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At least 595 records · Page 33Linked to original sources
USGS2025

What is the lowest latitude of discrete aurorae during superstorms?

From a survey of published accounts of visual sightings of aurorae, a compilation is presented of the lowest identified geomagnetic latitude at which discrete aurorae were seen at local zenith during magnetic storms having intensities with maximum − Dst > 200 nT. The compilation includes data for the superstorms of 2 September 1859, 4 February 1872, and 15 May 1921. A statistical model is developed representing the equatorward boundary of discrete aurorae versus storm intensity. The model indicates that a once-per-century storm would likely induce discrete aurorae at zenith down to a geomagnetic latitude of 34 ° . Insofar as aurorae can be taken as a proxy for electrojet currents, such a storm would expose many nighttime electric-power systems, in the contiguous United States or Europe, to high levels of geomagnetic disturbance. A Carrington-class storm would induce discrete aurorae down to 24 ° . These exposures are much greater than those indicated in recent numerical simulations of extreme magnetic storms. Using the model to infer storm intensity from reports of low-latitude aurorae, a storm on 28 August 1859, likely had maximum − Dst = 673 nT. That this storm occurred just a few days before the Carrington storm of 2 September (maximum − Dst = 964 nT) deserves attention. A storm that occurred on 17 September 1770 is estimated to have had maximum − Dst = 928 nT. The vision of Ezekiel could have been inspired by aurorae from a storm with maximum − Dst = 550 nT.

Space Weather↗
USGS2006

Continental crustal evolution observations

How has the continental crust evolved? What are the primary processes responsible for its composition, structure, and mode of deformation? What role do fluids play in deep crustal processes? In the last dozen years, geophysicists have obtained images of the deep continental crust that can be used to examine these questions and refine geologic models of crustal evolution. In this report we summarize recent progress in geophysical studies of the deep continental crust and highlight some of the more important implications of deep crustal processes.

Eos, Earth and Space Science News↗
USGS2019

Persistence of intense, climate-driven runoff late in Mars history

Mars is dry today, but numerous precipitation-fed paleo-rivers are found across the planet’s surface. These rivers’ existence is a challenge to models of planetary climate evolution. We report results indicating that, for a given catchment area, rivers on Mars were wider than rivers on Earth today. We use the scale (width and wavelength) of Mars paleo-rivers as a proxy for past runoff production. Using multiple methods, we infer that intense runoff production of >(3–20) kg/m 2 per day persisted until <3 billion years (Ga) ago and probably <1 Ga ago, and was globally distributed. Therefore, the intense runoff production inferred from the results of the Mars Science Laboratory rover was not a short-lived or local anomaly. Rather, precipitation-fed runoff production was globally distributed, was intense, and persisted intermittently over >1 Ga. Our improved history of Mars’ river runoff places new constraints on the unknown mechanism that caused wet climates on Mars.

Science Advances↗
USGS2020

Dendritic reidite from the Chesapeake Bay impact horizon, Ocean Drilling Program Site 1073 (offshore northeastern USA): A fingerprint of distal ejecta?

High-pressure minerals provide records of processes not normally preserved in Earth’s crust. Reidite, a quenchable polymorph of zircon, forms at pressures >20 GPa during shock compression. However, there is no broad consensus among empirical, experimental, and theoretical studies on the nature of the polymorphic transformation. Here we decipher a multistage history of reidite growth recorded in a zircon grain in distal impact ejecta (offshore northeastern United States) from the ca. 35 Ma Chesapeake Bay impact event which, remarkably, experienced near-complete conversion (89%) to reidite. The grain displays two distinctive reidite habits: (1) intersecting sets of planar lamellae that are dark in cathodoluminescence (CL); and (2) dendritic epitaxial overgrowths on the lamellae that are luminescent in CL. While the former is similar to that described in literature, the latter has not been previously reported. A two-stage growth model is proposed for reidite formation at >40 GPa in Chesapeake Bay impact ejecta: formation of lamellar reidite by shearing during shock compression, followed by dendrite growth, also at high pressure, via recrystallization. The dendritic reidite is interpreted to nucleate on lamellae and replace damaged zircon adjacent to lamellae, which may be amorphous ZrSiO 4 or possibly an intermediate phase, all before quenching. These results provide new insights on the microstructural evolution of the high-pressure polymorphic transformation over the microseconds-long interval of reidite stability during meteorite impact. Given the formation conditions, dendritic reidite may be a unique indicator of distal ejecta.

