Search USGS⌕ Search

SEARCH · Search USGS

Results for “Earth’s Future”

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

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

At least 829 records · Page 46Linked to original sources
USGS2004

The Cottage Lake aeromagnetic lineament: A possible onshore extension of the southern Whidbey Island fault, Washington

The northwest-striking southern Whidbey Island fault zone (SWIF) was mapped previously using borehole data and potential-field anomalies on Whidbey Island and marine seismic surveys beneath surrounding waterways. Abrupt subsidence at a coastal marsh on south-central Whidbey Island suggests that the SWIF experienced a MW 6.5 to 7.0 earthquake about 3000 years ago. Southeast of Whidbey Island, a hypothesized southeastward projection of the SWIF would make landfall between the cities of Seattle and Everett. As part of systematic, ongoing studies by the U.S. Geological Survey, University of Washington, and other earth science organizations to evaluate potentially active faults and other earth hazards throughout the Puget Lowland, we test this hypothesis using aeromagnetic, lidar, and borehole data. Linear, northwest-striking magnetic anomalies traversing the mainland region project southeastward toward the communities of Woodinville and Maltby, Washington. All of these magnetic anomalies are low in amplitude and best illuminated in residual magnetic fields. The most prominent of the residual magnetic anomalies extends at least 16 km, lies approximately on strike with the SWIF on Whidbey Island, and passes near Crystal and Cottage Lakes, about 27 km southeast of downtown Everett. In places, this magnetic anomaly is associated with topographic lineaments, but spectral analysis indicates that the source of the anomaly extends to depths greater than 2 km and cannot be explained entirely by topographic effects. The Alderwood #1 oil exploration well located on strike with the Cottage Lake aeromagnetic lineament shows evidence of deformation over a total depth range of 3000 m; some beds within this interval exhibit intense fracturing and shearing, although deformation within the well can only be constrained as post-early Oligocene and pre-Pleistocene. Boreholes acquired as part of a wastewater tunnel project show evidence of soil disturbance at locations where some topographic and aeromagnetic lineaments cross the tunnel alignment. Some of the disturbance is likely tectonic in origin, although other explanations are possible. Some of the soil disturbance demonstrably predates the 15-13 ka Fraser glaciation of the Puget Lowland; other samples have inconclusive ages and may be younger. Subtle scarps in Pleistocene surfaces are visible on high-resolution lidar topography at a number of locations along the Cottage Lake aeromagnetic lineament. Collectively, the scarps are parallel to the trend of the aeromagnetic lineament and extend a total distance of 18 km. In the field, scarps exhibit 1 to 5 m of north-side-up offset. The scarps provide targets for future paleoseismic trenching studies to test the hypothesis that they have a tectonic origin.

Washington↗
USGS2017

Rhenium

Rhenium is one of the rarest elements in Earth’s continental crust; its estimated average crustal abundance is less than 1 part per billion. Rhenium is a metal that has an extremely high melting point and a heat-stable crystalline structure. More than 80 percent of the rhenium consumed in the world is used in high-temperature superalloys, especially those used to make turbine blades for jet aircraft engines. Rhenium’s other major application is in platinum-rhenium catalysts used in petroleum refining. Rhenium rarely occurs as a native element or as its own sulfide mineral; most rhenium is present as a substitute for molybdenum in molybdenite. Annual world mine production of rhenium is about 50 metric tons. Nearly all primary rhenium production (that is, rhenium produced by mining rather than through recycling) is as a byproduct of copper mining, and about 80 percent of the rhenium obtained through mining is recovered from the flue dust produced during the roasting of molybdenite concentrates from porphyry copper deposits. Molybdenite in porphyry copper deposits can contain hundreds to several thousand grams per metric ton of rhenium, although the estimated rhenium grades of these deposits range from less than 0.1 gram per metric ton to about 0.6 gram per metric ton. Continental-arc porphyry copper-(molybdenum-gold) deposits supply most of the world’s rhenium production and have large inferred rhenium resources. Porphyry copper mines in Chile account for about 55 percent of the world’s mine production of rhenium; rhenium is also recovered from porphyry copper deposits in the United States, Armenia, Kazakhstan, Mexico, Peru, Russia, and Uzbekistan. Sediment-hosted strata-bound copper deposits in Kazakhstan (of the sandstone type) and in Poland (of the reduced-facies, or Kupferschiefer, type) account for most other rhenium produced by mining. These types of deposits also have large amounts of identified rhenium resources. The future supply of rhenium is likely to depend largely on the capacity of the specialized processing facilities needed to recover rhenium from molybdenite concentrates. The environmental consequences of rhenium recovery are closely linked to the consequences of mining large porphyry copper and strata-bound copper deposits; no additional environmental impact from recovery of rhenium from these deposits has been identified. No information is available regarding the potential toxic effects of rhenium on humans, partly because of the low natural abundance of rhenium.

