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At least 73 records · Page 4Linked to original sources
USGS2006

Spectrophotometric properties of materials observed by Pancam on the Mars Exploration Rovers: 1. Spirit

Multispectral observations of rocks and soils were acquired under varying illumination and viewing geometries in visible/near‐infrared wavelengths by the Panoramic Camera (Pancam) on the Spirit Mars Exploration Rover to provide constraints on the physical and mineralogical nature of geologic materials in Gusev Crater. Data sets were acquired at six sites located near the landing site, in the surrounding plains, and in the West Spur and Husband Hill regions of the Columbia Hills. From these ∼600 images, over 10,000 regions of interest were selected of rocks and soils over a wide range of phase angles (0–130°). Corrections for diffuse skylight incorporated sky models based on observations of atmospheric opacity throughout the mission. Disparity maps created from Pancam stereo images allowed inclusion of estimates of local facet orientations in the sky models. Single‐term and two‐term phase functions derived from Hapke scattering models exhibit a dominantly broad backscattering trend for soils and “Red” rocks inferred to be covered with variable amounts of dust and other coatings, consistent with the results from the Viking Lander and Imager for Mars Pathfinder cameras. Darker “Gray” rock surfaces (inferred to be relatively less dust covered) display more narrow, forward scattering behaviors, consistent with particles exhibiting little internal scattering. Gray and Red rocks are macroscopically rougher than most soil units, although a “dust‐cleaning” event observed near the Paso Robles site caused an increase in soil surface roughness in addition to a substantial decrease in surface single scattering albedo. Gray rocks near the rim of Bonneville Crater exhibit the largest macroscopic roughness ( ) among all units, as well as the greatest backscattering among Gray rocks. Photometric properties of coated Red rocks vary in the West Spur region, possibly as a result of weathering differences related to elevation‐dependent aeolian regimes.

Journal of Geophysical Research E: Planets↗
USGS2006

Spectrophotometric properties of materials observed by Pancam on the Mars Exploration Rovers: 2. Opportunity

The Panoramic Camera (Pancam) on the Mars Exploration Rover Opportunity acquired visible/near‐infrared multispectral observations of soils and rocks under varying viewing and illumination geometries that were modeled using radiative transfer theory to improve interpretations of the microphysical and surface scattering nature of materials in Meridiani Planum. Nearly 25,000 individual measurements were collected of rock and soil units identified by their color and morphologic properties over a wide range of phase angles (0–150°) at Eagle crater, in the surrounding plains, in Endurance crater, and in the plains between Endurance and Erebus craters through Sol 492. Corrections for diffuse skylight incorporated sky models based on observations of atmospheric opacity throughout the mission. Disparity maps created from Pancam stereo images allowed inclusion of local facet orientation estimates. Outcrop rocks overall exhibited the highest single scattering albedos (≤0.9 at 753 nm), and most spherule‐rich soils exhibited the lowest (≤0.6 at 753 nm). Macroscopic roughness among outcrop rocks varied but was typically larger than spherule‐rich soils. Data sets with sufficient phase angle coverage (resulting in well‐constrained Hapke parameters) suggested that models using single‐term and two‐term Henyey‐Greenstein phase functions exhibit a dominantly broad backscattering trend for most undisturbed spherule‐rich soils. Rover tracks and other compressed soils exhibited forward scattering, while outcrop rocks were intermediate in their scattering behaviors. Some phase functions exhibited wavelength‐dependent trends that may result from variations in thin deposits of airfall dust that occurred during the mission.

Journal of Geophysical Research E: Planets↗
USGS2023

Fracture-mesh faulting in the swarm-like 2020 Maacama sequence revealed by high-precision earthquake detection, location, and focal mechanisms

In August of 2020, an earthquake sequence initiated within the Maacama fault zone in northern California, raising questions about its relationship with the larger-scale fault. To investigate the faulting geometry and its implications for physical processes driving seismicity, we applied an integrated, multi-faceted seismic analysis including waveform-correlation-based event detection, relative relocation, and high-precision focal mechanisms. To determine mechanisms for a large population of very small earthquakes (predominantly M < 1), we combined correlation-derived polarity analysis with a recently developed technique to determine S/P amplitude ratios from single seismic components. Finally, we applied an iterative stress inversion to distinguish between the likely fault and auxiliary planes. This analysis reveals that although the sequence initiated on a right-lateral fault, plausibly a strand of the Maacama Fault, it also activated numerous en echelon left-lateral conjugate faults. Together, these interlocking faults form a fracture mesh, consistent with structures associated elsewhere with fluid-induced faulting and earthquake swarms.

