Many water quality and ecosystem functions performed by streams occur in the benthic biolayer, the biologically active upper (~5 cm) layer of the streambed. Solute transport through the benthic biolayer is facilitated by bedform pumping, a physical process in which dynamic and static pressure variations over the surface of stationary bedforms (e.g., ripples and dunes) drive flow across the sediment-water interface. In this paper we derive two predictive modeling frameworks, one advective and the other diffusive, for solute transport through the benthic biolayer by bedform pumping. Both frameworks closely reproduce patterns and rates of bedform pumping previously measured in the laboratory, provided that the diffusion model’s dispersion coefficient declines exponentially with depth. They are also functionally equivalent, such that parameter sets inferred from the advective model can be applied to the diffusive model, and vice versa. The functional equivalence and complementary strengths of these two models expands the range of questions that can be answered, for example by adopting the advective model to study the effects of geomorphic processes (such as bedform adjustments to land use change) on flow-dependent processes, and the diffusive model to study problems where multiple transport mechanisms combine (such as bedform pumping and turbulent diffusion). By unifying advective and diffusive descriptions of bedform pumping, our analytical results provide a straightforward and computationally efficient approach for predicting, and better understanding, solute transport in the benthic biolayer of streams and coastal sediments.

The 2020 Monte Cristo Earthquake sequence in western Nevada began with a M6.5 shock on 5/15/20, and was the largest to occur in Nevada since 1954. The event exhibited left-lateral slip along an eastward extension of the Candelaria fault and extensive distributed surface faulting in the epicentral area. Groundwater monitoring and strain analysis were conducted to evaluate hydrochemical effects on the regional groundwater systems following the initial event. Physio-chemical monitoring, (started on 5/16 and still ongoing) includes measurements of temperature (temp), pH, specific conductance (SpC), flow rate, alkalinity and collection of samples for major ions and trace element analysis. Since sites had not been monitored prior to the initial shock, measurements were evaluated against a year of post-event data to gauge response to seismicity. Four sites were monitored: a well from Columbus Marsh (CM) located 5 km from the epicenter; an artesian thermal well from Fish Lake Valley (FL); a well at Willow Ranch (WR) tapping cool water above the FL waters; and a spring along Mina Dump Road (MD) located 15 km north of the Candelaria fault on the Benton Springs Fault. GPS and InSAR measurements were used to create a model of the slip from which we estimated coseismic strain at each sampling location. All but one sample site, MD, experienced positive dilation and CM experienced the greatest amount of strain (15-17 microstrains). Hydrologic and chemical changes were observed following the initial shock, varying between sites. CM had significantly lower SpC values in the week following the event, as well as changes in major ion composition. Other sites showed minor changes; MD showed fluctuations in pH values and FL experienced a slight drop in temp. These waters showed minimal changes in major ions and trace elemental composition. Clear responses were observed throughout three >M5 aftershocks (6/30/20, 11/13/20, and 12/1/20), especially in SpC and alkalinity. A remarkable change in elemental concentration (an increase in Ca, K, SO4, Fe, and decrease in Na, Cl, Li, and Ba) was observed in CM. WR experienced a transient increase in temp measured two weeks prior to the 11/13/20 earthquake. Strain analyses of the smaller (>M5) events are planned to further evaluate observed responses and to clarify factors affecting groundwater response.

Permafrost active layer thickness (ALT) is a sensitive indicator of permafrost response to climate change. In recent decades, ALT has increased at sites across the Arctic, concurrent with observed increases in annual minimum streamflow (baseflow). The trends in ALT and baseflow are thought to be linked via: 1) increased soil water storage capacity due to an increased active layer, and 2) enhanced soil water mobility within a more continuous active layer, both of which support higher baseflow in Arctic rivers. One approach to analyzing these changes in ALT and baseflow is to use baseflow recession analysis, which is a classical method in hydrology that relates groundwater storage S to baseflow Q with a power law-like relationship Q = aSb. For the special case of a linear reservoir (b=1.0), the baseflow recession method has been extended to quantify changes in ALT from streamflow measurements alone. We test this approach at sites across the North American Arctic and find that catchments underlain by permafrost behave as nonlinear reservoirs, with scaling exponents b~1.5–3.0, undermining the key assumption of linearity that is commonly applied in this method. Despite this limitation, trends in a provide insight into the relationship between changing ALT and changing Arctic baseflow. Although care should be taken to ensure the theoretical assumptions are met, baseflow recession analysis shows promise as an empirical approach to constrain modeled permafrost change at the river basin scale.

