Groundwater occurrence in crystalline basement complex is mainly due to the development of secondary porosity and permeability arising from the weathering and fracturing of the low porosity igneous and metamorphic basement rocks. In this study, geophysical survey involving seismic refraction and 2D electrical resistivity tomography (ERT) was conducted to assess the hydrogeological characteristics of the weathering profile of the crystalline basement rocks in Olomore, Abeokuta, southwestern Nigeria. The 2D ERT survey was conducted along five Traverses using dipole-dipole array with a minimum electrode spacing of 5.0 m in Traverses 1, 2, 3 and 5, and 10.0 m in Traverse 4, and a dipole separation factor of 1 – 4 in all the traverses; the observed apparent resistivity data were inverted using RES2DINV. The seismic refraction survey was conducted along the same traverses using 10 Hz electromagnetic geophones; the refraction data were processed using SeisImager with the first arrival travel times picked using Pickwin module and inverted using Plotrefa to obtain velocity model of the subsurface. A good correlation exists between the 2D ERT images and the seismic refraction velocity models. The effective depth of investigation for both ERT and seismic refraction is approximately 43.0 m in all the traverses except for ERT of Traverse 4 which 66.0 m depth of investigation. Four lithologic layers may be inferred with varying model resistivity and P-wave velocity range of 546-974 m/s, 1456-1877 m/s, 2042-2944 m/s, and 3041-6894 m/s respectively. Both ERT and seismic refraction images indicate that the regolith (collapsed zone and saprolite) is relatively thin (< 10.0 m) and may be unable to support adequate drawdown for good yield. But the weathered and fractured basement is sufficiently thick to support adequate drawdown for high groundwater storativity and yield; depth-to-bedrock is greater than 20.0 m in most part of the study area. The study shows that the combination of ERT and seismic refraction is effective for near-surface characterisation for hydrogeological investigations in crystalline basement complex.

We are using radio occultation (RO) measurements from Mars Global Surveyor to investigate the nighttime structure and dynamics in the lower atmosphere of Mars. High-resolution temperature profiles retrieved from the RO data contain unique information about nocturnal mixed layers (NMLs) – detached layers of neutral stability that form at night in response to radiative cooling by a water-ice cloud layer. Basic properties of the NMLs and constraints on their spatial distribution and seasonal evolution can be obtained through analysis of the RO profiles. We have examined more than 3000 RO profiles in a latitude band centered on the Phoenix landing site (234°E, 68°N), where nighttime water-ice clouds were observed by the LIDAR instrument (Whiteway et al., Science 325, 68-70, 2009). NMLs appear routinely in the western hemisphere in RO observations at 5 h local time from early summer of MY27. There is a close resemblance in both thickness (a few km) and altitude (about 4 km above the surface) to the cloud layer observed at the same local time by the Phoenix LIDAR in MY29. The NMLs confirm that radiative cooling by the Phoenix cloud is sufficient to trigger convective instability, as predicted by a Large Eddy Simulation (Spiga et al., Nat. Geosci. 10, 652-657, 2017). We have also analyzed more than 800 RO profiles from the northern tropics near summer solstice of MY28. Tropical NMLs are largely confined to regions of elevated terrain, where the daytime convective boundary layer is deep. At 4 h local time, the top of the NML is about 10 km below the peak of Olympus Mons. The spatial distribution of the NMLs appears to be influenced by diverse processes ranging from topographic circulations to planetary-scale thermal tides. In addition, we are using a Mars Global Circulation Model and Large Eddy Simulations to interpret the RO results. Goals of the modeling effort include: to identify the atmospheric processes that control the formation of nocturnal water ice clouds; to understand the spatial distribution of the clouds and their evolution with time of day and season; and to assess the impact of NMLs on the nighttime weather and water transport in the lowest scale height above the surface.