Virginia↗
USGS2010

Normal-faulting slip maxima and stress-drop variability: A geological perspective

We present an empirical estimate of maximum slip in continental normal-faulting earthquakes and present evidence that stress drop in intraplate extensional environments is dependent on fault maturity. A survey of reported slip in historical earthquakes globally and in latest Quaternary paleoearthquakes in the Western Cordillera of the United States indicates maximum vertical displacements as large as 6–6.5 m. A difference in the ratio of maximum-to-mean displacements between data sets of prehistoric and historical earthquakes, together with constraints on bias in estimates of mean paleodisplacement, suggest that applying a correction factor of 1.4±0.3 to the largest observed displacement along a paleorupture may provide a reasonable estimate of the maximum displacement. Adjusting the largest paleodisplacements in our regional data set (∼6 m) by a factor of 1.4 yields a possible upper-bound vertical displacement for the Western Cordillera of about 8.4 m, although a smaller correction factor may be more appropriate for the longest ruptures. Because maximum slip is highly localized along strike, if such large displacements occur, they are extremely rare. Static stress drop in surface-rupturing earthquakes in the Western Cordillera, as represented by maximum reported displacement as a fraction of modeled rupture length, appears to be larger on normal faults with low cumulative geologic displacement (<2 km) and larger in regions such as the Rocky Mountains, where immature, low-throw faults are concentrated. This conclusion is consistent with a growing recognition that structural development influences stress drop and indicates that this influence is significant enough to be evident among faults within a single intraplate environment.

Bulletin of the Seismological Society of America↗
USGS2011

Natural phosphorus sources for the Pacific Northwest

Phosphorus is a naturally occurring element found in all rocks; the amount varies by the type of rock. The amount of phosphorus in sediments is expected to be correlated with the amount of phosphorus in the parent rocks. Streambed sediment collected by the National Uranium Resource Evaluation (NURE) Program were used to estimate the variation of phosphorus across the Pacific Northwest. This file provides an estimate of the mean concentration of phosphorus in soils for each incremental catchment of the USGS Pacific Northwest SPARROW model.

Idaho;Oregon;Washington↗
USGS2001

Summary of trends and status analysis for flow, nutrients, and sediments at selected nontidal sites, Chesapeake Bay basin, 1985-99

Water-quality and flow data from 31 sites in nontidal portions of the Chesapeake Bay Basin were analyzed to document annual nutrient and sediment loads and trends for the period 1985 through 1999 as part of an annual reevaluation and reporting for the Chesapeake Bay Program. Annual loads were estimated by use of the U.S. Geological Survey ESTIMATOR model. Trends were estimated using linear regression. Trends were reported for monthly mean flow, monthly load, flow-adjusted concentration, and flow-weighted concentration. Median yields and concentrations were calculated to help facilitate comparisons between basins. The drought of 1999 had pronounced effects on trend results. The trend in flow increased at 4 of the 31 sites, 8 fewer sites than in 1998. Ten less significant trends were estimated for nutrient and sediment loads compared to 1985-98. Trends in flow-weighted and flow-adjusted concentrations varied little by nutrient species and geographic location. Trends were generally downward or not significant for both the nitrogen and phosphorus species throughout the Chesapeake Bay Basin. Trends in flow-adjusted concentration indicated downward trends at most sites for nutrients and about half the sites for sediments, an indication that management actions are reducing nutrient and sediment concentrations.