Professional Paper↗
USGS2018

Quartz-pebble-conglomerate gold deposits

Quartz-pebble-conglomerate gold deposits represent the largest repository of gold on Earth, largely due to the deposits of the Witwatersrand Basin, which account for nearly 40 percent of the total gold produced throughout Earth’s history. This deposit type has had a controversial history in regards to genetic models. However, most researchers conclude that they are paleoplacer deposits that have been modified by metamorphism and hydrothermal fluid flow subsequent to initial sedimentation. The deposits are found exclusively within fault-bounded depositional basins. The periphery of these basins commonly consists of granite-greenstone terranes, classic hosts for lode gold that source the detrital material infilling the basin. The gold reefs are typically located along unconformities or, less commonly, at the top of sedimentary beds. Large quartz pebbles and heavy-mineral concentrates are found associated with the gold. Deposits that formed prior to the Great Oxidation Event (circa 2.4 giga-annum [Ga]) contain pyrite, whereas younger deposits contain iron oxides. Uranium minerals and hydrocarbons are also notable features of some deposits. Much of the gold in these types of deposits forms crystalline features that are the product of local remobilization. However, some gold grains preserve textures that are undoubtedly of detrital origin. Other heavy minerals, such as pyrite, contain growth banding that is truncated along broken margins, which indicates that they were transported into place as opposed to forming by in situ growth in a hydrothermal setting. The ore tailings associated with these deposits commonly contain uranium-rich minerals and sulfides. Oxidation of the sulfides releases sulfuric acid and mobilizes various metals into the environment. The neutralizing potential of the tailings is minimal, since carbonate minerals are rare. The continuity of the tabular ore bodies, such as those of the Witwatersrand Basin, has allowed these mines to be the deepest in the world. The extreme depths create engineering complications and safety issues for the miners, such as rock bursts as a result of pressure release. The richness of these deposits makes them a desirable exploration target. However, the likelihood of future discoveries is minimal. Small deposits found in the United States include those found at Nemo in the Black Hills of South Dakota and Deep Lake in the Sierra Madre of Wyoming.

Scientific Investigations Report↗
USGS2023

Evaluation of Copernicus DEM and comparison to the DEM used for Landsat collection-2 processing

Having highly accurate and reliable Digital Elevation Models (DEMs) of the Earth’s surface is critical to orthorectify Landsat imagery. Without such accuracy, pixel locations reported in the data are difficult to assure as accurate, especially in more mountainous landscapes, where the orthorectification process is the most challenging. To this end, the Landsat Calibration and Validation Team (Cal/Val) compared the Copernicus DEM (CopDEM) to the DEM that is currently used in Collection-2 processing (called “Collection-2 DEM”). NGS ground-surveyed and lidar-based ICESat-2 points were used, and the CopDEM shows improvement to be less than 1 m globally, except in Asia where the accuracy and resolution of the DEM were greater for the CopDEM compared to the Collection-2 DEM. Along with slightly improved accuracy, the CopDEM showed more consistent results globally due to its virtually seamless source and consistent creation methods throughout the dataset. While CopDEM is virtually seamless, having greater than 99% of their data coming from a single source (Tandem-X), there are significantly more voids in the higher elevations which were mostly filled with SRTM derivatives. The accuracy of the CopDEM fill imagery was also compared to the Collection-2 DEM and the results were very similar, showing that the choice of fill imagery used by CopDEM was appropriate. A qualitative assessment using terrain-corrected products processed with different DEMs and viewing them as anaglyphs to evaluate the DEMs proved useful for assessing orbital path co-registration. While the superiority of the CopDEM was not shown to be definitive by the qualitative method for many of the regions assessed, the CopDEM showed a clear advantage in Northern Russia, where the Collection-2 DEM uses some of the oldest and least accurate datasets in the compilation of the Collection-2 DEM. This paper presents results from the comparison study, along with the justification for proceeding with using the Copernicus DEM in future Landsat processing. As of this writing, the Copernicus DEM is planned to be used in Collection-3 processing, which is anticipated to be released no earlier than 2025.

Remote Sensing↗
USGS2023

Observing coastal wetland transitions using national land cover products

Over the coming century, climate change and sea-level rise are predicted to cause widespread change to coastal wetlands. Estuarine vegetated wetlands can adapt to sea-level rise through both vertical development (i.e., biophysical feedbacks and sedimentation) and upslope/horizontal migration. Quantifying changes to estuarine vegetated wetlands over time can help to inform current and future decisions regarding land management and resource stewardship. In this study, we show how coastal land cover maps readily available in the US can be used to assess and understand estuarine vegetated wetland changes. This assessment involves two steps: (1) identifying the net gain/loss of estuarine vegetated wetlands and (2) determining which land cover types contribute to the net gain/loss. From this information, we developed estuarine vegetated wetland change scenarios that evaluate whether estuarine vegetated wetland gain kept up with loss and whether the contribution was from: (1) estuarine vegetated wetland migration or tidal restoration; (2) land building (i.e., development); or (3) both. We assessed changes from 1996 to 2016 for: (1) the conterminous US; (2) each major US coastline; and (3) focal estuaries with the most change per coast. We found that the change scenario (1, 2, or 3) varied across coastlines. Moving forward, national coastal land cover programs can be informed by utilizing methodologies that leverage contemporary information for delineating the estuarine zone from upslope/adjacent wetlands. We highlight approaches that could be used to address this challenge and provide complementary information related to wetland condition changes.

