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At least 1,387 records · Page 77Linked to original sources

USGS2006

Migratory connectivity of a widely distributed songbird, the American redstart (Setophaga ruticilla)

Determining the degree of connectivity between breeding and wintering populations is critical for understanding the ecology and evolution of migratory systems. We analyzed stable hydrogen isotopic compositions in tail feathers ($Dw) collected from 26 sites in 11 countries throughout the wintering range of the American Redstart (Setophaga ruticilla), a Nearctic- Neotropical migratory passerine bird. Feathers were assumed to have molted on the breeding grounds, and $Dw was used to estimate breeding origin. Values of $Dw were highly correlated with longitude of sampling location, indicating that breeding populations were generally distributed along the east-west axis of the wintering grounds. Within the Caribbean region, Florida, and Bahamas, $Dw values were negatively correlated with winter latitude, which suggests that American Redstarts exhibit a pattern of chain migration in which individuals wintering at northern latitudes are also the most northern breeders. To identify the most probable breeding regions, we used a likelihood-assignment test incorporated with a prior probability of breeding abundance using Bayes?s rule. Expected $D values of feathers from five breeding regions were based on interpolated $D values from a model of continent-wide growing-season $D values in precipitation ($Dp) and were adjusted to account for a discrimination factor between precipitation and feathers. At most wintering locations, breeding assignments were significantly different from expected frequencies based on relative breeding abundance. Birds wintering in eastern and western Mexico had a high probability of breeding in northwest and midwest North America, whereas birds in the Greater and Lesser Antilles were likely to have originated from breeding regions in the northeast and southeast, respectively. Migratory connectivity, such as we report here, implies that the dynamics of breeding and nonbreeding populations may be linked at a regional scale. These results provide a key opportunity for studying the year-round ecology and evolution of spatially connected populations in a migratory species.

Book chapter↗

USGS1996

Morphology, geology and geochemistry of the "Salar del Gran Bajo del Gualicho" (Rio Negro, Argentina)

A multidisciplinary study of the Gran Bajo del Gualicho area (Rio Negro - Argentina) was carried out; the aim was to delineate its geological and geomorphological evolution and to estabilish the genesis of salts filling the depression. Climatic conditions were analized first to individuate their role in the present morphogenetic processes; moreover the main morphological features of present landscape were examined as well as the stratigraphy of the outcropping formations, and of the Gran Bajo del Gualicho Formation in particular. Finally, a possible geomorphological evolution of the studied area was traced. Geophysical analyses allowed to estabilish that the paleosurface shaped on the crystalline basement is strongly uneven and shows evidence of the strong tectonic phases it underwent. The result of isotope analyses confirmed that the salt deposits on the Gran Bajo del Gualicho bottom were produced by fresh water evaporation, while strontium isotope ratio suggested that such waters were responsible for solubilization of more ancient evaporitic deposits.

Geologica Romana↗

USGS1998

Geohistory and thermal maturation in the Cherokee Basin (Mid-Continent, U.S.A.): results from modeling

