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At least 289 records · Page 16Linked to original sources

USGS2008

Chemistry, mineralogy, and petrology of amphibole in Mount St. Helens 2004-2006 dacite

Textural, compositional, and mineralogical data are reported and interpreted for a large population of clinoamphibole phenocrysts in 22 samples from the seven successive dacite spines erupted at Mount St. Helens between October 2004 and January 2006. Despite the uniformity in bulk composition of magma erupted since 2004, there is striking textural and compositional diversity among amphibole phenocrysts and crystal fragments that have grown from, partly dissolved in, or been accidentally incorporated in the new dacite. This study demonstrates that magma erupted throughout the current dome-building episode is the end product of small-scale, thorough mixing of multiple generations of crystal-laden magma. The mixed amphibole population provides important clues to magma conditions within the dacite magma reservoir prior to ascent and, to some extent, the dynamics of mixing and ascent. The predominant amphibole in new dome rock ranges from moderate- to high-alumina tschermakite and magnesiohastingsite compositions. As substantiated by major- and trace-element geochemistry and barometry calculations, this compositional range of crystals, along with plagioclase, orthopyroxene, and iron-titanium oxide, is likely to have precipitated from dacite magma over a range of pressures and temperatures consistent with experimentally determined phase relations (~900°C to ~800°C between 100 MPa and ~350-400 MPa or ~4-km and 13.5-15-km depth). Along with traceelement characteristics, textural and compositional data help to distinguish some low-alumina magnesiohornblende crystals as xenocrysts. The diverse range in composition of amphibole in all samples of 2004-6 dacite, and the complex zonation observed in many phenocrysts, suggests a well-mixed source magma with components that are subjected to repeated heating and (or) pressurization within this pressure-temperature window. Amphibole textural and compositional diversity suggest dynamic conditions in the upper-reservoir zone, which has been tapped steadily during ~2 years of continuous and monotonous eruption. This well-mixed crystal mush is likely to have been subjected to repeated injection of hotter magma into cooler crystal-laden magma while simultaneously assimilating earlier generations of dacitic roof material and surrounding gabbroic rock. Decompression-related reaction rims around subhedral, rounded, resorbed, and fragmented amphibole phenocrysts, regardless of composition, indicate that this mixed-crystal assemblage was being broken, abraded, and dissolved in the magma as a result of mechanical mixing before and during early stages of ascent from conduit roots extending into a mushy cupola of the shallow reservoir. In the earliest lava samples (October 2004), amphiboles with <3-μm rims associated with a glassier matrix than later samples suggest a slightly faster ascent rate consistent with the relatively high eruptive flux of the earliest phases of dome extrusion. Reaction rim widths of ~5 μm on amphibole in all subsequently extruded lava result from a steady influx and upward transport of magma from 3.5-2.5-km to ~1-km depth at rates of ~600 to ~1,200 m/day, through a conduit less than 10 m in radius. Slower ascent rates inferred from volumetric-flux and matrixcrystallization parameters are explained by a widening of the conduit to greater than 60 m radius within 1 km of the surface.

Washington↗

USGS2025

Shear surface undulations modulate clayey gouge strength and contribute to divergent landslide acceleration

Landslides display a spectrum of speeds for incompletely known reasons. Sliding occurs along slickensided undulatory shear surfaces within boundary shear gouge. Laboratory tests reveal that gouge shear strength generally decreases with finite cumulative displacement during relatively rapid failure and may increase or decrease with increasing shear rate; these behaviors can result in accelerating or decelerating landslide motion, which significantly affects consequent hazards. However, mechanisms responsible for such behaviors are poorly understood. We performed advanced ring shear strength testing that revealed such variable strength of a landslide near Oso, Washington, USA. We hypothesized that millimeter-scale undulations along shear surfaces caused the strength variability by imparting shear strength but while also modifying stresses that locally increase and decrease the typically considered particle-scale shear strength. We tested our hypotheses in the laboratory and with finite element soil deformation modeling. Lab results suggest that undulations contribute strength that decays with finite cumulative displacement. Modeling similarly reveals this, and that rapid shearing across undulations locally reduces effective normal stress by persistently elevating pore-water pressure and causing dilation. Consequent effects on strength differ by material with granular-rich, high-friction gouge losing strength and clay-rich, low-friction gouge losing little or gaining strength as shear rates increase. Ample testing by others reveals similar patterns. Hence, the propensity for gouge-controlled accelerating or decelerating failure may be estimated from simple index tests. Our findings on the effects of undulations reveal previously unknown mechanisms that may help to explain why some landslides reactivate catastrophically while others do not.