Progress in Physical Geography: Earth and Environm↗
USGS2007

Forecast experiment: do temporal and spatial b value variations along the Calaveras fault portend M ≥ 4.0 earthquakes?

The power law distribution of earthquake magnitudes and frequencies is a fundamental scaling relationship used for forecasting. However, can its slope (b value) be used on individual faults as a stress indicator? Some have concluded that b values drop just before large shocks. Others suggested that temporally stable low b value zones identify future large-earthquake locations. This study assesses the frequency of b value anomalies portending M ≥ 4.0 shocks versus how often they do not. I investigated M ≥ 4.0 Calaveras fault earthquakes because there have been 25 over the 37-year duration of the instrumental catalog on the most active southern half of the fault. With that relatively large sample, I conducted retrospective time and space earthquake forecasts. I calculated temporal b value changes in 5-km-radius cylindrical volumes of crust that were significant at 90% confidence, but these changes were poor forecasters of M ≥ 4.0 earthquakes. M ≥ 4.0 events were as likely to happen at times of high b values as they were at low ones. However, I could not rule out a hypothesis that spatial b value anomalies portend M ≥ 4.0 events; of 20 M ≥ 4 shocks that could be studied, 6 to 8 (depending on calculation method) occurred where b values were significantly less than the spatial mean, 1 to 2 happened above the mean, and 10 to 13 occurred within 90% confidence intervals of the mean and were thus inconclusive. Thus spatial b value variation might be a useful forecast tool, but resolution is poor, even on seismically active faults.

California↗
USGS2011

A Bayesian network to predict coastal vulnerability to sea level rise

Sea level rise during the 21st century will have a wide range of effects on coastal environments, human development, and infrastructure in coastal areas. The broad range of complex factors influencing coastal systems contributes to large uncertainties in predicting long-term sea level rise impacts. Here we explore and demonstrate the capabilities of a Bayesian network (BN) to predict long-term shoreline change associated with sea level rise and make quantitative assessments of prediction uncertainty. A BN is used to define relationships between driving forces, geologic constraints, and coastal response for the U.S. Atlantic coast that include observations of local rates of relative sea level rise, wave height, tide range, geomorphic classification, coastal slope, and shoreline change rate. The BN is used to make probabilistic predictions of shoreline retreat in response to different future sea level rise rates. Results demonstrate that the probability of shoreline retreat increases with higher rates of sea level rise. Where more specific information is included, the probability of shoreline change increases in a number of cases, indicating more confident predictions. A hindcast evaluation of the BN indicates that the network correctly predicts 71% of the cases. Evaluation of the results using Brier skill and log likelihood ratio scores indicates that the network provides shoreline change predictions that are better than the prior probability. Shoreline change outcomes indicating stability (-1 < rate < 1 m/yr) or erosion (rate < -1 m/yr) tend to occur for two sets of input scenarios. Stable shoreline change rates occur mainly for low rates of relative sea level rise and occur in low-vulnerability geomorphic settings. Rates indicating erosion result for cases where the rate of relative sea level rise is high and moderate-to-high vulnerability geomorphic settings occur. In contrast, accretion (rate > 1 m/yr) was not well predicted. We find that BNs can assimilate important factors contributing to coastal change in response to sea level rise and can make quantitative, probabilistic predictions that can be applied to coastal management decisions. Copyright ?? 2011 by the American Geophysical Union.

Journal of Geophysical Research F: Earth Surface↗
USGS2011

Characterizing climate-change impacts on the 1.5-yr flood flow in selected basins across the United States: a probabilistic approach

The U.S. Geological Survey Precipitation-Runoff Modeling System (PRMS) model was applied to basins in 14 different hydroclimatic regions to determine the sensitivity and variability of the freshwater resources of the United States in the face of current climate-change projections. Rather than attempting to choose a most likely scenario from the results of the Intergovernmental Panel on Climate Change, an ensemble of climate simulations from five models under three emissions scenarios each was used to drive the basin models. Climate-change scenarios were generated for PRMS by modifying historical precipitation and temperature inputs; mean monthly climate change was derived by calculating changes in mean climates from current to various future decades in the ensemble of climate projections. Empirical orthogonal functions (EOFs) were fitted to the PRMS model output driven by the ensemble of climate projections and provided a basis for randomly (but representatively) generating realizations of hydrologic response to future climates. For each realization, the 1.5-yr flood was calculated to represent a flow important for sediment transport and channel geomorphology. The empirical probability density function (pdf) of the 1.5-yr flood was estimated using the results across the realizations for each basin. Of the 14 basins studied, 9 showed clear temporal shifts in the pdfs of the 1.5-yr flood projected into the twenty-first century. In the western United States, where the annual peak discharges are heavily influenced by snowmelt, three basins show at least a 10% increase in the 1.5-yr flood in the twenty-first century; the remaining two basins demonstrate increases in the 1.5-yr flood, but the temporal shifts in the pdfs and the percent changes are not as distinct. Four basins in the eastern Rockies/central United States show at least a 10% decrease in the 1.5-yr flood; the remaining two basins demonstrate decreases in the 1.5-yr flood, but the temporal shifts in the pdfs and the percent changes are not as distinct. Two basins in the eastern United States show at least a 10% decrease in the 1.5-yr flood; the remaining basin shows little or no change in the 1.5-yr flood.