The activation of landslides and shallow faults is related to the shear behavior of soft interlayers during groundwater infiltration. Regarding the water sensitivity of clay minerals, the shear behavior of soft interlayers may rely more on weathering and water content than the requirement of shear displacement and normal stress for quartz grains. Here, we present the reduction characteristics of the shear resistance and permeability of mudstone granules considering weathering under dry-wet cycling. Within a shear displacement of 20 mm, the shear mode transformation of the weathered mudstone granules from strain hardening to strain softening was revealed from dry to wet conditions. However, this transition was not observed for unweathered mudstone and weathered sandstone samples. Correspondingly, the permeability perpendicular to the shear zone reduced 10~45 times with increasing normal stress according to post-shear measurements. Because weathered particles exhibited more micropores, the addition of water resulted in mineral separation and generated mud that filled the specimen pores. Thus, the sealing and lubrication effect of the mud decreased the porosity and shear resistance of the soft interlayer, along with increasing particle roundness. This rapid transformation mechanism within a limited displacement reveals the effect of water softening and weathering on the shear behavior of soft interlayers, which helps to understand landslide occurrence and shallow fault activation.

Large igneous provinces (LIPs) are often associated with mass extinctions and are vital for life evolution on Earth. However, the precise relation between LIPs and their impacts on biodiversity is enigmatic as they can be asynchronous. If the environmental impacts are primarily related to sill emplacement, the structure of LIPs’ magma storage system becomes critical as it dictates the occurrence and timing of mass extinction. Here we use surface wave tomography to image the lithosphere under the Permian Emeishan Large Igneous Province (ELIP) in SW China. We find a NE-trending zone of high shear-wave velocity (Vs) and negative radial anisotropy (Vsv > Vsh) in the crust and lithosphere and interpret it as a mafic-ultramafic, dike-dominated magma storage system on the hidden hotspot track of the ELIP. An area of less-negative radial anisotropy, on the hotspot track but away from the eruption center, reflects an elevated proportion of sills emplaced at the incipient stage of the ELIP. Liberation of poisonous gases and mercury by the sills explains why the mid-Capitanian global biota crisis preceded the peak ELIP eruption by 2-3 million years.

Blasting experiments were performed that investigate multiple explosions that occur in quick succession in the ground and their effects on host material and atmosphere. Such processes are known to occur during volcanic eruptions at various depths, lateral locations, and energies. The experiments follow a multi-instrument approach in order to observe phenomena in the atmosphere and in the ground, and measure the respective energy partitioning. The experiments show significant coupling of atmospheric (acoustic)- and ground (seismic) signal over a large range of (scaled) distances (30–330 m, 1–10 mJ^-1/3). The distribution of ejected material strongly depends on the sequence of how the explosions occur. The overall crater sizes are in the expected range of a maximum size for many explosions and a minimum for one explosion at a given lateral location. The experiments also show that peak atmospheric over-pressure decays exponentially with scaled depth at a rate of d0 = 6.47×10-4 mJ-1/3; at a scaled explosion depth of 4×10-3 mJ-1/3 ca. 1% of the blast energy is responsible for the formation of the atmospheric pressure pulse; at a more shallow scaled depth of 2.75×10-3 mJ-1/3 this ratio lies at ca. 5.5–7.5%. A first order consideration of seismic energy estimates the sum of radiated airborne and seismic energy to be up to 20% of blast energy.

The Taurus Mountains form the southern margin of the Central Anatolian Plateau of Turkey and form an orographic barrier separating the cold, semi-arid interior to the north from the mild Mediterranean coast to the south. When and how they formed, and the extent which they have influenced the regional climate remains poorly constrained. The Attepe iron deposits sit on the northern part of the Eastern Taurus mountains at altitude of 1.5-2 km and consequently are ideally located to record interactions between climate and tectonics. (U-Th)/He ages of iron-oxide-oxyhydroxides from four mines within the Attepe iron deposits record ages of 1-5 Ma consistent with the persistence of hot humid climate conditions throughout the Pliocene and Pleistocene. In mines where samples are measured from different depths the age data are consistent with water table lowering rate of between 12.3 to 6.4 m/Myr. Translating these to rock uplift rates they are close to uplift/incision recorded within the Central Anatolian Plateau over the past 2 Ma, suggesting that the region was already at or close to its current elevation by the late Miocene. The latest goethite precipitation constrains the cessation of hot-humid climate to sometime in the last million years and implies that regional climate cooling, rather than surface uplift, was the main driver of aridification.