Washington↗

USGS2017

Assessment of an in-channel redistribution technique for large woody debris management in Locust Creek, Linn County, Missouri

The U.S. Geological Survey, in cooperation with the Missouri Department of Conservation and Missouri Department of Natural Resources, completed a study to assess a mechanical redistribution technique used for the management of large woody debris (LWD) jams in Locust Creek within Pershing State Park and Fountain Grove Conservation Area, Linn County, Missouri. Extensive LWD jams were treated from 1996 to 2009 using a low-impact technique in which LWD from the jams was redistributed to reopen the channel and to mimic the natural geomorphic process of channel migration and adjustment to an obstruction. The scope of the study included the comparison of selected channel geometry characteristics and bed material particle-size distribution in seven LWD treatment reaches with that of adjacent untreated reaches (unaffected by LWD accumulations) of Locust Creek. A comparison of 1996 and 2015 survey cross sections in treated and untreated reaches and photograph documentation were used to assess channel geomorphic change and the stability of redistributed LWD. The physical characteristics of LWD within jams present in the study reach during 2015–16 also were documented. Based on the general lack of differences in channel metrics between treated and untreated reaches, it can be concluded that the mechanical redistribution technique has been an effective treatment of extensive LWD jams in Locust Creek. Channel alterations, including aggradation, streamflow piracy, and diversions, have resulted in temporal and spatial changes in the Locust Creek channel that may affect future applications of the redistribution technique in Pershing State Park. The redistribution technique was used to effectively manage LWD in Locust Creek at a potentially lower financial cost and reduced environmental disturbance than the complete removal of LWD. A comparison of four channel metrics (bankfull cross-sectional area, channel width, streamflow capacity, and width-depth ratio) for individual treatment reaches with adjacent untreated reaches indicated no statistically significant difference in most comparisons. Where statistically significant differences in channel metrics were determined between individual reaches, the channel metrics in treatment reaches were significantly less than adjacent untreated reaches in some comparisons, and significantly greater than adjacent untreated reaches in others. Without immediate posttreatment cross sections in treated and untreated reaches for comparison, it is impossible to say with certainty that a lack of significant differences in channel metrics is a result of posttreatment channel adjustment or, conversely, that any significant differences that remain are a result of the treatment of LWD. Characteristics of LWD in accumulations sampled within the study area in 2015 indicate that most sampled pieces were in the 1–2 foot diameter size class, the 5–16 foot length class, and the advanced decay class. Most of documented LWD pieces were loose and not buried, about 20 percent on average had a root wad attached, and about 6.5 percent on average were sawn logs. Most of sampled material was less than one-half of the bankfull channel width, indicating it was easily transportable, and the advanced decay class of material entering the study area indicated that it was likely sourced from outside of Pershing State Park. Redistributed LWD associated with treatment seems to be intact in the 1996 treated reaches from direct observation and from inference because there was net channel aggradation between 1996 and 2015 in comparison surveys. The change in channel area resulting from aggradation in time (1996 to 2015) in treated and untreated reaches exceeded the differences in channel characteristics between the treated and untreated channels in 2015 surveys.

Missouri↗

USGS1998

Predicting CH4 adsorption capacity of microporous carbon using N2 isotherm and a new analytical model

A new analytical pore size distribution (PSD) model was developed to predict CH4 adsorption (storage) capacity of microporous adsorbent carbon. The model is based on a 3-D adsorption isotherm equation, derived from statistical mechanical principles. Least squares error minimization is used to solve the PSD without any pre-assumed distribution function. In comparison with several well-accepted analytical methods from the literature, this 3-D model offers relatively realistic PSD description for select reference materials, including activated carbon fibers. N2 and CH4 adsorption data were correlated using the 3-D model for commercial carbons BPL and AX-21. Predicted CH4 adsorption isotherms, based on N2 adsorption at 77 K, were in reasonable agreement with the experimental CH4 isotherms. Modeling results indicate that not all the pores contribute the same percentage Vm/Vs for CH4 storage due to different adsorbed CH4 densities. Pores near 8-9 A?? shows higher Vm/Vs on the equivalent volume basis than does larger pores.

