USGS Science⌕ Search

SEARCH · USGS Science

Results for “Physics in Perspective”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
USGS2004

Postfire management in forested public lands of the western USA

Forest ecosystems in the western United States evolved over many millennia in response to disturbances such as wildfires. Land use and management practices have altered these ecosystems, however, including fire regimes in some areas. Forest ecosystems are especially vulnerable to postfire management practices because such practices may influence forest dynamics and aquatic systems for decades to centuries. Thus, there is an increasing need to evaluate the effect of postfire treatments from the perspective of ecosystem recovery. We examined, via the published literature and our collective experience, the ecological effects of some common postfire treatments. Based on this examination, promising postfire restoration measures include retention of large trees, rehabilitation of firelines and roads, and, in some cases, planting of native species. The following practices are generally inconsistent with efforts to restore ecosystem functions after fire: seeding exotic species, livestock grazing, placement of physical structures in and near stream channels, ground-based postfire logging, removal of large trees, and road construction. Practices that adversely affect soil integrity, persistence or recovery of native species, riparian functions, or water quality generally impede ecological recovery after fire. Although research provides a basis for evaluating the efficacy of postfire treatments, there is a continuing need to increase our understanding of the effects of such treatments within the context of societal and ecological goals for forested public lands of the western United States.

Western United States↗
USGS1985

Wildlife health implications of sewage disposal in wetlands

Wildlife health concerns associated with disposal of sewage effluent in wetlands are of three primary types: (1) introduction of pathogens, (2) introduction of pollutants that adversely impact on host body defense mechanisms, and (3) changes in the physical and chemical properties of wetlands that favor the development and maintenance of disease problems. Unlike the situation with human health concerns, introduction of pathogens is not the major concern regarding wildlife health. Instead, the focus of attention needs to be directed at environmental changes likely to take place as a result of effluent discharges into different types of wetlands. Unless these changes are adequately addressed from a disease perspective, marshes utilized for sewage disposal could become disease incubators and wildlife death traps. This result would be unfortunate because the backlash would likely negate the potentially beneficial aspects of the use of sewage wastewater for the creation of new wetlands and have a severe impact on progress being made towards evaluation of the compatibility of wildlife and sewage effluents.

Book chapter↗
USGS2004

Titanic exploration with GIS

To help teachers and students investigate one of the world's most famous historical events using the geographic perspective and GIS tools and methods, the U.S. Geological Survey (USGS) created a set of educational lessons based on the RMS Titanic's April 1912 sailing. With these lessons, student researchers can learn about latitude and longitude, map projections, ocean currents, databases, maps, and images through the analysis of the route, warnings, sinking, rescue, and eventual discovery of the submerged ocean liner in 1985. They can also consider the human and physical aspects of the maiden voyage in the North Atlantic Ocean at a variety of scales, from global to regional to local. Likewise, their investigations can reveal how the sinking of the Titanic affected future shipping routes.

GeoSpatial Solutions↗
USGS1985

Quantitative analysis of saltwater-freshwater relationships in groundwater systems-A historical perspective

Although much progress has been made toward the mathematical description of saltwater-freshwater relationships in groundwater systems since the late 19th century, the advective and dispersive mechanisms involved are still incompletely understood. This article documents the major historical advances in this subject and summarizes the major direction of current studies. From the time of Badon Ghyben and Herzberg, it has been recognized that density is important in mathematically describing saltwater-freshwater systems. Other mechanisms, such as hydrodynamic dispersion, were identified later and are still not fully understood. Quantitative analysis of a saltwater-freshwater system attempts to mathematically describe the physical system and the important mechanisms using reasonable simplifications and assumptions. This paper, in developing the history of quantitative analysis discusses many of these simplifications and assumptions and their effect on describing and understanding the phenomenon.