Earth Interactions↗
USGS2012

Forecast model for moderate earthquakes near Parkfield, California

Earthquake instability models have possible application to earthquake forecasting because the models simulate both preseismic and coseismic changes of fault slip and ground deformation. In the forecast procedure proposed here, repeated measurements of preseismic fault slip and ground deformation constrain the values of model parameters. The early part of the model simulation corresponds to the available field data, and the subsequent part constitutes an estimate of future faulting and ground deformation. In particular, the time, location, and size of unstable faulting are estimates of the pending earthquake parameters. The forecast accuracy depends on the model realism and parameter resolution. The forecast procedure is applied to fault creep and trilateration data measured near Parkfield, California, where at least five magnitude 5.5 to 6 earthquakes have occurred regularly since 1881, the last in 1966. The quasi-static model consists of a flat vertical plane embedded in an elastic half space. Spacially variable fault slip of strike-slip sense is driven by an increasing regional shear stress but is impeded by a relatively strong patch of brittle, strain-softening fault. The field data are consistent with these approximate values of patch parameters: radius of 3 km, patch center 5 km deep and 8 km southeast of the 1966 epicenter, and maximum brittle strength of 26 bars. Fluctuations in the available field data prevent estimating the earthquake time with any more precision than use of the 21±8 year recurrence interval. However, the model may later give a more precise estimate of the earthquake time if the fault slip rate near the inferred patch increases before the earthquake, as predicted by the model.

Journal of Geophysical Research Solid Earth↗
USGS1967

Ground-water research in the U.S.A.

Ground-water reservoirs and the overlying unsaturated zone-collectively, the "subsurface"-have an enormous capacity to supply water to wells and useful plants, to store water to meet future needs for the same purposes, and, under suitable precautions, to accept wastes. This capacity can be exploited on a maximum scale, however, only on the basis of information one or more orders of magnitude greater than that available at present on the distribution, recoverability, and replenishability of subsurface water. Because usable water must be made available, and waste water must be disposed of, at costs of only a cent or a few cents per cubic meter, there is a critical need for research to devise methods of accomplishing these water-management tasks at reasonable cost. Among the chief target areas for research in subsurface hydrology are permeability distribution, including vertical permeability; prediction of the departure of the storage coefficient from the theoretically "instantaneous" property assumed in flow equations; theory of unsaturated flow based on fundamental soil characteristics that can be measured practicably; geochemical relations including the effects of injecting water of one composition into zones occupied by waters of different composition, generation of acid mine water, occurrence of saline water, and salt-fresh-water relations in coastal and other areas; prediction of the fate of wastes injected underground; geophysical techniques both surface and subsurface to extend, at low cost, information obtained by other means; and practical techniques of artificial recharge, especially through wells. ?? 1967.

Earth-Science Reviews↗
USGS2013

The utility of atmospheric analyses for the mitigation of artifacts in InSAR

The numerical weather models (NWMs) developed by the meteorological community are able to provide accurate analyses of the current state of the atmosphere in addition to the predictions of the future state. To date, most attempts to apply the NWMs to estimate the refractivity of the atmosphere at the time of satellite synthetic aperture radar (SAR) data acquisitions have relied on predictive models. We test the hypothesis that performing a final assimilative routine, ingesting all available meteorological observations for the times of SAR acquisitions, and generating customized analyses of the atmosphere at those times will better mitigate atmospheric artifacts in differential interferograms. We find that, for our study area around Mount St. Helens (Amboy, Washington, USA), this approach is unable to model the refractive changes and provides no mean benefit for interferogram analysis. The performance is improved slightly by ingesting atmospheric delay estimates derived from the limited local GPS network; however, the addition of water vapor products from the GOES satellites reduces the quality of the corrections. We interpret our results to indicate that, even with this advanced approach, NWMs are not a reliable mitigation technique for regions such as Mount St. Helens with highly variable moisture fields and complex topography and atmospheric dynamics. It is possible, however, that the addition of more spatially dense meteorological data to constrain the analyses might significantly improve the performance of weather modeling of atmospheric artifacts in satellite radar interferograms.