The Cherokee basin in southeastern Kansas contains a stratigraphic section consisting mostly of Permian-Pennsylvanian alternating clastics and thin carbonates overlying carbonates of Mississippian and Cambrian-Ordovician age on a Precambrian crytalline basement. Based on a conceptual model of events of deposition, nondeposition, and erosion, a burial history model for (1) noncompaction, and a series of models for (2) compaction are computed for a borehole location in the south-central part of the basin. The models are copled with the calculation of nonsteady-state geothermal conditions. Maximum temperatures during basin evolution of about 70??C at the base of the organic-rich Pennsylvanian are predicted by our models, assuming pure heat conduction and a heat flow from the basement of 60 m W/m2. The maturation of organic matter as indicated by three different vitrinite reflectance (Ro) models is on the order og 0.3-0.5% Ro for Pennsylvanian rocks and 0.6% Ro for the Devonian-Mississippian Cattanooga Shale. Vitrinite reflectance was measured on subsurface smaples from three wells. The measured values correlate in the upper part of the sequence with modeled data, but diverge slightly in the Lower Pennsylvanian and Cattanooga Shale. The differences in maturation may be a result of differing local geological conditions within the basin. The relatively high Ro-depth gradients observed in one borehole may be explained by conditions in the Teeter oil field, which is a typical plains-type anticline that has been affected by fluid flow through vertical faults. Higher Ro values correlate positively with the grade of sulfidfe mineralization in the sediment, which may be a hint of fluid impact. The high Ro values relative to the shallow depth of the Mississippian and the Chattanooga Shale in the Brown well are on the order of Ro values modeled for the same stratigraphic units at present-day greater depths and may reflect uplift of the Ozark dome, located further east, affecting the eastern side of the Cherokee Basin.Based on a concept model of deposition, nondeposition and erosion, a burial history model for noncompaction, and a series of models for compaction are developed for a borehole location in a south-central part of the Cherokee basin in southeastern Kansas. Coupled with the calculation of nonsteady state-state geothermal conditions, the models predict maximum temperatures during evolution of about 70 ??C at the base of the organic-rich Pennsylvanian. A difference in organic matter maturation in the Pennsylvanian and the Chattanooga shale exhibited by vitrinite reflectance models indicate probably differing local geological conditions within the basin.

American Association of Petroleum Geologists Bulle↗

USGS1999

The rise and fall of late Paleozoic trilobites of the United States

Based on range data and generic composition, four stages of evolution are recognized for late Paleozoic trilobites of the contiguous United States. Stage 1 occurs in the Lower Mississippian (Kinderhookian-Osagean) and is characterized by a generically diverse association of short-ranging, stenotopic species that are strongly provincial. Stage 2 species are present in the Upper Mississippian and consist of a single, eurytopic, pandemic genus, Paladin. Species of Stage 2 are much longer-ranging than those of Stage 1, and some species may have persisted for as long as 12 m.y. Stage 3 is present within Pennsylvanian and Lower Permian strata and consists initially of the eurytopic, endemic genera Sevillia and Ameura as well as the pandemic genus Ditomopyge. During the middle Pennsylvanian the very long-ranging species Ameura missouriensis and Ditomopyge scitula survived for more than 20 m.y. During the late Pennsylvanian and early Permian, a number of pandemic genera appear to have immigrated into what is now North America. Stage 4 is restricted to the Upper Permian (late Leonardian-Guadalupian) strata and is characterized by short-ranging, stenotopic, provincial genera. The main causal factor controlling the four-stage evolution of late Paleozoic trilobites of the United States is interpreted to be eustacy. Whereas Stage 1 represents an adaptive radiation developed during the Lower Mississippian inundation of North America by the Kaskaskia Sequence, Stage 2 is present in strata deposited during the regression of the Kaskaskia sea. Stage 3 was formed during the transgression and stillstand of the Absaroka Sequence and, although initially endemic, Stage 3 faunas are strongly pandemic in the end when oceanic circulation patterns were at a maximum. A mid-Leonardian sea-level drop caused the extinction of Stage 3 fauna. Sea-level rise near the end of the Leonardian and into the Guadalupian created an adaptive radiation of stentopic species of Stage 4 that quickly became extinct with the latest Permian regression.

Journal of Paleontology↗

USGS2000

Utility of palmatolepids and icriodontids in recognizing Upper Devonian Series, Stage, and possible substage boundaries