Journal of Hydrology↗
USGS2022

Volcanic electrification: Recent advances and future perspectives

The electrification of volcanic plumes has been described intermittently since at least the time of Pliny the Younger and the 79 AD eruption of Vesuvius. Although sometimes disregarded in the past as secondary effects, recent work suggests that the electrical properties of volcanic plumes reveal intrinsic and otherwise inaccessible parameters of explosive eruptions. An increasing number of volcanic lightning studies across the last decade have shown that electrification is ubiquitous in volcanic plumes. Technological advances in engineering and numerical modelling, paired with close observation of recent eruptions and dedicated laboratory studies (shock-tube and current impulse experiments), show that charge generation and electrical activity are related to the physical, chemical, and dynamic processes underpinning the eruption itself. Refining our understanding of volcanic plume electrification will continue advancing the fundamental understanding of eruptive processes to improve volcano monitoring. Realizing this goal, however, requires an interdisciplinary approach at the intersection of volcanology, atmospheric science, atmospheric electricity, and engineering. Our paper summarizes the rapid and steady progress achieved in recent volcanic lightning research and provides a vision for future developments in this growing field.

Bulletin of Volcanology↗
USGS2020

Global physical controls on estuarine habitat distribution during sea levelchange: Consequences for genetic diversification through time

Determining the extrinsic (physical) factors controlling speciation and diversification of species through time is of key interest in paleontology and evolutionary biology. The role of sea-level change in shaping species richness patterns of marginal marine species has received much attention, but with variable conclusions. Recent work combining genetic data and Geographical Information Systems (GIS)-based habitat modeling yielded a framework for how geomorphology of continental margins mediates genetic connectivity of populations during sealevel change. This approach may ultimately yield insights on how distinct lineages, species, and biodiversity accumulate in coastal settings. Here, we expand this GIS work globally to different geomorphic settings to model estuarine habitat in a larger geographic framework and test how tectonic setting, oceanographic setting, climate, and margin age affect habitat distribution during sea-level change. In addition, independent of estuaries we explore paleobiologic (e.g. Olsson, 1961) and neontolologic effects of sea-level change on evolution, and test the relation between overall shelf area and species richness using data of 1721 fish species. We find 82% global reduction of estuarine habitat abundance at lowstand relative to highstand, and find large habitats change in size much more than small habitats. Consistent with prior work, narrow continental margins have significantly less habitat at highstand and lowstand than wide margins, and narrow margins significantly associate with fore-arc settings, effectively linking tectonic setting to habitat abundance. Surprisingly, narrow margins host greater species richness, a finding which violates the canonical species-area relation. This finding can be explained if: 1) the physical isolation imposed by narrow margins facilitates the formation of new species over time; 2) the sizestability of small habitats, which disproportionately occur on narrow margins, accumulate and retain species extirpated in the more variable habitats on wide margins; or 3) the smaller habitats on narrow margins facilitate greater species richness through greater habitat heterogeneity. These results are generally at odds with prior interpretations, but the combination of richness data and population genetic principles offer a different perspective on these long-studied questions. Finally, we emphasize that the nuance of Pleistocene-Holocene sea level oscillations should be more explicitly considered in genetic studies.

Global and Planetary Change↗
USGS2011

Global amphibian declines: perspectives from the United States and beyond

Over recent decades, amphibians have experienced population declines, extirpations and species-level extinctions at an alarming rate. Numerous potential etiologies for amphibian declines have been postulated including climate and habitat degradation. Other potential anthropogenic causes including overexploitation and the frequent introductions of invasive predatory species have also been blamed for amphibian declines. Still other underlying factors may include infectious diseases caused by the chytrid fungus Batrachochytrium dendrobatidis, pathogenic viruses (Ranavirus), and other agents. It is nearly certain that more than one etiology is to blame for the majority of the global amphibian declines, and that these causal factors include some combination of climatological or physical habitat destabilization and infectious disease, most notably chytridiomycosis. Scientific research efforts are aimed at elucidating these etiologies on local, regional, and global scales that we might better understand and counteract the driving forces behind amphibian declines. Conservation efforts as outlined in the Amphibian Conservation Action Plan of 2005 are also being made to curtail losses and prevent further extinctions wherever possible.

