USGS Science⌕ Search

SEARCH · USGS Science

Results for “Natural Hazards”

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.

1,195 records · Page 67Linked to original sources
USGS1996

Hydrogeology and ground-water quality of the chromic acid pit site, U.S. Army Air Defense Artillery Center and Fort Bliss, El Paso, Texas

The Chromic Acid Pit site is an inactive waste disposal site that is regulated by the Resource Conservation and Recovery Act of 1976. The 2.2-cubic-yard cement-lined pit was operated from 1980 to 1983 by a contractor to the U.S. Army Air Defense Artillery Center and Fort Bliss. The pit, located on the Fort Bliss military reservation, in El Paso, Texas, was used for disposal and evaporation of chromic acid waste generated from chrome plating operations. The site was certified closed in 1989 and the Texas Natural Resources Conservation Commission issued Permit Number HW-50296 (U.S. Environmental Protection Agency Permit Number TX4213720101), which approved and implemented post-closure care for the Chromic Acid Pit site. In accordance with an approved post-closure plan, the U.S. Geological Survey is cooperating with the U.S. Army in evaluating hydrogeologic conditions and ground- water quality at the site. One upgradient and two downgradient ground-water monitoring wells were installed adjacent to the chromic acid pit by a private contractor. Quarterly ground-water sampling of these wells by the U.S. Geological Survey began in December 1993. The Chromic Acid Pit site is situated in the Hueco Bolson intermontane valley. The Hueco Bolson is a primary source of ground water in the El Paso area. City of El Paso and U.S. Army water-supply wells are located on all sides of the study area and are completed 600 to more than 1,200 feet below land surface. The ground-water level in the area of the Chromic Acid Pit site has declined about 25 feet from 1982 to 1993. Depth to water at the Chromic Acid Pit site in September 1994 was about 284 feet below land surface; ground-water flow is to the southeast. Ground-water samples collected from monitoring wells at the Chromic Acid Pit site contained dissolved-solids concentrations of 442 to 564 milligrams per liter. Nitrate as nitrogen concentrations ranged from 2.1 to 2.7 milligrams per liter; nitrite plus nitrate as nitrogen concentrations ranged from 2.3 to 3.0 milligrams per liter. Nitrate concentrations are abnormally high in the Old Mesa well field located about 5,000 feet southwest of the Chromic Acid Pit site. Volatile and semivolatile organic compounds in water samples were analyzed for the first sampling round; no confirmed volatile or semivolatile organic compounds were detected above the laboratory reporting limits. Total chromium concentrations ranged from 0.0099 to 0.092 milligram per liter; dissolved chromium concentrations ranged from 0.0068 to 0.0094 milligram per liter. Overall, water-quality characteristics in water from the chromic acid pit ground-water monitoring wells are similar to those in the surrounding area. Detected chemical concentrations in water from the chromic acid pit monitoring wells during the four sampling periods were below U.S. Environmental Protection Agency-established maximum contaminant levels for public drinking water supplies. Statistical analyses were performed on 39 of the chemical constituents analyzed for in ground water from the chromic acid pit monitoring wells. Concentrations of chloride and fluoride were significantly less in water from the downgradient wells than in water from the upgradient well, whereas concentrations of nitrate as nitrogen, nitrite plus nitrate as nitrogen, and dissolved solids were significantly greater in water from the downgradient wells than in water from the upgradient well. Concentrations of nitrate as nitrogen were significantly different in water from the two downgradient wells. Differences detected through statistical analysis of chemical constituents of water in the chromic acid pit monitoring wells did not appear to indicate a release of hazardous chemicals from the chromic acid pit. There was no indication of ground-water contamination in either downgradient well.

Texas↗
USGS1972

Regional and other general factors bearing on evaluation of earthquake and other geologic hazards to coastal communities of southeastern Alaska

