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At least 361 records · Page 20Linked to original sources
USGS2024

A new database of giant impacts over a wide range of masses and with material strength: A first analysis of outcomes

In the late stage of terrestrial planet formation, planets are predicted to undergo pairwise collisions known as giant impacts. Here, we present a high-resolution database of giant impacts for differentiated colliding bodies of iron–silicate composition, with target masses ranging from 1 × 10 −4 M ⊕ up to super-Earths (5 M ⊕ ). We vary the impactor-to-target mass ratio, core–mantle (iron–silicate) fraction, impact velocity, and impact angle. Strength in the form of friction is included in all simulations. We find that, due to strength, the collisions with bodies smaller than about 2 × 10 −3 M ⊕ can result in irregular shapes, compound-core structures, and captured binaries. We observe that the characteristic escaping velocity of smaller remnants (debris) is approximately half of the impact velocity, significantly faster than currently assumed in N -body simulations of planet formation. Incorporating these results in N -body planet formation studies would provide more realistic debris–debris and debris–planet interactions.

The Planetary Science Journal↗
USGS2016

Algorithms used in the Airborne Lidar Processing System (ALPS)

The Airborne Lidar Processing System (ALPS) analyzes Experimental Advanced Airborne Research Lidar (EAARL) data—digitized laser-return waveforms, position, and attitude data—to derive point clouds of target surfaces. A full-waveform airborne lidar system, the EAARL seamlessly and simultaneously collects mixed environment data, including submerged, sub-aerial bare earth, and vegetation-covered topographies. ALPS uses three waveform target-detection algorithms to determine target positions within a given waveform: centroid analysis, leading edge detection, and bottom detection using water-column backscatter modeling. The centroid analysis algorithm detects opaque hard surfaces. The leading edge algorithm detects topography beneath vegetation and shallow, submerged topography. The bottom detection algorithm uses water-column backscatter modeling for deeper submerged topography in turbid water. The report describes slant range calculations and explains how ALPS uses laser range and orientation measurements to project measurement points into the Universal Transverse Mercator coordinate system. Parameters used for coordinate transformations in ALPS are described, as are Interactive Data Language-based methods for gridding EAARL point cloud data to derive digital elevation models. Noise reduction in point clouds through use of a random consensus filter is explained, and detailed pseudocode, mathematical equations, and Yorick source code accompany the report.

Open-File Report↗
USGS1995

Hydrological and thermal response of lakes to climate: Description and modeling

Lake systems continually respond to climatic conditions that vary over broad scales of space and time. The spatial distribution of lakes on the Earth’s surface is indicative of long-term patterns of atmospheric circulation, and the annual cycle of climate over lake basins is reflected in seasonal change in the size and temperature of lakes. Lake size is determined by the balance of water inputs and outputs, and lake temperature is governed by the balance of heat inputs and outputs. The lake hydrological and energy balances are coupled to the atmosphere. In response to the inputs of mass, energy, and momentum (precipitation, radiation, and wind stress), lakes return heat and moisture to the atmosphere through conduction and evaporation. Global, regional, or local change in the hydrological or thermal states of lakes thus represent interactive responses to climatic variation in the supply of water and energy.

Book chapter↗
USGS2024

Oil and gas development influences potential for dust emission from the Upper Colorado River Basin, USA

Wind erosion and dust emission from drylands have large consequences for ecosystem function and human health. Wind erosion is naturally reduced by soil crusting and sheltering by non-erodible roughness elements such as plants. Land uses that reduce surface roughness and disturb the soil surface can dramatically increase dust emission. Extraction of oil and gas is a common and growing land use in the western United States (US) that removes vegetation and other roughness elements for construction of well pads and unpaved access roads, resulting in thousands of small (1–4 ha), discrete patches of unprotected soil. Here, we use a satellite albedo-based model to assess the effect of oil/gas activity on surface roughness in the Uinta-Piceance Basin, an area of the Upper Colorado River Basin (UCRB) with dense oil and natural gas development and modelled how the change in surface roughness could impact aeolian sediment flux and dust emission. We also investigated how regional drought influences the response of surface roughness to well pads and access roads. Oil/gas activity reduced surface roughness and increased modelled aeolian sediment flux at the landscape scale across much of the study region, resulting in a modest increase of 10 139 kg of dust per year, which is small relative to dust loads from a single regional dust event observed in the region, but downwind impact could be significant. The magnitude of surface roughness reductions by oil/gas activity was generally consistent among land cover types. However, in parts of the basin that had high cover of annual forbs and grasses, oil/gas activity was associated with larger surface roughness and smaller potential dust emission. Drought decreased surface roughness across disturbed and undisturbed sites, but there was no interactive effect of oil/gas activity and drought on surface roughness. These results suggest that oil/gas activity may increase sediment fluxes and likely contributes to dust emission from landscapes in the UCRB. Understanding how drought and land use change contribute to dust emissions will benefit mitigation of undesirable impacts of wind erosion and dust transport.