Conference Paper↗
USGS2025

A scientific vision and roadmap for earthquake rupture forecast developments, a USGS perspective

We articulate a scientific vision and roadmap for the development of improved Earthquake Rupture Forecast models, which are one of the two main modeling components used in modern seismic hazard and risk analysis. One primary future objective is to provide fully time-dependent models that include both elastic rebound and spatiotemporal clustering nationwide, which is particularly important for shorter-term hazard and risk considerations (e.g., earthquake insurance products). We also discuss the importance and perennial challenges associated with quantifying epistemic uncertainties, including those associated with deformation-model slip rates, un-quantified sampling errors with respect to off-fault seismicity, and any spatial covariances. The need for more physics-based approaches is also emphasized, as is the benefit of adding model valuation (quantifying usefulness) to our verification and validation protocols. Given the multidisciplinary and system-level nature of this activity, modular design is critical. Future updates will also draw from best-available science by both the United States Geological Survey and the external community. The primary goal of this paper is to highlight plans that guide research and facilitate community engagement with model development, especially with respect to lowering the entry barrier for early career scientists and engineers. The paper is written so readers can focus on the sections that interest them most (see table of contents), with the Introduction and Discussion providing a stand-alone overview and summary.

Bulletin of the Seismological Society of America↗
USGS2005

The Colorado Plateau II: biophysical, socioeconomic, and cultural research

The publication of The Colorado Plateau: Cultural, Biological, and Physical Research in 2004 marked a timely summation of current research in the Four Corners states. This new volume, derived from the seventh Biennial Conference on the Colorado Plateau in 2003, complements the previous book by focusing on the integration of science into resource management issues. The 32 chapters range in content from measuring human impacts on cultural resources, through grazing and the wildland-urban interface issues, to parameters of climate change on the Plateau. The book also introduces economic perspectives by considering shifting patterns and regional disparities in the Colorado Plateau economy. A series of chapters on mountain lions explores the human-wildland interface. These chapters deal with the entire spectrum of challenges associated with managing this large mammal species in Arizona and on the Colorado Plateau, conveying a wealth of timely information of interest to wildlife managers and enthusiasts. Another provocative set of chapters on biophysical resources explores the management of forest restoration, from the micro scale all the way up to large-scale GIS analyses of ponderosa pine ecosystems on the Colorado Plateau. Given recent concerns for forest health in the wake of fires, severe drought, and bark-beetle infestation, these chapters will prove enlightening for forest service, park service, and land management professionals at both the federal and state level, as well as general readers interested in how forest management practices will ultimately affect their recreation activities. With broad coverage that touches on topics as diverse as movement patterns of rattlesnakes, calculating watersheds, and rescuing looted rockshelters, this volume stands as a compendium of cutting-edge research on the Colorado Plateau that offers a wealth of insights for many scholars.

Utah;Colorado;Arizona;New Mexico↗
USGS2021

Uncovering process domains in large rivers: Patterns and potential drivers of benthic substrate heterogeneity in two North American riverscapes

Identifying and understanding functional process domains (sensu Montgomery, 1999) in rivers is paramount for linking the physical habitat template to ecosystem structure and function. To date, efforts to do this have been rare, especially in large rivers, as they require appropriate tools for quantifying habitat heterogeneity with fine-scale resolution across broad spatial extents. In this study, we used side-scan sonar technology to map riverbed substrate at six sites in the Yellowstone and Missouri rivers. Substrate maps were then analyzed and visualized using geospatial analysis to relate fine-grained spatial substrate patterns to process domain structure. Our findings revealed two distinct nested domains of substrate patchiness, suggesting that different factors are responsible for shaping patterns of substrate at different scales. Although small-scale patchiness in substrate was likely driven by internal, or autogenic, physical processes, patterns at larger segment extents (>3 km) were often driven by abrupt transitions in habitat related to exogenous factors such as lateral erosion of talus, tributary inputs, and bank armoring. Additionally, we found that heterogeneity in benthic substrate increased with spatial extent at all of our study sites; however, this relationship was lower in the Missouri River, which is altered by impoundment. Our study represents one of the first efforts to relate benthic habitat heterogeneity to nested process domain structure in large riverscapes, and offers a unique perspective for linking landscape processes, geomorphological habitat heterogeneity, and biological structure and function in large rivers.