ACS Division of Fuel Chemistry, Preprints↗

USGS1999

Volcanogenic Sulfur on Earth and Io: Composition and Spectroscopy

The causes of Io's variegated surface, especially the roles of sulfur, and the geochemical history of sulfur compounds on Io are not well understood. Suspecting that minor impurities in sulfur might be important, we have investigated the major and trace element chemistry and spectroscopic reflectance of natural sulfur from a variety of terrestrial volcanic-hydrothermal environments. Evidence suggests that Io may be substantially coated with impure sulfur. On Earth, a few tenths of a percent to a few percent of chalcophile trace elements (e.g., As and Se) comonly occur in sulfur and appear to stabilize material of yellow, brown, orange, and red hues, which may persist even at low temperatures. Percentage levels of chalcophile impurities are reasonably expected to occur on Io in vapor sublimate deposits and flows derived from such deposits. Such impurities join a host of other mechanisms that might explain Io's reds and yellows. Two-tenths to two percent opaque crystalline impurities, particularly pyrite (FeS2), commonly produces green, gray, and black volcanic sulfur on Earth and might explain areas of Io having deposits of these colors. Pyrite produces a broad absorption near 1 ??m that gradually diminishes out to 1.6 ??m - similar but not identical to the spectrum of Io seen in Galileo NIMS data. Percentage amounts of carbonaceous impurities and tens of percent SiO2 (as silicates) also strongly affect the spectral properties of Earth's sulfur. Io's broad absorption between 0.52 and 0.64 ??m remains unexplained by these data but could be due to sodium sulfides, as suggested previously by others, or to As, Se, or other impurities. These impurities and others, such as P and Cl (which could exist on Io's surface in amounts over 1% that of sulfur), greatly alter the molecular structure of molten and solid sulfur. Minor impurities could impact Io's geology, such as the morphology of sulfur lava flows and the ability of sulfur to sustain high relief. We have not found any natural sulfur containing significant Na beyond that attributable to silicate inclusions. In sum, the unique physical-chemical properties of S-rich systems and the strong affinity of certain elements for S may have broad implications for the appearance, spectroscopic interpretation, and geologic processes of Io. Identification of impurities in sulfur may be helpful in tracing the geochemical evolution of surface deposits on Io. Perhaps foretelling of new areas of investigation, Cl has recently been reported in the Io torus (M. Kueppers and N. M. Schneider 1999, Eos Trans.80, 5207), suggesting the presence on Io of either salts, such as halite, or sulfur chlorides. Further evidence of minor iogenic impurities should be sought in Io's neutral cloud and plasma torus as well as in further scrutiny of Io's reflectance spectra. ?? 1999 Academic Press.

Icarus↗

USGS1990

Geochemical hosts of solubilized radionuclides in uranium mill tailings

The solubilization and subsequent resorption of radionuclides by ore components or by reaction products during the milling of uranium ores may have both economic and environmental consequences. Particle-size redistribution of radium during milling has been demonstrated by previous investigators; however, the identification of sorbing components in the tailings has received little experimental attention. In this study, uranium-bearing sandstone ore was milled, on a laboratory scale, with sulfuric acid. At regular intervals, filtrate from this suspension was placed in contact with mixtures of quartz sand and various potential sorbents which occur as gangue in uranium ores; the potential sorbents included clay minerals, iron and aluminum oxides, feldspar, fluorspar, barite, jarosite, coal, and volcanic glass. After equilibration, the quartz sand-sorbent mixtures were separated from the filtrate and radioassayed by gamma-spectrometry to determine the quantities of 238 U, 230 Th, 226 Ra, and 210 Pb sorbed, and the radon emanation coefficients. Sorption of 238 U was low in all cases, with maximal sorptions of 1–2% by the bentonite- and coal-bearing samples. 230 Th sorption also was generally less than 1%; maximal sorption here was observed in the fluorspar-bearing sample and appears to be associated with the formation of gypsum during milling. 226 Ra and 210 Pb generally showed higher sorption than the other nuclides - more than 60% of the 26 Ra solubilized from the ore was sorbed on the barite-bearing sample. The mechanism (s) for this sorption by a wide variety of substrates is not yet understood. Radon emanation coefficients of the samples ranged from about 5 to 30%, with the coal-bearing samples clearly demonstrating an emanating power higher than any of the other materials.

Hydrometallurgy↗

USGS1997

Radiation-induced diamond crystallization: Origin of carbonados and its implications on meteorite nano-diamonds

Ten carbonados from Central Africa were studied for U-Th-Pb systematics. To extract U, Th, and Pb from the samples, we developed a cold combustion technique wherein diamond was burnt in liquid oxygen. The technique gave low blanks; 25–50 pg for Pb, 3 pg for U, and 5 pg for Th. After very thorough acid treatments of the carbonados with hot HNO 3 , HF, and HCl over one week, most of U, Th, and Pb were removed from the samples. Lead in the acid-leached diamonds was highly radiogenic ( 206 Pb/ 204 Pb up to 470). However, the amounts of U and Th in the acid-leached diamonds are too low to account for the radiogenic Pb even if we assume 4.5 Ga for the age of the diamonds. Therefore, we conclude that the radiogenic Pb was implanted into the diamonds from surroundings by means of recoil energy of radioactive decays of U and Th. From the radiogenic lead isotopic composition, we estimate a minimum age of 2.6 Ga and a maximum age of 3.8 Ga for the formation of the carbonados. The above findings of the implantation of recoiled radiogenic Pb into carbonados is consistent with the process of radiation-induced crystallization which was proposed for carbonado by Kaminsky (1987). We show from some theoretical considerations that when highly energetic particles, such as those emitted from radioactive decay of U and Th, interact with carbonaceous materials, they give rise to cascades of atomic disturbance (over regions of about a few nanometer), and the disturbed atoms are likely to recrystallize to form micro-diamonds because of increasing surface energy due to small size. The radiation-induced diamond formation mechanism may be relevant to the origin of nano-diamonds in primitive meteorites.