Colorado, Utah↗
USGS2026

ENSO and PDO drive shoreline position anomalies in the U.S. Pacific Northwest

Sandy beaches act as buffers against various coastal hazards but are vulnerable to episodic (seasonal) and chronic (interannual) erosion. Understanding the variation of shoreline position, a key metric in coastal morphology, over a spectrum of time scales is therefore crucial in assessing hazard vulnerability. Long-standing research has investigated the role of El Niño-Southern Oscillation (ENSO), the dominant mode of climate variability in the Pacific Basin, in seasonal shoreline variability. Yet, ENSO’s chronic influence—and that of another Pacific climate mode, the Pacific Decadal Oscillation (PDO)—on shoreline anomalies remains poorly understood. Here, we examine the variability of sandy beaches in the US Pacific Northwest, a ∼750 km long coastal region on the US West Coast. We leverage 40 years (1984–2024) of shoreline data from publicly available Earth-observing (Landsat) satellite imagery at a high spatial resolution (>10,000 shore-normal transects at 50-m alongshore spacing) and employ Convergent Cross Mapping (CCM), a methodology for inferring causality in dynamical systems. We discover that strong El Niño years are signified by erosion (75.1% of transects), and strong La Niña years exhibit accretional behavior (73.4% of transects). Furthermore, we establish, for the first time, that both ENSO and PDO exert a statistically significant control on interannual shoreline variability, particularly on the alongshore component (in 95 and 100% of littoral cells, respectively), with water level fluctuations playing a critical role. This effort advances our understanding of the seasonal-to-interannual interactions between Pacific Basin climate variability and the PNW’s coastal morphodynamics, with implications for sediment management and coastal adaptation.

California, Oregon, Washington↗
USGS2023

Editorial: Remote sensing of volcanic gas emissions from the ground, air, and space

When magma rises in volcanic systems, volatile species exsolve from the melt and are outgassed to the atmosphere. The melt composition and temperature, depth at which degassing occurs, extent of gas-water-rock interactions, and volume of ascending magma are all factors that determine the composition and rate of gas emissions at the surface. Interpreted in a petrological framework, gas measurements thus provide information on these fundamental parameters of volcanic systems. Volcanic gases have traditionally been sampled in the field and later analyzed with standard laboratory methods, but remote sensing measurements are playing an increasingly central role in characterizing emissions and the volcanoes from which they originate. The 17 contributions in this Research Topic summarize the state-of-the-art in volcanic gas remote sensing and identify key areas in which the field could further improve our understanding of global volcanism and its impact on Earth’s environment in the next decade.

Frontiers in Earth Science↗
USGS2026

USGS Geochron Database

Introduction Geochronology helps us understand Earth’s history by determining when important events, like volcanic eruptions, the rise of mountains, the formation of mineral resources, and changes in the landscape, happened. Geochronological data directly support geologic mapping and can inform decisions about geologic hazard mitigation, natural resource management, and infrastructure resilience. The U.S. Geological Survey (USGS) Geochron database provides access to more than 300,000 published, publicly available age measurements from more than 40,000 geological samples. This database is the result of a collaborative effort with State geological surveys and geoscientists from across the globe. The USGS Geochron database is the most comprehensive collection of geochronological data available for the United States. Users can view data through an interactive map explorer, download datasets, and integrate data into geospatial software or other analysis tools.

