Deep-sea hydrothermal vent systems are a key mechanism for fluid and heat exchanges between the solid Earth and the ocean, but the inaccessible location, scattered occurrence, and meter scale size of vent chimneys make finding them challenging. Now that chimney-sized structures are resolved by near-bottom bathymetric maps, methods to identify potential hydrothermal chimneys in an efficient and reproducible way can be used to develop catalogs of chimney distribution and size. This study investigates the use of a previously developed machine learning Chimney Identification Tool (CIT) to identify potential chimneys in 1 m gridded bathymetric data collected by autonomous underwater vehicle Sentry in 2019-2021. The CIT uses a convolutional neural network, a deep learning model that is well suited to recognize textures and shapes in rasters, that was trained on examples from two other spreading ridge environments. This neural network is combined with a selective search to output individual point locations from input gridded bathymetric data. The CIT picked 119 chimney-like structures up to 4000 m away from the ridge axis and summit collapse trough at the East Pacific Rise between 9 degrees 43 ' N and 9 degrees 57 ' N, suggesting an abundance of off-axis hydrothermal activity that has not been previously acknowledged in estimates or models of hydrothermal activity. This machine learning approach is also compared to interpretations by two expert human analysts. We observe a wide range between the human interpretations, primarily resulting from different levels of including smaller features, with the outputs of the CIT falling within this range. These results illustrate how uncertainty is inherent to identifying seafloor chimneys from bathymetric data, whether manually or algorithmically, due to variation and ambiguity in chimney morphology. We suggest that our results underscore the promise of using an algorithmic method to produce reproducible inventories of potential chimneys with consistent criteria that can be used for broader spatial distribution insights.

The major ion chemistry of the ocean has been assumed to be controlled by river input, hydrothermal circulation at mid-ocean ridges, carbonate production, and low-temperature alteration of seafloor basalt, but marine chemical budgets remain difficult to balance. Here we propose that large-scale groundwater flow and diagenetic reactions in continental shelf sediments have been overlooked as an important contributor to major ion budgets in the ocean. Based on data synthesized from 17 passive margin basins, continental shelves contribute fluid exchanges comparable to hydrothermal circulation at mid-ocean ridges. Chemical exchange is similarly significant, indicating removal of Mg 2+ from the oceans at rates similar to mid-ocean ridge convection. Continental shelves likely contribute Ca 2+ and K + to the oceans at rates that, in combination with low-temperature basalt alteration, can close current budget deficits. Flow and reaction in continental shelf sediments should be included in a new generation of studies addressing marine isotope budgets.

The spatial variations in Quaternary sediments on the inner continental shelf are produced by the progression of depositional environments during the latest sea-level rise, and this sedimentary architecture plays a fundamental role in controlling groundwater discharge. However, coincident seismic mapping, sediment cores, and hydrological studies are rare. Here, we combine high-resolution, 0.5–10 kHz, high-frequency seismic profiles with sediment cores to examine the nature of the sediment deposits, including paleochannels, where submarine groundwater discharge has also been studied in a 150 km2 area of the inner shelf north of Charleston, South Carolina. We used high-frequency seismic reflection to interpret seismic facies boundaries, including 16 paleochannel crossings, to 20 km offshore. From 13 vibracores taken at the intersections of the seismic lines, we defined seven lithofacies representative of specific depositional environments. The paleochannels that we cored contain thick layers of structureless mud sometimes interbedded with silt, and mud is common in several of the nearshore cores. Our results indicate that paleochannels are often mud-lined or filled in this area and were most likely former estuarine channels. Neither the paleochannels nor a mud layer were found farther than 11 km off the present shoreline. This offshore distance coincides with the strongest pulses of groundwater discharge, emerging just beyond the paleochannels. This suggests that the muddy paleochannel system acts as a confining layer for submarine groundwater flow.

[ 1 ] The spatial density of hydrothermal activity along most mid-ocean ridges is a robust linear function of spreading rate (or magmatic budget), but extreme crustal properties may alter this relationship. In 2005– 2006 we tested the effect of thickened crust on hydrothermal activity using high-resolution mapping of plumes overlying the hot spot–affected Gala´pagos Spreading Center from 95 (cid:1) to 89 (cid:1) 42 0 W ( (cid:2) 560 km of ridge crest). Plume mapping discovered only two active, high-temperature vent fields, subsequently confirmed by camera tows, though strong plume evidence indicated minor venting from at least six other locations. Total plume incidence ( p h ), the fraction of ridge crest overlain by significant plumes, was 0.11 ± 0.014, about half that expected for a non–hot spot mid-ocean ridge with a similar magmatic budget. Plume distributions on the Gala´pagos Spreading Center were uncorrelated with abrupt variations in the depth of the along-axis