Geochimica et Cosmochimica Acta↗

USGS2019

Data Report: Permeability, porosity, and frictional strength of core samples from IODP Expedition 366 in the Mariana forearc

Core samples from the International Ocean Discovery Program (IODP) Expedition 366 were tested in the laboratory to determine permeability, porosity, density, and frictional strength and their relation to mineralogy as part of an effort to understand hydro-mechanical processes at convergent plate margins. Seven samples were tested from a depth range of 19.6 to 197.9 m below the sea floor. The samples were derived from three serpentinite mud volcanoes in the Mariana forearc region, formed where slab-derived fluids and materials ascend along faults. The physical characteristics mirror compositional differences between predominantly serpentine-rich and saponite-rich samples. Permeability values ranged from 10-17 to 10-19 m2, low enough to facilitate the formation of high fluid pressures, which have been observed in the Mariana and other subduction megathrust environments. Porosities ranged from 0.37 to 0.51 and densities from 1.66 to 2.01 gm/cc. Serpentine-rich samples have coefficients of friction of 0.2 to 0.4, consistent with crustal serpentinite from a variety of fault zones, whereas saponite-rich samples have friction values below 0.2, consistent with saponite fault gouge from the San Andreas Fault Zone at Depth (SAFOD) drillhole in California.

Book chapter↗

USGS1993

Sulfidization and magnetization above hydrocarbon reservoirs

Post-depositional iron-sulfide (Fe-S) minerals that are related to hydrocarbon seepage have changed the original magnetizations at Cement oil field (Anadarko basin, Oklahoma), at Simpson oil field (North Slope basin, Alaska), and above deep Cretaceous oil and gas reservoirs, south Texas coastal plain. At Cement, ferrimagnetic pyrrhotite (Fe 7 S 8 ) formed with pyrite and marcasite in Permian red beds. The Fe-S minerals contain sulfur from two sources: (1) abiogenic sulfide, which has positive δ 34 S values, derived from thermochemical reduction of sulfate in deep reservoirs; and (2) biogenic sulfide, which has negative δ 34 S values, produced by reactions mediated by sulfate-reducing bacteria fed by leaking hydrocarbons. At Simpson, ferrimagnetic greigite (Fe 3 S 4 ) dominates magnetizations in nonmarine Upper Cretaceous clastic beds that contain epigenetic sulfide (δ 34 S > +20 per mil) and seeping biodegraded oil. In this setting, the authigenic magnetic sulfide mineral apparently incorporated sulfide produced by bacterial sulfate reduction under limited sulfate conditions. An inferred hydrocarbon food source for the sulfate-reducing bacteria links the hydrocarbon seepage to the greigite. The greigite is perhaps forming today. In middle Tertiary sandstones of southeast Texas, pyrite and marcasite formed when abiogenic H 2 S (enriched in 34 S) migrated upward from deep reservoirs, or when H 2 S (depleted in 34 S) was produced at shallow depths by bacteria that used organic material dissolved in migrating water from depth. The pyrite and marcasite replaced detrital magnetic iron-titanium oxide minerals. The degree of such replacement appears to increase toward faults that connect deep petroleum reservoirs to shallow sandstone. Our results show that abiologic and biologic mechanisms can generate different magnetic sulfide minerals in some sulfidic zones of hydrocarbon seepage. More commonly the magnetizations in such zones would be diminished as a result of the replacement of detrital magnetic minerals by the common nonmagnetic sulfide minerals, or would remain unchanged if such detrital minerals were originally absent.

Book chapter↗

USGS2019

Climate-driven state shifts in the Prairie Pothole Region: Assessing future impacts relevant to the management of wetland habitats critical to waterfowl

Embedded within the North American Prairie Pothole Region (PPR) are millions of small, depressional wetlands that annually support 50–80% of the continent’s waterfowl production. We recently assembled evidence that demonstrates a change towards a wetter climate that is driving a shift in the state of the region’s wetland ecosystems. This ecological state-shift has been primarily the result of a sustained wet climate that has influenced timing and magnitude of surface-water inputs to wetlands, connections to groundwater, and inputs of dissolved salts. As climate influences continue to change in the PPR, it is important to understand the potential of these changes to impact wetland habitats important for waterfowl production. Previous model simulations of prairie-pothole wetlands under future climate scenarios projected decreases in the ability of wetlands to facilitate waterfowl production throughout the majority of what is currently the most productive portion of the region. Results from these modeling efforts also suggested that suitable waterfowl breeding-habitat would be limited mostly to the southeastern portion of the PPR, a portion of the region in which most depressional wetlands (> 90%) have been drained. Thus, if these modeled outcomes materialize, a significant restoration effort would be needed in the southeastern PPR to support waterfowl production. However, the models used in earlier efforts were developed from a small number of wetlands using data from a relatively dry period and did not allow for changing mechanisms influencing surface-water, groundwater and dissolved salt inputs to prairie-pothole wetlands. The primary objective of our research is to improve our understanding of future climate change on impacts to wetland ecosystems and breeding waterfowl habitat in the PPR. We used a newly developed Pothole Hydrology Linked Systems Simulator (PHyLiSS) model to estimate wetland ecosystem responses to 32 distinct climate models under 2 different emissions scenarios. Unlike previous wetland hydrology models, the PHyLiSS model allows for shifting hydrological and geochemical mechanisms influencing wetland ecosystems. We modeled one average-sized seasonal wetland basin at 18 different geographic locations (hereafter “sites”) across the PPR with 3 sites represented for each of 6 ecoregions coincident to early research. We applied the PHyLiSS model using historical daily precipitation and temperature data from 1982–2015 and developed linear models relative to ponded water depth in the simulated wetlands and the observed regional WBPHS May Pond count number for 16 of the 18 sites. Based on the output of 32 climate models and 2 emission scenarios we found a projected change in May pond numbers from -23% to +.02% when comparing the most recent climate period (1989–2018) to the end of the 21 st century (2070–2099). We also found no evidence that the distribution of May ponds will shift in the future. These results suggest that management and conservation strategies for wetlands in the PPR should continue to focus on areas where high densities of intact wetland basins support large numbers of breeding duck pairs.