Conodonts are accepted internationally to define Devonian Series and Stage boundaries. Hence, the evolution and taxonomy of pelagic palmatolepids, primarily Palmatolepis and its direct ancestor Mesotaxis, and shallow-water icriodontids, Icriodus, Pelekysgnathus, and "Icriodus", are the major tools for recognizing subdivisions of the Upper Devonian. Palmatolepids are the basis for the Late Devonian Standard Conodont Zonation (ZIEGLER & SANDBERG 1990), whereas icriodontids are the basis for the alternative, integrated shallow-water zonation (SANDBERG & DREESEN 1984). However, an alternative palmatolepid taxonomy for some Frasnian species has been employed recently by some conodont workers using the Montagne Noire (M.N.) zonation, shape analyses of Pa elements, and multielement reconstructions of KLAPPER (1989), KLAPPER & FOSTER (1993); and KLAPPER et al. (1996). Herein, the evolution of palmatolepids and icriodontids is summarized in terms of our zonation and some of the taxonomic differences with the alternative M.N. zonation are exemplified. One of the problems in relating the Standard and M.N. zonations arises from previous errors of interpretation and drafting of the Martenberg section in Germany. This section was designated the reference section for the Frasnian transitans through jamieae Zones by ZIEGLER & SANDBERG (1990). Herein, the early and middle Frasnian zonal boundaries at Martenberg are improved by re-study of our old and recent collections from three profiles, spaced only 4 m apart. Serious problems exist with the Global Stratotype Sections and Points (GSSP's), selected by the Subcommission on Devonian Stratigraphy, following the paleontologic definition of the bases of the Frasnian, Famennian, and Tournaisian Stages, because of the difficulty in making global correlations from these GSSP's. Our summary of these problems should be helpful if future workers decide to relocate these GSSP's.

CFS Courier Forschungsinstitut Senckenberg↗

USGS2004

Comparison of AMSR-E and SSM/I snow parameter retrievals over the Ob river basin

Passive microwave observations from the Advanced Microwave Scanning Radiometer - EOS (AMSR-E) and from the Special Sensor Microwave Imager (SSM/I) are used to analyse the evolution of the snow pack in the Ob river basin during the snow season of 2002-03. The Ob river is the biggest Russian river with respect to its watershed area (2 975 000 km2). The Ob originates in the Altai mountains and flows northward across the vast West Siberian lowland towards the Arctic Ocean. The majority of snow cover is contained in the lowlands rather than in mountainous regions and persists for six months or more. During the snow season, surface air temperatures are very cold. Therefore, the combination of cold dry snow and large areas of uniform topography is ideal for snowpack extent and water equivalent retrievals from passive microwave observations. The thermal gradient through the snow pack is estimated and used to model the growth of the snow grain size and to compute the evolution of the passive microwave derived snow depth over the region. A comparison between the AMSR-E and SSM/I estimates is performed and the differences between the snow parameters from the two satellite instruments are analysed.

Conference Paper↗

USGS2007

Reconstructing late Cenozoic stream gradients from high-level chert gravels in central Eastern Kansas

Interpreting the evolution of Kansas' landscape east of the Flint Hills provides major challenges. In the Neogene (late Tertiary) and perhaps part of the Pleistocene, streams transported a variety of sedimentary materials, including chert gravels derived from the Flint Hills. Gentle intermittent uplift stimulated the system system to cut down, locally removing and reworking the gravels to create stream-terrace deposits that consist mostly of chert pebbles, which now lie well above the floodplains of modern streams. By correlating the elevations of these gravels, the gradients of the trunk streams that deposited them can be reconstructed. Interestingly, these ancient streams flowed southeast at a little more than a foot per mile (0.2 m/km), roughly the same as the gradient of the trunk streams in the region today. The evolving landscape in eastern Kansas also has been strongly influenced by an extensive network of fractures that is widespread in the midcontinent region and may be worldwide in extent. In northeastern Kansas, glaciation during the Pleistocene disrupted the southeasterly drainage and established the present location of the Kansas River. South of the Kansas River and its immediate tributaries, however, the general southeasterly drainage has been preserved. We have made use of the wealth of topographic-elevation data now available in digital form known as DEMs or digital elevation models. Coupled with GIS procedures, the DEMs helped link the mapped distribution of chert gravels with hypothetical fitted surfaces that represent ancient stream gradients. Furthermore, DEM data placed in shaded-relief map form emphasize the influence of fractures in evolution of the drainage system.

