SEARCH · Geology Reports

Results for “Basic Data Report”

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

SourceResearch connectionFrom yearThrough year

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

At least 775 records · Page 43Linked to original sources

USGS1980

Petroleum-resource appraisal and discovery rate forecasting in partially explored regions

PART A: A model of the discovery process can be used to predict the size distribution of future petroleum discoveries in partially explored basins. The parameters of the model are estimated directly from the historical drilling record, rather than being determined by assumptions or analogies. The model is based on the concept of the area of influence of a drill hole, which states that the area of a basin exhausted by a drill hole varies with the size and shape of targets in the basin and with the density of previously drilled wells. It also uses the concept of discovery efficiency, which measures the rate of discovery within several classes of deposit size. The model was tested using 25 years of historical exploration data (1949-74) from the Denver basin. From the trend in the discovery rate (the number of discoveries per unit area exhausted), the discovery efficiencies in each class of deposit size were estimated. Using pre-1956 discovery and drilling data, the model accurately predicted the size distribution of discoveries for the 1956-74 period. PART B: A stochastic model of the discovery process has been developed to predict, using past drilling and discovery data, the distribution of future petroleum deposits in partially explored basins, and the basic mathematical properties of the model have been established. The model has two exogenous parameters, the efficiency of exploration and the effective basin size. The first parameter is the ratio of the probability that an actual exploratory well will make a discovery to the probability that a randomly sited well will make a discovery. The second parameter, the effective basin size, is the area of that part of the basin in which drillers are willing to site wells. Methods for estimating these parameters from locations of past wells and from the sizes and locations of past discoveries were derived, and the properties of estimators of the parameters were studied by simulation. PART C: This study examines the temporal properties and determinants of petroleum exploration for firms operating in the Denver basin. Expectations associated with the favorability of a specific area are modeled by using distributed lag proxy variables (of previous discoveries) and predictions from a discovery process model. In the second part of the study, a discovery process model is linked with a behavioral well-drilling model in order to predict the supply of new reserves. Results of the study indicate that the positive effects of new discoveries on drilling increase for several periods and then diminish to zero within 2? years after the deposit discovery date. Tests of alternative specifications of the argument of the distributed lag function using alternative minimum size classes of deposits produced little change in the model's explanatory power. This result suggests that, once an exploration play is underway, favorable operator expectations are sustained by the quantity of oil found per time period rather than by the discovery of specific size deposits. When predictions of the value of undiscovered deposits (generated from a discovery process model) were substituted for the expectations variable in models used to explain exploration effort, operator behavior was found to be consistent with these predictions. This result suggests that operators, on the average, were efficiently using information contained in the discovery history of the basin in carrying out their exploration plans. Comparison of the two approaches to modeling unobservable operator expectations indicates that the two models produced very similar results. The integration of the behavioral well-drilling model and discovery process model to predict the additions to reserves per unit time was successful only when the quarterly predictions were aggregated to annual values. The accuracy of the aggregated predictions was also found to be reasonably robust to errors in predictions from the behavioral well-drilling equation.

Professional Paper↗

USGS1993

Geology and ground-water resources in the Zebulon area, Georgia

The current (1991) surface-water source of drinking-water supply for the city of Zebulon, Pike County, Georgia, no longer provides an adequate water supply and periodically does not meet water-quality standards. The hydrogeology of crystalline rocks in the Zebulon area was evaluated to assess the potential of ground-water resources as a supplemental or alternative source of water to present surface-water supplies. As part of the ground-water resource evaluation, well location and construction data were compiled, a geologic map was constructed, and ground water was sampled and analyzed. Three mappable geologic units delineated during this study provide a basic understanding of hydrogeologic settings in the Zebulon area. Rock types include a variety of aluminosilicate schists, granitic rocks, amphibolites/honblende gneisses, and gondites. Several geologic features that may enhance ground-water availability were identified in the study area. These features include contacts between contrasting rock types, where a high degree of differential weathering has occurred, and well-developed structural features, such as foliation and jointing are present. High-yielding wells (greater than 25 gallons per minute) and low-yielding wells (less than one gallon per minute) were located in all three geologic units in a variety of topographic settings. Well yields range from less than one gallon per minute to 250 gallons per minute. The variable total depths and wide ranges of casing depths of the high-yielding wells are indicative of variations in depths to water-bearing zones and regolith thicknesses, respectively. The depth of water-bearing zones is highly variable, even on a local scale. Analyses of ground-water samples indicate that the distribution of iron concentration is as variable as well yield in the study area and does not seem to be related to a particular rock type. Iron concentrations in ground-water samples ranged from 0.02 to 5.3 milligrams per liter. Both iron concentration and well yield vary substantially over a relatively small area. Implementation and Verification of a One-Dimensional, Unsteady-Flow Model for Spring Brook near Warrenville, Illinois By Mary J. Turner, Anthony P. Pulokas, and Audrey L. Ishii Abstract A one-dimensional, unsteady-flow model, Full EQuations (FEQ) model, based on de Saint-Venant equations for dynamic flow in open channels, was calibrated and verified for a 0.75-mile reach of Spring Brook, a tributary to the West Branch Du Page River, near Warrenville in northeastern Illinois. The model was used to simulate streamflow in a small urban stream reach with two short culverts, one with overbank flow around the culvert during high flows. Streamflow data were collected on the reach during three high-flow periods. Data from one period were used to calibrate the model, and data from the other two periods were used to verify the model. Stages and discharges over the periods were simulated, and the results were compared graphically with stage and discharge data collected at 10 sites in the study reach. Errors in simulated stage and discharge were small except when debris, not represented in the model, clogged the culvert. The effects of changes in physical and computational model parameters also were studied. The model was insensit'lve to replacement of measured cross sections with interpolated cross sections, especially if the measured thalweg elevation was preserved. Variation of the roughness, slope, and length of the culvert over-bank section, as well as the chosen representative measured cross section, caused only slight changes in the simulated peak stage and discharge. Changes in the modeled culvert area caused large differences in the simulated highflows in the vicinity of the culvert, whereas simulated low flows were unaffected. At all flows, the misrepresentation of the culvert area caused the simulated water-surface elevations to deviate from the measured elevations, especially on the falling

Georgia↗

USGS2006

Comprehensive water quality of the Boulder Creek Watershed, Colorado, during high-flow and low-flow conditions, 2000

