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At least 739 records · Page 41Linked to original sources
USGS2010

Field response of tadpoles to conspecific and heterospecific alarm

Many organisms use chemical cues from a variety of sources to mediate predator avoidance. Response to heterospecific alarm cues has been demonstrated for tadpoles within but not among taxa and alarm response behavior has seldom been examined under field conditions. This study examined the response of three sympatric amphibian larvae and predaceous larval Dytiscus sp. (diving beetle) to damage-release signals in natural ponds by using capture rates from treated funnel traps as an index of larval behavior. Hyla regilla (Pacific tree frog) tadpoles avoided traps treated with either crushed conspecifics or with Rana aurora (red-legged frog) tadpoles but the larger ranids and Ambystoma macrodactylum (long-toed salamander) did not respond to either treatment. H. regilla tadpoles were likely susceptible to any potential predators of ranid tadpoles in these ponds and this result is consistent with the hypothesis that a response to heterospecific alarm occurs in sympatric prey with shared predators.

Ethology↗
USGS2012

History of earthquakes and tsunamis along the eastern Aleutian-Alaska megathrust, with implications for tsunami hazards in the California Continental Borderland

During the past several years, devastating tsunamis were generated along subduction zones in Indonesia, Chile, and most recently Japan. Both the Chile and Japan tsunamis traveled across the Pacific Ocean and caused localized damage at several coastal areas in California. The question remains as to whether coastal California, in particular the California Continental Borderland, is vulnerable to more extensive damage from a far-field tsunami sourced along a Pacific subduction zone. Assuming that the coast of California is at risk from a far-field tsunami, its coastline is most exposed to a trans-Pacific tsunami generated along the eastern Aleutian-Alaska subduction zone. We present the background geologic constraints that could control a possible giant (M w ~9) earthquake sourced along the eastern Aleutian-Alaska megathrust. Previous great earthquakes (M w ~8) in 1788, 1938, and 1946 ruptured single segments of the eastern Aleutian-Alaska megathrust. However, in order to generate a giant earthquake, it is necessary to rupture through multiple segments of the megathrust. Potential barriers to a throughgoing rupture, such as high-relief fracture zones or ridges, are absent on the subducting Pacific Plate between the Fox and Semidi Islands. Possible asperities (areas on the megathrust that are locked and therefore subject to infrequent but large slip) are identified by patches of high moment release observed in the historical earthquake record, geodetic studies, and the location of forearc basin gravity lows. Global Positioning System (GPS) data indicate that some areas of the eastern Aleutian-Alaska megathrust, such as that beneath Sanak Island, are weakly coupled. We suggest that although these areas will have reduced slip during a giant earthquake, they are not really large enough to form a barrier to rupture. A key aspect in defining an earthquake source for tsunami generation is determining the possibility of significant slip on the updip end of the megathrust near the trench. Large slip on the updip part of the eastern Aleutian-Alaska megathrust is a viable possibility owing to the small frontal accretionary prism and the presence of arc basement relatively close to the trench along most of the megathrust.

Alaska↗
USGS2020

Monitoring nearshore ecosystem health using Pacific razor clams (Siliqua patula) as an indicator species

An emerging approach to ecosystem monitoring involves the use of physiological biomarker analyses in combination with gene transcription assays. For the first time, we employed these tools to evaluate the Pacific razor clam ( Siliqua patula ), which is important both economically and ecologically, as a bioindicator species in the northeast Pacific. Our objectives were to (1) develop biomarker and gene transcription assays with which to monitor the health of the Pacific razor clam, (2) acquire baseline biomarker and gene transcription reference ranges for razor clams, (3) assess the relationship between physiological and gene transcription assays and (4) determine if site-level differences were present. Pacific razor clams were collected in July 2015 and 2016 at three sites within each of two national parks in southcentral Alaska. In addition to determining reference ranges, we found differences in biomarker assay and gene transcription results between parks and sites which indicate variation in both large-scale and local environmental conditions. Our intent is to employ these methods to evaluate Pacific razor clams as a bioindicator of nearshore ecosystem health. Links between the results of the biomarker and gene transcription assays were observed that support the applicability of both assays in ecosystem monitoring. However, we recognize the need for controlled studies to examine the range of responses in physiology and gene transcripts to different stressors. sors.

Alaska↗
USGS2015

Evaluating turbidity and suspended-sediment concentration relations from the North Fork Toutle River basin near Mount St. Helens, Washington; annual, seasonal, event, and particle size variations - a preliminary analysis.