Journal of Geophysical Research B: Solid Earth↗
USGS2022

Marine minerals in Alaska — A review of coastal and deep-ocean regions

Minerals occurring in marine environments span the globe and encompass a broad range of mineral categories, forming within varied geologic and oceanographic settings. They occur in coastal regions, either from the continuation or mechanical reworking of terrestrial mineralization, as well as in the deep ocean, from diagenetic, hydrogenetic, and hydrothermal processes. The oceans cover most of the Earth’s surface and as a result, any inventory of global resources is incomplete without the inclusion of marine minerals. This study by the U.S. Geological Survey reviews current knowledge regarding deep-ocean and coastal marine minerals within the marine areas surrounding Alaska, including the Alaska Outer Continental Shelf (OCS). For the purposes of this study, we have divided these areas in to eight regions: (1) Gulf of Alaska seamounts, (2) Chukchi Borderland, (3) Canada Basin, (4) Aleutian Arc, (5) Seward Peninsula, (6) Goodnews Bay, (7) Bristol Bay and Alaska Peninsula, and (8) southern and southeastern Alaska. The Alaska OCS encompasses several areas broadly conducive to marine mineral formation, including extensional basins resulting from an active subduction zone where massive sulfide deposits may form, deep abyssal plains with conditions that may lead to manganese nodule formation, seamounts that can provide substrate for the growth of ferromanganese crusts, and erosional settings and submerged continental crust where placer deposits are found. For deep-ocean hydrothermal minerals and manganese nodules, the Alaska OCS contains prospective regions, including the Canada Basin and the Aleutian Arc; however, no such minerals have yet been identified. We explore the probability that these minerals occur based on reviews of existing geologic and oceanographic data within the relevant sections. In regions far from shore data are limited. Deep-ocean ferromanganese crusts are known to occur in two regions: (1) the Gulf of Alaska seamounts and (2) the Chukchi Borderland in the Arctic Ocean. Limited sampling has occurred in both regions, and along the Chukchi Borderland the sampling was outside of the OCS and the U.S. Exclusive Economic Zone. Data relevant to coastal minerals is more extensive, and in some places fairly systematic sampling was conducted. Several nearshore placer deposits have been exploited for decades; however, the potential for nearshore extension of terrestrial ore deposits is less well considered. This contribution considers the state of knowledge regarding marine mineral occurrences within the Alaska regions and identifies the data gaps in order to help inform future marine mineral related research efforts around Alaska.

Alaska↗
USGS2019

Rare earth element mineral deposits in the United States

Because of their unique special chemical properties, many of the metals in the group of rare earth elements (REEs) have essential applications in 21st century technologies. Examples of products that use REEs are cell phones, computers, fluorescent and light-emitting-diode lights, flat-screen television and computer monitors, and in high-strength magnets used by clean energy technologies such as the generators of wind turbines and batteries of hybrid and electric vehicles. REEs are used in many defense applications, such as in components of jet engines, missile guidance systems, antimissile defense systems, satellites, and communication systems. The rare earth elements have become vital to manufacturing numerous high-tech products, which has been accompanied by a large increase in their demand. At the same time, there has been concern by the United States and many other Nations about the near-monopoly of mining, processing, and supply of REEs from one Nation, China. Between 2011 and 2017, China produced approximately 84 percent of the world’s REEs, and during this time the United States only produced REEs between 2012 and 2015. The U.S. production came entirely from the Mountain Pass mine in California, providing only about 4 percent of the world REE supply. Because REEs are essential for technological applications and are primarily supplied by one Nation, there has been an increased concern in identifying new sources of REEs, including economic REE deposits. In response to these concerns, since 2009, the U.S. Geological Survey (USGS) has conducted numerous studies focused on the distribution, geology, and potential resources for the REE-bearing mineral deposits in the United States. The basic characteristics of mineral deposit types that host REE enrichments in the United Sates are summarized in this report, with selected examples. Several types of REE-enriched mineral deposits are reviewed, including deposits in carbonatites, alkaline igneous rocks, sedimentary phosphate-rich rocks (phosphorite), regions containing REE-rich veins, iron oxide deposits containing REE-bearing apatite, monazite-xenotime-bearing placer deposits (heavy-mineral sands), and ion-adsorption clay deposits (REE in granite-derived regolith). A better understanding of these mineral deposits will assist in identifying domestic resources to help alleviate the dependence on imported REEs. The economic development of REE mineral deposits is affected by many factors beyond mining, such as commodity prices and mineral processing costs. Most of the REEs are hosted by minerals that have complex chemical formulas; this presents more challenges to process and extract the REEs. Continued advancements and refinements in mineral processing techniques may allow REE deposits with complex mineralogy to be economically developed in the future.