Executive Summary The Boulder Creek Watershed, Colorado, is 1160 square kilometers in area and ranges in elevation from 1480 to 4120 meters above sea level. Streamflow originates primarily as snowmelt near the Continental Divide, and thus discharge varies seasonally and annually (Chapter 1). Most of the water in Boulder Creek is diverted for domestic, agricultural, and industrial use. Some diverted water is returned to the creek as wastewater effluent and by ditch returns, and additional water enters as groundwater and by transbasin diversions. These diversions and returns lead to complex temporal and spatial variations in discharge. The variations in discharge, along with natural factors such as geology and climate, and anthropogenic factors such as wastewater treatment, agriculture, mining, and urbanization, can affect water chemistry. As with many watersheds in the American West, dependable water quality and sufficient water supply are issues facing local water managers and users. Detailed water-quality and sediment sampling allows the identification of sources and sinks of chemical constituents and an understanding of the processes at work in a river system. This study, the most comprehensive water-quality analysis performed for Boulder Creek to date, was a cooperative effort of the U.S. Geological Survey (USGS) and the city of Boulder. Geographic information systems and modeling programs were used to delineate watershed boundaries, land cover, and geology (Chapter 2). During high-flow (June 2000) and low-flow (October 2000) conditions, researchers evaluated 226 water-quality variables, including basic water-quality indicators (Chapter 3), major ions and trace elements (Chapter 4), wastewater-derived organic compounds (Chapter 5), and pesticides (Chapter 6). Discharge (Chapter 1) and bed-sediment particle size and mineralogy (Chapter 7) were also evaluated. This cooperative study was facilitated by the Boulder Area Sustainability Information Network (BASIN), which provides public access to environmental information about the Boulder Creek Watershed on a website, www.basin.org. In addition to the USGS and city of Boulder data, researchers at the Institute of Arctic and Alpine Research at the University of Colorado provided water chemistry data for the headwaters of North Boulder Creek, upstream of the reach of the USGS/city of Boulder sampling sites (Chapter 8). Snowmelt produces high flows in Boulder Creek in late spring to early summer (Chapter 1). Because precipitation falling in the headwaters is very dilute (specific conductance about 5 microsiemens per centimeter), most chemical constituents are present in lower concentrations during high flows (Chapters 3, 4, 5, 6, and 8). However, concentrations of some constituents, such as total suspended solids (Chapter 3) and organic carbon (Chapter 5), increase during the spring snowmelt flush. The upper basin, which consists of alpine, subalpine, montane, and foothills regions west of the mouth of Boulder Canyon, is underlain by Precambrian igneous and metamorphic rocks (Chapter 1). Major dissolved inorganic constituents in headwater sites were found to be enriched by factors of 10 to 20 relative to precipitation; this is consistent with minor weathering of the local crystalline bedrock (Chapter 4). Some anthropogenic input is observed in the headwaters; precipitation introduces nitrogen derived from fossil fuel combustion and agricultural activities (Chapter 8). The lower basin, which consists of the plains region east of the mouth of Boulder Canyon, is underlain by Mesozoic sedimentary rock and Quaternary alluvium, and has substantially more anthropogenic sources. Concentrations of most dissolved inorganic constituents increased in the lower basin. Differentiation between natural and anthropogenic sources of some dissolved constituents is difficult because both sources contribute to the water composition in this region. The increase of most major constituents (bicarbonate, calcium, chloride, magnesium, sodium, and sulfate) is consistent with weathering of the underlying sedimentary bedrock (Chapter 4). It is likely that anthropogenic loading of constituents in this reach occurs during storm events. Fecal coliform concentrations were variable and in some cases exceeded state standards, primarily during low-flow conditions (Chapter 3). Effluent from Boulder’s 75th Street Wastewater Treatment Plant (WWTP) has a substantial impact on the water chemistry of lower Boulder Creek. The WWTP increases the concentrations of nutrients such as nitrogen and phosphorus (Chapter 3), major ions and trace metals (Chapter 4), and organic carbon (Chapter 5) in Boulder Creek. The effluent contained a spike in gadolinium, a rare earth element that is ingested for magnetic resonance imaging as a contrasting agent and then excreted to the urban wastewater system. The effluent also contained trace organic compounds such as surfactants, pharmaceuticals, hormones (Chapter 5), and pesticides (Chapter 6), which also were detected at downstream Boulder Creek sites. Water chemistry of Boulder Creek downstream of the WWTP is largely controlled by the degree of dilution of the wastewater effluent, which varies depending on the baseflow of Boulder Creek, the volume of wastewater effluent, and depletion by agricultural diversions. Coal Creek, a tributary of Boulder Creek, contains wastewater effluent from four additional WWTPs, and increases the load of many constituents in Boulder Creek. In addition to the impact from wastewater effluent, lower Boulder Creek is affected by agricultural land use. Eleven of 84 analyzed pesticides were detected in Boulder Creek or its inflows, primarily in the eastern section of the watershed (Chapter 6). This collaborative study provides an in-depth evaluation of the hydrology, water chemistry, and sediment mineralogy of North Boulder Creek, Middle Boulder Creek, Boulder Creek, and major inflows. The detailed sampling and analysis in this report provide a baseline for future reference, as well as information on the effect of land use and geology on water chemistry.

Colorado↗

USGS2012

Evaluating lake stratification and temporal trends by using near-continuous water-quality data from automated profiling systems for water years 2005-09, Lake Mead, Arizona and Nevada

The U.S. Geological Survey, in cooperation with the National Park Service and Southern Nevada Water Authority, collected near-continuous depth-dependent water-quality data at Lake Mead, Arizona and Nevada, as part of a multi-agency monitoring network maintained to provide resource managers with basic data and to gain a better understanding of the hydrodynamics of the lake. Water-quality data-collection stations on Lake Mead were located in shallow water (less than 20 meters) at Las Vegas Bay (Site 3) and Overton Arm, and in deep water (greater than 20 meters) near Sentinel Island and at Virgin and Temple Basins. At each station, near-continual depth-dependent water-quality data were collected from October 2004 through September 2009. The data were collected by using automatic profiling systems equipped with multiparameter water-quality sondes. The sondes had sensors for temperature, specific conductance, dissolved oxygen, pH, turbidity, and depth. Data were collected every 6 hours at 2-meter depth intervals (for shallow-water stations) or 5-meter depth intervals (for deep-water stations) beginning at 1 meter below water surface. Data were analyzed to determine water-quality conditions related to stratification of the lake and temporal trends in water-quality parameters. Three water-quality parameters were the main focus of these analyses: temperature, specific conductance, and dissolved oxygen. Statistical temporal-trend analyses were performed for a single depth at shallow-water stations [Las Vegas Bay (Site 3) and Overton Arm] and for thermally-stratified lake layers at deep-water stations (Sentinel Island and Virgin Basin). The limited period of data collection at the Temple Basin station prevented the application of statistical trend analysis. During the summer months, thermal stratification was not observed at shallow-water stations, nor were major maxima or minima observed for specific-conductance or dissolved-oxygen profiles. A clearly-defined thermocline and well-defined maxima and minima in specific-conductance and dissolved-oxygen profiles were observed at deep-water stations during the summer months. Specific-conductance maxima were likely the result of inflow of water from either the Las Vegas Wash or Muddy/Virgin Rivers or both, while the minima were likely the result of inflow of water from the Colorado River. Maxima and minima for dissolved oxygen were likely the result of primary productivity blooms and their subsequent decay. Temporal-trend analyses indicated that specific conductance decreased at all stations over the period of record, except for Las Vegas Bay (Site 3), where specific conductance increased. Temperature also decreased over the period of record at deep-water stations for certain lake layers. Decreasing temperature and specific conductance at deep-water stations is the result of decreasing values in these parameters in water coming from the Colorado River. Quagga mussels (Dreissena rostriformis bugensis), however, could play a role in trends of decreasing specific conductance through incorporation of calcite in their shells. Trends of decreasing turbidity and pH at deep-water stations support the hypothesis that quagga mussels could be having an effect on the physical properties and water chemistry of Lake Mead. Unlike other stations, Las Vegas Bay (Site 3) had increasing specific conductance and is interpreted as the result of lowering lake levels decreasing the volume of lake water available for mixing and dilution of the high-conductance water coming from Las Vegas Wash. Dissolved oxygen increased over the period of record in some lake layers at the deep-water stations. Increasing dissolved oxygen at deep-water stations is believed to result, in part, from a reduction of phosphorus entering Lake Mead and the concomitant reduction of biological oxygen demand.

Arizona;California;Nevada;Utah↗

USGS2003

Catalog of earthquake hypocenters at Alaskan volcanoes: January 1 through December 31, 2002

The Alaska Volcano Observatory (AVO), a cooperative program of the U.S. Geological Survey, the Geophysical Institute of the University of Alaska Fairbanks, and the Alaska Division of Geological and Geophysical Surveys, has maintained seismic monitoring networks at historically active volcanoes in Alaska since 1988 (Power and others, 1993; Jolly and others, 1996; Jolly and others, 2001; Dixon and others, 2002). The primary objectives of this program are the seismic monitoring of active, potentially hazardous, Alaskan volcanoes and the investigation of seismic processes associated with active volcanism. This catalog presents the basic seismic data and changes in the seismic monitoring program for the period January 1, 2002 through December 31, 2002. Appendix G contains a list of publications pertaining to seismicity of Alaskan volcanoes based on these and previously recorded data. The AVO seismic network was used to monitor twenty-four volcanoes in real time in 2002. These include Mount Wrangell, Mount Spurr, Redoubt Volcano, Iliamna Volcano, Augustine Volcano, Katmai Volcanic Group (Snowy Mountain, Mount Griggs, Mount Katmai, Novarupta, Trident Volcano, Mount Mageik, Mount Martin), Aniakchak Crater, Mount Veniaminof, Pavlof Volcano, Mount Dutton, Isanotski Peaks, Shishaldin Volcano, Fisher Caldera, Westdahl Peak, Akutan Peak, Makushin Volcano, Great Sitkin Volcano, and Kanaga Volcano (Figure 1). Monitoring highlights in 2002 include an earthquake swarm at Great Sitkin Volcano in May-June; an earthquake swarm near Snowy Mountain in July-September; low frequency (1-3 Hz) tremor and long-period events at Mount Veniaminof in September-October and in December; and continuing volcanogenic seismic swarms at Shishaldin Volcano throughout the year. Instrumentation and data acquisition highlights in 2002 were the installation of a subnetwork on Okmok Volcano, the establishment of telemetry for the Mount Veniaminof subnetwork, and the change in the data acquisition system to an EARTHWORM detection system. AVO located 7430 earthquakes during 2002 in the vicinity of the monitored volcanoes. This catalog includes: (1) a description of instruments deployed in the field and their locations; (2) a description of earthquake detection, recording, analysis, and data archival systems; (3) a description of velocity models used for earthquake locations; (4) a summary of earthquakes located in 2002; and (5) an accompanying UNIX tar-file with a summary of earthquake origin times, hypocenters, magnitudes, and location quality statistics; daily station usage statistics; and all HYPOELLIPSE files used to determine the earthquake locations in 2002. The AVO seismic network was used to monitor twenty-four volcanoes in real time in 2002. These include Mount Wrangell, Mount Spurr, Redoubt Volcano, Iliamna Volcano, Augustine Volcano, Katmai Volcanic Group (Snowy Mountain, Mount Griggs, Mount Katmai, Novarupta, Trident Volcano, Mount Mageik, Mount Martin), Aniakchak Crater, Mount Veniaminof, Pavlof Volcano, Mount Dutton, Isanotski Peaks, Shishaldin Volcano, Fisher Caldera, Westdahl Peak, Akutan Peak, Makushin Volcano, Great Sitkin Volcano, and Kanaga Volcano (Figure 1). Monitoring highlights in 2002 include an earthquake swarm at Great Sitkin Volcano in May-June; an earthquake swarm near Snowy Mountain in July-September; low frequency (1-3 Hz) tremor and long-period events at Mount Veniaminof in September-October and in December; and continuing volcanogenic seismic swarms at Shishaldin Volcano throughout the year. Instrumentation and data acquisition highlights in 2002 were the installation of a subnetwork on Okmok Volcano, the establishment of telemetry for the Mount Veniaminof subnetwork, and the change in the data acquisition system to an EARTHWORM detection system. AVO located 7430 earthquakes during 2002 in the vicinity of the monitored volcanoes. This catalog includes: (1) a description of instruments deployed in the field and their locations; (2) a description of earthquake detection, recording, analysis, and data archival systems; (3) a description of velocity models used for earthquake locations; (4) a summary of earthquakes located in 2002; and (5) an accompanying UNIX tar-file with a summary of earthquake origin times, hypocenters, magnitudes, and location quality statistics; daily station usage statistics; and all HYPOELLIPSE files used to determine the earthquake locations in 2002.