Fact Sheet↗
USGS2016

A multi-decade record of high-quality fCO2 data in version 3 of the Surface Ocean CO2 Atlas (SOCAT)

The Surface Ocean CO 2 Atlas (SOCAT) is a synthesis of quality-controlled f CO 2 (fugacity of carbon dioxide) values for the global surface oceans and coastal seas with regular updates. Version 3 of SOCAT has 14.7 million f CO 2 values from 3646 data sets covering the years 1957 to 2014. This latest version has an additional 4.6 million f CO 2 values relative to version 2 and extends the record from 2011 to 2014. Version 3 also significantly increases the data availability for 2005 to 2013. SOCAT has an average of approximately 1.2 million surface water f CO 2 values per year for the years 2006 to 2012. Quality and documentation of the data has improved. A new feature is the data set quality control (QC) flag of E for data from alternative sensors and platforms. The accuracy of surface water f CO 2 has been defined for all data set QC flags. Automated range checking has been carried out for all data sets during their upload into SOCAT. The upgrade of the interactive Data Set Viewer (previously known as the Cruise Data Viewer) allows better interrogation of the SOCAT data collection and rapid creation of high-quality figures for scientific presentations. Automated data upload has been launched for version 4 and will enable more frequent SOCAT releases in the future. High-profile scientific applications of SOCAT include quantification of the ocean sink for atmospheric carbon dioxide and its long-term variation, detection of ocean acidification, as well as evaluation of coupled-climate and ocean-only biogeochemical models. Users of SOCAT data products are urged to acknowledge the contribution of data providers, as stated in the SOCAT Fair Data Use Statement. This ESSD (Earth System Science Data) “living data” publication documents the methods and data sets used for the assembly of this new version of the SOCAT data collection and compares these with those used for earlier versions of the data collection (Pfeil et al., 2013; Sabine et al., 2013; Bakker et al., 2014).

Earth System Science Data↗
USGS2012

Assessment of boreal forest historical C dynamics in the Yukon River Basin: relative roles of warming and fire regime change

Carbon (C) dynamics of boreal forest ecosystems have substantial implications for efforts to mitigate the rise of atmospheric CO 2 and may be substantially influenced by warming and changing wildfire regimes. In this study we applied a large-scale ecosystem model that included dynamics of organic soil horizons and soil organic matter characteristics of multiple pools to assess forest C stock changes of the Yukon River Basin (YRB) in Alaska, USA, and Canada from 1960 through 2006, a period characterized by substantial climate warming and increases in wildfire. The model was calibrated for major forests with data from long-term research sites and evaluated using a forest inventory database. The regional assessment indicates that forest vegetation C storage increased by 46 Tg C, but that total soil C storage did not change appreciably during this period. However, further analysis suggests that C has been continuously lost from the mineral soil horizon since warming began in the 1970s, but has increased in the amorphous organic soil horizon. Based on a factorial experiment, soil C stocks would have increased by 158 Tg C if the YRB had not undergone warming and changes in fire regime. The analysis also identified that warming and changes in fire regime were approximately equivalent in their effects on soil C storage, and interactions between these two suggests that the loss of organic horizon thickness associated with increases in wildfire made deeper soil C stocks more vulnerable to loss via decomposition. Subbasin analyses indicate that C stock changes were primarily sensitive to the fraction of burned forest area within each subbasin and that boreal forest ecosystems in the YRB are currently transitioning from being sinks to sources at ∼0.7% annual area burned. We conclude that it is important for international mitigation efforts focused on controlling atmospheric CO 2 to consider how climate warming and changes in fire regime may concurrently affect the CO 2 sink strength of boreal forests. It is also important for large-scale biogeochemical and earth system models to include organic soil dynamics in applications to assess regional C dynamics of boreal forests responding to warming and changes in fire regime.

Ecological Applications↗
USGS2017

Best practices for virtual participation in meetings: Experiences from synthesis centers

The earth environment is a complex system, in which collaborative scientific approaches can provide major benefits by bringing together diverse perspectives, methods, and data, to achieve robust, synthetic understanding (Fig. 1). Face-to-face scientific meetings remain extremely valuable because of the opportunity to build deep mutual trust and understanding, and develop new collaborations and sometimes even lifelong friendships (Alberts 2013, Cooke and Hilton 2015). However, it has been argued that ecologists should be particularly sensitive to the environmental footprint of travel (Fox et al. 2009); such concerns, along with the time demands for travel, particularly for multi-national working groups, provide strong motivation for exploring virtual attendance. While not replacing the richness of face-to-face interactions entirely, it is now feasible to virtually participate in meetings through services that allow video, audio, and file sharing, as well as other Web-enabled communication.