We present a seismo-acoustic analysis of the debris-flow activity between 2017 and 2019 at the Illgraben catchment (Switzerland). To understand fluid dynamic processes involved in the seismo-acoustic energy generation by debris-flows, seismic and acoustic amplitudes (maximum root mean square amplitude, RMSA) and peak frequencies are compared with flow measurements (front velocity, maximum flow depth and density). Front velocity, maximum depth, peak discharge and peak mass flux show a positive correlation with both infrasonic and seismic maximum RMSA, suggesting that seismo-acoustic radiation is controlled by these flow parameters. Comparison between seismo-acoustic peak frequencies and flow parameters reveal that, unlike seismic signals, characterized by a constant peak frequency regardless of the magnitude of the flow, infrasound peak frequency decreases with increasing flow velocity, depth and discharge. Based on all collected evidence, we suggest that infrasound signals of debris-flows are generated by flow waves and water splashes that develop at the free-surface of the flow, whose dimension scales with flow magnitude. According to fluid dynamics, such surface oscillations are mostly generated wherever the flow encounters significant channel irregularities, such as topographic steps and planform steep bends, that therefore likely constitute preferential sources of infrasound. As for seismic waves, results are consistent with previous theoretical models and field observations, which attribute debris-flow seismicity to solid particle collisions, friction and fluid dynamic structures. Finally, the observed positive correlations between seismo-acoustic signal features and flow parameters highlight the potential to use infrasound and seismic measurements for debris-flow monitoring and risk management.

Channels and the water they convey control the spatial extent of aquatic ecosystems and the evolution of landscapes. Over geologic time scales (millions of years), flow rates have varied with changes in climate, glacial extent and tectonics; however, over shorter time scales, flow rates have remained stable enough to permit the establishment of unique ecosystems that depend on and interact with specific flow and sediment transport regimes. On the Olympic Peninsula, that relative stability was altered when humans converted vast areas of old-growth forest to tree plantations during the 20th century; however, because of the remote location and unstable nature of the channels affected by the tree farms, exactly how stream flow has changed is unknown. This study presents preliminary flow observations in the Olympic Experimental State Forest (OESF), a 110,000 ha block of public land on the west side of the Olympic Peninsula that is presently being managed for both timber and ecosystem values. Through repeat flow measurements and channel surveys and the installation of pressure transducers and staff gages, we are developing a long-term record of flow in small, (basin area 50 to 700 ha) step-pool to cascade channels that transport pulses of sediment and violently swing between low and high flows. Preliminary flow observations indicate that the geologic setting of the basin plays a large role in hydrograph characteristics and that picking out a vegetation signal in the flow record may be difficult. Nonetheless, the long-term goal of these observations is to quantify flow trends and help humans (The Washington State Department of Natural Resources) better understand how past and present tree harvests on the Olympic Peninsula may be altering natural hydrologic and geomorphic processes. Monitoring techniques we are using to measure flow in these small, dynamic streams, including the use of BaRatin (Le Coz et al., 2013) to develop rating curves, are presented. Future monitoring goals and plans to use the flow records for geomorphic and hydrologic modeling studies are also discussed.

