signifies the existence of ejecta blocks. (3) Apart from volumetric compaction, some ghost craters show eruption of underground substances. Generally, after the VB unit located on the surface of the Zhurong landing site formed at 3.43 Ga, the current geomorphology of the landing site was altered due to the differentiation of water evaporation above ground and underground, underground thermal activity, and meteorite impacts.

The paper focuses on spatial orientations of hydraulically conductive shear fractures existing in naturally fractured fluid saturated rocks. Hydraulic conductivity of such fractures is considered from the current stress state of these rocks. The concept of critically stressed fractures is generally used to establish such relationship. The paper presents an analytical solution to the problem of obtaining all possible spatial orientations of critically stressed fractures for an arbitrary stress tensor. The proposed solution is explicit, providing an opportunity to predict the spatial orientations of hydraulically conductive fractures based on results of any sort of solutions to geomechanical problems considering naturally fractured rocks. The obtained results may be directly used for planning the development of oil fields, characterized by considerable contribution of fractures to permeability in cases when geomechanical modeling takes place. Several examples of applying the obtained solution in practice are presented in the paper: critically stressed fractures spatial orientations are considered for cases of gradual changes in stress tensor components under specific conditions providing an understanding of the main tendencies in these spatial orientations.

The fumarole ice caves of Mount Rainier in the Cascade Volcanic Arc in Washington, USA, provide unique insight into the dynamic equilibrium between thermal flux on volcanic edifices and snow accumulation on summit glaciers. More than 3.5 km of surveyed cave passage nearly circumnavigate the East Crater, reaching within 19 m of the 4392-m summit and extending to 144-m-deep along the glacier-crater boundary. The large circum-crater passage connects entrances on the crater rim to steep transverse passages, and cave morphology is maintained by fumarole gas convection and advection. A melt- and condensate-formed lake, Lake Adélie, occupies a portion of the circum-crater passage. Hourly data were collected between August 2016 and August 2017 and included the measured temperatures at three fumarole, the cave air temperature and pressure, the lake water temperature and depth, and the outside temperature and snow depth at Paradise Visitors Center. Time-series analyses of these data reveal complex associations between synoptic to seasonal weather, fumarole activity, and lake level. On seasonal and longer scales, fumarole temperatures follow independent pathways connected to spatial and temporal changes in volcanic heat flux and the circulation of glacial melt. For synoptic-scale meteorology, major snowfall seals the cave entrances, increasing cave air temperature and pressure from fumarole output and causing rising lake levels from increased melt until entrances reopen. Repeating freeze-thaw cycles observed in the cave monitoring data are a primary cause of crater mass wasting. Despite these variations, the scale and morphology of the caves is preserved over decadal or longer scales.

Interferometric synthetic-aperture radar (InSAR) interferograms contain valuable information about the fault systems hidden beneath the surface of the Earth. In a new approach, we aim to fit InSAR ground deformation data using a volumetric distribution of multiple seismic point sources whose parameters are found by a genetic algorithm. The resulting source distribution could provide another useful tool in solving the difficult problem of accurately mapping earthquake faults. To test the algorithm, we first apply it to synthetic data, followed by applications to an ALOS-2 InSAR interferogram. We report first results and discuss advantages and disadvantages of this approach.

The ln(Zr/Rb) count ratio derived from X-ray fluorescence (XRF) core scanning holds potential as a high-resolution tracer for grain-size variations of glaciomarine sediments. To evaluate this approach, we conducted high-resolution grain-size measurements, together with Rb and Zr measurements by XRF core scanning and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), on a series of sediment cores from different regions of the Southern Ocean. We find that downcore changes of the ln(Zr/Rb) count ratio from XRF core scanning are consistent with Zr/Rb concentration ratios derived from ICP-MS analyses, even though Rb and Zr counts deviate significantly from concentrations due to specimen and matrix effects. The ln(Zr/Rb) count ratio displays discrepancies with the bulk mean grain-size, but correlates well with the mean grain-size of the sediment fractions that do not include unsorted coarse IRD (i.e. IRD-corrected mean grain-size). These observations are supported by evidence from a grain-size separation experiment, which indicates that Zr and Rb are concentrated in different grain-size fractions. Consistent with its lack of sensitivity to coarse grain-size fractions, the ln(Zr/Rb) ratio records similar trends to the sortable silt percent (SS%) and sortable silt mean (SSM) grain-size. Universal gradients exist in plots of ln(Zr/Rb) versus SS% (34.1), and ln(Zr/Rb) versus SSM (12.7), such that the ln(Zr/Rb) ratio provides a convenient way to estimate the magnitude of changes in SS% and SSM. Overall, our results support the use of the ln(Zr/Rb) ratio as an indicator of bottom current strength in cases where the sediment is current-sorted.