Alaska↗

USGS1981

Waterfowl and their wintering grounds in Mexico, 1937-64

The U.S. Fish and Wildlife Service has been interested in migratory birds, especially waterfowl, in Mexico for many years, An early period of cooperation in waterfowl administration was culminated in 1937 with the final ratification of the Convention Between the United States and the United Mexican States for the Protection of Migratory Birds and Game Mammals, usually referred to as the Migratory Bird Treat. Management of waterfowl on this continent is primarily carried out by hunting regulations. Current information on the status of each species must be obtained each year to serve as a basis for any needed modifications in the regulations. In the United States and Canada, wildlife biologists of the U.S. Fish and Wildlife Service and the Canadian Wildlife Service annually make the surveys to obtain this basic information. But the Government of Mexico has made no comparable surveys. Mexicans are not interested in hunting waterfowl to the extent that citizens of the United States and Canada are. As a consequence, Mexico's Department of Game emphasizes activities other than waterfowl management. Waterfowl, especially ducks, winter in or migrate through Mexico in large numbers, so it is obvious that and continental surveys of the winter population should include Mexico. Some general investigations of waterfowl distribution there were made in 1926 and earlier by E. A. Goldman. He was familiar with much of Mexico because he and E. W. Nelson studied mammals and biota there for many years. In the 1930's, because of the greater emphasis on waterfowl conservation and management, more detailed surveys were made of the continental breeding and wintering populations. One of these activities was designated as the midwinter, or January, inventory. In the early 1940's the senior author, who had been the Central Flyaway Biologist since 1937, recommended that the waterfowl wintering grounds in Mexico be included in the coverage of the midwinter waterfowl inventory. This was arranged in 1947, and the first aerial coverage, which only included coastal localities, was made in January-February of that year. The information obtained confirmed the value and advisability of including the Mexican wintering grounds in the annual survey; beginning in 1951 the wintering grounds in the Mexican highlands also were included. The surveys of Mexico were continued, except in 1957, through 1965; after 1965 they were greatly reduced. Ground reconnaissance and surveys had begun in Mexico with the preliminary work of Goldman in 1926, but quantitative studies were not started until 1937. The ground surveys continued at intervals in various parts of the Republic until 1960. Ground surveys are invaluable for such purposes as securing ecological information, specimens of birds and plants, and historical data about the areas from local residents, but the only satisfactory method of obtaining accurate quantitative information on waterfowl populations and their distribution is by airplane. Consequently, the major emphasis since 1947 has been on the annual aerial surveys. Ground studies were made much less frequently and were carried out mainly to obtain correlative information on the waterfowl foods available, the ecology of habitats, and for liaison with wildlife officials and biologists in Mexico. An important reason for the surveys of the waterfowl wintering grounds in Mexico was to determine their adequacy for the population of birds using them, and their potential to accommodate additional waterfowl if the wintering grounds in the United States became inadequate and larger flights entered Mexico. Other advantages included providing accurate information to hunters and other interested persons in the United States regarding the waterfowl shooting in Mexico, and determining the current status of these birds and their habitats in that country. Some of these findings were previously summarized by us (Saunders and Saunders 1949; Saunders 1964).

Resource Publication↗

USGS2000

Preliminary report on the 16 October 1999 M 7.1 Hector mine, California, earthquake

The M w 7.1 Hector Mine, California, earthquake occurred at 9:46 GMT on 16 October 1999. The event caused minimal damage because it was located in a remote, sparsely populated part of the Mojave Desert, approximately 47 miles east-southeast of Barstow, with epicentral coordinates 34.59°N 116.27°W and a hypocentral depth of 5 ± 3 km. Twelve foreshocks, M 1.9-3.8, preceded the mainshock during the previous twelve hours. All of these events were located close to the hypocenter of the mainshock. The Hector Mine earthquake occurred within the Eastern California Shear Zone (ECSZ). By virtue of its remote location, the societal impact of the Hector Mine earthquake was, fortunately, minimal in spite of the event's appreciable size. The ECSZ is characterized by high seismicity, a high tectonic strain rate, and a broad, distributed zone of north-northwest-trending faults (ECSZ; Figure 1 ; Dokka and Travis, 1990 ; Sauber et al., 1986 ; Sauber et al., 1994 ; Sieh et al., 1993 ). Data regarding the slip rates of faults within the ECSZ suggest that on the order of 15% of the Pacific-North American plate motion occurs along this zone ( Sauber et al., 1986 ; Wesnousky, 1986 ). Most of the faults in the ECSZ have low slip rates and long repeat times for major earthquakes, on the order of several thousands to tens of thousands of years. The occurrence of the Hector Mine earthquake within seven years and only about 30 km east of the 1992 M w 7.3 Landers earthquake suggests that the closely spaced surface faults in the ECSZ are mechanically related. The Hector Mine event involved rupture on two previously mapped fault zones—the Bullion Fault and an unnamed, more northerly-trending fault that is informally referred to in this paper as the Lavic Lake Fault (Dibblee, 1966 , 1967a , b ). Traces of the Bullion Fault exhibit evidence of Holocene displacement and were zoned as active in 1988 under California's Mquist-Priolo Earthquake Fault Zoning Act ( Hart and Bryant, 1997 ). The pattern of rupture along more than one named fault was also observed from the 1992 Landers earthquake ( Hauksson et al., 1993 ; Sieh et al., 1994). Much of the fault zone that produced the Hector Mine earthquake had been buried by relatively young stream deposits, and the fault scarps in bedrock have a subdued morphology. It appears that these faults have not experienced significant offset for perhaps 10,000 years or more ( Hart, 1987 ). Planned future investigations will refine the age of the last event on these faults. The portion of the Lavic Lake Fault that ruptured between the northern end of the Bullion Mountains and Lavic Lake had not previously been mapped. However, our field investigations have identified ancient, subdued fault scarps along portions of the 1999 rupture zone in this area. It thus appears that the entire segment of the Lavic Lake Fault that was involved in the 1999 event had ruptured in the past. As is typical for most faults within the Eastern California Shear Zone, the rate of movement along the Lavic Lake Fault may be quite slow (<1 mm/yr) and should produce earthquakes only infrequently. This event is a reminder that faults that have ruptured in late Quaternary time, but that lack evidence of Holocene displacement, can still produce earthquakes in this low-slip-rate tectonic setting. Additionally, the Hector Mine earthquake is noteworthy for a couple of other reasons. First, it clearly produced triggered seismicity over much of southern California, from the rupture zone toward the south-southwest in particular. Second, as we will discuss, the event may provide new data and insight into recently developed paradigms concerning earthquake interactions and the role of static stress changes. Questions such as these will, of course, be the subject of extensive detailed analyses in years to come. Fortunately, the Hector Mine sequence will provide one of the best data sets obtained to date for a significant earthquake in the United States. Because it occurred when major upgrades to both the regional seismic network (TriNet) and the regional geodetic network (SCIGN) were well underway, the Earth science community will have abundant high-quality data with which to explore the important and interesting questions that have been raised. In this paper, we present and discuss the basic data and preliminary results from the Hector Mine earthquake.