Identifying the locations of hydrothermal chimneys across mapped areas of seafloor spreading ridges unlocks the ability to research questions about their correlations to geology, the cooling of the lithosphere, and deep-sea biogeography. We developed a Chimney Identification Tool (CIT) that utilizes a Convolutional Neural Network (CNN) to classify 1 m gridded AUV bathymetry and identify the locations of hydrothermal vent chimneys. A CNN is a type of Machine-Learning model that is able to classify raster data based on the shapes and textures in the input, making it ideal for this task. The criteria that have been used in previous manual classifications of chimneys have focused on the round base and spire shape of the features, and are not easily quantifiable. Machine-Learning techniques have previously been implemented with sonar data to classify seafloor geology, but this is the first application of these methods to hydrothermal systems. In developing the CIT, we compiled the bathymetry data from two rasters from the Endeavor Ridge—each gridded at a 1 m resolution—containing 34 locations of known hydrothermal chimneys, and from the 92° W segment of the Galapagos Spreading Center (GSC) containing 14. The CIT produced a primary group of outputs with 96% agreement with the manual classification; moreover, it correctly caught 29 of the 34 known chimneys from Endeavor and 10 of the 14 from the GSC. The CIT is trained to identify features with the characteristic shape of a hydrothermal vent chimney; therefore, it is susceptible to the misclassification of unusually shaped cases, given the limited training data. As a result, to provide the option of having a more inclusive application, the CIT also produced a secondary group of output locations with 61% agreement with the manual classification; moreover, it caught three of the four additional known chimneys from the GSC and four of the five from Endeavor. The CIT will be used in future investigations where an inventory of individual chimneys is important, such as the cataloguing of off-axis hydrothermal venting and the investigation of chimney distribution in connection to seafloor eruptions.

[ 1 ] New, high-resolution bathymetry for the East Pacific Rise between 8 (cid:1) N and 12 (cid:1) N was collected over a 6 km wide swath centered on the ridge axis using the 30 kHz Simrad EM300 multibeam system. The coverage area corresponds latitudinally to the designated Ridge2000 Integrated Studies Site (ISS) for fast spreading ridges. The EM300 data, gridded at 30 m latitude by 50 m longitude, represent a greater than 4X improvement in horizontal resolution over previously available multibeam data and a 2X improvement in depth resolution. The new bathymetry was used to update the locations and hierarchy of ridge offsets for this area. Among the many applications for this data, it enables us to tabulate volcanoes half the size that could be previously detected. The distribution of near-axis volcanic cones >25 m high suggests that this population of small, near-axis cones results from low effusion rate eruptions of the ridge axis.

Knowledge of coastal groundwater flow is critical for managing coastal groundwater resources and quantifying submarine groundwater discharge (SGD), but this flow occurs over multiple scales that can be difficult to study in an integrated way. We designed a field and modeling study to investigate groundwater flow and the distribution of salinity during sea level rise in a domain that included beaches, salt marshes and the first major confined aquifer, which reached 10–15 km offshore. Numerical models were based on the flat‐lying, passive margin coastline of North Inlet, SC, and were constrained by field studies including subsurface resistivity surveys and hydraulic head observations. Simulations that included tidal fluctuations showed that the salt marsh generated more than three times as much SGD as the beach and inner shelf, per unit length of coastline. Groundwater exchange between scales was small, suggesting that physical fluxes of groundwater can be considered independently at different scales. However, salinization of the first major confined aquifer occurred by downward transport from overlying aquifers rather than intrusion from the seaward end, suggesting that studies of aquifer salinization should consider multiscale flow. During simulated sea level rise, fresh‐to‐brackish groundwater persisted in the first confined aquifer as far as the seaward end of the overlying confining unit, 10–20 km offshore. Total fluxes of SGD decreased significantly with future sea level rise, dominated by declining SGD in the salt marsh, and portending a marked decline in the flux of nutrients and carbon to estuaries and the coastal ocean.

Marine tracer studies indicate that large volumes of saline groundwater discharge to the ocean in passive margin settings. These results have not found widespread recognition because the location and cause(s) of this submarine groundwater discharge (SGD) are unclear. Here we report observations from a new long-term seafloor monitoring network in the South Atlantic Bight that support large-scale SGD far from shore. In the study area near Charleston, South Carolina, we determined hydrostratigraphy via vibracoring and chirp seismic surveys, collected water samples from seafloor wells, and used heat as a tracer to monitor SGD. We detected significant pulses of saline SGD issuing from the seafloor 10-15 km from shore. These pulses coincided with abrupt sea level declines of up to 30 cm. Based on an analysis of marine conditions at the time, we propose that upwelling-favorable winds depressed sea level in the region, causing saline groundwater to discharge from confined coastal aquifers that connect land and ocean. The combination of stacked confined aquifers and variations in sea level are nearly ubiquitous in passive coastal margins. This previously overlooked combination can explain a wide range of other published observations and promotes more dynamic flows than simple tidal fluctuations. This new mechanism may explain Ra tracer signals in the coastal Atlantic Ocean and supports significant nutrient inputs to the ocean. These large natural geochemical fluxes may be sensitive to groundwater usage on land.