Open-File Report↗
USGS2002

Progress on geoenvironmental models for selected mineral deposit types

Since the beginning of economic geology as a subdiscipline of the geological sciences, economic geologists have tended to classify mineral deposits on the basis of geological, mineralogical, and geochemical criteria, in efforts to systematize our understanding of mineral deposits as an aid to exploration. These efforts have led to classifications based on commodity, geologic setting (Cox and Singer, 1986), inferred temperatures and pressures of ore formation (Lindgren, 1933), and genetic setting (Park and MacDiarmid, 1975; Jensen and Bateman, 1979). None of these classification schemes is mutually exclusive; instead, there is considerable overlap among all of these classifications. A natural outcome of efforts to classify mineral deposits is the development of &ldquo;mineral deposit models.&rdquo; A mineral deposit model is a systematically arranged body of information that describes some or all of the essential characteristics of a selected group of mineral deposits; it presents a concept within which essential attributes may be distinguished and from which extraneous, coincidental features may be recognized and excluded (Barton, 1993). Barton (1993) noted that the grouping of deposits on the basis of common characteristics forms the basis for a classification, but the specification of the characteristics required for belonging to the group is the basis for a model. Models range from purely descriptive to genetic. A genetic model is superior to a descriptive model because it provides a basis to distinguish essential from extraneous attributes, and it has flexibility to accommodate variability in sources, processes, and local controls. In general, a descriptive model is a necessary prerequisite to a genetic model.

Open-File Report↗
USGS2004

Death Valley regional ground-water flow system, Nevada and California -- hydrogeologic framework and transient ground-water flow model

A numerical three-dimensional (3D) transient ground-water flow model of the Death Valley region was developed by the U.S. Geological Survey for the U.S. Department of Energy programs at the Nevada Test Site and at Yucca Mountain, Nevada. Decades of study of aspects of the ground-water flow system and previous less extensive ground-water flow models were incorporated and reevaluated together with new data to provide greater detail for the complex, digital model. A 3D digital hydrogeologic framework model (HFM) was developed from digital elevation models, geologic maps, borehole information, geologic and hydrogeologic cross sections, and other 3D models to represent the geometry of the hydrogeologic units (HGUs). Structural features, such as faults and fractures, that affect ground-water flow also were added. The HFM represents Precambrian and Paleozoic crystalline and sedimentary rocks, Mesozoic sedimentary rocks, Mesozoic to Cenozoic intrusive rocks, Cenozoic volcanic tuffs and lavas, and late Cenozoic sedimentary deposits of the Death Valley Regional Ground-Water Flow System (DVRFS) region in 27 HGUs. Information from a series of investigations was compiled to conceptualize and quantify hydrologic components of the ground-water flow system within the DVRFS model domain and to provide hydraulic-property and head-observation data used in the calibration of the transient-flow model. These studies reevaluated natural ground-water discharge occurring through evapotranspiration and spring flow; the history of ground-water pumping from 1913 through 1998; ground-water recharge simulated as net infiltration; model boundary inflows and outflows based on regional hydraulic gradients and water budgets of surrounding areas; hydraulic conductivity and its relation to depth; and water levels appropriate for regional simulation of prepumped and pumped conditions within the DVRFS model domain. Simulation results appropriate for the regional extent and scale of the model were provided by acquiring additional data, by reevaluating existing data using current technology and concepts, and by refining earlier interpretations to reflect the current understanding of the regional ground-water flow system. Ground-water flow in the Death Valley region is composed of several interconnected, complex ground-water flow systems. Ground-water flow occurs in three subregions in relatively shallow and localized flow paths that are superimposed on deeper, regional flow paths. Regional ground-water flow is predominantly through a thick Paleozoic carbonate rock sequence affected by complex geologic structures from regional faulting and fracturing that can enhance or impede flow. Spring flow and evapotranspiration (ET) are the dominant natural ground-water discharge processes. Ground water also is withdrawn for agricultural, commercial, and domestic uses. Ground-water flow in the DVRFS was simulated using MODFLOW-2000, a 3D finite-difference modular ground-water flow modeling code that incorporates a nonlinear least-squares regression technique to estimate aquifer parameters. The DVRFS model has 16 layers of defined thickness, a finite-difference grid consisting of 194 rows and 160 columns, and uniform cells 1,500 m on each side. Prepumping conditions (before 1913) were used as the initial conditions for the transient-state calibration. The model uses annual stress periods with discrete recharge and discharge components. Recharge occurs mostly from infiltration of precipitation and runoff on high mountain ranges and from a small amount of underflow from adjacent basins. Discharge occurs primarily through ET and spring discharge (both simulated as drains) and water withdrawal by pumping and, to a lesser amount, by underflow to adjacent basins, also simulated by drains. All parameter values estimated by the regression are reasonable and within the range of expected values. The simulated hydraulic heads of the final calibrated transient model gener