California↗

USGS2013

Tectonic map of the Circum-Pacific region, Pacific basin sheet

Circum-Pacific Map Project : The Circum-Pacific Map Project was a cooperative international effort designed to show the relationship of known energy and mineral resources to the major geologic features of the Pacific basin and surrounding continental areas. Available geologic, mineral, and energy-resource data are being complemented by new, project-developed data sets such as magnetic lineations, seafloor mineral deposits, and seafloor sediment. Earth scientists representing some 180 organizations from more than 40 Pacific-region countries are involved in this work. Six overlapping equal-area regional maps at a scale of 1:10,000,000 form the cartographic base for the project: the four Circum-Pacific Quadrants (Northwest, Southwest, Southeast, and Northeast), and the Antarctic and Arctic Sheets. There is also a Pacific Basin Sheet at a scale of 1:17,000,000. The Base Map Series and the Geographic Series (published from 1977 to 1990), the Plate-Tectonic Series (published in 1981 and 1982), the Geodynamic Series (published in 1984 and 1985), and the Geologic Series (published from 1984 to 1989) all include six map sheets. Other thematic map series in preparation include Mineral-Resources, Energy-Resources and Tectonic Maps. Altogether, more than 50 map sheets are planned. The maps were prepared cooperatively by the Circum-Pacific Council for Energy and Mineral Resources and the U.S. Geological Survey and are available from the Branch of Distribution, U. S. Geological Survey, Box 25286, Federal Center, Denver, Colorado 80225, U.S.A. The Circum-Pacific Map Project is organized under six panels of geoscientists representing national earth-science organizations, universities, and natural-resource companies. The six panels correspond to the basic map areas. Current panel chairmen are Tomoyuki Moritani (Northwest Quadrant), R. Wally Johnson (Southwest Quadrant), Ian W.D. Dalziel (Antarctic Region), vacant. (Southeast Quadrant), Kenneth J. Drummond (Northeast Quadrant), and George W. Moore (Arctic Region). Project coordination and final cartography was being carried out through the cooperation of the Office of the Chief Geologist of the U.S. Geological Survey, under the direction of General Chairman, George Gryc of Menlo Park, California. Project headquarters were located at 345 Middlefield Road, MS 952, Menlo Park, California 94025, U.S.A. The framework for the Circum-Pacific Map Project was developed in 1973 by a specially convened group of 12 North American geoscientists meeting in California. The project was officially launched at the First Circum-Pacific Conference on Energy and Mineral Resources, which met in Honolulu, Hawaii, in August 1974. Sponsors of the conference were the AAPG, Pacific Science Association (PSA), and the Coordinating Committee for Offshore Prospecting for Mineral Resources in Offshore Asian Areas (CCOP). The Circum-Pacific Map Project operates as an activity of the Circum-Pacific Council for Energy and Mineral Resources, a nonprofit organization that promotes cooperation among Circum-Pacific countries in the study of energy and mineral resources of the Pacific basin. Founded by Michel T. Halbouty in 1972, the Council also sponsors conferences, topical symposia, workshops and the Earth Science Series books. Tectonic Map Series : The tectonic maps distinguish areas of oceanic and continental crust. Symbols in red mark active plate boundaries, and colored patterns show tectonic units (volcanic or magmatic arcs, arc-trench gaps, and interarc basins) associated with active plate margins. Well-documented inactive plate boundaries are shown by symbols in black. The tectonic development of oceanic crust is shown by episodes of seafloor spreading. These correlate with the rift and drift sequences at passive continental margins and episodes of tectonic activity at active plate margins. The recognized episodes of seafloor spreading seem to reflect major changes in plate kinematics. Oceanic plateaus and other prominences of greater than normal oceanic crustal thickness such as hotspot traces are also shown. Colored areas on the continents show the ages of deformation and metamorphism of basement rocks and the emplacement of igneous rocks. Transitional tectonic (molassic) and reactivation basins are shown by a colored boundary, and if they are deformed, a colored horizontal line pattern indicates the age of deformation. Colored bands along basin boundaries indicate age of inception, and isopachs indicate thickness of platform strata on continental crust and cover on oceanic crust. Colored patterns at separated continental margins show the age of inception of rift and drift (breakup) sequences. Symbols mark folds and faults, and special symbols show volcanoes and other structural features. Affiliations are as of compilation of the data. This map was created in quadrants and then compiled together. They are the Northwest land, Northwest Marine (different compilers), Northeast, Southwest and Southeast, and parts in plate-boundary sections.

Circum-Pacific Map↗

USGS1988

National water summary 1986: Hydrologic events and ground-water quality

Ground water is one of the most important natural resources of the United States and degradation of its quality could have a major effect on the welfare of the Nation. Currently (1985), ground water is the source of drinking water for 53 percent of the Nation's population and for more than 97 percent of its rural population. It is the source of about 40 percent of the Nation's public water supply, 33 percent of water for irrigation, and 17 percent of freshwater for selfsupplied industries. Ground water also is the source of about 40 percent of the average annual streamflow in the United States, although during long periods of little or no precipitation, ground-water discharges provide nearly all of the base streamflow. This hydraulic connection between aquifers and streams implies that if a persistent pollutant gets into an aquifer, it eventually could discharge into a stream. Information presented in the 1986 National Water Summary clearly shows that the United States has very large amounts of potable ground water available for use. Although naturally occurring constituents, such as nitrate, and human-induced substances, such as synthetic organic chemicals, frequently are detected in ground water, their concentrations usually do not exceed existing Federal or State standards or guidelines for maximum concentrations in drinking water. Troublesome contamination of ground water falls into two basic categories related to the source or sources of the contamination. Locally, high concentrations of a variety of toxic metals, organic chemicals, and petroleum products have been detected in ground water associated with point sources such as wastedisposal sites, storage-tank leaks, and hazardous chemical spills. These types of local problems commonly occur in densely populated urban areas and industrialized areas. Larger, multicounty areas also have been identified where contamination frequently is found in shallow wells. These areas generally are associated with broad-scale, or nonpoint, sources of contamination such as agricultural activities or highdensity domestic waste disposal (septic systems) in urban centers. At present, only a very small percentage of the total volume of potable ground water in the United States is contaminated from both point and nonpoint sources; however, available data, especially data about the occurrence of synthetic organic and toxic substances, generally are inadequate to determine the full extent of ground-water contamination in the Nation's aquifers or to define trends in groundwater quality. Most information about the occurrence of these substances has come from the study of individual sites or areas where contamination had already been detected or suspected. Management and protection of ground water present a major challenge to the Nation. Current and projected costs of detection and cleanup of existing ground-water contamination are staggering and, even so, complete removal of pollutants from ground water in the vicinity of some waste sites might not be technically feasible. At all levels of government, the task of protecting the resource for its most beneficial uses is difficult and controversial. Despite increasing awareness that some of the Nation's ground water is contaminated with a variety of toxic metals, synthetic organic chemicals, radionuclides, pesticides, and other contaminants that might present a long-term risk to human health, public policy towards ground-water protection is still in the formative stages. Despite increasing efforts devoted to ground-water protection by State and Federal regulatory and resource-management agencies, the extent of ground-water contamination is likely to appear to increase over the next few years because more agencies will be searching for evidence of contamination, and they will be using increasingly sensitive analytical procedures. Increased technology and expanded monitoring activities probably will detect the effects of past contamination and land uses on water quality. The significant time lag between a waterquality change in one part of an aquifer system and the effects of that change at a downgradient site, such as a well, results from the generally slow movement of ground water. This lag between cause and observed effect needs to be considered in evaluating the effectiveness of current and future ground-water policies and remedial measures. Conclusive answers to questions about the location, extent, and severity of ground-water contamination, and about trends in ground-water quality, must await further collection and analysis of data from the Nation's aquifers. Generalizations, however, can be made, and the 1986 National Water Summary, which describes the natural quality of ground-water resources in each State and the major contamination problems that have been identified as of 1986, provides a national perspective of the ground-water-quality situation. The 1986 National Water Summary follows the format of previous volumes. It contains three parts, and the contents of each of these parts are highlighted below.