Bulletin of the Ecological Society of America↗
USGS2022

MTH5: An archive and exchangeable data format for magnetotelluric time series data

Magnetotellurics (MT) is a passive electromagnetic geophysical method that measures variations in subsurface electrical resistivity. MT data are collected in the time domain and processed in the frequency domain to produce estimates of a transfer function representing the Earth’s electrical structure. Unfortunately, the MT community lacks metadata and data standards for time series data. As the community grows and findability, accessibility, interoperability, and reuse of digital assets (FAIR) data principles are enforced by government and funding agencies, a standard is needed for time series data. Presented here is a hierarchical data format (MTH5) that is logically formatted to how MT data are collected. Open-source Python packages are also described to read, write, and manipulate MTH5 files. These include a package to deal with metadata ( mt_metadata ) based on standards developed by the Working Group for Magnetotelluric Data Handling and Software assembled by the Incorporated Research Institutions for Seismology (IRIS), and mth5 : a package to interact with MTH5 files that uses mt_metadata . Example code and workflows are presented.

Computers & Geosciences↗
USGS1998

Rare earth element metasomatism in hydrothermal systems: The Willsboro-Lewis wollastonite ores, New York, USA

Wollastonite ores and garnet-pyroxene skarns in the Willsboro-Lewis district, New York, USA were formed in a complex hydrothermal system associated with the emplacement of a large anorthosite pluton. Contact-metamorphic marbles were replaced by wollastonite, garnet, and clinopyroxene during infiltration metasomatism involving large volumes of water of chiefly meteoric origin. Rare earth elements (REE) in these rocks show large departures from the protolith REE distribution, indicative of substantial REE mobility. Three types of chondrite-normalized REE distribution patterns are present. The most common, found in ores and skarns containing andradite-rich garnet, is convex-up in the light REE (LREE) with a maximum at Pr and a positive Eu anomaly. Europium anomalies and Pr/Yb ratios are correlated with X(Ad) in garnet. This pattern (type C) results from uptake of REE from hydrothermal fluids by growing crystals of calcsilicate minerals, principally andradite, with amounts of LREE controlled by the difference in ionic radius between Ca++ and REE3+ in garnet X sites. The Eu anomaly results either from prior interaction of the fluids with plagioclase-rich, Eu-positive anorthositic rocks in and near the ore zone, or by enrichment of divalent Eu on growth surfaces of garnet followed by entrapment, or both. Relative enrichment in heavy REE (type H) occurs in ores and skarn where calcsilicates, including grossularitic garnet, in contact-metamorphic marble have been concentrated by dissolution of calcite. In most cases a negative Eu anomaly is inherited from the marble protolith. Skarns containing titanite and apatite exhibit high total REE, relative light REE enrichment, and negative Eu anomalies (type L). These appear to be intrusive igneous rocks (ferrodiorites or anorthositic gabbros) that have been converted to skarn by Ca metasomatism. REE, sequestered in titanite, apatite, and garnet, preserve the approximate REE distribution pattern of the igneous protolith. Post-ore granulite facies metamorphism homogenized zoned mineral grains without causing complete intergranular reequilibration and does not appear to have significantly affected the whole-rock REE distributions. These results demonstrate that extensive REE metasomatism can occur in hydrothermal systems at shallow to intermediate depths and that REE geochemistry may be useful in discerning the origin of skarns and skarn-related ore deposits.