Current Research in Earth Sciences↗

USGS2008

A review of the endemic Hawaiian Drosophilidae and their host plants

The Hawaiian Drosophilidae is one of the best examples of rapid speciation in nature. Nearly 1,000 species of endemic drosophilids have evolved in situ in Hawaii since a single colonist arrived over 25 million years ago. A number of mechanisms, including ecological adaptation, sexual selection, and geographic isolation, have been proposed to explain the evolution of this hyperdiverse group of species. Here, we examine the known ecological associations of 326 species of endemic Hawaiian Drosophilidae in light of the phylogenetic relationships of these species. Our analysis suggests that the long-accepted belief of strict ecological specialization in this group does not hold for all taxa. While many species have a primary host plant family, females will also oviposit on non-preferred host plant taxa. Host shifting is fairly common in some groups, especially the grimshawi and modified mouthparts species groups of Drosophila, and the Scaptomyza subgenus Elmomyza. Associations with types of substrates (bark, leaves, flowers) are more evolutionarily conserved than associations with host plant families. These data not only give us insight into the role ecology has played in the evolution of this large group, but can help in making decisions about the management of rare and endangered host plants and the insects that rely upon them for survival. Copyright ?? 2008 Magnolia Press.

Zootaxa↗

USGS2011

Zircon U-Pb age of the Pescadero felsite: A late Cretaceous igneous event in the forearc, west-central California Coast Ranges

Downstream grain-size fining in stratigraphy is driven primarily by selective deposition of sediment, and the long-term efficiency of this process is determined by: (1) the magnitude and characteristics of the input sediment supply; (2) the spatial distribution of subsidence rate, which creates accommodation for sediment preservation; and (3) the dynamics of sediment transport and deposition. A key challenge is to determine how these first two factors control the caliber and spatial distribution of deposits over time scales of 10 4 –10 6 yr without incorporating sediment transport details that are largely unknowable for time-averaged stratigraphy in the geological past. We address this using grain-size data collected from fluvial conglomerates in the Eocene Pobla Basin, Spanish Pyrenees, a synorogenic basin where the timing of sediment deposition is well-constrained; the sediment budget is closed; and good exposure enables time lines within stratigraphy to be picked out unambiguously. For successive stratigraphic horizons, downstream trends in grain size and composition are derived for basin-filling sediment-routing systems with length scales of 6 and 40 km, respectively. Our data show that the rate of grain-size fining varies over time and with system length and can be linked to changes in source area. These results are contrasted with grain-size data from the Antist Group, a 60-km-long Oligocene system that mantles the Southern Pyrenees, where very slow rates of grain-size fining on the wedge top of this fold-and-thrust belt are observed. We apply a self-similarity–based selective deposition model to quantify the competing controls of tectonic subsidence and sediment supply on derived grain-size trends, and model results are compared with independent constraints on the Eocene–Oligocene evolution of the Pyrenees. Our results suggest that it is now possible to invert time-averaged grain-size trends in stratigraphy to gain quantitative information on the geological boundary conditions governing the evolution of sedimentary basins.

Geological Society of America Bulletin↗

USGS2011

An approach to modeling coupled thermal-hydraulic-chemical processes in geothermal systems

Interactions between hydrothermal fluids and rock alter mineralogy, leading to the formation of secondary minerals and potentially significant physical and chemical property changes. Reactive transport simulations are essential for evaluating the coupled processes controlling the geochemical, thermal and hydrological evolution of geothermal systems. The objective of this preliminary investigation is to successfully replicate observations from a series of hydrothermal laboratory experiments [Morrow et al., 2001] using the code TOUGHREACT. The laboratory experiments carried out by Morrow et al. [2001] measure permeability reduction in fractured and intact Westerly granite due to high-temperature fluid flow through core samples. Initial permeability and temperature values used in our simulations reflect these experimental conditions and range from 6.13 × 10−20 to 1.5 × 10−17 m2 and 150 to 300 °C, respectively. The primary mineralogy of the model rock is plagioclase (40 vol.%), K-feldspar (20 vol.%), quartz (30 vol.%), and biotite (10 vol.%). The simulations are constrained by the requirement that permeability, relative mineral abundances, and fluid chemistry agree with experimental observations. In the models, the granite core samples are represented as one-dimensional reaction domains. We find that the mineral abundances, solute concentrations, and permeability evolutions predicted by the models are consistent with those observed in the experiments carried out by Morrow et al. [2001] only if the mineral reactive surface areas decrease with increasing clay mineral abundance. This modeling approach suggests the importance of explicitly incorporating changing mineral surface areas into reactive transport models.