Water Supply Paper↗

USGS2010

Hydrogeology and water quality of the Floridan aquifer system and effect of Lower Floridan aquifer pumping on the Upper Floridan aquifer at Hunter Army Airfield, Chatham County, Georgia

Test drilling and field investigations, conducted at Hunter Army Airfield (HAAF), Chatham County, Georgia, during 2009, were used to determine the geologic, hydraulic, and water-quality characteristics of the Floridan aquifer system and to evaluate the effect of Lower Floridan aquifer (LFA) pumping on the Upper Floridan aquifer (UFA). Field investigation activities included (1) constructing a 1,168-foot (ft) test boring and well completed in the LFA, (2) collecting drill cuttings and borehole geophysical logs, (3) collecting core samples for analysis of vertical hydraulic conductivity and porosity, (4) conducting flowmeter and packer tests in the open borehole within the UFA and LFA, (5) collecting depth-integrated water samples to assess basic ionic chemistry of various water-bearing zones, and (6) conducting aquifer tests in the new LFA well and in an existing UFA well to determine hydraulic properties and assess interaquifer leakage. Using data collected at the site and in nearby areas, model simulation was used to quantify the effects of interaquifer leakage on the UFA and to determine the amount of pumping reduction required in the UFA to offset drawdown resulting from the leakage. Borehole-geophysical and flowmeter data indicate the LFA at HAAF consists of limestone and dolomitic limestone between depths of 703 and 1,080 ft, producing water from six major permeable zones: 723-731; 768-785; 818-837; 917-923; 1,027-1,052; and 1,060-1,080 ft. Data from a flowmeter survey, conducted at a pumping rate of 748 gallons per minute (gal/min), suggest that the two uppermost zones contributed 469 gal/min or 62.6 percent of the total flow during the test. The remaining four zones contributed from 1.7 to 18 percent of the total flow. Grab water samples indicate that with the exception of fluoride, constituent concentrations in the LFA increased with depth; water from the deepest interval (1,075 ft) contained chloride and sulfate concentrations of 480 and 240 milligrams per liter (mg/L), respectively. These relatively high concentrations were interpreted to have little effect on the overall quality of the well because flowmeter results indicated that water from 1,060 to 1,080 ft contributed less than 2 percent of the total flow to the completed well. Results of a 72-hour aquifer test indicate that pumping a LFA well at a rate of 748 gal/min produced a drawdown response of 0.76 ft in a well completed in the UFA located 176 ft from the pumped well. A revised regional groundwater-flow model was used to simulate long-term (steady-state) leakage response of the UFA to pumping from the LFA and to estimate the equivalent amount of pumping from the UFA that would produce similar drawdown. Pumping the well at a rate of 748 gal/min (about 1 million gallons per day [Mgal/d]) resulted in a maximum simulated steady-state drawdown of 36.2 ft in the LFA and was greater than 1 ft over a 146 square-mile area. Simulated steady-state drawdown in the overlying UFA that resulted from interaquifer leakage was greater than 1 ft over a 141 square-mile area and was 2.03 ft at the pumped well. Flow to the pumped well was derived from increased lateral flow across the specified-head boundary (0.02 Mgal/d) and increased leakage from the UFA (0.52 Mgal/d), and by reductions in discharge to the Lower Floridan confining unit (0.53 Mgal/d) and to the lateral specified-head boundary (0.53 Mgal/d). Sixty-five percent of the leakage from the UFA occurred within 1 mile of the pumped well. This larger contribution results from a larger head gradient between the pumped well and the overlying aquifer in areas close to the pumped well. The Georgia Environmental Protection Division interim permitting strategy for the LFA requires simulation of (1) aquifer leakage from the UFA to LFA resulting from pumping the new LFA well, and (2) the equivalent rate of UFA pumping that induces the identical maximum drawdown in the UFA that would be expected as a result of pumping th

Georgia↗

USGS2005

Environmental setting, water budget, and stream assessment for the Broad Run watershed, Chester County, Pennsylvania

The Broad Run watershed lies almost entirely in West Bradford Township, Chester County, Pa., and drains 7.08 square miles to the West Branch Brandywine Creek. Because of the potential effect of encroaching development and other stresses on the Broad Run watershed, West Bradford Township, the Chester County Water Resources Authority, and the Chester County Health Department entered into a cooperative study with the U.S. Geological Survey to complete an annual water budget and stream assessment of overall conditions. The annual water budget quantified the basic parameters of the hydrologic cycle for the climatic conditions present from April 1, 2003, to March 31, 2004. These water-budget data identified immediate needs and (or) deficits that were present within the hydrologic cycle during that period, if present; however, an annual water budget encompassing a single year does not identify long-term trends. The stream assessment was conducted in two parts and assessed the overall condition of the watershed, an overall assessment of the fluvial-geomorphic conditions within the watershed and an overall assessment of the stream-quality conditions. The data collected will document present (2004) conditions and identify potential vulnerabilities to future disturbances. For the annual period from April 1, 2003, to March 31, 2004, determination of an annual water budget indicated that of the 67.8 inches of precipitation that fell on the Broad Run watershed, 38.8 inches drained by way of streamflow to the West Branch Brandywine Creek. Of this 38.8 inches of streamflow, local-minimum hydrograph separation techniques determined that 7.30 inches originated from direct runoff and 31.5 inches originated from base flow. The remaining precipitation went into ground-water storage (1.71 inches) and was lost to evapotranspiration (27.3 inches). Ground-water recharge for this period-35.2 inches-was based on these values and an estimated ground-water evapotranspiration rate of 2 inches. Assessment of fluvial-geomorphic conditions included large-scale mapping of stream classes within the Broad Run watershed and in-depth study of three representative stream reaches also within the Broad Run watershed. Based on the total distance of all stream reaches classified within the Broad Run watershed, 61 percent were classified as C-class, 14 percent as E-class, 13 percent as B-class, 5 percent as F-class, 4 percent as undifferentiated B- and F-class, 2 percent as G-class, and less than 1 percent as A-class. The map of stream classes indicates that the Broad Run watershed currently has no large-scale areas of stream impairment and that, generally, the stream is not entrenched and the main branch of the Broad Run has an available, functioning flood plain. Smaller tributary streams, however, showed signs of localized entrenchment due to site-specific influences such as natural stream-channel evolution, localized channelization, localized contraction due to road and driveway crossings, and (or) increased localized runoff. For example, one small reach along a tributary channel was observed to become entrenched due to runoff originating from a new housing development. Entrenched stream reaches are merely located by large-scale mapping and require individual assessment to determine potential causes of entrenchment and (or) future restorative actions. Three in-depth geomorphic study sites showed that the Broad Run can currently be considered graded or in a state of dynamic equilibrium. The sites did, however, identify certain vulnerabilities to future changes within the watershed. These vulnerabilities included disruption of the present sediment supply, including both increases and (or) reductions in the current sediment loads within the Broad Run; increases in both magnitude and duration of storm-water runoff; encroachment of development onto present flood-plain areas, and (or) alterations to riparian zones. Assessment of stream-quality conditions includ

Scientific Investigations Report↗

USGS2019

Sediment classification and the characterization, identification, and mapping of geologic substrates for the glaciated Gulf of Maine seabed and other terrains, providing a physical framework for ecological research and seabed management

