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At least 1,477 records · Page 82Linked to original sources

USGS2004

Using magnetic susceptibility to facilitate more rapid, reproducible and precise delineation of hydric soils in the midwestern USA

Standard field indicators, currently used for hydric soil delineations [USDA-NRCS, 1998. Field indicators of hydric soils in the United States, Version 4.0. In: G.W. Hurt et al. (Ed.), United States Department of Agriculture-NRCS, Fort Worth, TX], are useful, but in some cases, they can be subjective, difficult to recognize, or time consuming to assess. Magnetic susceptibility (MS) measurements, acquired rapidly in the field with a portable meter, have great potential to help soil scientists delineate and map areas of hydric soils more precisely and objectively. At five sites in Illinois (from 5 to 15 ha in area) with contrasting soil types and glacial histories, the MS values of surface soils were measured along transects, and afterwards mapped and contoured. The MS values were found to be consistently higher in well-drained soils and lower in hydric soils, reflecting anaerobic deterioration of both detrital magnetite and soil-formed ferrimagnetics. At each site, volumetric MS values were statistically compared to field indicators to determine a critical MS value for hydric soil delineation. Such critical values range between 22??10-5 and 33??10-5 SI in silty loessal or alluvial soils in Illinois, but are as high as 61??10-5 SI at a site with fine sandy soil. A higher magnetite content and slower dissolution rate in sandy soils may explain the difference. Among sites with silty parent material, the lowest critical value (22??10-5 SI) occurs in soil with low pH (4.5-5.5) since acidic conditions are less favorable to ferrimagnetic mineral neoformation and enhance magnetite dissolution. Because of their sensitivity to parent material properties and soil pH, critical MS values must be determined on a site specific basis. The MS of studied soil samples (0-5 cm depth) is mainly controlled by neoformed ultrafine ferrimagnetics and detrital magnetite concentrations, with a minor contribution from anthropogenic fly ash. Neoformed ferrimagnetics are present in all samples but, based on high ??FD% (???5% to 10%), are most prevalent in high pH Mollisols of northeastern Illinois. Scanning electron microscope images display significantly more detrital magnetite alteration in hydric soils, substantiating that reductive dissolution of magnetite (aided by microorganisms) is a primary cause for lower MS. Fly ash comprises 8-50% of the >5 ??m strongly magnetic particles and typically accounts for 5-15% of the total MS signal. The proportion of fly ash in >5 ??m strongly magnetic fractions is greater in hydric soils because of lower natural magnetite contents, possibly combined with historical topsoil accumulation in lower landscapes. Magnetic fly ash particles are also more altered in low MS soils, implying that significant magnetite dissolution can occur in less than 150 years. ?? 2004 Elsevier B.V. All rights reserved.

Catena↗

USGS1996

Effects of a legal drain clean-out on wetlands and waterbirds: a recent case history

Repairs to legal drains in the United States may be regulated to protect adjacent wetlands under Section 404 of the Federal Water Pollution Control Act, commonly known as the Clean Water Act (CWA). However, few studies have examined effects of legal drain clean-outs on adjacent wetlands and associated migratory waterbird populations. I compare water regimes, cover-to-open water ratios, and waterbird use on Bruns, Big, Meszaros, and Kraft sloughs (BBMK) in Sargent County, North Dakota before and after the clean-out of Crete-Cogswell Drain No. 11, and relate wetland habitat loss to observed disease-related mortality among staging waterfowl in fall 1990 and spring 1991. Water regimes of BBMK were exceptionally stable, with few records of drawdowns before 1984 when the clean-out began. After the clean-out (1987-90), BBM were dry by mid-summer in all years and open area declined by 96% by 1990, whereas Kraft Slough (a control area) had water throughout all years and percent open area did not change. Numerous species of waterbirds nested in BBMK before the clean-out, and mean ranks of waterbird density were similar. After the clean-out, waterbirds failed to breed successfully in all years at BBM, and use as major waterfowl staging areas and for waterfowl hunting also ended. At Kraft Slough, use by breeding and staging waterbirds continued in all years, as did waterfowl hunting. Reduced access to fresh water after the Drain No. 11 clean-out may have contributed to a dieoff of 487 lesser snow geese (Chen caerulescens) from necrotic enteritis in Kraft Slough in November 1990. Loss of three major staging areas in Sargent County as a result of the drain clean-out has further concentrated migrant waterfowl, particularly during drought periods, increasing the magnitude of risk when epizootics occur in southeastern North Dakota. Ducks and geese banded in Sargent County have been recovered from 34 and 14 states, 7 and 6 provinces of Canada, and 13 and 1 other countries, respectively, indicating waterfowl populations from a wide area are potentially vulnerable to epizootics when crowded into limited roosting habitat. Despite causing the loss of wetland habitat for thousands of midcontinent waterfowl and other waterbirds, a Federal Court in North Dakota ruled that the clean-out of Drain No. 11 met the criteria necessary to be considered maintenance under Section 404 clause (f)(1)(c) and was not recaptured under clause (f)(2). This outcome suggests current law does not protect wetland functions needed to support migratory waterbird populations or associated recreational values when sites have become naturally restored through lack of maintenance of legal drains.