Tidal salt marshes are the most productive “Blue Carbon” ecosystem and play a significant role in the Global Carbon Cycle (Mcleod et al., 2011, Chung et al., 2011). Salt marshes account for 75% of the organic carbon (C) found in “Blue Carbon” systems, yet cover less than 1% of Earth’s surface (Hopkinson et al., 2012, Howard et al., 2014). They have a high C storage capacity due to a continuous sediment C accumulation rate (CAR) greater than that of any other “Blue Carbon” ecosystem (Murray et al., 2011, Chmura, 2013, Ouyang and Lee, 2014). However, Global estimates of salt marsh C-stocks and CAR are subject to large uncertainties (Duarte et al, 2013, Chastain et al, 2018). The Delaware Bay (DB) salt marshes have been developing for ~2000 years. When these systems are degraded they become a potential source of C-emissions. 8.85 km2 of salt marsh has converted to open water between 1996-2010 and future losses are estimated to reach 5 km2/yr by 2100 (Partnership for the Delaware Estuary, 2017). Conversion could outpace C storage if the depth of erosion is ≥ the thickness of the marsh sediments (Theuerkauf et al., 2015). Most salt-marsh sediment C-stock assessments are reported within the top 1 m of the sediment column (Ouyang and Lee, 2014), thereby representing ~ 100 years of salt-marsh accumulation as compared to the actual 1-6 m sediment sequences accumulated throughout the life span of most U.S. Mid-Atlantic regional salt marshes (Nikitina et al., 2015, Kirwan et al., 2013, Kemp et al., 2013). We estimate the average thickness of the DB salt marsh sediments is 2.6 m, C-stock is 0.1020 MgC/m2 and salt marsh C-stock loss over the 14 yr period is ~0.9 TgC (3.3MMT CO2 equivalents). As this critical “Blue Carbon” habitat reportedly declines, the resulting CO2 degassing flux has a significant impact on the Global Carbon Budget contributing to climate change and ocean acidification (Cai W-J, 2011). Recognition of this sink-to-source conversion emphasized the need for more accurate stock estimates and risk assessments based on estimates of CO2 emissions from lost and degraded salt marshes (Lovelock et al., 2017). The results show that the DB salt marshes sequester significant amounts of C, suggesting that C-stock assessments focused on the top 1 m of sediment underestimate the total C-stock and potential C-emissions by more than three-fold

As sources of fresh water and critical components of the global climate system, terrestrial glaciers are important features to monitor, particularly in light of anthropogenic climate change. Remote sensing techniques are being increasingly used to gather information on Earth’s shrinking complex glacial terrains. However, these methods possess critical challenges, including capturing firn dynamics and the presence of ice lenses. Meltwater percolation and retention, as well as thermodynamic effects on snow and firn density can complicate the relationship between surface height and mass balance changes; lowering of the glacier surface may masquerade as a mass change as detected by remote sensing technologies. The St. Elias Mountains, straddling the border between Yukon Territory, Canada and Alaska, USA, are home to extensive icefields. While numerous mass balance studies have been conducted in this region using remote sensing, there is a significant lack of in situ measurements of accumulation zone processes and firn properties. Our research examines refrozen ice layers and firn densification processes in the accumulation zone of Kaskawulsh Glacier in the St. Elias Mountains. In spring 2018, we extracted two firn cores (20 m and 35 m) from the study area and conducted a snow stratigraphy and ice lens survey on both core sections. After subsampling and melting the cores, we analyzed major ion and isotope chronology to identify extreme meltwater percolation and refreezing events, both of which critically affect firn density. The snow stratigraphy analysis from both of the cores showed numerous refrozen ice layers, indicating surface melt and refreezing processes in the accumulation zone. Preliminary results from isotope chronology analysis reveal a wash-out of the glaciochemical pattern in the 35 m and the 20 m ice core at 15 m depth, thus indicating severe surface warming events and subsequent changes in the density of the firn. This may indicate errors in the assumed density of the accumulation zone snow and firn when using remote sensing technologies to infer mass balance of Kaskawulsh Glacier.

Nucleation of earthquake slip at the plate boundary fault (décollement) in subduction zones has been widely linked to the frictional properties of subducting sedimentary facies. However, recent seismological and geological observations suggest that the décollement develops in the subducting oceanic crust in the depth range of the seismogenic zone, at least in some cases. To understand the frictional properties of oceanic crustal material and their influence on seismogenesis, we performed hydrothermal friction experiments on simulated fault gouges of altered basalt, at temperatures of 100-550 ℃. The friction coefficient (μ) lies around 0.6 at most temperature conditions but a low μ down to 0.3 was observed at the highest temperature and lowest velocity condition. The velocity dependence of μ, a−b, changes with increasing temperature from positive to negative at 100-200 ºC and from negative to positive at 450-500 ºC. Compared to gouges derived from sedimentary facies, the altered basalt gouge showed potentially unstable velocity weakening over a wider temperature range. Microstructural observations and microphysical interpretation infer that competition between dilatant granular flow and viscous compaction through pressure-solution creep of albite contributed to the observed transition in a−b. Alteration of oceanic crust during subduction produces fine grains of albite and chlorite through interactions with interstitial water, leading to reduction in its frictional strength and an increase in its seismogenic potential. Therefore, shear deformation possibly localizes within the altered oceanic crust leading to a larger potential for the nucleation of a megathrust earthquake in the depth range of the seismogenic zone.