A geologic substrate is a surface (or volume) of sediment or rock where physical, chemical, and biological processes occur, such as the movement and deposition of sediment, the formation of bedforms, and the attachment, burrowing, feeding, reproduction, and sheltering of organisms. Seabed mapping surveys in the Stellwagen Bank region off Boston, Massachusetts, from 1993 to 2004 have led to the development of a methodology for characterizing, identifying, and mapping geologic substrates. The resulting high-resolution interpretive maps (1:25,000) show the distribution of substrates in a glaciated terrain of banks and basins in water depths of 30 to 185 meters. Data sources used to characterize substrates are multibeam sonar bathymetric and backscatter imagery to document seabed topography and patterns of sediment and rock distribution, grain-size analyses of sediment samples to determine substrate composition, and video and photographic imagery of the seabed to aid in the interpretation of multibeam sonar imagery and to provide information on substrate layering and mobility, seabed structures, and sediments and nonsediment materials that cannot be physically sampled. Sediment composition is a major property of many seabed substrates. Sediment grains belong to a continuum of grain-diameter sizes previously classified into grades (for example, fine sand, medium sand) and into aggregates (mud, sand, gravel). The definition of grade and aggregate boundaries in a classification is arbitrary, and a useful classification is limited to as few classes as are needed to effectively organize and apply information. For the purpose of mapping substrates, sediment grades and aggregates were simplified and re-classified into eight composite grades based on grain-size content, mode of transport, and ecological role. Five composite grades are identified using grain-size analysis and three are identified using video and photographic imagery of the seabed. Naturally occurring sediments contain various amounts of the aggregates mud, sand, and gravel. The separation of naturally occurring sediments into sediment classes, based on grain-size analysis, requires that limits be set on the amount of mud, sand, and gravel each class contains. Fifteen previously identified basic sediment classes provided interpretive information on sediment transport by emphasizing gravel content (a low 0.01-weight-percent threshold) and on winnowing processes based on the sand-to-mud ratio. The present study recognizes 20 basic sediment classes that are combinations of aggregates in which the lower limits for recognition of mud and sand are 10 weight percent and of gravel, 25 weight percent. These sediment classes can be made more specific by listing their content of the composite grades fine-grained sand (3 and 4 phi), which is transported in suspension, and coarse-grained sand (0, 1, and 2 phi), which is transported as bedload. Additional sediment classes and nonsediment classes that cannot be sampled are recognized on the basis of visual analysis of seabed video and photographic imagery and include pebble, cobble, and boulder gravel, rock outcrops, and shell beds, among others. Substrates are not classified because their properties are too varied for a classification to be concise and useful. Rather, substrates are characterized and identified by sediment grain-size composition (the sediment class); the distribution, in millimeters, of grain diameters in the sediment; the presence of nonsediments (for example, rock outcrops); substrate mobility based on the presence of sediment ripples; substrate layering (for example, a partial veneer of sand on gravel); and seabed structures. These properties have interpretive value by providing information about sedimentary processes acting on a substrate and about its ecological function. A geologic substrate, when it is associated with one or more species, is an important element of a habitat. This methodology was developed to map a glaciated terrain characterized by geologic substrates that typify a wide range of erosional and depositional sedimentary environments, and it likely will be useful for mapping substrates in other terrains. Substrate maps provide the physical framework required for identifying sediment transport processes, validating sediment transport models, studying the ecology of species and communities, and managing marine resources and seabed usage.

Massachusetts↗

USGS2014

Groundwater-quality data in the Klamath Mountains study unit, 2010: results from the California GAMA Program

Groundwater quality in the 8,806-square-mile Klamath Mountains (KLAM) study unit was investigated by the U.S. Geological Survey (USGS) from October to December 2010, as part of the California State Water Resources Control Board (SWRCB) Groundwater Ambient Monitoring and Assessment (GAMA) Program’s Priority Basin Project (PBP). The GAMA-PBP was developed in response to the California Groundwater Quality Monitoring Act of 2001 and is being conducted in collaboration with the SWRCB and Lawrence Livermore National Laboratory (LLNL). The KLAM study unit was the thirty-third study unit to be sampled as part of the GAMA-PBP. The GAMA Klamath Mountains study was designed to provide a spatially unbiased assessment of untreated-groundwater quality in the primary aquifer system and to facilitate statistically consistent comparisons of untreated-groundwater quality throughout California. The primary aquifer system is defined by the perforation intervals of wells listed in the California Department of Public Health (CDPH) database for the KLAM study unit. Groundwater quality in the primary aquifer system may differ from the quality in the shallower or deeper water-bearing zones; shallower groundwater may be more vulnerable to surficial contamination. In the KLAM study unit, groundwater samples were collected from sites in Del Norte, Siskiyou, Humboldt, Trinity, Tehama, and Shasta Counties, California. Of the 39 sites sampled, 38 were selected by using a spatially distributed, randomized grid-based method to provide statistical representation of the primary aquifer system in the study unit (grid sites), and the remaining site was non-randomized (understanding site). The groundwater samples were analyzed for basic field parameters, organic constituents (volatile organic compounds [VOCs] and pesticides and pesticide degradates), inorganic constituents (trace elements, nutrients, major and minor ions, total dissolved solids [TDS]), radon-222, gross alpha and gross beta radioactivity, and microbial indicators (total coliform and Escherichia coli [E. coli]). Isotopic tracers (stable isotopes of hydrogen and oxygen in water, isotopic ratios of dissolved strontium in water, and stable isotopes of carbon in dissolved inorganic carbon), dissolved noble gases, and age-dating tracers (tritium and carbon-14) were measured to help identify sources and ages of sampled groundwater. Quality-control samples (field blanks, replicate sample pairs, and matrix spikes) were collected at 13 percent of the sites in the KLAM study unit, and the results were used to evaluate the quality of the data from the groundwater samples. Field blank samples rarely contained detectable concentrations of any constituent, indicating that contamination from sample collection or analysis was not a significant source of bias in the data for the groundwater samples. More than 99 percent of the replicate pair samples were within acceptable limits of variability. Matrix-spike sample recoveries were within the acceptable range (70 to 130 percent) for approximately 91 percent of the compounds. This study did not evaluate the quality of water delivered to consumers. After withdrawal, groundwater typically is treated, disinfected, and (or) blended with other waters to maintain water quality. Regulatory benchmarks apply to water that is delivered to the consumer, not to untreated groundwater. However, to provide some context for the results, concentrations of constituents measured in the untreated groundwater were compared with regulatory and non-regulatory health-based benchmarks established by the U.S. Environmental Protection Agency (USEPA) and CDPH, and to non-health-based benchmarks established for aesthetic concerns by the CDPH. Comparisons between data collected for this study and benchmarks for drinking water are for illustrative purposes only and are not indicative of compliance or non-compliance with those benchmarks. All concentrations of organic constituents from grid sites sampled in the KLAM study unit were less than health-based benchmarks. In total, VOCs were detected in 16 of the 38 grid sites sampled (approximately 42 percent), pesticides and pesticide degradates were detected in 8 grid sites (about 21 percent), and microbial indicators were detected in 14 grid sites (approximately 37 percent). Inorganic constituents (trace elements, major and minor ions, nutrients, and uranium and other radioactive constituents) and microbial indicators were sampled for at 38 grid sites, and all concentrations were less than health-based benchmarks, with the exception of one detection of boron greater than the CDPH notification level of 1,000 micrograms per liter (μg/L). Generally, concentrations of inorganic constituents with non-health-based benchmarks (iron, manganese, chloride, and TDS) were less than the CDPH secondary maximum contaminant level (SMCL-CA). Exceptions include three detections of iron greater than the SMCL-CA of 300 μg/L, four detections of manganese greater than the SMCL-CA of 50 μg/L, one detection of chloride greater than the recommended SMCL-CA of 250 μg/L, and one detection of TDS greater than the recommended SMCL-CA of 500 μg/L.

California↗

USGS2010

Timing, distribution, and volume of proximal products of the 2006 eruption of Augustine Volcano: Chapter 8 in The 2006 eruption of Augustine Volcano, Alaska

During and after the 2006 eruption of Augustine Volcano, we compiled a geologic map and chronology of new lava and flowage deposits using observational flights, oblique and aerial photography, infrared imaging, satellite data, and field investigations. After approximately 6 months of precursory activity, the explosive phase of the eruption commenced with two explosions on January 11, 2006 (events 1 and 2) that produced snow-rich avalanches; little or no juvenile magma was erupted. Seismicity suggests that a small lava dome may have extruded on January 12, but, if so, it was subsequently destroyed. A series of six explosions on January 13–14 (events 3–8) produced widespread but thin (0–30 cm) pyroclastic-current deposits on the upper flanks above 300 m altitude and lobate, 0.5- to 2-m-thick pyroclastic flows that traveled down most flanks of the volcano. Between January 14 and 17, a smooth lava lobe formed in the east half of the roughly 400-m-wide summit crater and was only partially covered by later deposits. An explosion on January 17 (event 9) opened a crater in the new lava dome and produced a ballistic fall deposit and pyroclastic flow on the southwest flank. During the interval from January 17 to 27, a rubbly lava dome effused. On January 27, explosive event 10 generated a pyroclastic current that left a deposit, rich in dense clasts, on the north-northwest flank. Immediately following the pyroclastic current, a voluminous 4.7-km-long pyroclastic flow swept down the north flank. Three more explosive blasts on January 27 and 28 produced unknown but likely minor on-island deposits. The cumulative volume of erupted material from the explosive phase, including domes, flows, and fall deposits (Wallace and others, this volume), was 30×10 6 m 3 dense-rock equivalent (DRE). The continuous phase of the eruption (January 28 through February 10) began with a 4-day period of nearly continuous block-and-ash flows, which deposited small individual flow lobes that cumulatively formed fans to the north and northeast of the summit. A single larger pyroclastic flow on January 30 formed a braided deposit on the northwest flank. Roughly 9×10 6 m 3 (DRE) of magma erupted during this period. Around February 2, the magma flux rate waned and a northward lava flow effused and reached a length of approximately 900 m by February 10. Approximately 11×10 6 m 3 (DRE) of magma erupted during the second half of the continuous phase. After a 23-day hiatus, lava effusion recommenced in early March (the effusive phase) and was accompanied by frequent (but volumetrically minor) block-and-ash flows. From March 7 to 14, extrusion increased markedly; two blocky lava-flow lobes, each tens of meters thick, moved down the north and northeast flank of the volcano; and a new summit lava dome grew to be ~70 m taller than the pre-2006 summit. This phase produced 26×10 6 m 3 (DRE) of lava. Active effusion had ceased about March 16, but, in April and May, three gravitational collapses from the west margin of the north lava flow produced additional block-and-ash flows. The basic sequence of the 2006 eruption closely matches that of eruptions in 1976 and 1986.