Wetlands↗

USGS2001

Ground-water flow to Death Valley, as inferred from the chemistry and geohydrology of selected springs in Death Valley National Park, California and Nevada

Death Valley lies downgradient from adjacent valleys to the north, south, east, and west in California and Nevada, and is the site of substantial ground-water discharge. The sources of the discharging waters have been discussed by several investigators in the past and are of heightened concern because of the potential disposal of high-level radioactive waste at Yucca Mountain, Nevada, and because of ground-water withdrawals attendant to commercial mining in the northwestern Amargosa Valley region. This report describes high- and low-discharge springs in and along the Amargosa Range that were sampled to augment the level of understanding of the extent and distribution of westward ground-water flow through the range. The Black Mountains do not seem to be part of a significant path of ground-water flow from the Amargosa region. This is attributed to the complex lithology and geologic history of the Black Mountains structural block and to the presence of the intervening Furnace Creek fault zone. The only ground-water discharge associated with the Black Mountains where water chemistry reflects an external source or sources is Saratoga Spring, for which δ 2 H and δ 18 O data indicate recharge in the Spring Mountains to the east. The southern part of the Funeral Mountains transmits a large volume of water through faulted and fractured rocks of Cambrian age that lie at or along the distal part of the northeast -oriented Spotted Range-Mine Mountain structural zone. Waters discharging from springs in the Furnace Creek Ranch vicinity (Travertine and Nevares) both compositionally and isotopically resemble waters from the Ash Meadows spring group in the Amargosa Desert. The Ash Meadows springs and water in the Amargosa Valley alluvium likely are chemically representative of ground water entering the southern Funeral Mountains. Much less ground water flows through the central and northern Funeral Mountains than flows through the southern part, as indicated by the geologic setting and chemistry of Keane Wonder Spring. The northern one-half of the mountains comprises early-to-middle Proterozoic metamorphic rocks that are the core of the Funeral Mountains anticlinorium. The core is largely unfaulted, plunges to the northeast and southwest, and is truncated to some extent on the east by the shallow-dipping Boundary Canyon fault. This structural setting and the paucity of springs in the northern one-half of the Funeral Mountains indicate a long traveltime from the Amargosa region to the western margin of the northern and central parts of the mountains. The Grapevine Mountains include the highest elevations in the Amargosa Range. Substantial precipitation and recharge above about 2,000 meters are evinced by numerous small springs and seeps along the east and west margins. The local nature of the recharge is reflected in δ 2 H and δ 18 O values and in the spring chemistries that indicate control by Tertiary volcanic rocks. The highest spring discharges associated with the Grapevine Mountains are near the north end of the mountains in the Grapevine Ranch area. The springs in this area are similar chemically and isotopically, except for one or two order-of-magnitude differences in calcium, magnesium, and strontium concentrations and a 1.2 per mil difference in δ 13 C values. These differences can be attributed to differences in the distal parts of the respective flow paths. The springs also lie at the end of a northeast -oriented structural zone in the Walker Lane Belt, and their δ 2 H, δ 13 C, and δ 18 O values indicate a recharge area likely to the northeast, outside of the Grapevine Mountains.

California;Nevada↗

USGS2015

Darcy’s law predicts widespread forest mortality under climate warming

Drought and heat-induced tree mortality is accelerating in many forest biomes as a consequence of a warming climate, resulting in a threat to global forests unlike any in recorded history . Forests store the majority of terrestrial carbon, thus their loss may have significant and sustained impacts on the global carbon cycle . We use a hydraulic corollary to Darcy ’ s law, a core principle of vascular plant physiology , to predict characteristics of plants that will survive and die during drought under warmer future climates. Plants that are tall with isohydric stomatal regulation, low hydraulic conductance, and high leaf area are most likely to die from future drought stress. Thus, tall trees of old-growth forests are at the greatest risk of loss, which has ominous implications for terrestrial carbon storage. This application of Darcy ’ s law indicates today ’ s forests generally should be replaced by shorter and more xeric plants, owing to future warmer droughts and associated wildfires and pest attacks. The Darcy ’ s corollary also provides a simple, robust framework for informing forest management interventions needed to promote the survival of current forests. Given the robustness of Darcy ’ s law for predictions of vascular plant function, we conclude with high certainty that today ’ s forests are going to be subject to continued increases in mortality rates that will result in substantial reorganization of their structure and carbon storage.

Nature Climate Change↗

USGS2019

Controls on organic matter distributions in Eocene Lake Uinta, Utah and Colorado

The Green River Formation deposited in Eocene Lake Uinta in the Uinta and Piceance Basins, Utah and Colorado, contains the largest oil shale resource in the world with an estimated 1.53 trillion barrels of oil in-place in the Piceance Basin and 1.32 trillion barrels in the Uinta Basin. The Douglas Creek arch, a slowly subsiding hinge-line between the two basins, created separate deep depocenters with shallow water conditions near the crest of the arch. Lake Uinta was a saline lake throughout its history with a lower saline to hypersaline layer (monimolimnion) and an upper less saline layer (mixolimnion). Most of the organic matter in the Green River Formation was derived primarily from algae that lived in the photic zone of the lake and is very hydrogen-rich and oil-prone. In many modern large and deep lakes, rates of organic matter production are highly variable due to differences in nutrient supply. However, cyclonic circulation often leads to winnowing out organic and mineral matter in the mixolimnion leading to organic and fine-grained mineral matter being deposited in increasing amounts toward hydro-dynamically dead zones in the center of the circulation producing concentric bands of increasing organic matter content. Organic matter transport through the dense, hypersaline monimolimnion may have been facilitated by low density organic matter attaching to more dense clay mineral particles. Most of the oil shale intervals deposited in Lake Uinta display similar patterns in their organic matter distributions, increasing in very regular fashion toward the central areas of the lake’s two depocenters. This concentric feature is particularly prominent in the most laminated oil shale zones. Here, we propose that cyclonic circulation was present in Lake Uinta. Each basin appears to have had its own circulation currents, separated by shallow water conditions near the Douglas Creek arch, as well as one hydro-dynamically dead zone. Sediment gravity flow processes were also very active in some strata of Lake Uinta, leading to the reworking and redepositing of sediments. Two general types of sediment gravity flows are recognized: (1) organic-rich sediment gravity flows that reworked and may have concentrated organic-rich material closer to the two deep depocenters, and (2) sandstone and siltstone-rich organic-poor mass movement deposits that originated on marginal shelves. Mass movements could have been triggered by various natural processes and/or possibly by the movement of dense brines that evolved on marginal shelves and moved along the bottom of the water column toward the deep part of the lake. The uppermost, poorly consolidated sediment layer was incorporated in sediment gravity flows as they moved, and in many cases sediment gravity flows scoured down significantly into the more consolidated underlying sediment producing large rip-up clasts of laminated sediments. Truncation of more than 100 ft occurs at the base of a sequence of sediment gravity flows in one well, indicating a significant incised channel. Coarser-grained sediment gravity flows terminated before reaching the lake’s deepest areas, forming thick concentric buildups of organically-lean sediment near the base of the marginal slopes. Intervals dominated by organic-rich fine-grained sediment gravity flows have tightly concentric bands of increasing organic matter toward the deepest parts of the lake and can be organically richer than the richest laminated intervals. There is some evidence that the hydro-dynamically quiet zones did not always correspond closely to the deepest areas of the lake, extending in some cases into shallower areas.