The Council on Undergraduate Research (CUR) is engaged in several formal and informal partnerships within the Geosciences community, and is vital for all faculty, staff, and students involved with undergraduate research. CUR is structured into thirteen (13) separate divisions, of which one of the most active is the Geosciences Division, affectionately known as GeoCUR. CUR has a formal Memorandum of Understanding (MOU) with the American Geophysical Union (AGU) to foster collaboration and mutual benefit. CUR is also an Associated Society of the Geological Society of America (GSA), and a Member Society of the American Geosciences Institute (AGI). Within CUR, the GeoCUR regularly sponsors technical sessions, awards, poster sessions, and/or workshops at the AGU and GSA annual meetings, and an exhibit booth at the GSA Annual Meeting to raise awareness of CUR and the benefits of undergraduate research (UR). For the first time ever, GeoCUR will have an exhibit booth at the AGU meeting in 2018, and will be actively recruiting and engaging AGU meeting attendees. CUR advocacy is expanded when CUR staff and members participate in GSA Associated Societies and AGI Member Societies meetings. CUR is the voice for the UR community, and has worked with both AGU and other scientific societies to advise and educate legislators and federal agency representatives of the importance of UR, and also the continued support of geoscience research priorities, such as climate change research. One of the CUR’s most effective advocacy avenues is its annual Posters on the Hill event, now entering its 23rd year. EvaluateUR is an important outgrowth of CUR partnerships, and illustrates CUR’s important role in UR assessment. EvaluateUR is an evidence-based model for improving UR student outcomes, funded by NSF WIDER, and partnering SUNY Buffalo State, NAGT/SERC and CUR. EvaluateUR started at SUNY Buffalo State, has expanded to a diverse array of institutions, and is actively seeking new potential partners.

Reconstructing patterns of topographic evolution is key to our understanding of the various processes responsible for landscape development. Suites of existing geodynamic models suggest the North American landscape has been influenced by a history of evolving dynamic support. This study investigates the extent to which this process has played a role in generating the elevation and long-wavelength topographic relief observed. Review of studies investigating distribution of magmatism, marine sedimentary rocks, sediment flux, thermochronology models, paleoaltimetry and geomorphic analyses all point towards a staged uplift history of North America since the Late Cretaceous. Another way to investigate regional uplift is to use deposits of known age, containing paleo-water depth indicators, as a datum against which post-depositional uplift can be measured. Compilations of paleobathymetry from interpreted biostratigraphic and stratigraphic markers, compared to their present-day elevations, are therefore exploited to give detailed geologic constraints on surface uplift. Our results indicate > 2 km of long-wavelength differential uplift has developed in the continental interior during the Cenozoic. In conjunction with these datasets, the uplift history of North America can be calculated by considering the geomorphic evolution of continental drainage. Results of a calibrated inverse stream-power model are presented, where > 4000 river longitudinal profiles are used to calculate best-fitting smooth spatio-temporal histories of uplift rate. The resulting model also points towards a staged uplift history in most regions of high elevation. Evaluation of results using the biostratigraphic and stratigraphic databases shows the model is broadly consistent with the geological record. As a further validation of the inversion we present a continental landscape evolution model, fed with the uplift history and erosional parameters from the inversion. This outputs elevation, discharge, denudation and sedimentary flux histories that are consistent with our inverse modeling schemes and compiled datasets of sediment flux and low temperature thermochronology. Data and modeling results are in agreement with geodynamic models predicting > 1 km dynamic support of the North American continent.

The paper presents results of bathymetric surveys in the remote foreshore of the south Baltic (c.a. 1-2 Nm off the shoreline at depths of around 16-20 m). Measurements were collected twice in the vicinity of the Coastal Research Station (CRS) in Lubiatowo (Poland), first on November 2017 and then on December 2018. The study site is an area with hydrodynamics and lithodynamics typical of the south Baltic coast built of fine sands. The analysis is based on a differential map calculated from the bathymetric data obtained. The results show changes in the sea bottom ranging from a few to 70 centimeters. Sonar measurements were also made in 2017. The images revealed bottom ripples with an approximate height of 5–20 cm and length of 100–200 cm. The uniqueness of this research lies in the fact that at such depths there should theoretically be no significant changes at the sea bottom.