Alberta, Iowa, Manitoba, Minnesota, Montana, North↗

USGS2017

Processing protocol for soil samples potentially contaminated with Bacillus anthracis spores [HS7.52.02 - 514]

This protocol describes the processing steps for 45 g and 9 g soil samples potentially contaminated with Bacillus anthracis spores. The protocol is designed to separate and concentrate the spores from bulk soil down to a pellet that can be used for further analysis. Soil extraction solution and mechanical shaking are used to disrupt soil particle aggregates and to aid in the separation of spores from soil particles. Soil samples are washed twice with soil extraction solution to maximize recovery. Differential centrifugation is used to separate spores from the majority of the soil material. The 45 g protocol has been demonstrated by two laboratories using both loamy and sandy soil types. There were no significant differences overall between the two laboratories for either soil type, suggesting that the processing protocol would be robust enough to use at multiple laboratories while achieving comparable recoveries. The 45 g protocol has demonstrated a matrix limit of detection at 14 spores/gram of soil for loamy and sandy soils.

Report↗

USGS2012

Lateral and vertical channel movement and potential for bed-material movement on the Madison River downstream from Earthquake Lake, Montana

The 1959 Hebgen Lake earthquake caused a massive landslide (Madison Slide) that dammed the Madison River and formed Earthquake Lake. The U.S. Army Corps of Engineers excavated a spillway through the Madison Slide to permit outflow from Earthquake Lake. In June 1970, high streamflows on the Madison River severely eroded the spillway channel and damaged the roadway embankment along U.S. Highway 287 downstream from the Madison Slide. Investigations undertaken following the 1970 flood events concluded that substantial erosion through and downstream from the spillway could be expected for streamflows greater than 3,500 cubic feet per second (ft 3 /s). Accordingly, the owners of Hebgen Dam, upstream from Earthquake Lake, have tried to manage releases from Hebgen Lake to prevent streamflows from exceeding 3,500 ft 3 /s measured at the U.S. Geological Survey (USGS) gaging station 0638800 Madison River at Kirby Ranch, near Cameron, Montana. Management of flow releases from Hebgen Lake to avoid exceeding the threshold streamflow at USGS gaging station 06038800 is difficult, and has been questioned for two reasons. First, no road damage was reported downstream from the Earthquake Lake outlet in 1993, 1996, and 1997 when streamflows exceeded the 3,500-ft 3 /s threshold. Second, the 3,500-ft 3 /s threshold generally precludes releases of higher flows that could be beneficial to the blue-ribbon trout fishery downstream in the Madison River. In response to concerns about minimizing streamflow downstream from Earthquake Lake and the possible armoring of the spillway, the USGS, in cooperation with the Madison River Fisheries Technical Advisory Committee (MADTAC; Bureau of Land Management; Montana Department of Environmental Quality; Montana Fish, Wildlife and Parks; PPL-Montana; U.S. Department of Agriculture Forest Service - Gallatin National Forest; and U.S. Fish and Wildlife Service), conducted a study to determine movement of the Madison River channel downstream from Earthquake Lake and to investigate the potential for bed material movement along the same reach. The purpose of this report is to present information about the lateral and vertical movement of the Madison River from 1970 to 2006 for a 1-mile reach downstream from Earthquake Lake and for Raynolds Pass Bridge, and to provide an analysis of the potential for bed-material movement so that MADTAC can evaluate the applicability of the previously determined threshold streamflow for initiation of damaging erosion. As part of this study channel cross sections originally surveyed by the USGS in 1971 were resurveyed in 2006. Incremental channel-movement distances were determined by comparing the stream centerlines from 14 aerial photographs taken between 1970 and 2006. Depths of channel incision and aggregation were determined by comparing the 2006 and 1971 cross-section and water-surface data. Particle sizes of bed and bank materials were measured in 2006 and 2008 using the pebble-count method and sieve analyses. A one-dimensional hydraulic-flow model (HEC-RAS) was used to calculate mean boundary-shear stresses for various streamflows; these calculated boundary-shear stresses were compared to calculated critical-shear stresses for the bed materials to determine the potential for bed-material movement. A comparison of lateral channel movement distances with annual peak streamflows shows that streamflows higher than the 3,500-ft 3 /s threshold were followed by lateral channel movement except from 1991 to 1992 and possibly from 1996 to 1997. However, it was not possible to discern whether the channel moved gradually or suddenly, or in response to one peak flow, to several peak flows, or to sustained flows. The channel moved between 2002 and 2005 even when streamflows were less than the threshold streamflow of 3,500 ft 3 /s. Comparisons of cross sections and aerial photographs show that the channel has moved laterally and incised and aggraded to varying degrees. The channel has developed meander bends and has incised as much as 5–12 feet (ft) through the upstream part of the Madison Slide (cross sections 1400–800). Near cross section 800, the stream has eroded into the steep right bank between the stream and the road where fill was mechanically placed after 1970. Channel movement also was noted downstream from the Madison Slide. Near Raynolds Pass Bridge, about 3 miles (mi) downstream from Earthquake Lake, elevations across the channel have changed by -1.4 ft to +1.9 ft, but these changes were local in nature and could represent a few rocks or depressions in the bed. Overall, it does not appear that the materials eroded from the Madison Slide are causing aggradation in the subreach near the Raynolds Pass Bridge. Comparisons of critical shear stresses to mean boundary-shear stresses indicate that the D50 particle sizes (median size) along the right side of the bed between cross sections 400 and 500 and along the right side of the bed between cross sections 1300 and 1400 could move at the threshold streamflow. In contrast, most of the D84 particle sizes at those two locations probably will not move at the threshold streamflow. This lack of movement for the larger particles at the threshold streamflow could lead to further armoring of the bed as the D50 and smaller-sized particles are removed from the bed and transported downstream. The Shields parameter values from 0.04 to 0.08 that were used to calculate critical shear stresses could be conservative for a high-gradient stream such as the Madison. A higher, less conservative, Shields parameter would result in higher critical shear stresses, meaning that higher streamflows would be required to move material than those reported herein. In addition, because materials in the channel thalweg are exposed to higher boundary-shear stresses than the materials along the sides of the channel, larger, more erosion-resistant materials likely exist in the deeper parts of the channel where high-flow depths and velocities prevented sediment sampling. Movement of these materials might require higher critical shear stresses than estimated in this report. Characterization of sediment sizes in the center of the stream and observation of bed-material movement for a range of streamflows could provide information to help refine the Shields parameter and critical-shear stress estimates for bed materials in the Madison River downstream from Earthquake Lake. Furthermore, resurveying cross sections and water-surface elevations more frequently (either annually or after high streamflows) could better define the relation between streamflow and lateral and vertical channel movement.