Colorado, Utah↗

USGS2015

Beyond temperature: Clumped isotope signatures in dissolved inorganic carbon species and the influence of solution chemistry on carbonate mineral composition

“Clumped-isotope” thermometry is an emerging tool to probe the temperature history of surface and subsurface environments based on measurements of the proportion of 13 C and 18 O isotopes bound to each other within carbonate minerals in 13 C 18 O 16 O 2 2- groups (heavy isotope “clumps”). Although most clumped isotope geothermometry implicitly presumes carbonate crystals have attained lattice equilibrium (i.e., thermodynamic equilibrium for a mineral, which is independent of solution chemistry), several factors other than temperature, including dissolved inorganic carbon (DIC) speciation may influence mineral isotopic signatures. Therefore we used a combination of approaches to understand the potential influence of different variables on the clumped isotope (and oxygen isotope) composition of minerals. We conducted witherite precipitation experiments at a single temperature and at varied pH to empirically determine 13 C- 18 O bond ordering (Δ 47 ) and δ 18 O of CO 3 2- and HCO 3 - molecules at a 25 °C equilibrium. Ab initio cluster models based on density functional theory were used to predict equilibrium 13 C- 18 O bond abundances and δ 18 O of different DIC species and minerals as a function of temperature. Experiments and theory indicate Δ 47 and δ 18 O compositions of CO 3 2- and HCO 3- ions are significantly different from each other. Experiments constrain the Δ 47- δ 18 O slope for a pH effect (0.011 ± 0.001; 12 ⩾ pH ⩾ 7). Rapidly-growing temperate corals exhibit disequilibrium mineral isotopic signatures with a Δ 47- δ 18 O slope of 0.011 ± 0.003, consistent with a pH effect. Our theoretical calculations for carbonate minerals indicate equilibrium lattice calcite values for Δ 47 and δ 18 O are intermediate between HCO 3 − and CO 3 2− . We analyzed synthetic calcites grown at temperatures ranging from 0.5 to 50 °C with and without the enzyme carbonic anhydrase present. This enzyme catalyzes oxygen isotopic exchange between DIC species and is present in many natural systems. The two types of experiments yielded statistically indistinguishable results, and these measurements yield a calibration that overlaps with our theoretical predictions for calcite at equilibrium. The slow-growing Devils Hole calcite exhibits Δ 47 and δ 18 O values consistent with lattice equilibrium. Factors influencing DIC speciation (pH, salinity) and the timescale for DIC equilibration, as well as reactions at the mineral–solution interface, have the potential to influence clumped-isotope signatures and the δ 18 O of carbonate minerals. In fast-growing carbonate minerals, solution chemistry may be an important factor, particularly over extremes of pH and salinity. If a crystal grows too rapidly to reach an internal equilibrium (i.e., achieve the value for the temperature-dependent mineral lattice equilibrium), it may record the clumped-isotope signature of a DIC species (e.g., the temperature-dependent equilibrium of HCO 3 − ) or a mixture of DIC species, and hence record a disequilibrium mineral composition. For extremely slow-growing crystals, and for rapidly-grown samples grown at a pH where HCO 3 - dominates the DIC pool at equilibrium, effects of solution chemistry are likely to be relatively small or negligible. In summary, growth environment, solution chemistry, surface equilibria, and precipitation rate may all play a role in dictating whether a crystal achieves equilibrium or disequilibrium clumped-isotope signatures.

Geochimica et Cosmochimica Acta↗

USGS2007

Sedimentation History of Halfway Creek Marsh, Upper Mississippi River National Wildlife and Fish Refuge, Wisconsin, 1846-2006