Virtual reality (VR) is an important tool for several applications in science, industry, and education. Previous studies have already shown how the use of VR at full scale is an effective tool for outcrops characterization even at centimetre scale [1]. We aim to extend the use of this approach in various fields of planetary exploration, from outcrop to regional scale. This regional approach may provide an effective support for the planning and management of future missions, but also for geological and geomorphological studies and mapping. Among the most obvious advantages of the use of virtual reality are the lack of optical deformations and approximate dimensions of the two-dimensional display (such as display, projections and printed cartography) and the opportunity to layer various levels of information through a new concept of superposition. The VR environment is derived from several multi-scale elements: medium to high-resolution elevation data, photogrammetric 3D models, orthophotos, multispectral data, thematic maps and vector data transformed into three-dimensional digital representations placed in the study context. The first tests are based on stereogrammetry (using USGS ISIS [2] and NASA ASP [3]) of the lunar LRO (LROC-NAC) [4] and Martian MRO (CTX and HiRISE) [5] and MEX (HRSC) [6] missions and on data and cartography realized through external open-source GIS tools (GDAL libraries, QGIS, GRASS) and virtual tools developed to be used within the VR environment. In our tests, for example, the Rock Abundance analysis results have been shown not only as thematic maps but also as digital representations of floating boulders on the surface. This has been achieved by placing major rock elements (>1m) in the position detected from satellite imagery and smaller elements, estimated from size-frequency distributions studies, with a preliminary semi-random distribution. References [1] Mouélic S. L. et al. (2019), Geophys. Res. Abstr, Vol. 21. [2] Becker K. J. et al. (2013), LPSC, Vol. 44. [3] Moratto Z. M. et al. (2010), LPSC, No. 1533, p. 2364. [4] Robinson M. S. et al. (2010), Space Sci. Rev., 150: 81-124. [5] McEwen A. S. et al. (2007), J. Geophys. Res. Planets, 112.E5 [6] Neukum G. & Jaumann R. (2004). Mars Express: The Scientific Payload, Vol. 1240, pp. 17-35.

The Colorado Rockies were initially raised during the Laramide Orogeny ca. 70-45 Ma. But consensus exists that the range experienced a second, post-Laramide episode of surface uplift; the timing and cause of that post-Laramide surface uplift event remains enigmatic. Low-temperature thermochronologic studies conducted by us and others using apatite (U-Th)/He (AHe), apatite fission track (AFT), and zircon (U-Th)/He (ZHe) techniques reveal that a dome of kilometer-scale exhumation occurred in Colorado’s Elk and West Elk mountains between ca. 18-6 Ma. We call this feature the “Gothic Dome” because it is centered on Gothic Mountain, near the town of Crested Butte. We suggest the ~100-km-diameter Gothic Dome likely experienced Miocene surface uplift, which triggered the dome-shaped exhumation pattern documented by the low-temperature thermochronometry. The exhumation magnitude exceeds 4 km in the center of the dome (as revealed by a 16 Ma ZHe date on an Oligocene pluton) and diminishes toward its perimeter. This diminution of exhumation magnitude toward the perimeter is revealed by progressively older AHe, AFT, and ZHe dates in all directions away from Gothic Mountain. AHe dates for samples that lie outside the perimeter are Laramide-age or older, further documenting the dome-shaped nature of this Miocene exhumation event and illustrating the low magnitude of Miocene to recent exhumation outside the dome’s perimeter. Outcrops of ca. 11 Ma basalt surround the Gothic Dome to the north, west, and south, requiring that Miocene exhumation outside the dome’s perimeter was minimal. A suite of alkaline, low-volume, felsic plutons and ultramafic lamprophyres intruded the Gothic Dome between ca. 18-12 Ma. This alkalic magmatism began either immediately prior to or contemporaneous with the onset of Gothic Dome exhumation, hinting that the same root cause might be responsible for both. Workers elsewhere, including Tibet, the Altiplano, and California’s Sierra Nevada mountains, have attributed small-volume alkalic magmatism, surface uplift, and exhumation to the activity of lithospheric drips. We offer that Miocene activity of such a drip beneath Colorado’s Elk and West Elk mountains is an appealing mechanism to explain the near simultaneity of those same phenomena here.