Geochimica et Cosmochimica Acta↗
USGS2012

Mineralogy and geochemistry of a sediment‐hosted hydrothermal sulfide deposit from the Southern Trough of Guaymas Basin, Gulf of California

Samples dredged from a 15‐m‐high hydrothermal mound atop the flat turbidite pond in the Southern Trough of Guaymas Basin consist of pyrrhotite‐rich massive sulfide, barite, barite + calcite, talc, and opaline silica as well as substrate material composed of fossiliferous, clay‐rich ooze. An 11‐m‐long sediment core taken near the dredge site shows increasing hydrothermal alteration with depth; anhydrite‐filled fractures near the base of the core appear to be channels for hydrothermal discharge. Oxidation of the sulfide‐rich samples to an assemblage of geothite, lepidocrocite, and amorphous Fe oxyhydroxide is ubiquitous. Compared to other massive sulfide deposits on sediment‐starved oceanic ridges, the hydrothermal deposit dredged in Guaymas Basin has a high pyrrhotite/pyrite ratio, a low Zn sulfide and combined ore metal (Cu + Zn + Pb + Ag + Cd) content, and a greater abundance of sulfate, carbonate, and silicate phases. Venting hydrothermal solutions are alkaline with moderately high p H; high Ca, Ba, and SiO 2 content; low ƒS 2 and ƒo 2 ; and very low transition metal content. Disequilibrium assemblages of pyrrhotite and sulfate minerals form during rapid mixing of this evolved vent fluid with ambient bottom waters at the discharge site. Talc is formed at a temperature near 270°C by mixing or entrainment of Mg‐rich bottom water or pore fluid with upwelling hydrothermal fluid that is saturated with silica. Calcite may precipitate from the alkaline, Ca‐rich fluid during degassing of CO 2 . The minimum temperature range for sulfide and nonsulfide deposition is approximately 190°–326°C. The composition of hydrothermal deposits, vent solutions, and altered sediment requires that circulating fluids evolve during deep penetration into the basaltic basement complex, further interaction with the organic‐and carbonate‐rich sediment pile, and near‐surface mixing with ambient seawater. Although the stable assemblage albite‐epidote‐clinochlore present at depth in the sediment pile requires very low dissolved Mg and Fe in the altering fluid, the addition of Mg to deeply buried sediment indicates significant recharge of the system by Guaymas Basin bottom water.

Southern Trough of Guaymas Basin↗
USGS2010

Dacite petrogenesis on mid-ocean ridges: Evidence for oceanic crustal melting and assimilation

Whereas the majority of eruptions at oceanic spreading centers produce lavas with relatively homogeneous mid-ocean ridge basalt (MORB) compositions, the formation of tholeiitic andesites and dacites at mid-ocean ridges (MORs) is a petrological enigma. Eruptions of MOR high-silica lavas are typically associated with ridge discontinuities and have produced regionally significant volumes of lava. Andesites and dacites have been observed and sampled at several locations along the global MOR system; these include propagating ridge tips at ridge-transform intersections on the Juan de Fuca Ridge and eastern Gal??pagos spreading center, and at the 9??N overlapping spreading center on the East Pacific Rise. Despite the formation of these lavas at various ridges, MOR dacites show remarkably similar major element trends and incompatible trace element enrichments, suggesting that similar processes are controlling their chemistry. Although most geochemical variability in MOR basalts is consistent with low-pressure fractional crystallization of various mantle-derived parental melts, our geochemical data for MOR dacitic glasses suggest that contamination from a seawater-altered component is important in their petrogenesis. MOR dacites are characterized by elevated U, Th, Zr, and Hf, low Nb and Ta concentrations relative to rare earth elements (REE), and Al2O3, K2O, and Cl concentrations that are higher than expected from low-pressure fractional crystallization alone. Petrological modeling of MOR dacites suggests that partial melting and assimilation are both integral to their petrogenesis. Extensive fractional crystallization of a MORB parent combined with partial melting and assimilation of amphibole-bearing altered crust produces a magma with a geochemical signature similar to a MOR dacite. This supports the hypothesis that crustal assimilation is an important process in the formation of highly evolved MOR lavas and may be significant in the generation of evolved MORB in general. Additionally, these processes are likely to be more common in regions of episodic magma supply and enhanced magma-crust interaction such as at the ends of ridge segments. ?? The Author 2010. Published by Oxford University Press. All rights reserved.