Montana, North Dakota↗
USGS2022

What is a biocrust? A refined, contemporary definition for a broadening research community

Studies of biological soil crusts (biocrusts) have proliferated over the last few decades. The biocrust literature has broadened, with more studies assessing and describing the function of a variety of biocrust communities in a broad range of biomes and habitats and across a large spectrum of disciplines, and also by the incorporation of biocrusts into global perspectives and biogeochemical models. As the number of biocrust researchers increases, along with the scope of soil communities defined as ‘biocrust’, it is worth asking whether we all share a clear, universal, and fully articulated definition of what constitutes a biocrust. In this review, we synthesize the literature with the views of new and experienced biocrust researchers, to provide a refined and fully elaborated definition of biocrusts. In doing so, we illustrate the ecological relevance and ecosystem services provided by them. We demonstrate that biocrusts are defined by four distinct elements: physical structure, functional characteristics, habitat, and taxonomic composition. We describe outgroups, which have some, but not all, of the characteristics necessary to be fully consistent with our definition and thus would not be considered biocrusts. We also summarize the wide variety of different types of communities that fall under our definition of biocrusts, in the process of highlighting their global distribution. Finally, we suggest the universal use of the Belnap, Büdel & Lange definition, with minor modifications: Biological soil crusts (biocrusts) result from an intimate association between soil particles and differing proportions of photoautotrophic (e.g. cyanobacteria , algae , lichens , bryophytes) and heterotrophic (e.g. bacteria , fungi , archaea) organisms , which live within , or immediately on top of , the uppermost millimetres of soil. Soil particles are aggregated through the presence and activity of these often extremotolerant biota that desiccate regularly , and the resultant living crust covers the surface of the ground as a coherent layer. With this detailed definition of biocrusts, illustrating their ecological functions and widespread distribution, we hope to stimulate interest in biocrust research and inform various stakeholders (e.g. land managers, land users) on their overall importance to ecosystem and Earth system functioning.

Biological Reviews↗
USGS2016

A geological perspective on the degradation and conservation of western Atlantic coral reefs

Continuing coral-reef degradation in the western Atlantic is resulting in loss of ecological and geologic functions of reefs. With the goal of assisting resource managers and stewards of reefs in setting and measuring progress toward realistic goals for coral-reef conservation and restoration, we examined reef degradation in this region from a geological perspective. The importance of ecosystem services provided by coral reefs—as breakwaters that dissipate wave energy and protect shorelines and as providers of habitat for innumerable species—cannot be overstated. However, the few coral species responsible for reef building in the western Atlantic during the last approximately 1.5 million years are not thriving in the 21st century. These species are highly sensitive to abrupt temperature extremes, prone to disease infection, and have low sexual reproductive potential. Their vulnerability and the low functional redundancy of branching corals have led to the low resilience of western Atlantic reef ecosystems. The decrease in live coral cover over the last 50 years highlights the need for study of relict (senescent) reefs, which, from the perspective of coastline protection and habitat structure, may be just as important to conserve as the living coral veneer. Research is needed to characterize the geological processes of bioerosion, reef cementation, and sediment transport as they relate to modern-day changes in reef elevation. For example, although parrotfish remove nuisance macroalgae, possibly promoting coral recruitment, they will not save Atlantic reefs from geological degradation. In fact, these fish are quickly nibbling away significant quantities of Holocene reef framework. The question of how different biota covering dead reefs affect framework resistance to biological and physical erosion needs to be addressed. Monitoring and managing reefs with respect to physical resilience, in addition to ecological resilience, could optimize the expenditure of resources in conserving Atlantic reefs and the services they provide.