Circular↗
USGS2014

U.S. Geological Survey Karst Interest Group Proceedings, Carlsbad, New Mexico, April 29-May 2, 2014

Karst aquifer systems are present throughout parts of the United States and some of its territories, and have developed in carbonate rocks (primarily limestone and dolomite) that span an interval of time encompassing more than 550 million years. The depositional environments, diagenetic processes, post-depositional tectonic events, and geochemical weathering processes that form karst aquifers are varied and complex, and involve biological, chemical, and physical changes. These factors, combined with the diverse climatic regimes under which karst development in these rocks has taken place, result in the unique dual- or triple-porosity nature of karst aquifers. These complex hydrogeologic systems typically represent challenging and unique conditions to scientists attempting to study groundwater flow and contaminant transport in these terrains. The dissolution of carbonate rocks and the subsequent development of distinct and beautiful landscapes, caverns, and springs has resulted in the most exceptional karst areas of the United States being designated as national or state parks; commercial caverns and known privately owned caves number in the tens of thousands. Both public and private properties provide access for scientists to study the flow of groundwater in situ. Likewise, the range and complexity of landforms and groundwater flow systems associated with karst terrains are enormous, perhaps more than for any other aquifer type. Karst aquifers and landscapes that form in tropical areas, such as the cockpit karst along the north coast of Puerto Rico, differ greatly from karst landforms in more arid climates, such as the Edwards Plateau in west-central Texas or the Guadalupe Mountains near Carlsbad, New Mexico, where hypogenic processes have played a major role in speleogenesis. Many of these public and private lands also contain unique flora and fauna associated with these karst hydrogeologic systems. As a result, numerous federal, state, and local agencies have a strong interest in the study of karst terrains. Many of the major springs and aquifers in the United States have developed in carbonate rocks, such as the Floridan aquifer system in Florida and parts of Alabama, Georgia, and South Carolina; the Ozark Plateaus aquifer system in parts of Arkansas, Kansas, Missouri, and Oklahoma; and the Edwards-Trinity aquifer system in west-central Texas. These aquifers, and the springs that discharge from them, serve as major water-supply sources and as unique ecological habitats. Competition for the water resources of karst aquifers is common, and urban development and the lack of attenuation of contaminants in karst areas can impact the ecosystem and water quality of these aquifers. The concept for developing a platform for interaction among scientists within the U.S. Geological Survey (USGS) working on karst-related studies evolved from the November 1999 National Ground-Water Meeting of the USGS. As a result, the Karst Interest Group (KIG) was formed in 2000. The KIG is a loose-knit, grass-roots organization of USGS and non-USGS scientists and researchers devoted to fostering better communication among scientists working on, or interested in, karst science. The primary mission of the KIG is to encourage and support interdisciplinary collaboration and technology transfer among scientists working in karst areas. Additionally, the KIG encourages collaborative studies between the different mission areas of the USGS as well as other federal and state agencies, and with researchers from academia and institutes. The KIG also encourages younger scientists by participation of students in the poster and oral sessions. To accomplish its mission, the KIG has organized a series of workshops that are held near nationally important karst areas. To date (2014) six KIG workshops, including the workshop documented in this report, have been held. The workshops typically include oral and poster sessions on selected karst-related topics and research, as well as field trips to local karst features. Proceedings of the workshops are published by the USGS and are available online at http://water.usgs.gov/ogw/karst/kig . The first KIG workshop was held in St. Petersburg, Florida, February 13–16, 2001, in the vicinity of the large springs and other karst features of the Floridan aquifer system. The second KIG workshop was held August 20–22, 2002, in Shepherdstown, West Virginia, in proximity to the carbonate aquifers of the northern Shenandoah Valley and highlighted an invited presentation on karst literature by the late Barry F. Beck of P.E. LaMoreaux and Associates. The third KIG workshop was held September 12–15, 2005, in Rapid City, South Dakota, nearby to karst features in evaporites and limestones of the Madison Group in the Black Hills of South Dakota, including Wind Cave National Park and Jewel Cave National Monument. The workshop also included a featured presentation by Thomas Casadevall, Central Region Director, USGS, on the status of earth science at the USGS and evening trips to Jewel Cave led by Mike Wiles, National Park Service (NPS) and Wind Cave led by Rod Horrocks, NPS. The fourth KIG workshop was held May 27–29, 2008, and hosted by the Hoffman Environmental Research Institute and Center for Cave and Karst Studies at Western Kentucky University in Bowling Green, Kentucky, near Mammoth Cave National Park and karst features of the Chester Upland and Pennyroyal Plateau. The workshop featured a late-night field trip into Mammoth Cave with Rickard Toomey and Rick Olsen, NPS. The fifth workshop was held April 26–29, 2011, and was a joint meeting of the USGS KIG and University of Arkansas HydroDays, hosted by the Department of Geosciences at the University of Arkansas in Fayetteville. The workshop featured an outstanding field trip to the unique karst terrain along the Buffalo National River of the southern Ozarks and a keynote presentation on paleokarst in the United States by Art and Peggy Palmer. This sixth and current 2014 KIG workshop is hosted by the National Cave and Karst Research Institute (NCKRI) in Carlsbad, New Mexico, with Director of NCKRI, George Veni, serving as co-chair of the workshop with Eve Kuniansky, USGS. The session planning committee for this sixth workshop includes Van Brahana, USGS retired and University of Arkansas Professor Emeritus; Tom Byl, USGS and Tennessee State University; Zelda Bailey, former Director of NCKRI and retired Director, National Institute of Standards and Technology, Boulder Laboratory, Colorado; Patrick Tucci, USGS retired; and Mike Bradley, Allan Clark, Geoff Delin, Daniel Doctor, James Kaufmann, Eve Kuniansky, Randy Orndorff, Larry Spangler, and Dave Weary of the USGS. The karst hydrology field trip on Thursday will be led by Lewis Land (NCKRI karst hydrologist) and the optional Friday field trip on the geology of Carlsbad Caverns National Park will be led by George Veni. The keynote speaker is Dr. Penelope Boston, Director of Cave and Karst Studies at New Mexico Tech, Socorro, and Academic Director at NCKRI, who will address the future of karst research. Additionally, there is a featured presentation “Irish karst and its management,” by Caoimhe Hickey, The Geological Survey of Ireland, preceding a panel discussion on “Collaboration During Times of Limited Resources.” The extended abstracts of USGS authors were peer reviewed and approved for publication by the U.S. Geological Survey. Articles submitted by university researchers and other federal and state agencies did not go through the formal USGS peer review and approval process, and therefore may not adhere to our editorial standards or stratigraphic nomenclature and is not research conducted or data collected by the USGS. However, all articles had at a minimum of two peer reviews, and all articles were edited for consistency of appearance in the published Proceedings. The use of trade, firm or product names in any article is for descriptive purposes only and does not imply endorsement by the U.S. Government. The USGS, Office of Groundwater, provides technical support for the Karst Interest Group website and public availability of the Proceedings from these workshops, and the USGS Groundwater Resources Program funds the publication costs. Finally, the cover illustration is the work of Ann Tihansky, USGS, used since the first KIG workshop in 2000.