Journal of Petrology↗
USGS2023

Toward conciliation in the habitat fragmentation and biodiversity debate

Landscape-scale conservation planning is urgent given the extent of anthropogenic land-use change and its pervasive impacts on Earth’s biodiversity. However, such efforts are hindered by disagreements over the effects of habitat fragmentation on biodiversity that have persisted since the mid-1970s. We contend that nearly 50 years later, these disagreements have become a locked-in debate characterized by polarized, unproductive discourse and a lack of consistent guidance for landscape managers and policy makers. Here, we highlight the need for a unified set of principles regarding conservation in fragmented landscapes, identify potential reasons for disparate conclusions in fragmentation research, and suggest ways for the ecological community to advance research that leads to consensus rather than the perpetuation of disagreement. Explicit efforts to develop and test multiple competing hypotheses, inter-laboratory collaborations, and acknowledgement of multiple interacting effects will be vital for moving the fragmentation debate forward. We argue that we in the ecology community should be responsible for helping to reconcile different views across scales, systems, and methodological approaches to advance conservation planning within a landscape ecology framework.

Landscape Ecology↗
USGS2024

A conserved interdomain microbial network underpins cadaver decomposition despite environmental variables

Microbial breakdown of organic matter is one of the most important processes on Earth, yet the controls of decomposition are poorly understood. Here we track 36 terrestrial human cadavers in three locations and show that a phylogenetically distinct, interdomain microbial network assembles during decomposition despite selection effects of location, climate and season. We generated a metagenome-assembled genome library from cadaver-associated soils and integrated it with metabolomics data to identify links between taxonomy and function. This universal network of microbial decomposers is characterized by cross-feeding to metabolize labile decomposition products. The key bacterial and fungal decomposers are rare across non-decomposition environments and appear unique to the breakdown of terrestrial decaying flesh, including humans, swine, mice and cattle, with insects as likely important vectors for dispersal. The observed lockstep of microbial interactions further underlies a robust microbial forensic tool with the potential to aid predictions of the time since death.

Nature Microbiology↗
USGS2002

Osmium isotope constraints on lower crustal recycling and pluton preservation at Lassen Volcanic Center, CA

Osmium isotope compositions of intermediate- to silicic-composition calc-alkaline volcanic rocks from the Lassen volcanic region of the Cascade arc are significantly more radiogenic ( γ Os =+23 to +224) than typical mantle. These evolved arc rocks in the Lassen region have unradiogenic Sr, Nd, and Pb isotope compositions which overlap with those of contemporaneous mafic lavas. Crystal fractionation of mafic- to intermediate-composition magmas produces Re/Os ratios that are high enough to evolve to very radiogenic Os isotope compositions in only a few million years, providing a potential fingerprint for detecting the involvement of such young, relatively mafic crust in magmatic systems. However, the Sr, Nd, and Pb isotope compositions will remain constant over such short time intervals due to relatively low parent/daughter enrichment during magmatic evolution. The radiogenic Os isotope compositions in typically evolved Lassen rocks are interpreted to reflect significant interaction with lower crustal material that has radiogenic Os isotope compositions. Beneath this section of the Cascade arc, large amounts of such high- γ Os lower crust may have formed and been isolated from MASH zone mixing and homogenization processes during the Pliocene or Late Miocene. The results from this study indicate that Os isotopes may provide a unique glimpse into lower crustal processes, such as recycling, in primitive orogenic arcs.

California↗
USGS2015

On a report that the 2012 M 6.0 earthquake in Italy was predicted after seeing an unusual cloud formation

Several recently published reports have suggested that semi-stationary linear-cloud formations might be causally precursory to earthquakes. We examine the report of Guangmeng and Jie (2013), who claim to have predicted the 2012 M 6.0 earthquake in the Po Valley of northern Italy after seeing a satellite photograph (a digital image) showing a linear-cloud formation over the eastern Apennine Mountains of central Italy. From inspection of 4 years of satellite images we find numerous examples of linear-cloud formations over Italy. A simple test shows no obvious statistical relationship between the occurrence of these cloud formations and earthquakes that occurred in and around Italy. All of the linear-cloud formations we have identified in satellite images, including that which Guangmeng and Jie (2013) claim to have used to predict the 2012 earthquake, appear to be orographic – formed by the interaction of moisture-laden wind flowing over mountains. Guangmeng and Jie (2013) have not clearly stated how linear-cloud formations can be used to predict the size, location, and time of an earthquake, and they have not published an account of all of their predictions (including any unsuccessful predictions). We are skeptical of the validity of the claim by Guangmeng and Jie (2013) that they have managed to predict any earthquakes.

Natural Hazards and Earth System Sciences↗