The history of overbank sedimentation in the vicinity of Halfway Creek Marsh near La Crosse, Wis., was examined during 2005?06 by the U.S. Geological Survey and University of Wisconsin?Madison as part of a broader study of sediment and nutrient loadings to the Upper Mississippi River bottomlands by the U.S. Environmental Protection Agency, U.S. Fish and Wildlife Service, and U.S. Geological Survey. Historical sedimentation patterns and rates were interpreted from field-scale topographic surveys and sediment cores collected from the marsh and upstream flood plains. Historical maps and aerial photographs were used to establish the timing of disturbances and to document changes in channel patterns after Euro-American settlement (post 1846). Episodic overbank sedimentation patterns and rates were linked to watershed agricultural activity, large floods, artificial levee construction, channel alterations, and dam failures over the past 160 years. These forces affected sedimentation on and between levees, the development of alluvial fans and flood-plain splays, and the general pattern of flood-plain sedimentation through the upper and lower marsh. Historical overbank deposits, episodically deposited after about 1860, are as much as 6 feet thick in the upper marsh and as much as 4 feet thick in the lower marsh, representing a total volume of approximately 1.8 million cubic yards. These stratified deposits consist of multiple layers of silt and clay, very fine to fine sand, and some medium to very coarse sand. Coarse-grained deposits are associated with flood-plain splays caused by breaches in artificial levees during large floods. Estimated sedimentation rates were highest from 1919 to 1936 [26,890 cubic yards per year (yd3/yr)] and exceeded by about 30 times the 1846?85 rate of 920 yd3/yr and exceeded by 7 times the 1994?2006 rate of 3,740 yd3/yr. The 1994?2006 sedimentation rate was the lowest since Euro-American settlement, but natural levees along the 1994?2006 channel of Halfway Creek through the lower marsh continued to form and are currently (2006) about 1 foot higher than the surrounding marsh. Natural levee building in the lower marsh from 1994?2006 was accentuated by the lack of overbank sediment storage in the upper marsh. The historical storage of sediment in the upper and lower marsh affects modern streamflow and sediment transport processes of Halfway Creek and Sand Lake Coulee through the marsh, and it also affects marsh vegetation and wildlife habitat. Results from this investigation will help improve the understanding of how past overbank sedimentation patterns continue to influence modern and future water quality, sediment transport, nutrient loads, and water-related resources in riparian habitats common to the Upper Mississippi River National Wildlife and Fish Refuge.

Scientific Investigations Report↗

USGS1995

Forest-killing diffuse CO2 emission at Mammoth Mountain as a sign of magmatic unrest

Mammoth Mountain, in the western United States, is a large dacitic volcano with a long history of volcanism that began 200 kyr ago and produced phreatic eruptions as recently as 500 ± 200 yr BP. Seismicity, ground deformation and changes in fumarole gas composition suggested an episode of shallow dyke intrusion in 1989–90. Areas of dying forest and incidents of near asphyxia in confined spaces, first reported in 1990, prompted us to search for diffuse flank emissions of magmatic CO 2 , as have been described at Mount Etna and Vulcano . Here we report the results of a soil-gas survey, begun in 1994, that revealed CO 2 concentrations of 30–96% in a 30-hectare region of killed trees, from which we estimate a total CO 2 flux of ≥1,200 tonnes per day. The forest die-off is the most conspicuous surface manifestation of magmatic processes at Mammoth Mountain, which hosts only weak fumarolic vents and no summit activity. Although the onset of tree kill coincided with the episode of shallow dyke intrusion, the magnitude and duration of the CO 2 flux indicates that a larger, deeper magma source and/or a large reservoir of high-pressure gas is being tapped.

California↗

USGS1995

Radiocarbon evidence for extensive plate-boundary rupture about 300 years ago at the Cascadia subduction zone

The Cascadia subduction zone, a region of converging tectonic plates along the Pacific coast of North America, has a geological history of very large plate-boundary earthquakes1,2, but no such earthquakes have struck this region since Euro-American settlement about 150 years ago. Geophysical estimates of the moment magnitudes (Mw) of the largest such earthquakes range from 8 (ref. 3).to 91/2 (ref. 4). Radiocarbon dating of earthquake-killed vegetation can set upper bounds on earthquake size by constraining the length of plate boundary that ruptured in individual earthquakes. Such dating has shown that the most recent rupture, or series of ruptures, extended at least 55 km along the Washington coast within a period of a few decades about 300 years ago5. Here we report 85 new 14C ages, which suggest that this most recent rupture (or series) extended at least 900 km between southern British Columbia and northern California. By comparing the 14C ages with written records of the past 150 years, we conclude that a single magnitude 9 earthquake, or a series of lesser earthquakes, ruptured most of the length of the Cascadia subduction zone between the late 1600s and early 1800s, and probably in the early 1700s.

California, Oregon, Washington↗

USGS2009

Modelling predation by transient leopard seals for an ecosystem-based management of Southern Ocean fisheries

Correctly quantifying the impacts of rare apex marine predators is essential to ecosystem-based approaches to fisheries management, where harvesting must be sustainable for targeted species and their dependent predators. This requires modelling the uncertainty in such processes as predator life history, seasonal abundance and movement, size-based predation, energetic requirements, and prey vulnerability. We combined these uncertainties to evaluate the predatory impact of transient leopard seals on a community of mesopredators (seals and penguins) and their prey at South Georgia, and assess the implications for an ecosystem-based management. The mesopredators are highly dependent on Antarctic krill and icefish, which are targeted by regional fisheries. We used a state-space formulation to combine (1) a mark-recapture open-population model and individual identification data to assess seasonally variable leopard seal arrival and departure dates, numbers, and residency times; (2) a size-based bioenergetic model; and (3) a size-based prey choice model from a diet analysis. Our models indicated that prey choice and consumption reflected seasonal changes in leopard seal population size and structure, size-selective predation and prey vulnerability. A population of 104 (90-125) leopard seals, of which 64% were juveniles, consumed less than 2% of the Antarctic fur seal pup production of the area (50% of total ingested energy, IE), but ca. 12-16% of the local gentoo penguin population (20% IE). Antarctic krill (28% IE) were the only observed food of leopard seal pups and supplemented the diet of older individuals. Direct impacts on krill and fish were negligible, but the "escapement" due to leopard seal predation on fur seal pups and penguins could be significant for the mackerel icefish fishery at South Georgia. These results suggest that: (1) rare apex predators like leopard seals may control, and may depend on, populations of mesopredators dependent on prey species targeted by fisheries; and (2) predatory impacts and community control may vary throughout the predator's geographic range, and differ across ecosystems and management areas, depending on the seasonal abundance of the prey and the predator's dispersal movements. This understanding is important to integrate the predator needs as natural mortality of its prey in models to set prey catch limits for fisheries. Reliable estimates of the variability of these needs are essential for a precautionary interpretation in the context of an ecosystem-based management. ?? 2009 Elsevier B.V.