Conference Paper↗

USGS2003

Large carnivores, moose, and humans: A changing paradigm of predator management in the 21st century

We compare and contrast the evolution of human attitudes toward large carnivores between Europe and North America. In general, persecution of large carnivores began much earlier in Europe than North America. Likewise, conservation programs directed at restoration and recovery appeared in European history well before they did in North America. Together, the pattern suggests there has been an evolution in how humans perceive large predators. Our early ancestors were physically vulnerable to large carnivores and developed corresponding attitudes of respect, avoidance, and acceptance. As civilization evolved and man developed weapons, the balance shifted. Early civilizations, in particular those with pastoral ways, attempted to eliminate large carnivores as threats to life and property. Brown bears (Ursus arctos) and wolves (Canis lupus) were consequently extirpated from much of their range in Europe and in North America south of Canada. Efforts to protect brown bears began in the late 1880s in some European countries and population reintroductions and augmentations are ongoing. They are less controversial than in North America. On the other hand, there are no wolf introductions, as has occurred in North America, and Europeans have a more negative attitude towards wolves. Control of predators to enhance ungulate harvest varies. In Western Europe, landowners own the hunting rights to ungulates. In the formerly communistic Eastern European countries and North America, hunting rights are held in common, although this is changing in some Eastern European countries. Wolf control to increase harvests of moose (Alces alces) occurs in parts of North America and Russia; bear control for similar reasons only occurs in parts of North America. Surprisingly, bears and wolves are not controlled to increase ungulates where private landowners have the hunting rights in Europe, although wolves were originally exterminated from these areas. Both the inability of scientific research to adequately predict the effect of predator control on ungulate populations and a shift in public attitudes toward large carnivores have resulted in an accelerating number of challenges to predator management in places where it is still espoused. Utilitarian attitudes towards wildlife are declining in Western cultures and people now increasingly recognize the intrinsic value of wildlife, including large predators. In the future, agencies responsible for managing resident wildlife will face increased pressure to balance the needs of the hunting public with the desires of non-hunting publics. We suggest that in the next century we will witness a continued shift in how wildlife agencies manage both moose and large carnivores. More attention will be paid to maintaining and restoring intact ecosystems and less toward sustainable yield of meat.

Alces↗

USGS1999

United States streamflow probabilities based on forecasted La Nina, winter-spring 2000

Although for the last 5 months the TahitiDarwin Southern Oscillation Index (SOI) has hovered close to normal, the “equatorial” SOI has remained in the La Niña category and predictions are calling for La Niña conditions this winter. In view of these predictions of continuing La Niña and as a direct extension of previous studies of the relations between El NiñoSouthern Oscil-lation (ENSO) conditions and streamflow in the United States (e.g., Redmond and Koch, 1991; Cayan and Webb, 1992; Redmond and Cayan, 1994; Dettinger et al., 1998; Garen, 1998; Cayan et al., 1999; Dettinger et al., in press), the probabilities that United States streamflows from December 1999 through July 2000 will be in upper and lower thirds (terciles) of the historical records are estimated here. The processes that link ENSO to North American streamflow are discussed in detail in these diagnostics studies. Our justification for generating this forecast is threefold: (1) Cayan et al. (1999) recently have shown that ENSO influences on streamflow variations and extremes are proportionately larger than the corresponding precipitation teleconnections. (2) Redmond and Cayan (1994) and Dettinger et al. (in press) also have shown that the low-frequency evolution of ENSO conditions support long-lead correlations between ENSO and streamflow in many rivers of the conterminous United States. (3) In many rivers, significant (weeks-to-months) delays between precipitation and the release to streams of snowmelt or ground-water discharge can support even longer term forecasts of streamflow than is possible for precipitation. The relatively slow, orderly evolution of El Niño-Southern Oscillation episodes, the accentuated dependence of streamflow upon ENSO, and the long lags between precipitation and flow encourage us to provide the following analysis as a simple prediction of this year’s river flows.