Alaska↗

USGS1996

Trends in surface-water quality in Connecticut, 1969-88

Surface-water-quality data from selected monitoring stations in Connecticut were analyzed for trend, using the Seasonal Kendall test, for water years 1969-88, 1975-88, and 1981-88. The number of constituents and stations evaluated varied with the different time periods. The 39 monitoring stations included 26 freshwater streams with associated discharge data, 7 tidally affected streams, 4 harbor stations, and 2 surface impoundments. Flow-adjustment procedures were used where possible to minimize the effects of stream- flow variability on trend results. The drainage area of the monitoring stations includes approximately 5,000 mi 2 covering the State of Connecticut and about 11,000 mi 2 in upstream drainage areas outside of the State. Drainage basin size for the freshwater streams ranges from 4.1 mi 2 to 9,660 mi 2 . Land uses in the drainage basins range from undeveloped forested areas to highly urbanized metropolitan areas. During the period covered by the trend study, the State's population has grown, suburban development has increased, agricultural land use has decreased, and wastewater-treatment practices have improved. Increases in specific conductance and in the concentrations of calcium, magnesium, chloride, sulfate, dissolved solids, and total solids were geographically widespread and numerous during water years 1975-88 and indicate a general increase statewide in dissolved constituents in streamflow, both in urbanized and less developed areas. The effects of increasing urbanization, including municipal and industrial wastewater, septic system leachate, nonpoint runoff, and atmospheric deposition of contaminants, are possible causes for these increases. Decreases in turbidity and in the concentrations of total phosphorus, total organic carbon, and fecal coliform bacteria were geographically widespread and numerous during 1975-88. This general decrease in suspended material and bacteria may be attributable to basic improvements in the treatment of municipal and industrial wastewater during the period of record. Decreasing concentrations of total phosphorus may also be related to decreases in agricultural land use and to a decline in the use of detergents containing phosphorus. Detected decreases in total organic carbon and turbidity may have been caused, in part, by changes in sampling or analytical methods. Increases in total nitrogen, total organic nitrogen, and total nitrite-plus- nitrate were geographically widespread and numerous during 1975-88 and appear to indicate effects from both point sources in urbanized basins and nonpoint sources in less developed basins. The number of stations with increasing concentrations of nitrogen constituents was much smaller during 1981-88 than during 1975-88. Decreases in total ammonia nitrogen were detected at 11 stations during 1981-88. Decreases in total ammonia, sometimes paired with increases in total nitrite-plus-nitrate, may result from improvements in wastewater treatment. Increases in the concentration of dissolved oxygen, or dissolved oxygen as a percent of saturation, were geographically widespread and numerous during 1969-88 and 1975-88. Increases were less common during 1981-88. Increases in dissolved oxygen in urbanized basins may be related to major improvements in wastewater treatment during the 1970's and 1980's. The magnitude of the trends detected during 1969-88 may have been affected in part by a change, around 1974, in the model of the instrument used to measure dissolved oxygen in the field. Statewide increases in pH were detected during 1969-88, 1975-88, and 1981-88, in both urbanized and less developed basins. The widespread increases in pH were unexpected, given the relatively acidic quality of precipitation in the region during the study period. Only two decreases in pH were detected, both in relatively undeveloped basins. Increases in pH in urbanized areas may be related to decreasing concentrations of ammonia and to requirements for neutralization of municipal and industrial wastewater.

Connecticut↗

USGS1972

Preliminary photointerpretation map of landslide and other surficial deposits of the Mount Hamilton quadrangle and parts of the Mount Boardman and San Jose quadrangles, Alameda and Santa Clara Counties, California

The nine San Francisco Bay region counties lie within a geologically active, young, and dynamic part of the central and northern Coast Ranges of California. Significant movements of the earth's crust are occurring here at the present time, posing numerous problems to urbanization, including some of special concern. Geological processes such as fault movements, earthquakes, land subsidence, landsliding, slow downslope movement of bedrock and surficial materials, coastal and stream erosion, flooding, and sedimentation are all potentially hazardous. Because of these factors, an understanding of the operation of physical processes in the bay region is desirable for harmonious, efficient, and safe land-use planning, particularly now, with greatly expanded pressures for urban growth. This map presents preliminary information about one aspect of the physical environment necessary to sound land-use planning--the nature and distribution of surficial deposits. Because surficial deposits are common and well developed in much of the bay region, it is useful to know how and why they have formed, as well as what properties they possess. When maps like this are used in combination with other types of environmental information, such as data on soils, bedrock geology, slopes, vegetation, climatic variation, seismic response, and hydrology, it should be easier to arrive at sound decisions regarding the physical aspects of land use. The U.S. Geological Survey is studying many of these factors in the bay region and hopes to provide the community with much of the required information as part of its San Francisco Bay Region Study in cooperation with the Department of Housing and Urban Development. The representation of surficial deposits on this map reflects the way in which a geologist, working exclusively with aerial photographs, interpreted the origin of various elements of the present landscape. The deposits shown here have not been examined in the field. However, by viewing overlapping vertical aerial photographs through a stereoscope, the geologist sees a three-dimensional relief model of the ground surface and can study and interpret the origins of landforms with considerable ease. In fact, for mapping surficial deposits, particularly in reconnaissance-type studies, photointerpretation has advantages over both ground observations and laboratory studies of surficial materials. Of course, better information can be provided when all aspects of the study are integrated. These preliminary photointerpretation maps are only the first stage in a detailed study of surficial deposits in the bay region, but they should provide land-use planners with immediately useful information about the regional distribution of landslide and other surficial deposits. This map indicates the dominant surficial processes that have probably been operative by showing the distribution of different types of surficial deposits. Processes such as weathering, erosion, sedimentation, and the slow as well as rapid downslope movement of earth materials have constantly reshaped the land surface in the past and will continue to in the future, although at varying rates. The processes are interrelated to varying degrees. For example, crustal uplift of the Coast Ranges will lead to increased erosion and downcutting by streams that in turn generally results in increased deposition of sediments in river valleys, lakes, and shoreline areas. Older flood planes and river deposits may be eroded, leaving elevated terrace deposits. In addition, downcutting by streams may cause adjacent slopes to become unstable, thereby increasing the possibility of slope failures. Man's activities can alter natural physical processes in many ways. Simple acts such as overwatering a lawn or placing a septic tank drainfield in ground that is marginally stable may weaken the bedrock and surficial materials enough to induce landsliding. Relatively stable areas may be made unstable as a result of construction activities that involve cutting or oversteepening of natural slopes. Engineers, builders, conservationists, and others concerned with land use must evaluate the potential effects of all types of development, and maps that show the nature and distribution of surficial deposits should provide much of the basic information they need. This map, then, shows the cumulative effects of various processes that have yielded surficial deposits up to the time the photographs used for photointerpretation were taken. It does not indicate directly areas where processes will be most active, nor does it show the rate at which they will operate. However, knowledge of the history of geologic events is a key to understanding and predicting the evolution of an area, even where man's activities significantly change the character of the land. Almost all new landslides, for example, occur in areas with a history of landslide activity.