This study reports the presence of Australasian microtektites in a deep-sea core (U1452) retrieved during International Ocean Discovery Program (IODP) Expedition 354: Bengal Fan. These microtektites are found within a foraminifera-rich calcareous clay layer beneath the Brunhes–Matuyama (B–M) magnetostratigraphic boundary. Most of them are spherical and are less than one millimeter in diameter. Typical splash (dumbbell, teardrop, button etc.) and irregular-shaped forms were recovered. The most abundant microtektites are pale green in color, followed by opaque, pale brown, translucent and transparent varieties. They are characterized by various surficial attributes including pits, mounds, grooves and fractures. Geochemical analyses suggest that the major oxide compositions are very similar to Australasian microtektites, Australasites reported elsewhere and also to the average composition of upper crustal rocks. Transparent bottle green microtektites are relatively richer in MgO content and lower in silica to other microtektites found in U1452. Minor and trace elements show a wide range of distribution and individual samples show variation. Differences in minor and trace elements concentration are possibly due to the contamination from the impact ejecta. Other than microtektites, presence of possibly polymetallic exsolution texture, shocked minerals and unmelted and partly melted ejecta within the microtektite-bearing layer in the northern Indian Ocean provides further evidence that the Australasites and Australasian microtektites might have been formed by the impact of an extraterrestrial projectile at ~0.8 Ma, somewhere in Indochina.

In this talk, I will draw distinction between linear plasma waves and strong turbulent fluctuations and argue general characteristics of 3He rich solar energetic particle events favor the scenario that 3He ions are mostly energized via cyclotron resonance with proton cyclotron waves. These waves can be produced via magnetic reconnection at the ion diffusion scale and/or via cascade of turbulence energy from low to high frequencies. Both PIC and hybrid simulations can be used to verify these scenarios.

e-Navigation—the digitalization and harmonization of data collection, integration, exchange, presentation, and analysis on board and ashore—is an International Maritime Organization initiative that enhances marine navigation and supports safety of life at sea. As e-Navigation and marine activities continue to grow and become more diverse, data providers and users are also becoming more diverse, and the number of data types and sources and amount of data are increasing. Thus, there is an important need to standardize the data into uniform, usable formats so that 1) navigation systems can easily integrate and seamlessly display the data, and 2) mariners can make effective, accurate, and swift navigation decisions based on those data. Effective international standards are developed in consideration of all stakeholder countries’ needs, with the flexibility to evolve to cater to new user requirements. Following these principles, the International Hydrographic Organization has developed a framework for standardization of maritime data products (the S-100 Universal Hydrographic Data Model)—a “standard for standards.” S-100 serves as the umbrella structure by which all other data products should follow, such as high resolution bathymetry (S-102), water levels (S-104), surface currents (S-111), and weather (S-412). This presentation will provide insight into the development and application of international standards for three maritime data products: S-104, S-111, and S-412. Further, we will provide examples of how a data provider employs the international S-100 standard, via state-of-the-art work at the NOAA/National Ocean Service (NOS)/Office of Coast Survey that is converting in real-time, gridded NOS Operational Forecast System surface current predictions into an S-100/S-111 compliant format. Future work includes developing interoperability standards and testing products to ensure they meet user needs.

We perform a suite of laboratory friction experiments on saw-cut Westerly Granite surfaces and probe frictional state evolution in response to step changes in normal stress. The experiments are conducted with the objective of illuminating the origin of friction memory effects and the fundamental processes that yield friction rate and state dependence. In contrast to previous works, we measure directly the fault slip rate and account for changes in slip rate caused by normal stress perturbations. Further, we complement mechanical data acquisition by continuously probing the faults with ultrasonic pulses. We conduct the experiments at room temperature and humidity conditions in a servo controlled biaxial testing apparatus in the double direct shear configuration. The normal stress perturbations are carried out during steady shearing over a range of shear velocities, from 0.02 - 100 μm/s. We report observations of a transient shear stress and friction evolution with step increases and decreases in normal stress. Specifically, we show that shear stress evolves in a two-stage fashion – first linear-elastically, then inelastically in response to the normal stress step. We find that the excursions in slip rate resulting from the changes in normal stress must be accounted for in order to accurately predict fault strength evolution. The effects of induced changes in fault slip rate are also apparent in elastic wave properties. Ultrasonic wave amplitudes increase instantly in response to normal stress steps and then gradually decrease to a new steady state value, in part due to changes in fault slip rate. This decrease is strongly related to accelerated creep at the fault interface. We also demonstrate that steady state amplitudes are a reliable proxy for real contact area (RCA) at the fault interface. Previous descriptions of frictional state evolution during normal stress perturbations have not adequately accounted for large slip velocity excursions. Here, we do so by using the measured ultrasonic amplitudes as a proxy for frictional state during transient shear stress evolution. Our work improves understanding of induced seismicity and triggered earthquakes with particular focus on simulating static triggering and stress transfer phenomena using rate-and-state frictional formulations in earthquake rupture models.