Scientific Investigations Report↗
USGS2020

Zircon-hosted melt inclusion record of silicic magmatism in the Mesoproterozoic St. Francois Mountains terrane, Missouri: Origin of the Pea Ridge iron oxide-apatite rare earth element deposit and implications for regional crustal pathways of mineralization

Voluminous silicic magmatism was coeval with iron ore mineralization in the St. Francois Mountains terrane in southeast Missouri, part of the broader Mesoproterozoic Granite-Rhyolite province along the eastern margin of Laurentia. Some of the iron deposits contain extraordinary endowments of critical elements, such as the Pea Ridge iron oxide-apatite (IOA) deposit, which has an average grade of ~12 wt% rare earth oxides in breccia pipes that flank the ore body. To assess the role of silicic magmatism in the genesis of the Pea Ridge deposit, we present a high-spatial resolution study of zirconhosted melt inclusions from rhyolitic ash-flow tuffs. Melt inclusion data are combined with textural, geochemical, and geochronological analyses of zircon hosts to elucidate the magmatic-hydrothermal evolution of the Pea Ridge system. Two contemporaneous silicic igneous centers in the St. Francois Mountains terrane, Bourbon and Eminence, were studied for comparison. Pea Ridge melt inclusions are trachydacitic to rhyolitic (~63-79 wt% SiO2, ~5.6-11.7 wt% Na2O+K2O) with very high Cl in the least-evolved and most alkaline melt inclusions (~2,000-5,000 ppm Cl). Rare earth elements (REE) in melt inclusions have identical chondrite-normalized patterns to the mineralized breccia pipes, but with systematically lower absolute concentrations. Haplogranite ternary pressures range from ~0.5-10 kbar, with an average of ~2-3 kbar (7-12 km depth), and liquidus temperatures are ~850-950 °C, with an average of ~920 °C. Silicate and phosphate mineral inclusions have compositions that overlap minerals from the iron ore body and breccia pipes, recording a transition from igneous to hydrothermal zircon growth. Igneous iron oxide inclusions have compositions that indicate Pea Ridge magmas were reduced to moderately oxidized (log fO2 of -0.8 to -1.84 NNO). Zircons from two Pea Ridge samples have 207Pb/206Pb concordia ages of 1456 ± 9 Ma and 1467 ± 13 Ma that overlap published ages for the breccia pipes and iron ore zones of the Pea Ridge deposit. A population of texturally and chemically disrupted zircons have discordant domains that correspond to high Fe, U, and REE concentrations, consistent with the unique geochemical attributes of the IOA-REE ore body. Inherited cores in Pea Ridge and Bourbon zircons have concordant 207Pb/206Pb dates of 1550-1618 Ma, providing direct evidence of cratonic basement beneath these centers. Oxygen isotope data for inherited and autocrystic igneous zircons span from mantle to crustal values (18Ozircon=5.5-7.9‰). Our data are consistent with a model in which metasomatized mantle components were mixed with cratonic and accreted crustal material in a back-arc or rifted segment of a volcanic arc, with ore fluids derived from Cl-rich melts to transport Fe and REE in a long-lived (tens of Myr), pulsed, magmatic-hydrothermal system. Bourbon, which also possesses IOA mineralization, shares key petrologic similarities with the Pea Ridge system, whereas Eminence, which is not mineralized, has disparate geochemical and isotopic signatures that indicate it formed in a different crustal setting. The location of Pea Ridge and Bourbon along a cratonic margin may have been important in focusing silicic melts and mineralization in the upper crust, serving as a guide for future exploration efforts.