Regression of in-stream turbidity with concurrent sample-based suspended-sediment concentration (SSC) has become an accepted method for producing unit-value time series of inferred SSC (Rasmussen et al., 2009). Turbidity-SSC regression models are increasingly used to generate suspended-sediment records for Pacific Northwest rivers (e.g., Curran et al., 2014; Schenk and Bragg, 2014; Uhrich and Bragg, 2003). Recent work developing turbidity-SSC models for the North Fork Toutle River in Southwest Washington (Uhrich et al., 2014), as well as other studies (Landers and Sturm, 2013, Merten et al., 2014), suggests that models derived from annual or greater datasets may not adequately reflect shorter term changes in turbidity-SSC relations, warranting closer inspection of such relations. In-stream turbidity measurements and suspended-sediment samples have been collected from the North Fork Toutle River since 2010. The study site, U.S. Geological Survey (USGS) streamgage 14240525 near Kid Valley, Washington, is 13 river km downstream of the debris avalanche emplaced by the 1980 eruption of Mount St. Helens (Lipman and Mullineaux, 1981), and 2 river km downstream of the large sediment retention structure (SRS) built from 1987–1989 to mitigate the associated sediment hazard. The debris avalanche extends roughly 25 km down valley from the edifice of the volcano and is the primary source of suspended sediment moving past the streamgage (NF Toutle-SRS). Other significant sources are debris flow events and sand deposits upstream of the SRS, which are periodically remobilized and transported downstream. Also, finer material often is derived from the clay-rich original debris avalanche deposit, while coarser material can derive from areas such as fluvially reworked terraces.

Washington↗
USGS2010

Surface elevation change and susceptibility of different mangrove zones to sea-level rise on Pacific high islands of Micronesia

Mangroves on Pacific high islands offer a number of important ecosystem services to both natural ecological communities and human societies. High islands are subjected to constant erosion over geologic time, which establishes an important source of terrigeneous sediment for nearby marine communities. Many of these sediments are deposited in mangrove forests and offer mangroves a potentially important means for adjusting surface elevation with rising sea level. In this study, we investigated sedimentation and elevation dynamics of mangrove forests in three hydrogeomorphic settings on the islands of Kosrae and Pohnpei, Federated States of Micronesia (FSM). Surface accretion rates ranged from 2.9 to 20.8 mm y −1 , and are high for naturally occurring mangroves. Although mangrove forests in Micronesian high islands appear to have a strong capacity to offset elevation losses by way of sedimentation, elevation change over 6½ years ranged from −3.2 to 4.1 mm y −1 , depending on the location. Mangrove surface elevation change also varied by hydrogeomorphic setting and river, and suggested differential, and not uniformly bleak, susceptibilities among Pacific high island mangroves to sea-level rise. Fringe, riverine, and interior settings registered elevation changes of −1.30, 0.46, and 1.56 mm y −1 , respectively, with the greatest elevation deficit (−3.2 mm y −1 ) from a fringe zone on Pohnpei and the highest rate of elevation gain (4.1 mm y −1 ) from an interior zone on Kosrae. Relative to sea-level rise estimates for FSM (0.8–1.8 mm y −1 ) and assuming a consistent linear trend in these estimates, soil elevations in mangroves on Kosrae and Pohnpei are experiencing between an annual deficit of 4.95 mm and an annual surplus of 3.28 mm. Although natural disturbances are important in mediating elevation gain in some situations, constant allochthonous sediment deposition probably matters most on these Pacific high islands, and is especially helpful in certain hydrogeomorphic zones. Fringe mangrove forests are most susceptible to sea-level rise, such that protection of these outer zones from anthropogenic disturbances (for example, harvesting) may slow the rate at which these zones convert to open water.