California↗
USGS1999

Ventifacts at the Pathfinder landing site

About half of the rocks at the Mars Pathfinder Ares Vallis landing site appear to be ventifacts, rocks abraded by windborne particles. Comparable resolution images taken by the Imager for Mars Pathfinder (IMP) camera and the Viking landers show that ventifacts are more abundant at the Pathfinder site. The ventifacts occur in several forms, including rocks with faceted edges, finger‐like projections, elongated pits, flutes, grooves, and possible rills. The trends of elongated pits, flutes, grooves, and rills cluster at ∼280–330° clockwise from north and generally dip 10–30° away from their trend direction. These orientations are indicative of southeast to northwest winds and differ from the trend of wind tails at the landing site, the direction of local wind streaks, and predictions of the Global Circulation Model, all of which indicate northeast to southwest winds. The disparity between these data sets strongly suggests that local circulation patterns have changed since the abrasion of the ventifacted rocks. The greater number of ventifacts at the Pathfinder site compared to either of the Viking sites is most easily explained as being due to a larger supply of abrading particles, composed of either sand‐sized grains or indurated dust aggregates, and higher surface roughness, which should increase the momentum of saltating grains. The Pathfinder ventifacts may have formed shortly after the deposition of outflow channel sediments nearly 2 Gry ago, when a large local supply of abrading particles should have been abundant and atmospheric conditions may have been more conducive to rock abrasion from saltating grains. Based on how ventifacts form on Earth, the several ventifact forms seen at the Pathfinder site and their presence on some rocks but not on others are probably due to local airflow conditions, original rock shape, exposure duration, rock movement, and to a lesser extent, rock lithology. The abundance of ventifacts at the Pathfinder site, together with other evidence of weathering, indicates that unaltered rock surfaces are rare on Mars.

Journal of Geophysical Research E: Planets↗
USGS2014

Report of the Committee on Land Erosion, 1950–1951

Activities of the Committee on Land Erosion, since the present Committee was appointed in September, 1950, have been confined mainly to correspondence among members as a means of becoming better acquainted and of deciding on a suitable program for consideration of the Committee Erosion being such a far-flung and complex phenomenon defies any small group to consider all of its many facets. It is obvious, therefore, that greatest practical results would be obtained if Committee activities were confined in the main to those investigations in which members are currently engaged. Colman and Sinclair state that one of their chief current interests is the study of possibilities for decreasing creep on steep mountain slopes in Southern California. They have reason to believe that a considerable part (the precise amount being unknown) of the debris issuing from the canyons starts its way to channels as dry sliding or other type of soil movement that takes place during the dry seasons although the actual damage occurs during wet periods. Initially they hope to obtain more information on channel accumulations and to learn more about where the material comes from and how and when it moves to the channel. With this information they expect to be in a better position to study means of decreasing debris movement. The importance of debris movement into the densely populated valleys of Southern California is of such an order that additional planning along these lines can be well justified.

California↗
USGS2010

Some basic considerations in the design of hydrologic data networks

Two preeminent considerations of data network design are the random nature of the hydrologic phenomena and the uses that will be made of the data. Information distilled from the data is usually measured in a parametric statistical sense, although the data user is more concerned with the integrated measure of information - what impact does the lack of perfect hydrologic information have on the ensuing decisions? Two facets of the network, the efficiency of the data collection and the effectiveness of the resulting information, must be integrated to achieve a complete network design.