Montana↗

USGS2003

Processes affecting the trihalomethane concentrations associated with the third injection, storage, and recovery rest at Lancaster, Antelope Valley, California, March 1998 through April 1999

The formation and fate of trihalomethanes (THM) during the third injection, storage, and recovery test at Lancaster, Antelope Valley, California, were investigated as part of a program to assess the long-term feasibility of using injection, storage, and recovery as a water-supply method and as a way to reduce water-level declines and land-subsidence in the Antelope Valley. The program was conducted by the U.S. Geological Survey in cooperation with the Los Angeles County Department of Public Works and the Antelope Valley-East Kern Water Agency. The water used for injection, storage, and recovery must be disinfected before injection and thus contains THMs and other disinfection by-products. THMs (chloroform, CHCl 3 , bromodichloromethane, CHCl 2 Br, dibromochloromethane, CHClBr 2 , and bromoform, CHBr 3 ) are formed by reaction between natural dissolved organic carbon that is present in water and chlorine that is added during the disinfection step of the drinking water treatment process. THMs are carcinogenic compounds, and their concentrations in drinking water are regulated by the U.S. Environmental Protection Agency. During previous cycles of the Lancaster program, extracted water still contained measurable concentrations of THMs long after continuous pumping had extracted a greater volume of water than had been injected. This raised concerns about the potential long-term effect of injection, storage, and recovery cycles on ground-water quality in Antelope Valley aquifers. The primary objectives of this investigation were to determine (1) what controlled continued THM formation in the aquifer after injection, (2) what caused of the persistence of THMs in the extracted water, even after long periods of pumping, (3) what controlled the decrease of THM concentrations during the extraction period, and (4) the potential for natural attenuation of THMs in the aquifer. Laboratory experiments on biodegradation of THMs in microcosms of aquifer materials indicate that aquifer bacteria did not degrade CHCl 3 or CHBr 3 under aerobic conditions, but did degrade CHBr 3 under anaerobic conditions. However, the aquifer is naturally aerobic and CHCl 3 is the dominant THM species; therefore, biodegradation is not considered an important attenuation mechanism for THMs in this aquifer. The alluvial-fan sediments comprising the aquifer have very low contents of organic matter; therefore, sorption is not considered to be an important attenuation mechanism for THMs in this aquifer. Laboratory experiments on formation of THMs in the injection water indicate that continued THM formation in the injection water after injection into the aquifer was limited by the amount of residual chlorine in the injection water at the time of injection. After accounting for THMs formed by reaction of this residual chlorine, THMs behaved as conservative constituents in the aquifer, and the only process affecting the concentration of THMs was mixing of the injection water and the ground water. The mixing process was quantified using mass balances of injected constituents, the sulfur hexafluoride (SF 6 ) tracer that was added to the injected water, and a simple descriptive mathematical mixing model. Mass balance calculations show that only 67 percent of the injected THMs and chloride were recovered by the time that a volume of water equivalent to 132 percent of the injection water volume was extracted. Pumping 250 percent of the injection water volume only increased recovery of injected THMs to 80 percent. THM and SF 6 concentrations in the extracted water decreased concomitantly during the extraction period, and THM concentrations predicted from SF 6 concentrations closely matched the measured THM concentrations. Because SF 6 is a conservative tracer that was initially only present in the injection water, parallel decreases in SF 6 and THM concentrations in the extracted water must be due to dilution of injection water with ground water. The simple descriptive mixing model mathematically described mixing of injection water and ground water that was displaced by injection