Ecosystems↗
USGS1990

Reconnaissance study of the thickness of the unsaturated zone in the western conterminous United States

In 1984, the U.S. Geological Survey began a study of the geologic and hydrologic characteristics of the unsaturated zone in the western conterminous United States. The study area extends from the eastern edge of the Rocky Mountains westward and includes all or parts of the 12 westernmost conterminous States. The goal of the study is to characterize unsaturated flow systems to aid in identifying environments in the western United States that may merit further study for isolation of hazardous waste, including high- and low-level radioactive waste and other toxic waste. The major physiographic areas discussed in this report (see index map below thickness map) are: (1) Rocky Mountain System consisting of the Southern, Middle, and Northern Rocky Mountains, and the Wyoming Basin; (2) Intermontane Plateaus consisting of the Basin and Range province, and the Colorado and Columbia Plateaus; and (3) Pacific Mountain System (Fenneman, 1946). Two of these areas, the Colorado and Columbia plateaus, exhibit a variety of geohydrologic conditions, and therefore are further subdivided in the discussions that follow. Outstanding features peculiar to the mountainous area of the Rocky Mountain and the Pacific Mountain Systems are the high rugged mountains and steep relief. These mountains receive greater precipitation than do the lower parts of the otherwise dry western United States. Generally moisture-laden air masses move eastward across the continent, and the mountains force them to higher, cooler altitudes. As the air cools, moisture condenses and precipitates. As a result, the Rocky Mountain and Pacific Mountain Systems have annual precipitation in excess of 30 in. The Wyoming Basin of the Rocky Mountain System and the Basin and Range province, Colorado Plateaus, and Columbia Plateaus of the Intermontane Plateaus generally have lower altitudes and less relief than do the mountainous areas. The climate throughout most of these provinces generally is semiarid to arid. Annual precipitation is generally less than 16 in. throughout most of the area, and is less than 4 in. in some parts. The mean annual free-water-surface evaporation ranges from 20 to 100in. A large part of the study area is subject to a water deficit because potential evapotranspiration exceeds precipitation. As a consequence of the large water deficit, ground-water recharge generally is small, surface runoff is small, perennial streams and lakes are few, and the depth to ground water commonly is large. The generalized thickness of the unsaturated zone (the depth to ground water), in the western conterminous United States is presented on the map.

Hydrologic Atlas↗
USGS2007

Introduction to Regional Geology, Tectonics, and Metallogenesis of Northeast Asia

Purpose This introduction presents an overview of the regional geology, tectonics, and metallogenesis of Northeast Asia. The major purposes are to provide a relatively short summary of these features for readers who are unfamiliar with Northeast Asia; a general scientific introduction for the succeeding chapters of this volume; and an overview of the methodology of metallogenic and tectonic analysis employed for Northeast Asia. The introduction also describes how a high-quality metallogenic and tectonic analysis, including synthesis of an associated metallogenic-tectonic model will greatly benefit refinement of mineral deposit models and deposit genesis; improvement of assessments of undiscovered mineral resources as part of quantitative mineral resource assessment studies; land-use and mineral exploration planning; improvement of interpretations of the origins of host rocks, mineral deposits, and metallogenic belts; and suggestions for new research. The compilation, synthesis, description, and interpretation of metallogenesis and tectonics of major regions, such as Northeast Asia (Eastern Russia, Mongolia, northern China, South Korea, and Japan) and the Circum-North Pacific (Russian Far East, Alaska, and Canadian Cordillera) requires a complex methodology. The methodology includes: (1) definitions of key terms; (2) compilation of a regional geologic base map that can be interpreted according to modern tectonic concepts and definitions; (3) compilation of a mineral deposit database that enables the determination of mineral deposit models, and relations of deposits to host rocks and tectonic origins; (4) synthesis of a series of mineral deposit models that characterize the known mineral deposits and inferred undiscovered deposits of the region; (5) compilation of a series of maps of metallogenic belts constructed on the regional geologic base map; and (6) formulation of a unified metallogenic and tectonic model. The summary of regional geology and metallogenesis in this introduction is based on publications of the major international collaborative studies of the metallogenesis and tectonics of Northeast Asia that were led by the U.S. Geological Survey. These studies have produced two broad types of publications. One type is a series of regional geologic, mineral deposit, and metallogenic belt maps and companion descriptions for the regions. Examples of major publications of this type are Obolenskiy and others (2003a, b, 2004), Parfenov and others (2003, 2004a, b), Nokleberg and others (2004), Rodionov and others (2004), and Naumova and others (2006). The other type is a suite of metallogenic and tectonic analyses of these same regions. Examples of major publications of this type are Rodionov and others (2004), Nokleberg and others (2000, 2004, 2005), and Naumova and others (2006). The Northeast Asia project area consists of eastern Russia (most of Siberia and most of the Russian Far East), Mongolia, Northern China, South Korea, Japan, and adjacent offshore areas. This area is approximately bounded by 30 to 82? N. latitude and 75 to 144? E. longitude. The major participating agencies are the Russian Academy of Sciences, Academy of Sciences of the Sakha Republic (Yakutia), VNIIOkeangeologia and Ministry of Natural Resources of the Russian Federation, Mongolian Academy of Sciences, Mongolian University of Science and Technology, Mongolian National University, Jilin University, Changchun, China, the China Geological Survey, the Korea Institute of Geosciences and Mineral Resources, the Geological Survey of Japan/AIST, University of Texas Arlington, and the U.S. Geological Survey. The Northeast Asia project extends and build on data and interpretations from a previous project on the Major Mineral Deposits, Metallogenesis, and Tectonics of the Russian Far East, Alaska, and the Canadian Cordillera that was conducted by the USGS, the Russian Academy of Sciences, the Alaska Division of Geological and Geophysical Surveys,