The Shenhu hydrate reservoirs of northern South China Sea are speculated to form and accumulate under the free gas-rich environment, and accord with the flow-transportation-reaction process. During this process, the area has also experienced simultaneous alternations of the local geological structures and ambient environmental conditions. First-order reaction kinetics, which controls the hydrate reaction, is coupled with the seafloor sedimentation to quest the dynamic formation and aggregation mechanism of the Shenhu hydrate layers. Firstly, based on the indications from Peclet number, the hydrate reaction shall play more active roles during the natural sedimentation in this process. Secondly, when the average seafloor sedimentation rate and the initial seafloor were 5 cm/ka and 988 m, respectively, three moments (50 ka, 3 Ma, and 5 Ma) are chosen to investigate the evolution process of the hydrate reservoirs and exhibit the change of the local pressures, temperatures, dissolved methane and salt, phase saturations, stratum permeability, and pore capillary pressure. The results show that after 5 Ma the occurrence and distribution of hydrate-bearing sediments proceed to be nearly consistent with the current status. Finally, the effects of five factors, including methane flux, kinetic coefficient, initial fluid position, permeability and seafloor sedimentation rate which simultaneously control the accumulation together in this zone, are quantitatively discussed. It verifies that the reaction-sedimentation mechanism is applicable for researching the Shenhu hydrate system. Under this model it should have a small methane flux and relatively small reaction coefficient here.

Allowing near-surface geophysics students to learn ground penetrating radar (GPR) data processing through hands-on exercises poses a challenge because of the high cost of professional GPR software. Free processing and visualization packages are scarce and often either require other commercial software such as Matab, which many students may not have on their own computers, or they are limited to specific operating systems. To allow students to process GPR data on their own computers, for example data collected as part of a class-based research project or online available data, the processing software needs to be (1) free, (2) platform independent, (3) easy to install and use, and should record the steps the students take to obtain their results in order to facilitate reproducibility and grading. GPRPy (https://github.com/NSGeophysics/GPRPy) is an open-source ground penetrating radar data processing and visualization software that has a graphical user interface and which is also scriptable. It is python-based, making it platform independent and independent of commercial programming environments. The graphical user interface allows for writing out humanly readable python scripts that can be run from the command line to automatize the data processing and visualization. GPRPy is hosted on the collaborative software development website GitHub, allowing educators and researchers to create and adapt their own versions to their needs.