Ecological Modelling↗

USGS1972

Clay deposits of the Connecticut River Valley, Connecticut: a special problem in land management

When man first settled the United States, two natural features favored settlement; flat land that was easy to build on and to farm, and a nearby river that could act as a source of water, transportation, and power. The Connecticut River Valley from Middletown, Ct. north past the Connecticut-Massachusetts state line satisfied these two needs, and was favored by many early Americans in New England. This area remains an area of rapid urbanization, partly because of the broad flat lowlands. The subdued topography of this area is due in large part to deposition of fine-grained materials into glacial Lake Hitchcock. This lake was formed during the Wisconsinan age when southward drainage in the Triassic valley of Connecticut was dammed by glacial drift in the area of Rocky Hill, Connecticut. Lake Hitchcock grew to and beyond St. Johnsbury, Vt. with much of the lake being filled with cyclical lake-bottom deposits during the 2,290 to 2,350 years of its life. Aside from the relative flatness inherent in the deposition of fine-grained lake-bottom deposits, these deposits present very few characteristics that are favorable for urbanization. Favorable characteristics are possible sources of clay for manufacturing and possible sources for waste storage sites. Unfavorable characteristics include low water yields resulting in poor urban water-supply sources, and very low flows in streams during dry periods; low percolation rates resulting In drainage and septic problems; and low or uneven bearing strength which create problems in construction. Fine-grained lake-bottom deposits have been mapped for six quadrangles in the Connecticut Valley lowlands; the quadrangles of Windsor Locks, Broad Brook, Hartford North, Manchester, Hartford South, and Glastonbury (all located in Connecticut). All the maps were prepared from existing information including well and test hole data on file at the Water Resources Division in Hartford, surficial geologic quadrangle maps, and bedrock contour maps. The maps also reflect geologic interpretations of the history of glacial Lake Hitchcock. The Hartford North maps were prepared as test maps to determine if the project was feasible. They were prepared using the previously described information plus additional subsurface data obtained from engineering firms and the State Highway Department. During preparation of the maps, an arcuate-shaped, ice-contact deposit composed of coarse sand and gravel was delineated in the Broad Brook and Windsor Locks quadrangles. This feature marks the location of a zone of stagnant ice In front of and marginal to active ice to the north. Two types of maps were prepared for the area in study; Thickness of the Principal Clay Deposit, and Thickness of Material Overlying the Principal Clay Deposit. The term "principal clay deposit" refers to the fine-grained lake-bottom deposits of Glacial Lake Hitchcock. These maps define the distribution of the deposit, and show the thickness of the deposit in 50 foot intervals and the thickness of the material overlying the deposit In 20 foot intervals. The maps indicate that much of the area is underlain with substantial thicknesses of finegrained lake-bottom deposits (50 feet thick or greater), and that much of the deposit is within 20 feet of the surface. The maps included in this report can be used for land-use planning. Uses include location of favorable sites for specific uses such as landfills, utility corridors, heavy construction, etc; location of problem areas for specific land uses; identification of possible problems for specific areas; design and construction cost estimates; and prospecting for exploitable clay deposits. It Is suggested that, for effective planning, these maps be used together or in conjunction with other maps such as maps showing surface materials, depth to bedrock, depth to water table, and flood prone areas.

Connecticut↗

USGS2004

Status of sea otter populations in southcentral and southeast Alaska, 2002-2003

During the years 2002-2004 estimated sea otter population sizes were calculated for Southeast Alaska, Prince William Sound, and the Kenai Peninsula and Cook Inlet regions of Alaska. Aerial surveys were conducted by a single observer from a float-equipped Bellanca Scout fixed-wing aircraft flying at 91 m altitude and 65 mph. The surveys followed protocols written by Bodkin and Udevitz (1999). The survey design consisted of systematic sampling of 400 m wide transects that were uniformly placed throughout the survey area. Selection and sampling of transects was proportional to expected sea otter abundance, with most effort taking place in transects over waters 0-40 m in depth. Intensive searches were periodically conducted within transects to estimate the proportion of sea otters not detected on strips. To obtain an adjusted population size estimate, strip counts are adjusted for the area not surveyed and by a correction factor.

Alaska↗

USGS1999

Data set incongruence and correlated character evolution: An example of functional convergence in the hind-limbs of stifftail diving ducks

The unwitting inclusion of convergent characters in phylogenetic estimates poses a serious problem for efforts to recover phylogeny. Convergence is not inscrutable, however, particularly when one group of characters tracks phylogeny and another set tracks adaptive history. In such cases, convergent characters may be correlated with one or a few functional anatomical units and readily identifiable by using comparative methods. Stifftail ducks (Oxyurinae) offer one such opportunity to study correlated character evolution and function in the context of phylogenetic reconstruction. Morphological analyses place stifftail ducks as part of a large clade of diving ducks that includes the sea ducks (Mergini), Hymenolaimus, Merganetta , and Tachyeres , and possibly the pochards (Aythyini). Molecular analyses, on the other hand, place stifftails far from other diving ducks and suggest, moreover, that stifftails are polyphyletic. Mitochondrial cytochrome b gene sequences of eight stifftail species traditionally supposed to form a clade were compared with each other and with sequences from 50 other anseriform and galliform species. Stifftail ducks are not the sister group of sea ducks but lie outside the typical ducks (Anatinae). Of the four traditional stifftail genera, monophyly of Oxyura and its sister group relationship with Nomonyx are strongly supported. Heteronetta probably is the sister group of that clade, but support is weak. Biziura is not a true stifftail. Within Oxyura , Old World species ( O. australis, O. leucocephala, O. maccoa ) appear to form a clade, with New World species ( O. jamaicensis, O. vittata ) branching basally. Incongruence between molecules and morphology is interpreted to be the result of adaptive specialization and functional convergence in the hind limbs of Biziura and true stifftails. When morphological characters are divided into classes, only hind-limb characters are significantly in conflict with the molecular tree. Likewise, null models of synonymous and nonsynonymous substitution based on patterns of codon-degeneracy and chemical dissimilarity indicate that the nucleotide and amino acid changes postulated by the molecular tree are more plausible than those postulated by the morphological tree. These findings teach general lessons about the utility of highly adaptive characters (in particular those related to foraging ecology) and underscore the problems that convergence can pose for attempts to recover phylogeny. They also demonstrate how the concept of natural data partitions and simple models of evolution (e.g., parsimony, likelihood, neutrality) can be used to test the accuracy of independent phylogenetic estimates and provide arguments in favor of one tree topology over another.