Carrot weevil, Listronotus oregonensis (LeConte) (Coleoptera: Curculionidae), is a pest of carrot (Daucus carota var. sativus Hoffmann; Apiaceae) throughout eastern Canada. Carrot weevil emergence and oviposition were monitored in commercial carrot fields in Nova Scotia. Cumulative degree days were calculated using a base temperature of 7 degrees C (DD7), and models were developed to predict cumulative emergence and oviposition using nonlinear regression. Cumulative emergence and oviposition were adequately explained as functions of DD7 by a three-parameter sigmoidal Hill equation. Our emergence model predicted initial and peak adult emergence at 35 and 387 DD7, respectively, with oviposition on carrot baits occurring as early as 42 DD7. Models were then validated to evaluate how well they performed. Oviposition on carrot plants began at the fourth true-leaf stage (342 DD7) and continued until eleventh true-leaf stage. Growers using these models can identify their window of opportunity to manage their carrot weevil populations targeting the majority of emerged adults before oviposition begins in the field.

The oceanic crust consists mostly of basalt, but more evolved compositions may be far more common than previously thought. To aid in distinguishing rhyolite from basaltic lava and help guide sampling and understand spatial distribution, we constructed a classifier using neural networks and fuzzy inference to recognize rhyolite from its lava morphology in sonar data. The Alarcon Rise is ideal to study the relationship between lava flow morphology and composition, because it exhibits a full range of lava compositions in a well-mapped ocean ridge segment. This study shows that the most dramatic geomorphic threshold in submarine lava separates rhyolitic lava from lower-silica compositions. Extremely viscous rhyolite erupts as jagged lobes and lava branches in submarine environments. An automated classification of sonar data is a useful first-order tool to differentiate submarine rhyolite flows from widespread basalts, yielding insights into eruption, emplacement, and architecture of the ocean crust.

Environmental monitoring and surveying operations on rivers currently are performed primarily with manually-operated boats. In this domain, autonomous coverage of areas is of vital importance, for improving both the quality and the efficiency of coverage. This paper leverages human expertise in river exploration and data collection strategies to automate and optimize these processes using autonomous surface vehicles(ASVs). In particular, three deterministic algorithms for both partial and complete coverage of a river segment are proposed,providing varying path length, coverage density, and turning patterns. These strategies resulted in increases in accuracy and efficiency compared to human performance.The proposed methods were extensively tested in simulation using maps of real rivers of different shapes and sizes. In addition, to verify their performance in real world operations, the algorithms were deployed successfully on several parts of the Congaree River in South Carolina, USA, resulting in total of more than 35km of coverage trajectories in the field.

Recently developed data collection techniques allow for improved characterization of sedimentary outcrops. Here, we outline a workflow that utilizes unmanned aerial vehicles (UAV) and structure-from-motion (SfM) photogrammetry to produce sub-meter-scale outcrop reconstructions in 3-D. SfM photogrammetry uses multiple overlapping images and an image-based terrain extraction algorithm to reconstruct the location of individual points from the photographs in 3-D space. The results of this technique can be used to construct point clouds, orthomosaics, and digital surface models that can be imported into GIS and related software for further study. The accuracy of the reconstructed outcrops, with respect to an absolute framework, is improved with geotagged images or independently gathered ground control points, and the internal accuracy of 3-D reconstructions is sufficient for sub-meter scale measurements. We demonstrate this approach with a case study from central Utah, USA, where UAV-SfM data can help delineate complex features within Jurassic fluvial sandstones.