Scientific Investigations Report↗
USGS2013

Application of sediment characteristics and transport conditions to resource management in selected main-stem reaches of the Upper Colorado River, Colorado and Utah, 1965-2007

The Colorado River Basin provides habitat for 14 native fish, including 4 endangered species protected under the Federal Endangered Species Act of 1973. These endangered fish species once thrived in the Colorado River system, but water-resource development, including the building of numerous diversion dams and several large reservoirs, and the introduction of non-native fish, resulted in large reductions in the numbers and range of the four species through loss of habitat and stream function. Understanding how stream conditions and habitat change in response to alterations in streamflow is important for water administrators and wildlife managers and can be determined from an understanding of sediment transport. Characterization of the processes that are controlling sediment transport is an important first step in identifying flow regimes needed for restored channel morphology and the sustained recovery of endangered fishes within these river systems. The U.S. Geological Survey, in cooperation with the Upper Colorado River Endangered Fish Recovery Program, Bureau of Reclamation, U.S. Fish and Wildlife Service, Argonne National Laboratory, Western Area Power Administration, and Wyoming State Engineer’s Office, began a study in 2004 to characterize sediment transport at selected locations on the Colorado, Gunnison, and Green Rivers to begin addressing gaps in existing datasets and conceptual models of the river systems. This report identifies and characterizes the relation between streamflow (magnitude and timing) and sediment transport and presents the findings through discussions of (1) suspended-sediment transport, (2) incipient motion of streambed material, and (3) a case study of sediment-transport conditions for a reach of the Green River identified as a razorback sucker spawning habitat (See report for full abstract).

Colorado;Utah↗
USGS2022

Continuous monitoring of nutrient and sediment loads from the Des Plaines River at Route 53 at Joliet, Illinois, water years 2018–20

The Des Plaines River in southern Wisconsin and northern Illinois is the principal conduit for the discharge of wastewater effluent and stormwater runoff from the greater Chicago metropolitan area. In November 2017, the U.S. Geological Survey, in cooperation with the Metropolitan Water Reclamation District of Greater Chicago, installed a continuous monitoring station to measure water quality and streamflow in the Des Plaines River at Joliet, Illinois. Surrogate models encompassing continuous data and discrete water-quality samples were used to estimate loads of nitrate, total phosphorus, and suspended sediment. Comparisons to other major rivers in Illinois show that the Des Plaines River is a substantial contributor to statewide loading estimates for nitrate and total phosphorus but only a minor contributor to suspended sediment. Future loading estimates of total phosphorus could include more research into the effects of combined sewage overflows because these effects likely increased model uncertainty. The results in this report document current loadings and provide a baseline from which to assess future water-quality management decisions.

Illinois↗
USGS2024

Characterization of groundwater resources near the southeastern part of Puget Sound, Washington

More than 1 million people live within the active model area (AMA) in the southeastern part of the lowlands surrounding Puget Sound, or Puget Lowland, Washington, and groundwater is the source for approximately one-half of their public, domestic, and irrigation water demands. The 887-square-mile AMA, located in King and Pierce Counties, represents the area of analysis for the conceptual hydrogeologic framework and numerical groundwater-flow models within the study area and includes the Puyallup River and Chambers-Clover Creek watersheds. To assess the potential hydrologic and anthropogenic impacts to groundwater and the connected surface-water resources, conceptual and numerical groundwater-flow models of groundwater flow were developed by the U.S. Geological Survey Washington Water Science Center in close cooperation with 18 water-resource agencies and stakeholders. This multichapter volume documents the development of the conceptual and numerical groundwater-flow models of groundwater flow. Chapters A, B, and C provide an overall introduction to the multichapter volume (Chapter A), the conceptual hydrogeologic framework (Chapter B), and the groundwater budget (Chapter C). Chapters D and E describe numerical groundwater-flow model construction and calibration (Chapter D) and the numerical groundwater-flow model results (Chapter E). Collectively, these reports present a characterization and simulation tool for groundwater resources near the southeastern part of Puget Sound, Washington.