using a single-zone mixing model. This simple model adequately predicted the concentrations of conservative constituents (SF 6 , THMs, and chloride) in the extracted water during the extraction period, providing further evidence to support the conclusion that mixing injection water and ground water in the aquifer was the primary process controlling the concentration of the THMs in the extracted water. Water-quality data and modeling results suggest that injection, storage, and recovery cycles will affect aquifer water quality. THM concentrations in water samples from piezometers located 80 horizontal feet from the injection/extraction well remained high and variable throughout the extraction period. This suggests that water entered regions of the aquifer during injection from which it was not efficiently recovered during extraction. In particular, water may have become stranded in the upper parts of the aquifer during injection and therefore could not be efficiently recovered during extraction owing to drawdown around the well. The descriptive mixing model was used to forecast the results of repeated annual cycles of injection, storage, and recovery. For the scenario of equal volumes of injected and extracted water, the model forecasts that the concentration of THMs (or of any conservative constituent in the injection water) in the ground water near the injection/extraction well would increase to nearly 100 percent of the concentration of THMs in the injection water within 10 years. This increase in THM concentration would be less if ground water from outside the region directly affected by injection also mixed with the injected water or if the volume of extracted water greatly exceeded the volume of injected water. Finally, the model results indicate that extraction of all injected constituents is difficult using existing extraction methods because the volume of water that must be extracted increases exponentially as the acceptance criteria for the concentration in the water remaining in the aquifer decreases.

California↗

USGS2007

Qualitative evaluation of rock weir field performance and failure mechanisms

River spanning loose-rock structures provide sufficient head for irrigation diversion, permit fish passage over barriers, protect banks, stabilize degrading channels, activate side channels, reconnect floodplains, and create in-channel habitat. These structures are called by a variety of names including rock weirs, alphabet (U-, A-, V-, W-) weirs, Jhooks, and rock ramps. These structures share the common characteristics of: Loose rock construction materials (individually placed or dumped rocks with little or no concrete); Extents spanning the width of the river channel; and An abrupt change in the water surface elevation at low flows.

Report↗

USGS2021

Uranium(VI) attenuation in a carbonate-bearing oxic alluvial aquifer

Uranium minerals are commonly found in soils and sediment across the United States at an average concentration of 2–4 mg/kg. Uranium occurs in the environment primarily in two forms, the oxidized, mostly soluble uranium(VI) form, or the reduced, sparingly soluble reduced uranium(IV) form. Here we describe subsurface geochemical conditions that result in low uranium concentrations in an alluvial aquifer with naturally occurring uranium in soils and sediments in the presence of complexing ligands under oxidizing conditions. Groundwater was saturated with respect to calcite and contained calcium (78–90 mg/L) with elevated levels of carbonate alkalinity (291–416 mg/L as HCO 3 − ). X-ray adsorption near edge structure (XANES) spectroscopy identified that sediment-associated uranium was oxidized as a uranium(VI) form (85%). Calcite was the predominant mineral by mass in the ultrafine fraction in uranium-bearing sediments (>16 mg/kg). Groundwater geochemical modeling indicated calcite and/or a calcium-uranyl-carbonate mineral such as liebigite in equilibrium with groundwater. The δ 13 C (0.57‰ ± 0.15‰) was indicative of abiotic carbonate deposition. Thus, solid-phase uranium(VI) associated with carbonate is likely maintaining uranium(VI) groundwater levels below the maximum contaminant level (MCL; 30 µg/L), presenting a deposition mechanism for uranium attenuation rather than solely a means of mobilization.