Systematic Biology↗

USGS2002

A reconnaissance method for delineation of tracts for regional-scale mineral-resource assessment based on geologic-map data

The U.S. Geological Survey (USGS) is proposing to conduct a global mineral-resource assessment using geologic maps, significant deposits, and exploration history as minimal data requirements. Using a geologic map and locations of significant pluton-related deposits, the pluton-related-deposit tract maps from the USGS national mineral-resource assessment have been reproduced with GIS-based analysis and modeling techniques. Agreement, kappa, and Jaccard's C correlation statistics between the expert USGS and calculated tract maps of 87%, 40%, and 28%, respectively, have been achieved using a combination of weights-of-evidence and weighted logistic regression methods. Between the experts' and calculated maps, the ranking of states measured by total permissive area correlates at 84%. The disagreement between the experts and calculated results can be explained primarily by tracts defined by geophysical evidence not considered in the calculations, generalization of tracts by the experts, differences in map scales, and the experts' inclusion of large tracts that are arguably not permissive. This analysis shows that tracts for regional mineral-resource assessment approximating those delineated by USGS experts can be calculated using weights of evidence and weighted logistic regression, a geologic map, and the location of significant deposits. Weights of evidence and weighted logistic regression applied to a global geologic map could provide quickly a useful reconnaissance definition of tracts for mineral assessment that is tied to the data and is reproducible.

Natural Resources Research↗

USGS1995

Volcanic and structural evolution of Taupo Volcanic Zone, New Zealand: A review

The Taupo Volcanic Zone (TVZ) in the central North Island is the main focus of young volcanism in New Zealand. Andesitic activity started at c. 2 Ma, joined by voluminous rhyolitic (plus minor basaltic and dacitic) activity from c. 1.6 Ma. The TVZ is c. 300 km long (200 km on land) and up to 60 km wide, as defined by vent positions and caldera structural boundaries. The total volume of TVZ volcanic deposits is uncertain because a sub-volcanic basement has not been identified, but present data suggest bulk volumes of 15–20,000 km 3 , and that faulted metasediments form most of the immediate subvolcanic basement. Rhyolite (≥15,000 km 3 bulk volume, typically 70–77% SiO 2 ) is the dominant magma erupted in the TVZ (mostly as calderaforming ignimbrite eruptions), andesite is an order of magnitude less abundant, and basalt and dacite are minor in volume (< 100 km 3 each). The history of the TVZ is here divided into ‘old TVZ’ from 2.0 Ma to 0.34 Ma, and ‘young TVZ’ from 0.34 Ma onwards, separated by the Whakamaru eruptions, which obscured much of the evidence for older activity within the zone. The TVZ shows a pronounced segmentation into northeastern and southwestern andesite-dominated extremities with composite cones and no calderas, and a central 125-km-long rhyolite-dominated segment. Eight rhyolitic caldera centres have so far been identified in the central segment, of which two (Mangakino and Kapenga) are composite features, and more centres will probably be delineated as further data accumulate. These centres account for 34 inferred caldera-forming ignimbrite eruptions, in the c. 1.6-Ma lifetime of the central TVZ. The modern central TVZ is the most frequently active and productive silicic volcanic system on Earth, erupting rhyolite at c. 0.28 m 3 s −1 , and available information suggests this has been so for at least the past 0.34 Ma. The rhyolites show no major compositional changes with time, though the extent of magma chamber zonation may have changed with the incoming of rifting and crustal extension in the past c. 0.9 Ma. Within the central TVZ, non-rhyolitic compositions have been erupted apparently irregularly in time and space; in particular there is no evidence for a geographic separation of basalts from andesites. Between 0.9 and 0.34 Ma, a major episode of uplift affected areas around the TVZ, while at the same time the main focus of activity may have migrated eastwards within the TVZ accompanying rifting along the axis of the zone. The modern TVZ is rifting at rates between 7 and 18 mm a −1 and restoration of the thin (15km) ‘crust’ ( V p ≤ 6.1 km s −1 ) beneath the central TVZ to its pre-rifting thickness (25 km) implies that rifting at such rates may have begun only at c. 0.9 Ma. The TVZ is a rifted arc, but its longitudinally segmented nature, high thermal flux and voluminous rhyolitic volcanism make it unique on Earth.