Open-File Report↗
USGS2016

Observing outer planet satellites (except Titan) with the James Webb Space Telescope: Science justification and observational requirements

The James Webb Space Telescope ( JWST ) will allow observations with a unique combination of spectral, spatial, and temporal resolution for the study of outer planet satellites within our Solar System. We highlight the infrared spectroscopy of icy moons and temporal changes on geologically active satellites as two particularly valuable avenues of scientific inquiry. While some care must be taken to avoid saturation issues, JWST has observation modes that should provide excellent infrared data for such studies.

Publications of the Astronomical Society of the Pa↗
USGS2012

Elevated streamflows increase dam passage by juvenile coho salmon during winter: Implications of climate change in the Pacific Northwest

A 4-year evaluation was conducted to determine the proportion of juvenile coho salmon Oncorhynchus kisutch passing Cowlitz Falls Dam, on the Cowlitz River, Washington, during winter. River and reservoir populations of coho salmon parr were monitored using radiotelemetry to determine if streamflow increases resulted in increased downstream movement and dam passage. This was of interest because fish that pass downstream of Cowlitz Falls Dam become landlocked in Riffe Lake and are lost to the anadromous population. Higher proportions of reservoir-released fish (0.391-0.480) passed Cowlitz Falls Dam than did river-released fish (0.037-0.119). Event-time analyses demonstrated that streamflow increases were important predictors of dam passage rates during the study. The estimated effect of increasing streamflows on the risk of dam passage varied annually and ranged from 9% to 75% for every 28.3 m 3 /s increase in streamflow. These results have current management implications because they demonstrate the significance of dam passage by juvenile coho salmon during winter months when juvenile fish collection facilities are typically not operating. The results also have future management implications because climate change predictions suggest that peak streamflow timing for many watersheds in the Pacific Northwest will shift from late spring and early summer to winter. Increased occurrence of intense winter flood events is also expected. Our results demonstrate that juvenile coho salmon respond readily to streamflow increases and initiate downstream movements during winter months, which could result in increased passage at dams during these periods if climate change predictions are realized in the coming decades.

Washington↗
USGS2017

Climate-induced trends in predator–prey synchrony differ across life-history stages of an anadromous salmonid

Differential climate-induced shifts in phenology can create mismatches between predators and prey, but few studies have examined predator–prey mismatch across multiple life-history stages. We used long-term data from a warming stream with shifting salmonid migration timings to quantify intra-annual migration synchrony between predatory Dolly Varden ( Salvelinus malma ) and Pacific salmon prey and examined how predator–prey synchrony has been influenced by climate change. We demonstrate that Dolly Varden have become increasingly mismatched with spring downstream migrations of abundant pink salmon ( Oncorhynchus gorbuscha ) juveniles. However, Dolly Varden have remained matched with fall upstream migrations of spawning Pacific salmon, including coho ( Oncorhynchus kisutch ), sockeye ( Oncorhynchus nerka ), and pink salmon. Downstream predator–prey migration synchrony decreased over time and with higher temperatures, particularly with pink salmon. In contrast, upstream migration synchrony was temporally stable and increased with rising temperatures. Differing trends in Dolly Varden predator–prey synchrony may be explained by the direct use of salmon to cue upstream migration, but not downstream migration. Overall, we show that climate change can have differing impacts on predator–prey synchrony across life-history stages.