Conservation Biology↗
USGS2002

Human impact on the planet: an earth system science perspective and ethical considerations

The modern Earth Narrative, the scientific story of the 4.5 billion-year natural and human history of the Earth, has emerged from the solid foundation of two factual concepts: Deep (or Geologic) Time and Biological Evolution. spread acceptance of the Earth Narrative is critically important as we begin the third millennium, because it provides a clear understanding of the growing impact of human population growth and associated activities on the Earth System, especially the negative impact on Earth?s biosphere. It is important for humans to realize that we are but one of 4,500 species of mammals that exist on Earth and that we are but one species in the estimated 30 to 100 million species that form the complex biosphere. We also need to recognize that all species exist within the physical limits imposed by the geosphere. We are totally dependent on the biosphere for food, oxygen, and other necessities of life. mans are one of the latest results of biological evolution operating over a long period of Geologic Time. We find ourselves on Earth, after 4.5 billion years of Earth history by chance, not by design. Humans have become so successful at modifying their environment that many of the natural limitations on the expansion of populations of our fellow animals have been overcome by technological and cultural innovations. According to Peter Raven, ?Humans, at a current population of 6 billion [expected to nearly double by 2050], are consuming or wasting about 50 percent of the total net biological productivity on land and 50 percent of the available supply of freshwater. The overwhelming and expanding human presence leaves less and less room in the environment for other biota.? st century will be a pivotal time in the fate of Earth?s biosphere. Whereas human modification of the geosphere will slowly recover over time, human changes to the biosphere are a far more consequential matter? extinction of a species is forever! Will humans effectively use our new knowledge of natural and human history to stop further degradation of Earth?s ecosystems and extinction of its biota? The fate of the biosphere, including humanity, depends on a reaffirmation by all humans of all cultures and religions of the global importance of a planet-wide conservation of the Earth?s biotic heritage. For the world?s religions it means elevation of stewardship of the Earth to a moral imperative and a goal of complete preservation of the Earth?s biotic inheritance, one which is based on a Do No Harm ethic.

Open-File Report↗
USGS2009

Environmental factors affecting contaminant toxicity in aquatic and terrestrial vertebrates

Physical and natural factors have long been known to influence the toxicity of environmental contaminants to vertebrates. The majority of data that address this topic have been derived from studies on fish, highly inbred laboratory rodents, and man.' The degree to which these factors modify toxicity has principally been elucidated by controlled laboratory experiments. Until recently, the significance of such effects to free-ranging vertebrates Figure 23.1 was frequently overlooked in ecological risk assessments.' Drawing upon controlled experiments and observational science, we overview environmental factors that influence pollutant toxicity in fish and wildlife, and present some perspective on their ecotoxicological significance.

Book chapter↗
USGS2003

US Atlantic coast striped bass: Issues with a recovered population

Striped bass, Morone saxatilis (Walbaum), is an anadromous species naturally occurring along the US Atlantic coast, which historically supported valuable commercial and recreational fisheries. In response to a near order-of-magnitude decline in landings, the Atlantic States Marine Fisheries Commission enacted a management plan in 1981 protecting fish until they could spawn at least once. By 1989, recruitment increased in natal rivers and regulations were relaxed, permitting limited fisheries by 1990. By 1995, the stock was declared fully recovered. Since the recovery, concern has increased over the health of the stocks. In the 1990s, fish in poor physical condition with dermal lesions became common in Chesapeake Bay. Pathogens of most concern in cultures from fish include the genus Mycobacterium. Coincident with declines in fish health were changes in diets, declines of preferred prey, and reduced growth and condition. Theories were suggested linking declines in condition to reductions in forage base or pathogens. Diets have changed since the 1950s and while many Chesapeake fish are infected with mycobacteria, it is still not known how or if these factors are linked. The highest priorities for research were considered to be: linking numerous local and regional studies to provide a coast-wide perspective; continuation of investigations linking population health to the prey-base; determination of the cause-effect of mycobacteria infections; and formulation of management options.