The Enriquillo-Plantain Garden Fault (EPGF), one of two left-lateral transforms that define the Caribbean-North American plate boundary in Haiti, plunges beneath Lake Azuei in the eastern part of the country. In 2017, we acquired 220 km of sub-bottom and multichannel seismic reflection profiles (CHIRP and MCS) in a 1.2 km grid pattern across the lake. The two seismic methods achieved subbottom penetration of up to 15 m and 200 m, respectively. CHIRP and MCS data reveal folded turbidites across the expected extension of the EPGF fault zone at the south end of the lake, although direct evidence for faulting is lacking. Along the west side of the lake, however, MCS data image a broad NW-SE monoclinal fold whose geometry is compatible with an underlying SW-dipping blind thrust fault. CHIRP profiles image patches of soft- sediment deformations above the monoclinal fold; they also image a distinctive 11 m-deep paleoshoreline all around the lake that is uplifted by 1-2 m above that fold. These results are compatible with a scenario where some large slip event(s) on the presumed blind thrust occurred after formation of the paleoshoreline, locally uplifting the lakebed and causing liquefaction. Two short sediment cores sampled a layer correlatable to a reflection in the CHIRP profiles. That reflection extends laterally below the 11m shoreline, and thus predates its formation. On-going 14C dating of material from the two cores are expected to provide a maximum age for the shoreline, and thus for some hypothetical slip event(s) on the presumed blind thrust fault. The prominent character of the paleoshoreline suggests that it was stable, something best achieved if the lake level was controlled by the sill depth of an outlet. Presently, no such outlet exists and the lake level fluctuates. Pending results from radiometric dating, we propose that, earlier in the Holocene, the lake overflowed eastward into adjacent Lake Enriquillo along the narrow valley marking the extension of the EPGF fault zone - a valley that is presently blocked by an alluvial fan. Regardless of the relevance of that model, the uplifted shoreline implies a significant uplift rate on a structure extending up to 10 km north of the EPGF fault zone and striking oblique to it, confirming that transpressional tectonics is partitioned over an area at least as broad as Lake Azuei.

Physical habitat losses for Pacific salmonids in California’s Central Valley motivate stream restoration. Considerable river morphodynamics affect the sustainability of habitat enhancing interventions. In addition, the presence of large dams in many river catchments causes low sediment supply. This study revises existing stream restoration techniques for their ecologically efficient and physically stable embedding in a 36-km testbed river. Ecological efficiency is evaluated in terms of a commonly used hydraulic habitat suitability index. Physical stability results from 2D hydrodynamic modelling of bed shear stress during steady flows of different flood frequencies. We differentiate between terraforming, stabilizing and maintaining stream restoration techniques, which constitute three feature layers. The first layer, terraforming, includes artificial terrain modifications such as grading or backwater creation to generate new habitat. These features require stabilization, which is provided by the second feature layer. The stabilization (layer two) is achieved by bioengineering such as placement of streamwood, angular boulders and vegetation plantings. The third feature layer has the purpose to maintain newly created habitat, e.g., through artificial gravel injections. We illustrate the application of the three-layer-approach at one major restoration site of the lower Yuba River using a self-written Python package. Ecohydraulic 2D modeling was applied to designs with incremental layer additions to evaluate newly created spawning habitat and feature sustainability. This procedure represents a pertinent way for stream restoration planning, which avoids non-sustainable habitat enhancement features and implements ecologically as well as physically sustainable features only.

Global environmental science challenges in the limnological research and applications communities can only be advanced when harnessing the collective expertise and capabilities of the satellite remote sensing community and well-established in situ communities such as the Global Lake Ecological Observatory Network (GLEON). At first glance, the groups seem wildly divergent: GLEON is a grass-roots effort which has been active since 2005 and connects researchers and practitioners from around the world to ask and answer questions about lake ecosystems. Earth observing missions can take a decade to plan, build, and launch. NASA and ESA have different missions as space agencies: one primarily focused on exploration and basic research with a year-to-year appropriations cycle, while the other presents a long-term commitment to address societal needs through the Copernicus program Sentinel satellite series. The Surface Biology and Geology (SBG) mission is a future NASA satellite that will launch toward the end of this decade as part of the Earth Systems Observatory. Working together to advance the science of lake ecosystem response to climate change, each group brings different complementary strengths and assets to this societal challenge. Increasing access through open science and cloud computing are creating opportunities for better collaboration. We describe our strategy for international engagement between these groups – cultural and methodological differences aside – to derive new information, learn new insights, and expand the body of knowledge around these unique natural resources.