Alaska↗
USGS2014

Effects of wetland management on carrying capacity of diving ducks and shorebirds in a coastal estuary

With global loss of natural wetlands, managed wetlands increasingly support energy requirements for wintering shorebirds and waterfowl. Despite numerous studies of avian bioenergetics in freshwater systems, less is known of the energetic capacity of estuarine systems. In San Francisco Bay, managed saline ponds converted from former commercial salt evaporation ponds form part of the largest wetland restoration project on the Pacific coast of North America. A daily-ration model was applied to assess carrying capacity for diving ducks and shorebirds during four winter seasons (2007–2010) in seasonal and circulation ponds, each in two salinity classes. Diving ducks comprised an estimated 35,450 ± 1,559 ( ± SE) in average years and 45,458 ± 1,653 in peak years with > 95% in circulation ponds. Shorebirds comprised 64,253 ± 14,838 ( ± SE) in average years and 108,171 ± 4,854 in peak years with > 64% in seasonal ponds. Macroinvertebrate energy density was highest in mesohaline (5–30 ppt) circulation ponds and lowest in seasonal ponds for both guilds. Energy requirements for diving ducks in mesohaline followed by low-hyperhaline (30–80 ppt) circulation ponds were mostly met by available prey energy. Available energy for shorebirds was substantially less than they required in seasonal ponds but exceeded their needs in mesohaline circulation ponds. Mesohaline circulation ponds supported 9,443 ± 1,649 ( ± SE) shorebird use-days·ha -1 of accessible habitat and 2,297 ± 402 diving duck use-days·ha -1 of accessible habitat, twice the capacity of low-hyperhaline circulation ponds and greater than five times that of seasonal ponds for both guilds. Our results indicated that reducing salinity to mesohaline levels and altering water depth to increase accessibility substantially increased energy available for these species in estuarine managed ponds.

California↗
USGS1982

Apparent episodicity of magmatic activity based on radiometric age determination: A section in The United States Geological Survey in Alaska: Accomplishments during 1980

Results of recent potassium-argon age studies in the Chignik region, Alaska, (Wilson, 1980; Wilson and others, 1982) have suggested a distinct episodicity in igneous activity during Tertiary time. To date work on the Aleutian magmatic arc indicates that plutonic activity took place along the present outer Pacific margin and in the northern Alaska-Aleutian Range batholith (Reed and Lanphere, 1973; Kienle and Turner, 1976; DeLong and others, 1978) in latest Cretaceous and earliest Tertiary time (70-58 m.y.) and was followed by a hiatus lasting until late Eocene ( 45 m.y~) time. Late Eocene to earliest Miocene ( 45-20 m.y.) magmatic activity was followed by a middle Miocene hiatus (10 m.y.). Since that time, magmatic activity in the Aleutian arc has been continuous.

Alaska↗
USGS2023

Gene expression and wildlife health: Varied interpretations based on perspective

We evaluated wildlife population health from the perspective of statistical means vs. variances. We outlined the choices necessary to provide the framework for our study. These consisted of spatial and temporal boundaries (e.g., choice of sentinel species, populations, time frame), measurement techniques (molecular to population level), and appropriate statistical analyses. We chose to assess the health of 19 sea otter populations, located in the north Pacific from the Aleutian Islands, AK, to Santa Barbara, CA, and varying in population growth rates and length of occupancy. Our focal metric was gene expression (i.e., mRNA transcripts) data that we had previously generated across sea otter populations as a measure of population health. We used statistical methods with different approaches (i.e., means vs. variances) and examined the subsequent interpretive outcomes and how these influence our assessment of “health.” Interpretations based on analyses using variances versus means overlapped to some degree. In general, sea otter populations with low variation in gene expression were limited by food resources and at or near carrying capacity. In populations where the variation in gene expression was moderate or high, four out of five populations were increasing in abundance, or had been recently increasing. Where we had additional information on sources of stressors at the level of the population, we were able to draw inferences from those stressors to specific gene expression results. For example, gene expression patterns of sea otters from Western Prince William Sound were consistent with long term exposure to petroleum hydrocarbons, whereas in Kachemak Bay, patterns were consistent with exposure to algal toxins. Ultimately, determination of population or ecosystem health will be most informative when multiple metrics are examined across disciplines in the context of specific scenarios and goals.