Scientific Investigations Report↗
USGS1986

ESTIMATION OF URBAN STORM-RUNOFF LOADS.

The United States was divided into three regions, on the basis of mean annual rainfall, to decrease the variability in storm-runoff constituent loads and to improve regression relations with basin and climatic characteristics. Multiple-regression analyses, in progress, are being refined to determine the best regression models for each of the storm-runoff constituent loads in each of the three regions. These techniques, when finalized, can be used to estimate storm-runoff constituent loads for gaged and ungaged urban watersheds. The preliminary standard errors of estimate for five constituents examined to date ranged from 54 to 223 percent, and the coefficients of determination (r**2) ranged from 0. 39 to 0. 94. Total storm rainfall and total contributing drainage area appear to be the most significant independent variables in the regression models. This paper is a progress report on preliminary results of estimating storm-runoff constituent loads for ungaged watersheds.

Conference Paper↗
USGS2013

The influence of precipitation, vegetation and soil properties on the ecohydrology of sagebrush steppe rangelands on the INL site

The INL Site and other landscapes having sagebrush steppe vegetation are experiencing a simultaneous change in climate and floristics that result from increases in exotic species. Determining the separate and combined/interactive effects of climate and vegetation change is important for assessing future changes on the landscape and for hydrologic processes. This research uses the 72 experimental plots established and initially maintained for many years as the “Protective Cap Biobarrier Experiment” by Dr. Jay Anderson and the Stoller ESER program, and the experiment is also now referred to as the “INL Site Ecohydrology Study.” We are evaluating long-term impacts of different plant communities commonly found throughout Idaho subject to different precipitation regimes and to different soil depths. Treatments of amount and timing of precipitation (irrigation), soil depth, and either native/perennial or exotic grass vegetation allow researchers to investigate how vegetation, precipitation and soil interact to influence soil hydrology and ecosystem biogeochemistry. This information will be used to improve a variety of models, as well as provide data for these models.

Report↗
USGS2005

Annual survival and site fidelity of northern pintails banded on the Yukon-Kuskokwim Delta, Alaska

We banded northern pintails (Anas acuta; n = 13,645) at a single site on the Yukon-Kuskokwim Delta (YKD), Alaska, USA, from 1990 to 2001. We used recaptures from our site in combination with hunter recoveries to model annual survival, recovery rates, and fidelity to our capture location. Most recoveries (>90%) occurred in the Pacific Flyway with 64% reported from California's Central Valley. Our top candidate models allowed survival to vary by sex but not by age or year. Estimated annual survival was 77.6% (95% CI: 73.9-81.0%) for males and 60.2% (95% CI: 53.2-67.0%) for females. Reporting rates varied by age, sex, and year; estimates for adult males exceeded those for adult females by 3.5 times. Within sexes, reporting rates of hatch-year pintails exceeded those of adults. Estimated recovery rates were considerably lower than those estimated during the 1950s-1970s for winter banded pintails (Hestbeck 1993b), but there were no differences in survival rates. This suggests that changes in harvest regulations may not have influenced annual survival in this population. The propensity of banded pintails to return to our capture site (fidelity rate) varied between sexes and was positively correlated with water conditions in prairie Canada. Our estimates of fidelity rates varied from 77.4% to 87.2% for males and 89.8% to 94.3% for females. Our fidelity estimates suggest that some level of subpopulation structuring may exist for northern pintails. Additionally, our estimates of fidelity support previous observations of northern pintails overflying poor wetland habitat conditions on the Canadian prairies.

Journal of Wildlife Management↗