Ecological zones in a salt marsh are influenced by many factors, including hydroperiod, soil salinity, groundwater flow, and nutrient/oxygen availability. In this project, high-resolution aerial images taken by a Helikite helium balloon-kite at 100 m altitude were used to develop a detailed flooding model and derive a spatially comprehensive map of ecological zones at the headwaters of a small tidal marsh creek at a forest-marsh boundary in North Inlet estuary, South Carolina. We constructed photomosaics from Helikite imagery over a 150 × 100 m area to identify ecological zones using an automated, maximum likelihood classification. In the same area, we developed a digital terrain model with ± 2 cm overall vertical accuracy, primarily from waterlines at known tide height tracked by Helikite imagery and GPS. These are low-cost, easily implemented methods for studying marsh processes where access is often challenging. Quantifying frequency of inundation, an approximation of hydroperiod, using our terrain model and comparing it to ecological zones revealed that there is not a linear relationship between elevation and inundation above mean high tide. Ecological zones exhibit complex spatial patterns that neither elevation nor hydroperiod alone can explain. In the northwestern basin, adjacent to a forest-marsh boundary, inflow of low salinity groundwater from a large freshwater lens beneath the forest prevents the development of Salicornia virginica zones and allows the high-marsh plant Juncus roemarianus to be present at middle-to-low marsh elevations. Conversely, in the southwestern portion of the basin adjacent to a relict beach ridge underlain by a smaller freshwater lens, saltwater infiltration during spring tides and evapotranspiration during neap tides allows Salicornia virginica zones to develop in hypersaline soils. Many of the current numerical models for predicting salt marsh ecological zonation consider hydroperiod as the main factor; however, the asymmetry of the basin in both ecological zones and freshened groundwater discharge imply groundwater and surface-water inundation should both be considered in the distribution of ecological zones in a coastal salt marsh.

Shallow (elevated) portions of mid-ocean ridges with enriched geochemical compositions near hotspots document the interaction of hot, geochemically-enriched plume mantle with shallow depleted upper mantle. Whereas the spatial variations in geochemical composition of ocean crust along the ridge axis in areas where plume-ridge interaction is taking place have been studied globally, only restricted information exists concerning temporal variations in geochemistry of ocean crust formed through plume-ridge interaction. Here we present a detailed geochemical study of 0–1.5Ma ocean crust sampled from the Western Galápagos Spreading Center (WGSC) axis to 50km north of the axis, an area that is presently experiencing a high influx of mantle material from the Galápagos hotspot. The tholeiitic to basaltic andesitic fresh glass and few bulk rock samples have incompatible element abundances and Sr–Nd–Pb isotopic compositions intermediate between depleted normal mid-ocean-ridge basalt (N-MORB) from >95.5°W along the WGSC and enriched lavas from the Galápagos Archipelago, displaying enriched (E-)MORB type compositions. Only limited and no systematic geochemical variations are observed with distance from the ridge axis for <1.0Ma old WGSC crust, whereas 1.0–1.5Ma old crust trends to more enriched isotopic compositions in 87Sr/86Sr, 143Nd/144Nd, 207Pb/204Pb and 208Pb/204Pb isotope ratios. On isotope correlation diagrams, the data set displays correlations between depleted MORB and two enriched components. Neither the geographically referenced geochemical domains of the Galápagos Archipelago nor the end members used for principal component analysis can successfully describe the observed mixing relations. Notably an off-axis volcanic cone at site DR63 has the appropriate composition to serve as the enriched component for the younger WGSC and could represent a portion of the northern part of the Galápagos plume not sampled south of the WGSC. Similar compositions to samples from volcanic cone DR63 have been found in the northern part of the 11–14Ma Galápagos hotspot track offshore Costa Rica, indicating that this composition is derived from the northern portion of the Galápagos plume. The older WGSC requires involvement of an enriched mantle two (EMII) type source, not recognized thus far in the Galápagos system, and is interpreted to reflect entrained material either from small-scale heterogeneities within the upper mantle or from the mantle transition zone. Overall the source material for the 0–1.5Ma WGSC ocean crust appears to represent mixing of depleted upper mantle with Northern Galápagos Plume material of relatively uniform composition in relatively constant proportions.

In the absence of any direct observations of an active submarine eruption at a mid-ocean ridge (MOR), our understanding of volcanic processes there is based on the interpretation of eruptive products. Submarine lava flow morphology serves as a primary indicator of eruption and emplacement processes; however, there is typically a lack of visual observations and bathymetric data at a scale and extent relevant to submarine lava flows, which display meter to submeter-scale morphological variability. In this paper, we merge submersible-based visual observations with high-resolution multibeam bathymetry collected by an autonomous underwater vehicle (AUV) and examine the fine-scale geomorphology of Ninos, a submarine lava flow field at the Galapagos Spreading Center (GSC).We identify separate morphological facies (i.e., morphofacies) within the lava flow field, each having distinct patterns of lava flow morphology and volcanic structures. The spatial and stratigraphic arrangement of morphofacies suggests that they were emplaced sequentially as the eruption progressed, implying that the Ninos eruption consisted of at least three eruptive phases. We estimate eruption parameters and develop a chronological model that describes the construction of the Ninos lava flow field. An initial phase with high effusion rates emplaced sheet flows, then an intermediate phase emplaced a platform of lobate lavas, and then an extended final phase with low effusion rates emplaced a discontinuous row of pillow lava domes. We then compare this model to mapped lava flow fields at other MORs. Despite disparities in scale, the morphological similarities of volcanic features at MORs with different spreading rates suggest common emplacement processes that are primarily controlled by local magma supply.