California↗

USGS2020

Smallmouth buffalo (Ictiobus bubalus) growth across a 1200km human use and ecological disturbance gradient in the Upper Mississippi River System

Smallmouth buffalo (Ictiobus bubalus) is a common and widely distributed large-bodied species of the family Catostomidae. It inhabits large rivers and reservoirs of the eastern continental United States (east of the continental Divide) and is most abundant and common in the large rivers of the Midwest and Central Plains, though it does occur as far north and east as the Hudson Bay drainage and as far south and west as Arizona (Edwards and Twoney 1982). Historically, smallmouth buffalo were an important component of commercial fisheries on both the Mississippi and Illinois Rivers. However, following the introduction of common carp (Cyprinus carpio) in the mid-1800s (Carlander 1954), the construction of a system of navigation dams on Upper Mississippi and Illinois River in the 1930s (USGS 1999), and water quality/pollution issues through the 1980s (Weiner 2010), the role of smallmouth buffalo in the overall UMRS fish community and commercial fishery has generally diminished relative to historical standards. Still, smallmouth buffalo remains an important and valued component of the UMRS commercial fishery. The study area is represented by three study reaches on the Illinois River and three study reaches on the Upper Mississippi River (Figure 1). Collectively, these study reaches represent nearly 1200 river km and exist across strong and pronounced ecological and disturbance gradients. For example, habitat composition, water quality, commercial navigation intensity, aquatic plant prominence, and the number and abundance of nonnative fish species vary strongly across the study domain, with northern Mississippi River reaches exhibiting less navigation traffic, better water quality, markedly greater aquatic plant prominence, more diverse habitat composition, and comparably much smaller numbers of nonnative species than the lower Mississippi River study reach and those on the Illinois River (USGS 1999; Johnson and Hagerty [eds] 2008; Irons et al. 2009). Long term monitoring efforts conducted under the auspices of the Upper Mississippi River Restoration program over the past 27 years have provided tremendous insights into shifts and changes of the overall UMRS fish community (Ickes et al. 2005; Garvey et al. 2010; Schramm and Ickes 2016). However, these monitoring efforts observe only the most basic aspects of the UMRS fish community (i.e., catch, length, weight, distribution, and occurrence). To gain a greater understanding of forces driving community level shifts and changes, more directed study is needed on the functional attributes of fish populations (i.e., growth, mortality, recruitment). Collectively, these functional attributes of populations are termed population dynamics and/or vital rates. It is important to note, the population dynamics of fishes in large rivers is generally poorly understood, especially for non-game species (Ickes 2018). The prevailing view is that abiotic factors largely govern inter-annual population dynamics, typically based upon rather short-term observations and correlations with assorted abiotic river attributes that vary on a seasonal or annual basis (for example, Risotto and Turner 1985). However, the role that longer-term abiotic factors play in regulating population abundance, or that biotic factors internal to the population (e.g., spawner-recruit dynamics, growth dynamics) or external to the population (e.g., predator-prey dynamics, sympatric competitors, disease) remain poorly understood. Achieving a greater understanding of these dynamics is important for stock, game, and invasive species management. In 2017, as part of a larger study designed to gain vital population rate information for smallmouth buffalo in the Upper Mississippi and Illinois Rivers (“Smallmouth Buffalo population demographics of the Upper Mississippi River System”; UMRR LTRM 2018SOW project items 2018MMBF1-2018MMBF6) annual growth patterns in smallmouth buffalo were determined and evaluated. This was accomplished by measuring growth histories recorded in annual growth increments on hard bony parts (here otoliths), a method known generically as biochronology, and somewhat analogous to dendrochronology practiced by foresters. These methods allow one to generate time-series of annual growth histories that depend upon age, year class (i.e., cohort), and annual environmental conditions experienced by the population over time (Weisberg, 1993). Biochronology methods were used to develop a 36-year time series of smallmouth buffalo growth in the Upper Mississippi and Illinois Rivers across a 1200 km ecological and human use disturbance gradient. Annual growth intervals were identified and measured from otoliths to determine fish age and growth history. A mixed model that parses the growth increment into age and year effects was fit to these data. Given the pronounced ecological and disturbance gradients inherent to the UMRS and the study domain, an a priori expectation of differing patterns in growth is accepted as a null hypothesis to test. The goal of this study was to model smallmouth buffalo growth as a function of the age of the fish and the growth year in which the growth was gained. The primary modeling objective was to parse growth observed on each annulus into a portion attributable to the age of the fish and the portion attributable to the year in which the growth was gained. In effect, this modeling approach removes the somewhat trivial age effects on growth so that a non-confounded growth year effect can be gained. Results attributable to growth year provide a time series of growth information that is of the same duration as the oldest fish observed and solely reflects environmental influences on growth. These model responses can then be investigated relative to environmental covariate time-series suspected of influencing growth of smallmouth buffalo in the Upper Mississippi and Illinois Rivers (e.g., temperature, discharge, population density, population mortality, forage availability, sympatric competition, habitat composition, navigation intensity, nonnative fish prominence, etc.). Thus, the primary scientific objective was to investigate if and how smallmouth buffalo growth varies in accordance with innate ecological and disturbance gradients across the study domain.

Illinois, Iowa, Minnesota, Missouri, Wisconsin↗

USGS2020

Trends in recent historical and projected climate data for the Colorado River Basin and potential effects on groundwater availability

Understanding recent historical and projected trends in precipitation and temperature in the Colorado River Basin, and estimating what the projected changes in these climate parameters may mean for groundwater resources in the region, is important for water managers and policymakers to sustainably manage water resources in the basin. Historical (1896–2019) precipitation and temperature data for the upper and lower Colorado River Basins were analyzed to better understand recent trends in climate data that may affect groundwater resources in the area. Historical data indicate multidecadal-scale cyclical patterns in precipitation in both the upper and lower basins. Although upper basin precipitation had no statistical trend over the recent historical period, the lower basin had a weak negative trend over this period. Multidecadal-scale cyclical patterns in temperature also are observed in historical climate data in both the upper and lower basins, at least until the early 1970s. Beginning at that time, both the upper and lower basins experienced strong, monotonic positive trends in temperature. Basic principles of hydrology indicate that periods of decreasing precipitation as well as increasing temperature would have a negative effect, that is, reduction in groundwater infiltration and hence, reduced recharge of aquifer systems. Projected climate data from 97 Coupled Model Intercomparison Project phase 5 (CMIP5) ensemble members across the full range of Representative Concentration Pathway (RCPs) from water years 1951 through 2099 were evaluated to understand what current global climate models are projecting about future conditions in the Colorado River Basin, and what this might mean for groundwater systems in the region. Precipitation in the upper basin is projected to increase throughout the rest of the century, rising to 6 percent above the 1951–2015 historical period by mid-century and to 9 percent above the historical period by the end of the century. Temperature in the upper basin also is projected to be above the recent historical median throughout the rest of the century, with steady warming in decadal average temperatures expected until the last quarter of this century. In contrast to projected precipitation in the upper basin, precipitation in the lower basin is projected to be the same as, or slightly less than, the historical period throughout most of the rest of this century. Like projected temperature in the upper basin, temperature in the lower basin also is projected to be above the recent historical median throughout the rest of the century. Comparing median projections for all future decades with median results from all historical decades, future precipitation is expected to be greater than that of the past in the upper basin, though no significant difference is projected for precipitation in the lower basin. Significant increases (p-value<0.05) are expected in temperature in both the upper and lower basins. To estimate the effects of projected precipitation and temperature on groundwater systems in the region, results from the 97 member CMIP5 climate projection ensemble were used as input in a Soil-Water Balance (SWB) groundwater infiltration model for the Colorado River Basin. SWB simulation results indicate that the upper Colorado River Basin is expected to experience decades of above-historical-average groundwater infiltration through the end of the century. For the lower Colorado River Basin, simulated groundwater infiltration is projected to be consistently less than the recent (1951–2015) historical period for most of the remaining century. A comparison of the distribution of all median simulated groundwater infiltration results between recent historical and future periods indicates projected groundwater infiltration in the upper basin is significantly (p-value<0.05) greater over the combined 2020–2099 future period than the recent (1951–2015) historical period. Moreover, in 41 of 71 (58 percent) possible future decades in this century, groundwater infiltration is projected to be greater than the 75th percentile of historical simulated groundwater infiltration. Projected groundwater infiltration in the lower Colorado River Basin across all future decades is significantly less than in the historical period. Of the 71 future decades in the century, projected groundwater infiltration in the lower basin is expected to be less than the 25th percentile of historical infiltration in 55 (77 percent) of the 10-year periods. Important differences in projected precipitation between the upper (increasing precipitation) and lower (decreasing precipitation) basins largely drive the different responses of simulated groundwater infiltration in the upper (increasing infiltration) and lower (decreasing infiltration) basins. It will be useful to revisit projections in groundwater infiltration in the Colorado River Basin when more up-to-date projections of precipitation become available from the next Coupled Model Intercomparison Project phases or by using climate input developments through Regional Climate Modeling efforts and stochastic weather generators.

Arizona, California, Colorado, Nevada, New Mexico,↗