Cenozoic strike-slip deformation and associated basin formation in Indochina provide critical clues on crustal response during India-Asia collision. Typically, Indochina is considered a rigid block during continental extrusion. We demonstrate that the Song Ca-Rao Nay Fault System (SCRNFS) in north central Vietnam and its offshore extension, the Hue Sub-basin, subdivided Indochina into discrete blocks. Using an integrated dataset including topographic maps, geologic maps, onshore fieldworks, and offshore seismic and well interpretation, the structural evolution of the SCRNFS and Hue Sub-basin is investigated. During Late Oligocene, the SCRNFS initiated with right-lateral motion, causing pull-apart onshore and Hue Sub-basin opening offshore. The End-Oligocene inversion affecting the northern Song Hong Basin also caused a major NE–SW reverse fault in the Hue Sub-basin. In Early Miocene, rifting resumed in the Hue Sub-basin with accelerated faulting and westward rift migration in the south. This is distinct from the Song Hong Basin, where the main rift period was Eocene(?) – Oligocene, and the Early Miocene only features mild extension. During latest Early Miocene – earliest Middle Miocene, the SCRNFS switched to left-lateral transpression. This caused inversion and prolonged uplift in the northern-most Hue Sub-basin. The inversion associated unconformity can be traced onshore where it separates a compositionally immature conglomerate from an overlying quartz conglomerate. Left-lateral transpression in the Hue Sub-basin coincides with that in the Song Hong Basin and other inversion events across SE Asia. This may have been caused by Australia-SE Asia collision restricting escape movement of Indochina away from the India-Asia collision zone.

Major and trace element proxies of the shale samples from the Middle Buanji Group of the Upper Paleoproterozoic (∼1.67 Ga) are reported in this paper to decipher the provenance and depositional environment in the study area. The analytical results of shales in the Middle Buanji Group indicates relatively low percentage of major oxides compositions such as; SiO2 (38.84 – 54.26 %), Al2O3 (6.8 – 10 %), K2O (2.22 – 3.04 %), TiO2 (0.21 – 0.28 %) and CaO (0.15 – 0.51 %) and moderately high Fe2O3 (4.34 – 10.4 %) and P2O5 (1.62 – 2.01 %). The trace element composition of the analyzed shale samples displays wide concentration variation such as Mn (29 -19600 ppm), Ti (468 - 35600 ppm), P (370 – 4610 ppm), Ba (400 – 7730 ppm), and S (5 – 2350 ppm), V (130 – 290 ppm), Zn (5 – 100 ppm), Sr (40 – 160 ppm), As (2 – 70 ppm), and Cr (100 – 250 ppm). Measured proxies of major oxides Al2O3 /TiO2 (10.86 to 15.31) and K2O/Al2O3 (0.23 – 0.35). Variation of Cr concentrations in the shale samples indicates diverse source compositions in the study area ranging from; ultramafic, mafic, intermediate, to feldspar-rich rocks. The measured Mn values in shales have an average of 2527.65 ppm, and proxies of V/Cr: 0.65 – 1.7, V/ (V + Cr): 0.39 – 0.63, and CuO/Zn: 0.004 – 1.7 elements suggest that shales and dominant clay minerals (illite and chamosite) were deposited in marine environment under oxidizing conditions.

Copper-Au magmatic-hydrothermal systems dominate in the Chibougamau area of the Neoarchean Abitibi subprovince (greenstone belt) of the Superior Province (craton), whereas orogenic gold mineralization is more common in the rest of the Abitibi. Understanding differences in metal endowment within the Abitibi greenstone belt requires insights into the geodynamic evolution of the Chibougamau area. This was addressed by imaging the crust using seismic reflection profiling acquired as part of the Metal Earth project. Seismic reflection sections display shallowly south-dipping reflectors located within the upper-crust (e.g., deep continuation of the Barlow fault) and a northward-dipping mid-crust imbricated with older crust (Opatica subprovince) to the north. Multiple reflectors characterize the upper part of the mid-crust, interpreted as faults superimposed on a major lithological boundary. These structures likely formed during terrane accretion prior to craton stabilization. Combining the new seismic data with known stratigraphic, structural and magmatic records, we propose that the study area was initially a normal (i.e., thick) Archean oceanic crust that formed at or before 2.80 Ga and that evolved through terrane imbrication at 2.73-2.70 Ga. Shortening caused rapid burial, devolatilization and partial melting of hydrated mafic rocks to produce tonalite magmas that may have mixed with mantle-derived melts to produce the diorite-tonalite suite associated with observed Cu-Au magmatic-hydrothermal mineralization.