Place-based field education is the foundation of Lamont-Doherty Earth Observatory’s Hudson River Field Station. The most effective method of engaging and connecting people with their local environment is through memorable and hands-on field investigations, with the Hudson River itself as the best educational tool. Our ‘Next Generation of Hudson River Educators’ is a six week summer internship program specifically designed to more effectively engage underrepresented minority (URM) students and communities with the Hudson River using a tiered mentoring structure. The high school interns first take a deep dive into the Hudson River to develop a better understanding of the historic to present human connection to the estuary, the dynamism of its biology, physics, chemistry, geology, and topography, and the challenges the Hudson faces, along with potential community solutions. These field investigations build an appreciation for the estuary that they can pass on to their communities. Unfortunately, the coronavirus introduced a unique challenge on place-based education making it impossible to run an in-person program. Through an innovative approach to place-based learning, we decided ‘if we couldn’t bring the students to the river, we would bring the river to the students’. The interns dedicated the first weeks to learning about the Hudson through “Virtual River” videos, games, interactive web activities, and live river demonstrations hosted down by the water. While the content is virtual, it simulates a place-based education that effectively engages students in the geosciences and increases science literacy. The interns then work in teams to create their own communication tools to share Hudson information that is captivating to a multigenerational and diverse audience. In order to offer information that is interesting and relevant to their communities, interns performed interviews to learn directly from their friends, family, and neighbors about their perceptions and existing knowledge of the Hudson. Involving the community in place-based education is crucial because residents provide key information that would be otherwise unknown to a visiting scientist or educator. They then use this information to build their communication outputs that are intended to better connect URM to their local waterways.

In the field of Astrobiology, a quantitative approach has not been made to predict the number of extraterrestrial intelligent civilizations that may have existed on a habitable exoplanet as well their corresponding properties, such as intelligence, lifespan, and recovery time. Prior research indicates that numerous planetary systems within the Milky Way Galaxy are of over six billion years in age, implying many exoplanets, if sustainable to life, may have had several cycles of civilizations emergence and self-destruction, suggesting the ruins of advanced civilizations should be commonplace within the galaxy. We investigate this problem by utilizing statistical algorithmic simulations to predict and estimate the number of civilizations (both future and extinct) that may arise within an exoplanetary continuum, further generating the accompanying characteristics of said civilizations. Within the model, factors such as self-induced extinction/destruction, natural civilization decay, planetary disasters, and civilization rediscovery have been incorporated to examine the pathways a civilization can encounter. Our results corroborate the notion that on many of the older exoplanets in our galaxy, civilizations may have existed, however most have ultimately died out within a short period, further limiting the search for current extraterrestrial intelligence, but strengthening the approach of interstellar archeology.

Interferometric Synthetic Aperture Radar (InSAR) is used to measure deformation rates over whole continents to constrain tectonic processes. The resulting velocity measurements are only relative, due to unknown integer ambiguities introduced during propagation of the signal through the atmosphere. However, these ambiguities mostly cancel when using spectral diversity to estimate along-track motion, allowing measurements to be made with respect to a global reference frame. Here, we calculate along-track velocities for a partial global dataset of Sentinel-1 acquisitions and find good agreement with ITRF2014 model values. We include corrections for solid-earth tides and gradients of ionospheric total electron content. By combining data from ascending and descending orbits we are able to estimate north and east velocities with average precision of 4 and 20 mm/year, respectively. Although we have calculated these over large 250x250 km areas, such measurements can also be made at much higher resolution, albeit with lower accuracy. These “absolute” measurements can be particularly useful for global velocity and strain rate estimation, where GNSS measurements are sparse.