Water Resources Research↗
USGS2020

Waterfowl occurrence and residence time as indicators of H5 and H7 avian influenza in North American Poultry

Avian influenza (AI) affects wild aquatic birds and poses hazards to human health, food security, and wildlife conservation globally. Accordingly, there is a recognized need for new methods and tools to help quantify the dynamic interaction between wild bird hosts and commercial poultry. Using satellite-marked waterfowl, we applied Bayesian joint hierarchical modeling to concurrently model species distributions, residency times, migration timing, and disease occurrence probability under an integrated animal movement and disease distribution modeling framework. Our results indicate that migratory waterfowl are positively related to AI occurrence over North America such that as waterfowl occurrence probability or residence time increase at a given location, so too does the chance of a commercial poultry AI outbreak. Analyses also suggest that AI occurrence probability is greatest during our observed waterfowl northward migration, and less during the southward migration. Methodologically, we found that when modeling disparate facets of disease systems at the wildlife-agriculture interface, it is essential that multiscale spatial patterns be addressed to avoid mistakenly inferring a disease process or disease-environment relationship from a pattern evaluated at the improper spatial scale. The study offers important insights into migratory waterfowl ecology and AI disease dynamics that aid in better preparing for future outbreaks.

Scientific Reports↗
USGS2012

Hydraulic modeling and scour analysis for the San Francisco - Oakland Bay Bridge

A study was conducted to determine potential maximum scour depths for the foundations of the replacement east span of the San Francisco-Oakland Bay Bridge, as part of the ongoing structural design. This effort presented unique challenges as strong tidal currents, large depths, and cohesive bottom sediments characterize the site. The authors met these challenges with a multi-faceted approach to the problem. First, design current velocities were determined using a two-dimensional hydrodynamic model of San Francisco Bay in conjunction with ADCP hydrographic surveys. Analytical scour calculations were performed and live-bed flume tests of the proposed foundations were also conducted. Finally, two separate methodologies were used to interpret the physical model tests in order to calculate potential scour depths around the foundations. Copyright ASCE 2004.

Conference Paper↗
USGS2017

Envisioning, quantifying, and managing thermal regimes on river networks

Water temperatures fluctuate in time and space, creating diverse thermal regimes on river networks. Temporal variability in these thermal landscapes has important biological and ecological consequences because of nonlinearities in physiological reactions; spatial diversity in thermal landscapes provides aquatic organisms with options to maximize growth and survival. However, human activities and climate change threaten to alter the dynamics of riverine thermal regimes. New data and tools can identify particular facets of the thermal landscape that describe ecological and management concerns and that are linked to human actions. The emerging complexity of thermal landscapes demands innovations in communication, opens the door to exciting research opportunities on the human impacts to and biological consequences of thermal variability, suggests improvements in monitoring programs to better capture empirical patterns, provides a framework for suites of actions to restore and protect the natural processes that drive thermal complexity, and indicates opportunities for better managing thermal landscapes.

Washington↗
USGS2025

Estimating recruitment of Largemouth Bass to exceptional weights using angler-reported catches

ABSTRACT Objective Although most facets of Largemouth Bass Micropterus nigricans ecology have been researched, the upper tiers of weight distributions (i.e., ≥3.6 kg; herein, “lunkers”) have received little attention due to the challenges of collecting sufficient sample sizes. Our aim was to estimate Largemouth Bass recruitment to higher weights after reaching 3.6 kg and to identify factors correlated with such recruitment. Methods We used an online database of angler-reported catches to investigate recruitment of Largemouth Bass after reaching lunker size and to identify associated factors. Recruitment was indexed by the slopes of the reversed cumulative counts relative to increasing weights, with gentler negative slopes indicating higher recruitment. The influence of environmental variables on these slopes identified the factors associated with recruitment. Results An average of 20% (minimum = 4%; maximum = 45%) of lunker bass were estimated to recruit after reaching 3.6 kg. When expanded, these estimates revealed that recruitment from 3.6 to 4.5 kg averaged 23.5% and recruitment from 3.6 to 5.9 kg averaged 2.5%. The observed recruitment was positively correlated with the frequency of Florida Bass M. salmoides alleles in the population and was inversely correlated with human population densities in the vicinity of the reservoir and with chlorophyll- a concentrations in the environment. Conclusions Recruitment of Largemouth Bass after reaching 3.6 kg appears to require a nuanced equilibrium enabled by a higher frequency of Florida Bass alleles, a remote location of the fishery, and a reservoir trophic state that balances adequate environmental conditions and food supply.