Taupo Volcanic Field↗

USGS2016

Introduction to the special issue on the 25 April 2015 Mw 7.8 Gorkha(Nepal) earthquake

On April 25, 2015, a moment magnitude (M w ) 7.8 earthquake struck central Nepal, breaking a section of the broader Himalayan Front that had been largely quiescent in moderate-to-large earthquakes for much of the modern seismological era. Ground shaking associated with the event resulted in a broad distribution of triggered avalanches and landslides. The ensuing aftershock sequence was punctuated by a Mw 7.3 event 17 days after the mainshock. The combined effects of these earthquakes and secondary hazards have led to the Gorkha earthquake becoming the worst natural disaster in Nepal since the 1934 Nepal-Bihar earthquake, causing close to 9000 deaths and severely injuring over 21,000 people ( OCHA, 2015 ). Despite the devastating effects of this earthquake, the convergent margin that hosted it is thought to be capable of much larger ruptures—perhaps as large as Mw 9 ( Feldl and Bilham, 2006 ). The 2015 Gorkha rupture lies just to the west of the 1934 M 8.0–8.4 event ( Sapkota et al., 2013; Bollinger et al., 2014 ). Unlike the 1934 event, which has been documented in paleoseismic trenches along the Himalayan Front (e.g., Sapkota et al., 2013 ), and other large ruptures along the arc (e.g., Lavé et al., 2005; Kumar et al., 2006 ), the 2015 event did not rupture to the surface (e.g., Galetzka et al., 2015 ). As a result, some researchers have suggested that the Gorkha earthquake was not as large, or as damaging, as might have been expected based on our (albeit limited) understanding of historic earthquakes, seismic hazard and risk (e.g., Bilham, 2015; Hough, 2015 ). Important questions surrounding the earthquake and its regional setting thus arise. What were the detailed characteristics of the rupture and the aftershock sequence, and what is the relationship between mainshock slip and subsequent seismicity? Why did this event not rupture to the surface? Was damage less than should have been expected; and if so, why? What role did path effects, such as basin amplification, play? Do details of the earthquake sequence allow us to better understand regional seismotectonics, and in turn, future risk? Discussion of these and other issues has been ongoing since the earthquake; a large body of literature already exists that characterizes details of the earthquake sequence and its effects. This special issue attempts to gather a wide variety of detailed studies that wholly characterize this event to a degree that has not yet been possible. The studies herein provide an improved understanding of the Gorkha earthquake, its impact on the region, and its place in the broader seismotectonic history of the Himalayan Front.

Gorkha↗

USGS2013

Amphibians and reptiles of Guyana, South America: illustrated keys, annotated species accounts, and a biogeographic synopsis

Guyana has a very distinctive herpetofauna. In this first ever detailed modern accounting, based on voucher specimens, we document the presence of 324 species of amphibians and reptiles in the country; 148 amphibians, 176 reptiles. Of these, we present species accounts for 317 species and color photographs of about 62% (Plates 1–40). At the rate that new species are being described and distributional records are being found for the first time, we suspect that at least 350 species will be documented in a few decades. The diverse herpetofauna includes 137 species of frogs and toads, 11 caecilians, 4 crocodylians, 4 amphisbaenians, 56 lizards, 97 snakes, and 15 turtles. Endemic species, which occur nowhere else in the world, comprise 15% of the herpetofauna. Most of the endemics are amphibians, comprising 27% of the amphibian fauna. Type localities (where the type specimens or scientific name-bearers of species were found) are located within Guyana for 24% of the herpetofauna, or 36% of the amphibians. This diverse fauna results from the geographic position of Guyana on the Guiana Shield and the isolated highlands or tepuis of the eastern part of the Pantepui Region, which are surrounded by lowland rainforest and savannas. Consequently, there is a mixture of local endemic species and widespread species characteristic of Amazonia and the Guianan Region. Although the size of this volume may mislead some people into thinking that a lot is known about the fauna of Guyana, the work has just begun. Many of the species are known from fewer than five individuals in scientific collections; for many the life history, distribution, ecology, and behavior remain poorly known; few resources in the country are devoted to developing such knowledge; and as far as we are aware, no other group of animals in the fauna of Guyana has been summarized in a volume such as this to document the biological resources. We briefly discuss aspects of biogeography, as reflected in samples collected at seven lowland sites (in rainforest, savanna, and mixed habitats below 500 m elevation) and three isolated highland sites (in montane forest and evergreen high-tepui forest above 1400 m elevation). Comparisons of these sites are preliminary because sampling of the local faunas remains incomplete. Nevertheless, it is certain that areas of about 2.5 km2 of lowland rainforest can support more than 130 species of amphibians and reptiles (perhaps actually more than 150), while many fewer species (fewer than 30 documented so far) occur in a comparable area of isolated highlands, where low temperatures, frequent cloudiness, and poor soils are relatively unfavorable for amphibians and reptiles. Furthermore, insufficient study has been done in upland sites of intermediate elevations, where lowland and highland faunas overlap significantly, although considerable work is being accomplished in Kaieteur National Park by other investigators. Comparisons of the faunas of the lowland and isolated highland sites showed that very few species occur in common in both the lowlands and isolated highlands; that those few are widespread lowland species that tolerate highland environments; that many endemic species (mostly amphibians) occur in the isolated highlands of the Pakaraima Mountains; and that each of the isolated highlands, lowland savannas, and lowland rainforests at these 10 sites have distinctive faunal elements. No two sites were identical in species composition. Much more work is needed to compare a variety of sites, and especially to incorporate upland sites of intermediate elevations in such comparisons. Five species of sea turtles utilize the limited areas of Atlantic coastal beaches to the northwest of Georgetown. All of these are listed by the International Union for the Conservation of Nature as being of global concern for long-term survival, mostly owing to human predation. The categories of Critically Endangered or Endangered are applied to four of the local sea turtles (80%). It is important to protect the few good nesting beaches for the sea turtles of Guyana. We have documented each of the species now known to comprise the herpetofauna of Guyana by citing specimens that exist in scientific collections, many of which were collected and identified by us and colleagues, including students of the University of Guyana (UG). We also re-identified many old museum specimens collected by others in the past (e.g., collections of William Beebe) and we used documented publications and collection records of colleagues, most of whom have been working more recently. We present dichotomous keys for identifying representatives of the species known to occur in Guyana, and we present brief annotated species accounts. The accounts provide the current scientific name, original name (with citation of the original description, which we personally examined in the literature), some outdated names used in the recent past, type specimens, type localities, general geographic distribution, examples of voucher specimens from Guyana, coloration in life (and often a color photograph), and comments pointing out interesting subjects for future research.