Fisheries Management and Ecology↗
USGS2013

Trajectory of the arctic as an integrated system

Although much remains to be learned about the Arctic and its component processes, many of the most urgent scientific, engineering, and social questions can only be approached through a broader system perspective. Here, we address interactions between components of the Arctic System and assess feedbacks and the extent to which feedbacks (1) are now underway in the Arctic; and (2) will shape the future trajectory of the Arctic system. We examine interdependent connections among atmospheric processes, oceanic processes, sea-ice dynamics, marine and terrestrial ecosystems, land surface stocks of carbon and water, glaciers and ice caps, and the Greenland ice sheet. Our emphasis on the interactions between components, both historical and anticipated, is targeted on the feedbacks, pathways, and processes that link these different components of the Arctic system. We present evidence that the physical components of the Arctic climate system are currently in extreme states, and that there is no indication that the system will deviate from this anomalous trajectory in the foreseeable future. The feedback for which the evidence of ongoing changes is most compelling is the surface albedo-temperature feedback, which is amplifying temperature changes over land (primarily in spring) and ocean (primarily in autumn-winter). Other feedbacks likely to emerge are those in which key processes include surface fluxes of trace gases, changes in the distribution of vegetation, changes in surface soil moisture, changes in atmospheric water vapor arising from higher temperatures and greater areas of open ocean, impacts of Arctic freshwater fluxes on the meridional overturning circulation of the ocean, and changes in Arctic clouds resulting from changes in water vapor content.

Ecological Applications↗
USGS2006

Landscape attributes and life history variability shape genetic structure of trout populations in a stream network

Spatial and temporal landscape patterns have long been recognized to influence biological processes, but these processes often operate at scales that are difficult to study by conventional means. Inferences from genetic markers can overcome some of these limitations. We used a landscape genetics approach to test hypotheses concerning landscape processes influencing the demography of Lahontan cutthroat trout in a complex stream network in the Great Basin desert of the western US. Predictions were tested with population- and individual-based analyses of microsatellite DNA variation, reflecting patterns of dispersal, population stability, and local effective population sizes. Complementary genetic inferences suggested samples from migratory corridors housed a mixture of fish from tributaries, as predicted based on assumed migratory life histories in those habitats. Also as predicted, populations presumed to have greater proportions of migratory fish or from physically connected, large, or high quality habitats had higher genetic variability and reduced genetic differentiation from other populations. Populations thought to contain largely non-migratory individuals generally showed the opposite pattern, suggesting behavioral isolation. Estimated effective sizes were small, and we identified significant and severe genetic bottlenecks in several populations that were isolated, recently founded, or that inhabit streams that desiccate frequently. Overall, this work suggested that Lahontan cutthroat trout populations in stream networks are affected by a combination of landscape and metapopulation processes. Results also demonstrated that genetic patterns can reveal unexpected processes, even within a system that is well studied from a conventional ecological perspective. ?? Springer 2006.

Landscape Ecology↗
USGS2005

Effectiveness of a confinement strategy for reducing campsite impacts in Shenandoah National Park

The expansion and proliferation of backcountry campsites is a persistent problem in many parks and protected areas. Shenandoah National Park (SNP) has one of the highest backcountry overnight use densities in the USA national parks system. SNP managers implemented a multi-option backcountry camping policy in 2000 that included camping containment with established campsites. These actions were intended to reduce the number of campsites and the area of camping disturbance at each site. This paper describes a longitudinal adaptive management assessment of the new campsite policies, applying quantitative measures of campsite conditions to evaluate the efficacy of management interventions. Physical campsite measurements combined with qualitative visitor interviews indicated SNP had successfully reduced the number of campsites and aggregate measures of camping-related disturbance in the Park, while minimizing the use of regulations, site facilities and staff resources. Implications for managers of other protected areas are that an established site camping policy can minimize camping disturbance, including the number and size of campsites, provided managers can sustain rehabilitation efforts to close and restore unneeded campsites. Experiential attributes, such as the potential for solitude, can also be manipulated through control over the selection of established campsites. Integrating resource and social science methods also provided a more holistic perspective on management policy assessments. Adaptive management research provided a timely evaluation of management success while facilitating effective modifications in response to unforeseen challenges. Conclusions regarding the effectiveness of a visitor impact containment strategy involving an established site camping option are offered.

Virginia↗