Experimental Long-Lead Forecast Bulletin↗

USGS2014

Multi-temporal mapping of a large, slow-moving earth flow for kinematic interpretation

Periodic movement of large, thick landslides on discrete basal surfaces produces modifications of the topographic surface, creates faults and folds, and influences the locations of springs, ponds, and streams (Baum, et al., 1993; Coe et al., 2009). The geometry of the basal-slip surface, which can be controlled by geological structures (e.g., fold axes, faults, etc.; Revellino et al., 2010; Grelle et al., 2011), and spatial variation in the rate of displacement, are responsible for differential deformation and kinematic segmentation of the landslide body. Thus, large landslides are often composed of several distinct kinematic elements. Each element represents a discrete kinematic domain within the main landslide that is broadly characterized by stretching (extension) of the upper part of the landslide and shortening (compression) near the landslide toe (Baum and Fleming, 1991; Guerriero et al., in review). On the basis of this knowledge, we used photo interpretive and GPS field mapping methods to map structures on the surface of the Montaguto earth flow in the Apennine Mountains of southern Italy at a scale of 1:6,000. (Guerriero et al., 2013a; Fig.1). The earth flow has been periodically active since at least 1954. The most extensive and destructive period of activity began on April 26, 2006, when an estimated 6 million m3 of material mobilized, covering and closing Italian National Road SS90, and damaging residential structures (Guerriero et al., 2013b). Our maps show the distribution and evolution of normal faults, thrust faults, strike-slip faults, flank ridges, and hydrological features at nine different dates (October, 1954; June, 1976; June, 1991; June, 2003; June, 2005; May, 2006; October, 2007; July, 2009; and March , 2010) between 1954 and 2010. Within the earth flow we recognized several kinematic elements and associated structures (Fig.2a). Within each kinematic element (e.g. the earth flow neck; Fig.2b), the flow velocity was highest in the middle, and lowest in the upper and lower parts. As the velocity of movement initiated and increased, stretching of the earth flow body induced the formation of normal faults. Conversely, decreasing velocity and shortening of the earth flow induced the formation of thrust faults. A zone with relatively few structures, bounded by strike-slip faults, was located between stretching and shortening areas. These kinematic elements indicate that the overall earth flow was actually composed of numerous linked internal earth flows, with each internal flow having a distinct pattern of structures representative of stretching and shortening (Guerriero et al., in review). These observations indicated that the spatial variation in movement velocity associated with each internal earth flow, mimicked the pattern of movement for the overall earth flow. That is, the earth flow displayed a self-similar pattern at different scales. Furthermore, the presence of other structures such as back-tilted surfaces, flank-ridges, and hydrological elements provide specific information about the shape of the basal topographic surface. Our multi-temporal maps provided a basis for interpretation of the long-term kinematic evolution of the earth flow and the influence of the basal-slip surface on the earth flow movement. Our maps showed that main faults remained stationary through time, despite extensive mobilization and movement of material. This observation indicated that the slip-surface has remained relatively stationary since at least 1954.