Volcanic activity occurring in tropical moist atmospheres can promote deep convection and trigger volcanic thunderstorms. Intense heating at ground surface and entrainment of moist air generates positive buoyancy, rapidly transporting volcanic gases and ash particles up to the tropopause and beyond. Volcanically-induced deep convection, however, is rarely observed to last continuously for more than a day and so insights into the dynamics, microphysics and electrification processes are limited. Here we present a multidisciplinary study on an extreme case, where this phenomenon lasted for six days. We show that this unprecedented event was triggered and sustained by phreatomagmatic activity at Anak Krakatau volcano, Indonesia from 22-28 December 2018. During this period, a deep convective plume formed over the volcano and acted as a ‘volcanic freezer’ producing ~3 × 10⁹ kg of ice on average with maxima reaching ~10¹⁰ kg. Our satellite analyses reveal that the convective anvil cloud, reaching 16-18 km above sea level, was ice-rich and ash-poor. Cloud-top temperatures hovered around -80 °C and ice particles produced in the anvil were notably small (effective radius from 20-30 μm). Our modelling suggests that ice particles began to form above 5 km and experienced vigorous updrafts (>30 m/s). These findings explain the impressive number of lightning strikes (~100,000) recorded near the volcano during this time. Our results, together with the unique dataset we have compiled, provide new insights into volcanic and meteorological thunderstorms alike.

Oxygen-isotope proxies for air temperature in Greenland ice cores, with time resolutions of years to decades, document 25 periods from 120,000 to 14,000 BP when air temperatures warmed 5 to 16 oC within decades and cooled slowly, incrementally, over millennia back down into ice-age conditions. These clearly-observed Dansgaard--Oeschger events averaged 4000 years in length but were highly erratic in time of onset, intensity, and duration. They were typically associated with volcanic sulfate deposits and floods of fresh water into the North Atlantic. They appear to be caused primarily by sub-glacial basaltic eruptions in Iceland, the most intense of which lasted from 12,000 to 9500 BP, long enough to warm the oceans out of the last ice age. Similar sequences of current and warmer temperatures are observed in fine-layered sediments in the Eocene Green River Formation where erratic sequences averaged 5000 years. The most rapid and intense changes in sedimentation and fossils in the geologic time scale are contemporaneous with massive basaltic lava flows covering millions of square kilometers of continental rifts at the end of the Paleozoic, Carnian, Triassic, Pliensbachian, Albian, Mesozoic, Paleocene, Eocene, etc. Large, explosive, subduction-related volcanic eruptions form aerosols in the lower stratosphere cooling the globe 0.5 oC for a few years. Modelling shows that such short-term cooling of the whole ocean surface affects ocean temperatures for as long as a century. In this way, several major explosive eruptions per century over millennia cause slow, incremental cooling down into ice-age conditions as clearly resolved in deep ocean cores. It is very hard to explain these well-observed footprints of climate change using greenhouse gases. While Pinatubo erupted as much as 234 megatons of CO2 in 1991, concentrations at Mauna Loa slowed their rise due to cooling of the ocean surface. A set of 16 short videos, numerous papers, a book, and dozens of web pages all referenced at WhyClimateChanges.com document evidence for major effusive basaltic lava flows being the primary cause of fast global warming and sequences of major explosive volcanic eruptions being the major cause of slow incremental global cooling. Furthermore, they explain why greenhouse-warming theory is not only mistaken, it is Physically-Impossible.com.

In this study, we for the first time applied a joint geodynamic-geophysical inversion (JGGI) approach to oceanic plateau subduction models, and compared the subduction style and corresponding topography and Bouguer gravity of two representative subduction scenarios with passive or active collision. We showed that the case of passive collision of the Ontong Java Plateau (OJP) crust better explains the topography, gravity, and seismic data than the active collision scenario. This implies that the OJP did not control the regional dynamics during the collisional process. We conclude that previous studies may have overestimated the role of the OJP in triggering subduction initiation, subduction polarity reversal, and even Pacific Plate rotation.