North American Journal of Fisheries Management↗
USGS2025

Viral outbreak dynamics and evolution in wildlife at the interface with humans

In this study, we used a multi-faceted approach to understand patterns of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission and persistence in a wild white-tailed deer ( Odocoileus virginianus ) population. Serology data indicated transmission of SARS-CoV-2 and persistence during the seven-month sampling period. Traditional disease modelling based on deer-to-deer transmission indicated relatively low prevalence with an R 0 of 1.9 and recovery period of 7 days; however, individual-based modelling informed by GPS tracked-movement data captured a potential transmission event. Phylogenetic analyses revealed a recurring pattern of divergent groups of deer-derived sequences with human-derived sequences falling close to each deer-derived cluster. Further, human-derived sequences were frequently sampled months prior to the deer-derived sequences, indicating repeated human to deer spillover. Using multiple types of data as well as both fine and broad scale analyses, we have characterized a pattern of localized outbreaks of SARS-CoV-2 within white-tailed deer populations that are likely recurring due to frequent spillover events. Our results suggest that while deer-to-deer transmission occurs over small spatiotemporal scales, SARS-CoV-2 persistence over longer periods and across larger regions is likely driven by repeated spillover from human populations.

Pennsylvania↗
USGS2023

Exploring the relevance of the multidimensionality of wildlife recreationists to conservation behaviors: A case study in Virginia

Wildlife recreationists' participation in conservation behaviors could provide key support to the conservation efforts of state fish and wildlife agencies. However, little is known about how identifying with multiple forms of wildlife recreation (i.e., hunters, anglers, birders, wildlife viewers) may influence participation in conservation behaviors, specifically for supporting state fish and wildlife agencies and their conservation goals. Using a mixed-mode survey of Virginia wildlife recreationists, we explored the hypothesized relationship between individuals' participation in conservation behaviors and their identification with multiple forms of consumptive and nonconsumptive wildlife recreation. We found wildlife recreation identity is multidimensional, with many individuals identifying with consumptive and nonconsumptive identities simultaneously. Further, consumptive-only recreationists (i.e., hunters and/or anglers) participated in conservation behaviors less often than nonconsumptive-only recreationists (i.e., birders and/or wildlife viewers) and recreationists with both consumptive and nonconsumptive identities were less likely to support a state fish and wildlife agency in the future. Our findings underscore the importance of all types of wildlife recreationists, especially those with intersecting identities, as state fish and wildlife agencies work to advance conservation. Hence, developing multi-faceted engagement strategies may enhance support for state fish and wildlife agencies among their growing wildlife recreation constituency.

Virginia↗
USGS2020

A bird's-eye view of reservoirs in the Mississippi Basin tips a need for large-scale coordination

Reservoirs are mostly managed at local scales as spatially independent units. A basin-scale perspective may increase awareness at a broader scope and generate insight not evident at local scales. We examined the array of reservoir attributes and fisheries in the Mississippi Basin to identify management opportunities. The basin is the third largest in the world and includes over 1,700 reservoirs >100 ha, the most of any river basin. Our bird's-eye view shows a piecemeal approach where reservoirs are mostly administered at the local level. Basin-wide or catchment coordination to holistically address problems that recur across the basin is mostly lacking. A basin-wide coordination arrangement could facilitate various facets of reservoir management. We reviewed governance arrangements in major river basins across the globe and concluded that the basin-wide administrative layer we encourage for the Mississippi Basin may already exist in some basins but may not be directly applicable everywhere.