Conference Paper↗

USGS1994

Geologic framework of the Aleutian arc, Alaska

The Aleutian arc is the arcuate arrangement of mountain ranges and flanking submerged margins that forms the northern rim of the Pacific Basin from the Kamchatka Peninsula (Russia) eastward more than 3,000 km to Cooke Inlet (Fig. 1). It consists of two very different segments that meet near Unimak Pass: the Aleutian Ridge segment to the west and the Alaska Peninsula-the Kodiak Island segment to the east. The Aleutian Ridge segment is a massive, mostly submerged cordillera that includes both the islands and the submerged pedestal from which they protrude. The Alaska Peninsula-Kodiak Island segment is composed of the Alaska Peninsula, its adjacent islands, and their continental and insular margins. The Bering Sea margin north of the Alaska Peninsula consists mostly of a wide continental shelf, some of which is underlain by rocks correlative with those on the Alaska Peninsula. There is no pre-Eocene record in rocks of the Aleutian Ridge segment, whereas rare fragments of Paleozoic rocks and extensive outcrops of Mesozoic rocks occur on the Alaska Peninsula. Since the late Eocene, and possibly since the early Eocene, the two segments have evolved somewhat similarly. Major plutonic and volcanic episodes, however, are not synchronous. Furthermore, uplift of the Alaska Peninsula-Kodiak Island segment in late Cenozoic time was more extensive than uplift of the Aleutian Ridge segment. It is probable that tectonic regimes along the Aleutian arc varied during the Tertiary in response to such factors as the directions and rates of convergence, to bathymetry and age of the subducting Pacific Plate, and to the volume of sediment in the Aleutian Trench. The Pacific and North American lithospheric plates converge along the inner wall of the Aleutian trench at about 85 to 90 mm/yr. Convergence is nearly at right angles along the Alaska Peninsula, but because of the arcuate shape of the Aleutian Ridge relative to the location of the plates' poles of rotation, the angle of convergence lessens to the west (Minster and Jordan, 1978). Along the central Aleutian Ridge, underthrusting is about 30° from normal to the volcanic axis. Motion between plates is approximately parallel along the western Aleutian Ridge. In this paper we briefly describe and interpret the Cenozoic evolution of the Aleutian arc by focusing on the onshore and offshore geologic frameworks in four of its sectors, two sectors each from the Aleutian Ridge and Alaska Peninsula-Kodiak Island segments (Fig. 1). We compare the geologic evolution of the segments and comment on the implications of some new, previously unpublished data.

Alaska↗

USGS2017

Tools for mapping ecosystem services

Mapping tools have evolved impressively in recent decades. From early computerised mapping techniques to current cloud-based mapping approaches, we have witnessed a technological evolution that has facilitated the democratisation of Geographic Information Systems (GIS). These advances have impacted multiple disciplines including ecosystem service (ES) mapping. The information that feeds different mapping tools is also increasingly accessible and complex. In this chapter, we review the evolution of mapping tools that are shaping the field of ES mapping together with the different sources of information that exist at this point. We discuss briefly the suitability of these approaches for mapping different ES types and for different scientific and policy aims. Finally, we elaborate on the integration of multiple tools (from desktop applications to sensor, web-based, or mobile devices) and on the future developments of these methods and the possibilities they may open for ES mapping.

Book chapter↗

USGS1964

Fluvial processes in geomorphology

This excellent text is a pioneering work in the study of landform development under processes associated with running water. Its primary emphasis is on subjects that were the focus of the authors' studies in both field and laboratory. Part I deals with the process of change in the evolving landscape. Part II explores process and form, and Part III, the effects of time. In Part I, the relation of geomorphology to field problems is analyzed in studies of a mountain block in a semiarid climate, a meandering river cut into bedrock, and benches along a sea coast. Part Two contains studies of weathering, climate, and such denudational processes as flooding and erosion. Here, too, are examinations of the drainage basin as a geomorphic unit, water and sediment in channels, channel form and process, and hillslope characteristics and processes. In Part III, the authors cover geochronology, drainage pattern evolution, channel changes with time, and the evolution of hillslopes. Two appendixes will help readers convert units and equivalents, and identify symbols and nomenclature.