Missouri↗
USGS2021

A multiproxy database of western North American Holocene paleoclimate records

Holocene climate reconstructions are useful for understanding the diverse features and spatial heterogeneity of past and future climate change. Here we present a database of western North American Holocene paleoclimate records. The database gathers paleoclimate time series from 184 terrestrial and marine sites, including 381 individual proxy records. The records span at least 4000 of the last 12 000 years (median duration of 10 725 years) and have been screened for resolution, chronologic control, and climate sensitivity. Records were included that reflect temperature, hydroclimate, or circulation features. The database is shared in the machine readable Linked Paleo Data (LiPD) format and includes geochronologic data for generating site-level time-uncertain ensembles. This publicly accessible and curated collection of proxy paleoclimate records will have wide research applications, including, for example, investigations of the primary features of ocean–atmospheric circulation along the eastern margin of the North Pacific and the latitudinal response of climate to orbital changes. The database is available for download at https://doi.org/10.6084/m9.figshare.12863843.v1 (Routson and McKay, 2020).

Earth System Science Data↗
USGS2010

The 2007 M5.4 Alum Rock, California, earthquake: Implications for future earthquakes on the central and southern Calaveras Fault

[1] The similarity of seismograms recorded by two seismic stations demonstrate that the 31 October 2007 moment magnitude M 5.4 Alum Rock earthquake is a repeat of a 1955 M L 5.5 earthquake. Both occurred on Oppenheimer et al.'s (1990) Zone V “stuck patch” on the central Calaveras fault, providing new support for their model of Calaveras fault earthquake activity. We suggest that Zone V fails only in a family of recurring M ∼ 5.4–5.5 earthquakes. The 1955 and 2007 earthquakes are the penultimate and ultimate Zone V events. Earthquakes in 1891 and 1864 are possible earlier Zone V events. The next Zone V event is not expected in the next few decades, assuming a time‐dependent recurrence model: the mean forecast date is 2064 (2035–2104, 95% confidence range). We further suggest that Zones I, II, III, and IV fail in recurring M ∼ 5.1–5.3, M ∼ 5.6–5.8, M ∼ 6.1–6.3, and M ∼ 4.9–5.0 earthquakes, respectively. If our earthquake recurrence model is correct, the next Zone I event is overdue and could occur anytime, and M 5–6 earthquakes should not occur on Zones II, III, and IV before 2014, 2012, and 2026, respectively. We cannot rule out the possibility that Zone VI, which lies at the southern end of the Mission Seismic Trend, where the southern Hayward and central Calaveras faults appear to connect at depth, fails aseismically or in large events on the southern Hayward fault, such as last occurred in 1868, or in large events on the adjoining northern Calaveras fault segment.

California↗
USGS2024

Awakening of Maunaloa linked to melt shared from Kilauea’s mantle source

Maunaloa—the largest active volcano on Earth—erupted in 2022 after its longest known repose period (~38 years) and two decades of volcanic unrest. This eruptive hiatus at Maunaloa encompasses most of the ~35-year-long Puʻuʻōʻō eruption of neighboring Kīlauea, which ended in 2018 with a collapse of the summit caldera and an unusually voluminous (~1 km 3 ) rift eruption. A long-term pattern of such anticorrelated eruptive behavior suggests that a magmatic connection exists between these volcanoes within the asthenospheric mantle source and melting region, the lithospheric mantle, and/or the volcanic edifice. The exact nature of this connection is enigmatic. In the past, the distinct compositions of lavas from Kīlauea and Maunaloa were thought to require completely separate magma pathways from the mantle source of each volcano to the surface. Here, we use a nearly 200-yr record of lava chemistry from both volcanoes to demonstrate that melt from a shared mantle source within the Hawaiian plume may be transported alternately to Kīlauea or Maunaloa on a timescale of decades. This process led to a correlated temporal variation in 206 Pb/ 204 Pb and 87 Sr/ 86 Sr at these volcanoes since the early 19th century with each becoming more active when it received melt from the shared source. Ratios of highly over moderately incompatible trace elements (e.g., Nb/Y) at Kīlauea reached a minimum from ~2000 to 2010, which coincides with an increase in seismicity and inflation at the summit of Maunaloa. Thereafter, a reversal in Nb/Y at Kīlauea signals a decline in the degree of mantle partial melting at this volcano and suggests that melt from the shared source is now being diverted from Kīlauea to Maunaloa for the first time since the early to mid-20th century. These observations link a mantle-related shift in melt generation and transport at Kīlauea to the awakening of Maunaloa in 2002 and its eruption in 2022. Monitoring of lava chemistry is a potential tool that may be used to forecast the behavior (e.g., eruption rate and frequency) of these adjacent volcanoes on a timescale of decades. A future increase in eruptive activity at Maunaloa is likely if the temporal increase in Nb/Y continues at Kīlauea.

Hawaii↗