Mississippi River basin↗
USGS2015

Urgent need for warming experiments in tropical forests

Although tropical forests account for only a fraction of the planet's terrestrial surface, they exchange more carbon dioxide with the atmosphere than any other biome on Earth, and thus play a disproportionate role in the global climate. In the next 20 years, the tropics will experience unprecedented warming, yet there is exceedingly high uncertainty about their potential responses to this imminent climatic change. Here, we prioritize research approaches given both funding and logistical constraints in order to resolve major uncertainties about how tropical forests function and also to improve predictive capacity of earth system models. We investigate overall model uncertainty of tropical latitudes and explore the scientific benefits and inevitable trade-offs inherent in large-scale manipulative field experiments. With a Coupled Model Intercomparison Project Phase 5 analysis, we found that model variability in projected net ecosystem production was nearly 3 times greater in the tropics than for any other latitude. Through a review of the most current literature, we concluded that manipulative warming experiments are vital to accurately predict future tropical forest carbon balance, and we further recommend the establishment of a network of comparable studies spanning gradients of precipitation, edaphic qualities, plant types, and/or land use change. We provide arguments for long-term, single-factor warming experiments that incorporate warming of the most biogeochemically active ecosystem components (i.e. leaves, roots, soil microbes). Hypothesis testing of underlying mechanisms should be a priority, along with improving model parameterization and constraints. No single tropical forest is representative of all tropical forests; therefore logistical feasibility should be the most important consideration for locating large-scale manipulative experiments. Above all, we advocate for multi-faceted research programs, and we offer arguments for what we consider the most powerful and urgent way forward in order to improve our understanding of tropical forest responses to climate change.

Global Change Biology↗
USGS2015

Beyond just sea-level rise: Considering macroclimatic drivers within coastal wetland vulnerability assessments to climate change

Due to their position at the land-sea interface, coastal wetlands are vulnerable to many aspects of climate change. However, climate change vulnerability assessments for coastal wetlands generally focus solely on sea-level rise without considering the effects of other facets of climate change. Across the globe and in all ecosystems, macroclimatic drivers (e.g., temperature and rainfall regimes) greatly influence ecosystem structure and function. Macroclimatic drivers have been the focus of climate-change related threat evaluations for terrestrial ecosystems, but largely ignored for coastal wetlands. In some coastal wetlands, changing macroclimatic conditions are expected to result in foundation plant species replacement, which would affect the supply of certain ecosystem goods and services and could affect ecosystem resilience. As examples, we highlight several ecological transition zones where small changes in macroclimatic conditions would result in comparatively large changes in coastal wetland ecosystem structure and function. Our intent in this communication is not to minimize the importance of sea-level rise. Rather, our overarching aim is to illustrate the need to also consider macroclimatic drivers within vulnerability assessments for coastal wetlands.

Global Change Biology↗
USGS2007

From buttes to bowls: Repeated relief inversion in the landscape of the Colorado Piedmont

Mesas and buttes of the central Colorado Piedmont are composed of at least two distinct rock types, which differ in their cohesiveness and resistance to erosion. The lower parts of the exposed stratigraphic section are poorly cemented, Upper Cretaceous to Middle Eocene sandstones of the Dawson Formation. The caprocks are composed of one or more resistant formations of Late Eocene age: the Castle Rock Conglomerate, Wall Mountain Tuff, and the conglomerate of Larkspur Butte. These formations were originally deposited in topographic lows, but due to their resistance,they now cap prominent buttes and mesas of the Colorado Piedmont. Erosion of the caprock through progressive retreat of the butte scarp produces colluvium that has a higher resistance to erosion than the poorly cemented underlying sandstone. Once the caprock of a butte has been removed by erosion, the underlying weakly cemented Dawson Formation is readily eroded. Ultimately, the armored lower slopes of the former butte remain as a circular ridge standing as much as 100 m above the surrounding topography. This process produces a topographic low surrounded by relict faceted slopes where the flat top of the butte once stood. Prominent alluvial fans are associated with some of these annular features, and they record the main phases of butte removal and excavation of the central part of the armored slopes. Multiple generations of alluvial fans contain coarse- and fine-grained facies that represent changes in effective stream power and record alternating phases of aggradation and erosion. The degree of soil development in the fan alluvium and height of the fan surfaces above streams indicates the oldest preserved gravel fan deposit is of late-middle Pleistocene age. The youngest luminescence (optically stimulated luminescence) dated alluvial fans were deposited during the late Pleistocene about the time of the Pinedale glacial maximum in Colorado, ca. 21,000 yr B.P.