Alaska, British Columbia, California, Oregon, Wash↗
USGS2013

Management, morphological, and environmental factors influencing Douglas-fir bark furrows in the Oregon Coast Range

Many land managers in the Pacific Northwest have the goal of increasing late-successional forest structures. Despite the documented importance of Douglas-fir tree bark structure in forested ecosystems, little is known about factors influencing bark development and how foresters can manage development. This study investigated the relative importance of tree size, growth, environmental factors, and thinning on Douglas-fir bark furrow characteristics in the Oregon Coast Range. Bark furrow depth, area, and bark roughness were measured for Douglas-fir trees in young heavily thinned and unthinned sites and compared to older reference sites. We tested models for relationships between bark furrow response and thinning, tree diameter, diameter growth, and environmental factors. Separately, we compared bark responses measured on trees used by bark-foraging birds with trees with no observed usage. Tree diameter and diameter growth were the most important variables in predicting bark characteristics in young trees. Measured environmental variables were not strongly related to bark characteristics. Bark furrow characteristics in old trees were influenced by tree diameter and surrounding tree densities. Young trees used by bark foragers did not have different bark characteristics than unused trees. Efforts to enhance Douglas-fir bark characteristics should emphasize retention of larger diameter trees' growth enhancement.

Oregon↗
USGS2017

Oregon OCS seafloor mapping: Selected lease blocks relevant to renewable energy

In 2014 the U.S. Geological Survey (USGS) and the Bureau of Ocean Energy Management (BOEM) entered into Intra-agency agreement M13PG00037 to map an area of the Oregon Outer Continental Shelf (OCS) off of Coos Bay, Oregon, under consideration for development of a floating wind energy farm. The BOEM requires seafloor mapping and site characterization studies in order to evaluate the impact of seafloor and sub-seafloor conditions on the installation, operation, and structural integrity of proposed renewable energy projects, as well as to assess the potential effects of construction and operations on archaeological resources. The mission of the USGS is to provide geologic, topographic, and hydrologic information that contributes to the wise management of the Nation's natural resources and that promotes the health, safety, and well being of the people. This information consists of maps, databases, and descriptions and analyses of the water, energy, and mineral resources, land surface, underlying geologic structure, and dynamic processes of the earth. For the Oregon OCS study, the USGS acquired multibeam echo sounder and seafloor video data surrounding the proposed development site, which is 95 km2 in area and 15 miles offshore from Coos Bay. The development site had been surveyed by Solmar Hydro Inc. in 2013 under a contract with WindFloat Pacific. The USGS subsequently produced a bathymetry digital elevation model and a backscatter intensity grid that were merged with existing data collected by the contractor. The merged grids were published along with visual observations of benthic geo-habitat from the video data in an associated USGS data release (Cochrane and others, 2015). This report includes the results of analysis of the video data conducted by Oregon State University and the geo-habitat interpretation of the multibeam echo sounder (MBES) data conducted by the USGS. MBES data was published in Cochrane and others (2015). Interpretive data associated with this publication is published in Cochrane (2017). All the data is provided as geographic information system (GIS) files that contain both Esri ArcGIS geotiffs or shapefiles. For those who do not own the full suite of Esri GIS and mapping software, the data can be read using Esri ArcReader, a free viewer that is available at http://www.esri.com/software/arcgis/arcreader/index.html (last accessed August 29, 2016). Web services, which consist of standard implementations of ArcGIS representational state transfer (REST) Service and Open Geospatial Consortium (OGC) GIS web map service (WMS), also are available for all published GIS data. Web services were created using an ArcGIS service definition file, resulting in data layers that are symbolized as shown on the associated report figures. Both the ArcGIS REST Service and OGC WMS Service include all the individual GIS layers. Data layers are bundled together in a map-area web service; however, each layer can be symbolized and accessed individually after the web service is ingested into a desktop application or web map. Web services enable users to download and view data, as well as to easily add data to their own workflows, using any browser-enabled, standalone or mobile device. Though the surficial substrate is dominated by combinations of mud and sand substrate, a diverse assortment of geomorphologic features are related to geologic processes—one anticlinal ridge where bedrock is exposed, a slump and associated scarps, and pockmarks. Pockmarks are seen in the form of fields of small pockmarks, a lineation of large pockmarks with methanogenic carbonates, and areas of large pockmarks that have merged into larger variously shaped depressions. The slump appears to have originated at the pockmark lineation. Video-supervised numerical analysis of the MBES backscatter intensity data and vector ruggedness derived from the MBES bathymetry data was used to produce a substrate model called a seafloor character raster for the study area. The seafloor character raster consists of three substrate classes: soft-flat areas, hard-flat areas, and hard-rugged areas. A Coastal and Marine Ecological Classification Standard (CMECS) geoform and substrate map was also produced using depth, slope, and benthic position index classes to delineate geoform boundaries. Seven geoforms were identified in this process, including ridges, slump scars, slump deposits, basins, and pockmarks. Statistical analysis of the video data for correlations between substrate, depth, and invertebrate assemblages resulted in the identification of seven biomes: three hard-bottom biomes and four softbottom biomes. A similar analysis of vertebrate observations produces a similar set of biomes. The biome between-group dissimilarity was very high or high. Invertebrates alone represent most of the structure of the whole benthic community into different assemblages. A biotope map was generated using the seafloor character raster and the substrate and depth values of the biomes. Hard substrate biotopes were small in size and were located primarily on the ridge and in pockmarks along the pockmark lineation. The soft-bottom bitopes consisted of large contiguous areas delimited by isobaths.