We propose a novel scheme that applies a multitasking convolutional neural network to learn the back azimuthal behavior from receiver function seismograms, which can effectively predict the depth and occurrence of the Moho beneath a single seismic station. Our scheme consists of three main steps: 1. Based on the style transfer technique, we generate 9000 synthetic receiver function seismograms blended by realistic noise as training data sets. 2. A multitasking convolutional neural network is trained to predict the depth and occurrence of the Moho. 3. All real receiver function seismograms are reconstructed by the accelerated joint iterative method before prediction. We apply the scheme to study the middle-southern of the Tanlu fault zone and adjacent regions and successfully achieve the depth and occurrence of the Moho beneath 10 permanent seismic stations. The predicted depths are in agreement with the results computed by conventional methods, and the predicted strikes and dip angles present an undulating Moho with near NE-striking. Moreover, the predicted strikes are nearly consistent with the strikes of the normal faults in the upper crust, which implies that intense continental extension in the Cretaceous play a prominent role in the tectonic deformation of the brittle upper crust and the ductile lower crust simultaneously. Besides, it helps to illustrate that the stress field orientation of the major geological event can be recorded and preserved in the lower crust.

In the last 20 years, there has been an international effort to develop approaches to experimentally measure the petrophysical and geomechanical properties of hydrate-bearing core samples. The measurements are extremely challenging because sub-sampling, sample preparation, and testing must be conducted at high pressure and low temperature. Despite these challenges, multiple laboratories are now measuring the geotechnical properties of hydrate-bearing sediments. However, there have been relatively few attempts to validate these measurements. We developed experimental protocols to accurately conduct zero-lateral strain tests at effective stresses up to 20 MPa using a pressure core triaxial device. We directly measure displacement during compression through periodic instantaneous undrained loading. To evaluate the accuracy of our measurement system, we conducted a benchmark study to compare properties obtained in our pressure core test chamber against classical geotechnical devices. We prepared a Boston Blue Clay specimen through re-sedimentation. Comprehensive properties databases favor the use of this material for comparison analyses. A compression test to 20 MPa accurately reproduced the compression, lateral stress, and permeability behavior demonstrated in previous testing programs. This experimental procedure provides a convenient framework for future validation studies in a broad range of pressure core laboratory devices.

From January 18, 2013 (175.16 m a.s.l.) to September 8, 2020 (177.82 m a.s.l.), Lake Michigan experienced its fastest and highest rise (2.67 m) since 1860 when instrumental measurements began. Extensive foredunes that developed since the last high lake levels in 1997 began eroding at fast rates. This study focuses on coastal morphodynamics along the 800 m coast within central Indiana Dunes State Park on Lake Michigan’s southern shores from January 2018 to January 2021. Throughout 2018, the easternmost foredunes exhibited the most erosion, totaling 4.25 m of linear loss. The central foredunes lost 2.16 m, and the westernmost foredunes lost only 1.79 m in width. An estimated 18.3 cubic meters of sand per 1 meter of coast was eroded from the foredunes and transferred to the backshore and foreshore. The lake levels were 6 - 42 cm higher in 2019 than in 2018 and amount of foredune erosion in 2019 was significantly higher than in 2018. The easternmost foredunes recorded a 9.5 m shortening, the central foredunes lost 1.84 m, and the westernmost foredunes lost only 0.6 m in width. A total of 27.51 m3 of sand per linear meter of coast was removed from the foredunes and transferred to the dry or submerged part of the beach. Lack of shelf ice along the shore, still rising lake levels, and convective storms triggering meteotsunamis changed the foredune erosion pattern in 2020. Erosion became most vigorous in the downdrift central and western study areas. From January through September 2021 Lake Michigan levels were 19 cm higher than in 2019. The total volume of eroded foredune sand (64.42 m3/m) in 2020 was more than double that of 2019 and almost quadruple that of 2018. Along the 200 m of coast in the central study area, the foredunes were completely eroded, losing 13.2 m in width. The foredunes in the western study area suffered extensive (11.2 m) erosion and were reduced to a total width of 6.8 m. Significant (7.8 m) erosion in the eastern study area reduced the foredunes to 8.85 m in width. After foredune erosion events, the beach rapidly recovered and maintained its width as the shoreline migrated landward.