Colorado↗
USGS2015

Crustal-scale tilting of the central Salton block, southern California

The southern San Andreas fault system (California, USA) provides an excellent natural laboratory for studying the controls on vertical crustal motions related to strike-slip deformation. Here we present geologic, geomorphic, and gravity data that provide evidence for active northeastward tilting of the Santa Rosa Mountains and southern Coachella Valley about a horizontal axis oriented parallel to the San Jacinto and San Andreas faults. The Santa Rosa fault, a strand of the San Jacinto fault zone, is a large southwest-dipping normal fault on the west flank of the Santa Rosa Mountains that displays well-developed triangular facets, narrow footwall canyons, and steep hanging-wall alluvial fans. Geologic and geomorphic data reveal ongoing footwall uplift in the southern Santa Rosa Mountains, and gravity data suggest total vertical separation of &sim;5.0&ndash;6.5 km from the range crest to the base of the Clark Valley basin. The northeast side of the Santa Rosa Mountains has a gentler topographic gradient, large alluvial fans, no major active faults, and tilted inactive late Pleistocene fan surfaces that are deeply incised by modern upper fan channels. Sediments beneath the Coachella Valley thicken gradually northeast to a depth of &sim;4&ndash;5 km at an abrupt boundary at the San Andreas fault. These features all record crustal-scale tilting to the northeast that likely started when the San Jacinto fault zone initiated ca. 1.2 Ma. Tilting appears to be driven by oblique shortening and loading across a northeast-dipping southern San Andreas fault, consistent with the results of a recent boundary-element modeling study.

California↗
USGS1993

Intensity and duration of chemical weathering: An example from soil clays of the southeastern Koolau Mountains, Oahu, Hawaii

Orographic precipitation on the southern flank of the southeastern Koolau Mountains produces a pronounced precipitation gradient. The corresponding gradient in the intensity of the chemical weathering environment provides an opportunity to address the effects of varying chemical weathering intensity on the composition of clay-size weathering products in soils developed on basalt. In addition, little-modified remnants of the constructional surface of the Koolau Volcano, isolated by stream dissection, remain as facets on the southern ends of the parallel ridges of the study area. By comparing clay mineralogy of soils developed on these older geomorphic surfaces with those developed on the younger sharp-crested ridges and steep side slopes, the effects of weathering duration on clay mineralogy can also be addressed. Soil clays in this part of the Koolau Mountains are mineralogically complex; principal phases include smectite, kaolinite, and halloysite, but pure end member phases are uncommon. Rather, most phases contain some amount of mixed layering. Smectite may contain small (<5%) amounts of randomly interstratified halloysite. Similarly, kaolinite commonly contains a small proportion of halloysite interlayers. A complex halloysitic phase shows evidence of interstratification with both smectite and kaolinite. Nonphyllosilicates found in the clay fraction include gibbsite, goethite, rare quartz, and perhaps cristobalite. The gradient in precipitation is reflected in soil clay mineralogy by varying proportions of dominantly smectitic, kaolinitic, and halloysitic phases. In regions of relatively low precipitation (<2,000 mm/yr), soils are dominated by the smectitic and halloysitic phases. With increased precipitation (as much as ∼4,000 mm/yr), kaolinitic and halloysitic phases become the dominant clay minerals, and goethite and gibbsite become increasingly abundant. Older soils developed on geomorphic surfaces representing the original constructional surface of Koolau Volcano are markedly more leached than those from younger landscapes in the same precipitation regime. Although smectite may be present, kaolinite is the dominant phase, and accumulations of Fe and Ti occur in the uppermost soil levels. Enrichment of Zr and Ti in these soils, as compared to concentrations in the original basaltic parent material, indicates that as much as 75% of the parent material has been lost. Thus weathering duration may affect soil clay composition in the same way as weathering intensity. Because smectite and halloysite are expandable clay minerals, their presence in soils may decrease slope stability and influence the nature of slope processes. Soil avalanches occur on steep slopes throughout the study area, whereas slow-moving landslides appear to be restricted to gentler slopes in drier parts of the study area where smectite is abundant. The clay mineralogy of soils thus appears to influence the nature of slope processes in the southeastern Koolau Mountains.

Special Paper of the Geological Society of America↗