Open-File Report↗
USGS2008

Landscape Features Shape Genetic Structure in Threatened Northern Spotted Owls

Several recent studies have shown that landscape features can strongly affect spatial patterns of gene flow and genetic variation. Understanding landscape effects on genetic variation is important in conservation for defining management units and understanding movement patterns. The landscape may have little effect on gene flow, however, in highly mobile species such as birds. We tested for genetic breaks associated with landscape features in the northern spotted owl (Strix occidentalis caurina), a threatened subspecies associated with old forests in the U.S. Pacific Northwest and extreme southwestern Canada. We found little evidence for distinct genetic breaks in northern spotted owls using a large microsatellite dataset (352 individuals from across the subspecies' range genotyped at 10 loci). Nonetheless, dry low-elevation valleys and the Cascade and Olympic Mountains restrict gene flow, while the Oregon Coast Range facilitates it. The wide Columbia River is not a barrier to gene flow. In addition, inter-individual genetic distance and latitude were negatively related, likely reflecting northward colonization following Pleistocene glacial recession. Our study shows that landscape features may play an important role in shaping patterns of genetic variation in highly vagile taxa such as birds.

Open-File Report↗
USGS1979

Manganese nodule resources in the northeastern equatorial Pacific

Recent publication of maps at scale 1:1,000,000 of the northeastern equatorial Pacific region showing publicly available information on the nickel plus copper content of manganese nodules has made it possible to outline the prime area between the Clarion and Clipperton fracture zones which has been the focus of several recent scientific and commercial studies. The area, defined as that in which the nodules contain more than 1.8 percent nickel plus copper, is about 2o5 million km 2 . The available evidence suggests that about half of it contains nodules in concentration (reported in wet weight units) greater than 5 kg/m 2 and averaging 11.9 kg/m 2 . If we assume that 20 percent of the nodules in this area of 1.25 million km 2 are recoverable, its potential recoverable resources are about 2.1 billion dry metric tons of nodules averaging about 25 percent Mn, 1.3 percent Ni, 1.0 percent Cu, 0.22 percent Co, and 0.05 percent Mo—enough to support about 27 mining operations each producing an average of 75 million metric tons of nodules over their lifetimes. Estimates based on other plausible assumptions would be higher or lower, but of the same order of magnitude. Thus it seems probable that the magnitude of the potentially recoverable nodule resources of the Clarion-Clipperton prime area—the most promising now known—is at most in the range of several tens of the average-size operations postulated.

Book chapter↗
USGS2012

Paleomagnetism of Middle Tertiary volcanic rocks from the Western Cascade Series, northern California

The Western Cascade Series (WCS) is a 3.5‐km‐thick, crudely homoclinal (east dipping) calcalkaline volcanic sequence of mid‐Oligocene to early Miocene age that crops out near the southern tip of the Cascade Range in northern California. The mean direction of remanent magnetization in the WCS is D, 4.9°; I, 57.6° (N, 53; k, 14.4; α 95 , 5.3°). When compared to a reference direction for the North American craton, the WCS direction indicates that the southern Cascade Range has rotated 14.0° ± 9.0° since the WCS accumulated. A difference in mean direction between the lower and upper halves of the WCS suggests that much of this rotation occurred during the late Oligocene. Six other paleomagnetic studies of rock units of an age roughly comparable to the WCS also are available from western Oregon, northwestern California, and southwestern Washington. All show statistically significant clockwise rotation (inclinations of all but one are concordant). Comparison of directions indicates that the Pacific Northwest did not rotate as a rigid body, but neither did it behave as a collection of small, independently rotating domains. The amount of rotation found throughout the area increases to the west or northwest, suggesting a driving force for rotation operating at the continental margin.

California↗