Proceedings of the Biological Society of Washingto↗

USGS2009

Optical satellite data volcano monitoring: a multi-sensor rapid response system

In this chapter, the use of satellite remote sensing to monitor active geological processes is described. Specifically, threats posed by volcanic eruptions are briefly outlined, and essential monitoring requirements are discussed. As an application example, a collaborative, multi-agency operational volcano monitoring system in the north Pacific is highlighted with a focus on the 2007 eruption of Kliuchevskoi volcano, Russia. The data from this system have been used since 2004 to detect the onset of volcanic activity, support the emergency response to large eruptions, and assess the volcanic products produced following the eruption. The overall utility of such integrative assessments is also summarized. The work described in this chapter was originally funded through two National Aeronautics and Space Administration (NASA) Earth System Science research grants that focused on the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument. A skilled team of volcanologists, geologists, satellite tasking experts, satellite ground system experts, system engineers and software developers collaborated to accomplish the objectives. The first project, Automation of the ASTER Emergency Data Acquisition Protocol for Scientific Analysis, Disaster Monitoring, and Preparedness , established the original collaborative research and monitoring program between the University of Pittsburgh (UP), the Alaska Volcano Observatory (AVO), the NASA Land Processes Distributed Active Archive Center (LP DAAC) at the U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center, and affiliates on the ASTER Science Team at the Jet Propulsion Laboratory (JPL) as well as associates at the Earth Remote Sensing Data Analysis Center (ERSDAC) in Japan. This grant, completed in 2008, also allowed for detailed volcanic analyses and data validation during three separate summer field campaigns to Kamchatka Russia. The second project, Expansion and synergistic use of the ASTER Urgent Request Protocol (URP) for natural disaster monitoring and scientific analysis , has expanded the project to other volcanoes around the world and is in progress through 2011. The focus on ASTER data is due to the suitability of the sensor for natural disaster monitoring and the availability of data. The instrument has several unique facets that make it especially attractive for volcanic observations (Ramsey and Dehn, 2004). Specifically, ASTER routinely collects data at night, it has the ability to generate digital elevation models using stereo imaging, it can collect data in various gain states to minimize data saturation, it has a cross-track pointing capability for faster targeting, and it collects data up to ±85° latitude for better global coverage. As with any optical imaging-based remote sensing, the viewing conditions can negatively impact the data quality. This impact varies across the optical and thermal infrared wavelengths as well as being a function of the specific atmospheric window within a given wavelength region. Water vapor and cloud formation can obscure surface data in the visible and near infrared (VNIR)/shortwave infrared (SWIR) region due mainly to non-selective scattering of the incident photons. In the longer wavelengths of the thermal infrared (TIR), scattering is less of an issue, but heavy cloud cover can still obscure the ground due to atmospheric absorption. Thin clouds can be optically-transparent in the VNIR and TIR regions, but can cause errors in the extracted surface reflectance or derived surface temperatures. In regions prone to heavy cloud cover, optical remote sensing can be improved through increased temporal resolution. As more images are acquired in a given time period the chances of a clear image improve dramatically. The Advanced Very High Resolution Radiometer (AVHRR) routine monitoring, which commonly collects 4-6 images per day of any north Pacific volcano, takes advantage of this fact. The rapid response program described in this chapter also improves the temporal resolution of the ASTER instrument. ASTER has been acquiring images of volcanic eruptions since soon after its launch in December 1999. An early example included the observations of the large pyroclastic flow deposit emplaced at Bezymianny volcano in Kamchatka, Russia. The first images in March 2000, just weeks after the eruption, revealed the extent, composition, and cooling history of this large deposit and of the active lava dome (Ramsey and Dehn, 2004). The initial results from these early datasets spurred interest in using ASTER data for expanded volcano monitoring in the north Pacific. It also gave rise to the multi-year NASA-funded programs of rapid response scheduling and imaging throughout the Aleutian, Kamchatka and Kurile arcs. Since the formal establishment of the programs, the data have provided detailed descriptions of the eruptions of Augustine, Bezymianny, Kliuchevskoi and Sheveluch volcanoes over the past nine years (Wessels et al., in press; Carter et al., 2007, 2008; Ramsey et al., 2008; Rose and Ramsey, 2009). The initial research focus of this rapid response program was specifically on automating the ASTER sensor’s ability for targeted observational scheduling using the expedited data system. This urgent request protocol is one of the unique characteristics of ASTER. It provides a limited number of emergency observations, typically at a much-improved temporal resolution and quicker turnaround with data processing in the United States rather than in Japan. This can speed the reception of the processed data by several days to a week. The ongoing multi-agency research and operational collaboration has been highly successful. AVO serves as the primary source for status information on volcanic activity, working closely with the National Weather Service (NWS), Federal Aviation Administration (FAA), military and other state and federal emergency services. Collaboration with the Russian Institute of Volcanology and Seismology (IVS)/Kamchatka Volcanic Eruption Response Team (KVERT) is also maintained. Once a volcano is identified as having increased thermal output, ASTER is automatically tasked and the volcano is targeted at the next available opportunity. After the data are acquired, scientists at all the agencies have access to the images, with the primary science analysis carried out at the University of Pittsburgh and AVO. Results are disseminated to the responsible monitoring agencies and the global community through e-mail mailing lists.

Book chapter↗