A precise and accurate timescale is critical for calibrating major events in Earth history and testing their spatiotemporal relationships for putative causes. The Newark-Hartford astrochronostratigraphic polarity timescale (APTS) was developed in cyclical lacustrine continental deposits spanning 27 million years of Late Triassic and earliest Jurassic time using the theoretically constant 405 kyr eccentricity cycle linked to gravitational interactions with Jupiter-Venus as a tuning target and provides a major calibration for the early Mesozoic. While this cycle is both unimodal and the most metronomic of the major orbital cycles thought to pace Earth’s climate in numerical solutions, there has been no empirical confirmation of that behavior, given the potential chaotic behavior of the Solar System. An additional criticism of the Newark-Hartford APTS is that it is anchored only at its younger end by U-Pb zircon dates at 201.6 Ma. To test the validity of the dangling APTS and orbital periodicities, we recovered a diagnostic magnetic polarity sequence providing an unambiguous correlation to the APTS in the volcaniclastic-bearing Chinle Formation in drill core PFNP-1A from Petrified Forest National Park (Arizona, US). New U-Pb CA-TIMS detrital zircon dates from the core are indistinguishable from ages predicted by the APTS back to 215 Ma. The APTS is evidently continuous to a small fraction of a remarkably constant 405 kyr orbital eccentricity cycle, thus extending the empirical evidence well beyond theoretical solutions regarded as reliable back to only 50 Ma. The Newark-Hartford APTS becomes the longest directly calibrated polarity sequence and can be used to resolve various Earth history problems, for example, to differentiate provinciality from global temporal patterns in the ecological rise of early dinosaurs.

A Helium Lidar system, which is being developed for measurements of metastable helium density in the thermosphere and exosphere, employs a CW 1083nm laser with power of 60W, a telescope array consisting of six 1m-diameter telescope and an area-array ICCD. To realize range-resolved remote sensing, the laser is located separately from the location of telescope with a distance of D and the laser beamed is leaned towards the Field-of-view (FOV) of the telescope array with an zenith angle of θ. The signal in a specific height is finally imaged onto a corresponding pixel of the ICCD. Before the retrieval of metastable helium density, the first procedure is to decide the relation between the pixels and corresponding heights. Based on the FOV of the telescope, the divergence angle of the laser beam, the geometry of the laser and telescope, and the size of the pixels, every pixel corresponds to a specific height range, as shown in Fig. 1. The darkest shade corresponds to one pixel of the ICCD. Therefore, the second procedure is to correct the height range overlap of the signal from adjacent pixels to decrease the smoothness of the signal profile caused by the height overlap of adjacent pixels. The signal received by the ICCD is simulated based on a metastable helium density model developed by Waldrop et. al. The results show that these two signal correcting procedures can improve the precision of each pixel’s signal by 5% in average.

In global climate models, CO2-driven warming causes strong and very widespread mean drying trends in climatic wetness indices like the Palmer Drought Severity Index, Aridity Index and Standardized Precipitation-Evapotranspiration Index. Yet, these same simulations also predict that runoff will not decline over most of Earth’s surface, that root-zone soil moisture and evaporative fraction will decline only regionally, and that vegetation will become broadly greener. Thus, actual drought impacts of warming in these models are far less broad and severe than implied by the drought indices. Here, I probe why this “index-impact gap” occurs, and whether it is a feature of reality as well as models. In particular, I show that the discrepancies are not just limited to simulations which assume a substantial direct CO2 effect on vegetation, but are also large in greenhouse-only simulations, implying that they occur for fundamental climatic reasons rather than via CO2-physiological pathways. I also review key observational evidence that the index-impact gap has also been large over the historical era and was very evident for the last glacial-to-interglacial warming, lending much additional credence to the model output.

We present in-situ ion composition and velocity measurements from the Enhanced Polar Outflow Probe during the August 2017 solar eclipse, which crossed the path of totality at ~640 km altitude within 10 minutes of totality passing. These measurements reveal two distinct H+ ion populations, and show a ~40% decrease in topside plasma density, a similar drop in upward but not downward H+ ion flux, and a downward O+ ion velocity of ~100 m/s. These features are directly linked to changes in the H+/O+ composition and field-aligned or interhemispheric light ion flow, and reduction in the negative spacecraft potential. These observed features were absent on the preceding, non-eclipse days, and corroborate the reduction in F-region plasma density and topside Total Electron Content (TEC) observed by the Global Position System (GPS) receivers onboard. They are attributed to the temporary reduction of photoionization in the eclipsed F-region.