Nebraska↗

USGS1980

Morphology of Lonar Crater, India: Comparisons and implications

Lonar Crater is a young meteorite impact crater emplaced in Deccan basalt. Data from 5 drillholes, a gravity network, and field mapping are used to reconstruct its original dimensions, delineate the nature of the pre-impact target rocks, and interpret the emplacement mode of the ejecta. Our estimates of the pre-erosion dimensions are: average diameter of 1710 m; average rim height of 40 m (30-35 m of rim rock uplift, 5-10 m of ejected debris); depth of 230-245 m (from rim crest to crater floor). The crater's circularity index is 0.9 and is unlikely to have been lower in the past. There are minor irregularities in the original crater floor (present sediment-breccia boundary) possibly due to incipient rebound effects. A continuous ejecta blanket extends an average of 1410 m beyond the pre-erosion rim crest. In general, 'fresh' terrestrial craters, less than 10 km in diameter, have smaller depth/diameter and larger rim height/diameter ratios than their lunar counterparts. Both ratios are intermediate for Mercurian craters, suggesting that crater shape is gravity dependent, all else being equal. Lonar demonstrates that all else is not always equal. Its depth/diameter ratio is normal but, because of less rim rock uplift, its rim height/diameter ratio is much smaller than both 'fresh' terrestrial and lunar impact craters. The target rock column at Lonar consists of one or more layers of weathered, soft basalt capped by fresh, dense flows. Plastic deformation and/or compaction of this lower, incompetent material probably absorbed much of the energy normally available in the cratering process for rim rock uplift. A variety of features within the ejecta blanket and the immediately underlying substrate, plus the broad extent of the blanket boundaries, suggest that a fluidized debris surge was the dominant mechanism of ejecta transportation and deposition at Lonar. In these aspects, Lonar should be a good analog for the 'fluidized craters' of Mars. ?? 1980 D. Reidel Publishing Co.

The Moon and the Planets↗

USGS2009

Size distributions and failure initiation of submarine and subaerial landslides

Landslides are often viewed together with other natural hazards, such as earthquakes and fires, as phenomena whose size distribution obeys an inverse power law. Inverse power law distributions are the result of additive avalanche processes, in which the final size cannot be predicted at the onset of the disturbance. Volume and area distributions of submarine landslides along the U.S. Atlantic continental slope follow a lognormal distribution and not an inverse power law. Using Monte Carlo simulations, we generated area distributions of submarine landslides that show a characteristic size and with few smaller and larger areas, which can be described well by a lognormal distribution. To generate these distributions we assumed that the area of slope failure depends on earthquake magnitude, i.e., that failure occurs simultaneously over the area affected by horizontal ground shaking, and does not cascade from nucleating points. Furthermore, the downslope movement of displaced sediments does not entrain significant amounts of additional material. Our simulations fit well the area distribution of landslide sources along the Atlantic continental margin, if we assume that the slope has been subjected to earthquakes of magnitude ??? 6.3. Regions of submarine landslides, whose area distributions obey inverse power laws, may be controlled by different generation mechanisms, such as the gradual development of fractures in the headwalls of cliffs. The observation of a large number of small subaerial landslides being triggered by a single earthquake is also compatible with the hypothesis that failure occurs simultaneously in many locations within the area affected by ground shaking. Unlike submarine landslides, which are found on large uniformly-dipping slopes, a single large landslide scarp cannot form on land because of the heterogeneous morphology and short slope distances of tectonically-active subaerial regions. However, for a given earthquake magnitude, the total area affected by subaerial landslides is comparable to that calculated by slope stability analysis for submarine landslides. The area distribution of subaerial landslides from a single event may be determined by the size distribution of the morphology of the affected area, not by the initiation process. ?? 2009 Elsevier B.V.

Earth and Planetary Science Letters↗

USGS2003

Analysis of aquifer mineralization by paleodrainage channels

Mineralization of groundwater resources is a problem in south-central Kansas, due to the penetration of saline water from Permian bedrock formations into the overlying alluvial aquifer. One of the mechanisms involved in the mineralization involves small bedrock features of high permeability located in places occupied by streams and rivers in past geological eras. These geological features are termed 'paleodrainage channels'. The permeability of the overlying aquifer can be significantly smaller than that of the channel fill material. The comparatively fast migration of saline water through these channels of high permeability is associated with the transfer of minerals into the overlying freshwater aquifer. This study applies a set of boundary layer approaches to quantify the process of mineral transfer from the channels into the aquifer. The methods used in the present study provide quick estimation and evaluation of the dilution of the channel flow, as well as mineral concentration profile changes in the mineralized zone created in the overlying aquifer. More generally, the method can also be useful for the analysis and evaluation of various types of groundwater contamination in heterogeneous aquifers. The application of the method is exemplified by a complete set of calculations characterizing the possible mineralization process at a specific channel in south central Kansas. Sensitivity analyses are performed and provide information about the importance of the various parameters that affect the mineralization process. Some possible scenarios for the aquifer mineralization phenomena are described and evaluated. It is shown that the channel mineralization may create either several stream tubes of the aquifer with high mineral concentration, or many stream tubes mineralized to a lesser extent. Characteristics of these two patterns of aquifer mineralization are quantified and discussed. ?? 2003 Published by Elsevier Science B.V.

Journal of Hydrology↗