Book↗

USGS2014

The future of nearshore processes research

The nearshore is the transition region between land and the continental shelf including (from onshore to offshore) coastal plains, wetlands, estuaries, coastal cliffs, dunes, beaches, surf zones (regions of wave breaking), and the inner shelf (Figure ES-1). Nearshore regions are vital to the national economy, security, commerce, and recreation. The nearshore is dynamically evolving, is often densely populated, and is under increasing threat from sea level rise, long-term erosion, extreme storms, and anthropogenic influences. Worldwide, almost one billion people live at elevations within 10 m of present sea level. Long-term erosion threatens communities, infrastructure, ecosystems, and habitat. Extreme storms can cause billions of dollars of damage. Degraded water quality impacts ecosystem and human health. Nearshore processes, the complex interactions between water, sediment, biota, and humans, must be understood and predicted to manage this often highly developed yet vulnerable nearshore environment. Over the past three decades, the understanding of nearshore processes has improved. However, societal needs are growing with increased coastal urbanization and threats of future climate change, and significant scientific challenges remain. To address these challenges, members of academia, industry, and federal agencies (USGS, USACE, NPS, NOAA, FEMA, ONR) met at the “The Past and Future of Nearshore Processes Research: Reflections on the Sallenger Years and a New Vision for the Future” workshop to develop a nearshore processes research vision where societal needs and science challenges intersect. The resulting vision is comprised of three broad research themes: Long-term coastal evolution due to natural and anthropogenic processes: As global climate change alters the rates of sea level rise and potentially storm patterns and coastal urbanization increases over the coming decades, an understanding of coastal evolution is critical. Improved knowledge of long-term morphological, ecological, and societal processes and their interactions will result in an improved ability to simulate coastal change. This will enable proactive solutions for resilient coasts and better guidance for reducing coastal vulnerability. Extreme Events: Flooding, erosion, and the subsequent recovery: Hurricane Sandy caused flooding and erosion along hundreds of miles of shoreline, flooded New York City, and impacted communities and infrastructure. Overall U.S. coastal extreme event related economic losses have increased substantially. Furthermore, climate change may cause an increase in coastal extreme events and rising sea levels could increase the occurrence of extreme events. Addressing this research theme will result in an improved understanding of the physical processes during extreme events, leading to improved models of flooding, erosion, and recovery. The resulting societal benefit will be more resilient coastal communities. The physical, biological and chemical processes impacting human and ecosystem health: Nearshore regions are used for recreation, tourism, and human habitation, and provide habitat and valuable ecosystem services. These areas must be sustained for future generations, however overall coastal water quality is declining due to microbial pathogens, fertilizers, pesticides, and heavy metal contamination, threatening ecosystem and human health. To ensure sustainable nearshore regions, predictive real-time water- and sediment-based based pollutant modeling capabilities must be developed, which requires expanding our knowledge of the physics, chemistry, and biology of the nearshore. The resulting societal benefits will include better beach safety, healthier ecosystems, and improved mitigation and regulatory policies. The scientists and engineers of the U.S. nearshore community are poised to make significant progress on these research themes, which have significant societal impact. The U.S. nearshore community, including academic, government, and industry colleagues, recommends multi-agency investment into a coordinated development of observational and modeling research infrastructure to address these themes, as discussed in the whitepaper. The observational infrastructure should include development of new sensors and methods, focused observational programs, and expanded nearshore observing systems. The modeling infrastructure should include improved process representation, better model coupling, incorporation of data assimilation techniques, and testing of real-time models. The observations will provide test beds to compare and improve models.

Report↗

USGS2011

Mechanics of flow and sediment transport in delta distributary channels

Predicting the planform and dimensions of a channel downstream from a confluence of two smaller channels with known sediment and water supplies is a fundamental, well-studied problem in geomorphology and engineering. An analogous but less well understood problem is found well downstream of such confluences, where large river channels split into two or more distributary channels on a river delta. In this case, both the flow and sediment supplies in the downstream distributaries are set by the dynamics near the bifurcation of the upstream channel and by downstream boundary conditions. Over time, the pattern of erosion and deposition in the distributary channels gives rise to variations in the amount of water and sediment routed into them. In the simplest case, this results in channel switching on deltas, but in a more general sense these dynamics produce a rich suite of interesting morphologic change contributing both to the evolution of the channel distributary network and the overall evolution of the delta. As part of a study to develop a better understanding of these processes, we conducted a field study measuring the detailed morphology of the Hong-Luoc junction on the Red River downstream of Hanoi, Vietnam. This junction was selected for such a study because it has a 1,000-year history, modern observations suggest that it is currently switching (changing the proportion of sediment and streamflow provided to each of the distributary channels), and hydrologic configuration of the junction allows for the study of two bifurcations and one confluence in a single junction complex. In this paper, our morphologic observations are used in computational flow models to show how flow and sediment transport changes as a function of total discharge upstream of the junction. This is a key component of understanding how the junction attains stability over a range of flows or how imbalances in the distribution of flow and sediment transport lead to destabilization of the channel bifurcation.

Conference Paper↗