The great Alaska earthquake of March 27, 1964, brought into sharp focus the need for engineering geologic studies in seismically active regions. As a result, nine communities in southeastern Alaska were selected for reconnaissance investigations as an integral part of an overall program to evaluate earthquake and other geologic hazards in most of the larger Alaska coastal communities. This report gives background information on the regional and other general factors that bear on these evaluations. Southeastern Alaska, about 525 miles long and averaging about 125 miles in width, consists of a narrow mainland strip and numerous islands. For the most part, it is a region of rugged relief with numerous glaciers capping many of the higher mountainous areas and with long linear fiords forming the inland waterways. A maritime climate prevails with mild winters and cool summers. The southeastern part of the region receives the highest precipitation in the continental United States. Ketchikan, with a population of 6,994 in 1970, is the largest city. Geology and structure of the area are complex. Igneous, metamorphic, and sedimentary rocks crop out and range in age from Paleozoic to Tertiary. Surficial deposits of Pleistocene and Holocene age mantle many areas. All of southeastern Alaska, except probably the highest peaks, was covered by glacier ice advances of late Pleistocene age. Major deglaciation was well advanced by 10,000 years ago--a time which approximately marks the end of the Pleistocene and the beginning of the Holocene. There followed a period of warm climate called the Hypsithermal, which in southeastern Alaska began 7,000-8,000 years ago and ended about 4,800-3,500 years ago. Glaciers in most places receded back of their present positions. The Hypsithermal was followed by an interval (termed Neoglaciation) of cooler climate and resurgence of glacier ice which continues to the present, although most glaciers are now rapidly receding. During the past 10,000 years worldwide sea level has risen about 100 feet, but during the past 4,000 years it has risen only about 10 feet or about 0.03 inch per year. With sea level used as a datum, the amount of sea-level rise must be added to the apparent uplift of land for the time under consideration to determine the actual amount of land uplift. The widespread presence of emergent marine deposits, several hundred feet above sea level, demonstrates that the land in southeastern Alaska has been uplifted since the last major deglaciation. The greatest known has been uplifted since the last major deglaciation. The greatest known uplift is in the vicinity of Juneau where glaciomarine deposits are present 750 feet above present sea level. Part of southeastern Alaska is presently undergoing one of the most rapid rates of uplift of any place in the world. The fastest emergence is occurring in the Glacier Bay area where the land is being uplifted relative to sea level approximately 3.9 cm per year. Most or all of the uplift appears to be due to rebound as a result of deglaciation. Southeastern Alaska lies within the circum-Pacific earthquake belt, one of the world's greatest zones of seismic activity. During historic time, there have been five earthquakes in the region with magnitudes of 8 or greater, three with magnitudes of 7 to 8, eight with magnitudes of 6 to 7, more than 15 with magnitudes of 5 to 6, and about 140 recorded earthquakes with magnitudes smaller than 5 or of unassigned magnitudes. All of the earthquakes with magnitudes 8 or greater, and a large proportion of the others, appear to be related to the active Fairweather- Queen Charlotte Islands fault system or its western extension, the Chugach-St. Elias fault. Earthquake epicenters on the Denali fault system, the other major fault system in southeastern Alaska, are few in comparison. However, because high microearthquake activity has been recorded recently on this system and earthquakes of moderate size have occurred on some of its segments, the Denali fault system probably should not be dismissed as a relict fault system of no current tectonic importance. There are numerous other known faults, as well as lineaments that may be faults of varying degrees of tectonic activity in southeastern Alaska, adjacent Canada, and eastern Alaska. One of these elements is the Totschunda fault system, which connects with the Denali fault system in eastern Alaska; it has been very active during Holocene time but few historical earthquake epicenters appear to be related to it. Both historical seismicity and geologic conditions, such as frequency and recency of faulting, must be considered together to permit an assessment of the future earthquake probability of an area. Data are too few for both factors for an accurate evaluation to be made of earthquake probability in southeastern Alaska. However, information compiled in the form of strain-release and seismic-zone maps permit some generalizations. Thus, it is tentatively concluded that most, if not all, of southeastern Alaska should be placed in seismic zone 3, a zone in which earthquakes of magnitude greater than 6 will occur from time to time and where there may be major damage to manmade structures. Inferred effects from future earthquakes in southeastern Alaska include: (1) surface displacement along faults and other tectonic land-level changes, (2) ground shaking, (3) compaction, (4) liquefaction in cohesionless materials, (5) reaction of sensitive and quick clays, (6) water-sediment ejection and associated subsidence and ground fracturing, (7) earthquake-induced sub aerial slides and slumps, (8) earthquake induced subaqueous slides, (9) effects on glaciers and related features, (10) effects on ground water and stream flow, and (11) tsunamis, seiches, and other abnormal water waves. Because of the reconnaissance nature of our studies in the coastal communities and the sparsity of laboratory data on physical properties of geologic units in each area studied, the inferred effects must be largely empirical and generalized. Therefore, the inferences are based in large part upon the effects of past major earthquakes in Alaska and elsewhere, particularly upon the well-documented effects of the Alaska earthquake of March 27, 1964. Buildings, highways, bridges, tunnels, harbor facilities, pipelines, canals, and other manmade structures may be severely damaged or destroyed by fault displacement or related tectonic land-level changes in southeastern Alaska. Direct damage from fault rupture would be restricted virtually to structures built directly athwart the fault. In California and Nevada, fault rupture almost always accompanies shocks of magnitude 6.5 or greater. The Alaska earthquake of March 27, 1964, and the Chilean earthquake of May 22, 1960, dramatically illustrated the severe adverse effects that can result from uplift or subsidence over a wide area. The variable most responsible for the degree of shaking at any epicentral distance is the type of ground. Generally, shaking is considerably greater in poorly consolidated deposits than in hard bedrock, particularly if the deposits are water saturated. Severe shaking of alluvial deposits and manmade fill, with resultant heavy damage, is well documented from the records of many past earthquakes. Damage commonly has been heavy as a result of ground settlement caused by compaction of loose sediments by shaking during an earthquake. This has been especially true where compaction was accompanied by tectonic downdrop of land, such as occurred during the Chilean earthquake of 1960 and the Alaska earthquake of 1964. Loosely emplaced manmade fill, deltaic deposits, beach deposits, and alluvial deposits may be susceptible to compaction in southeastern Alaska during a severe earthquake. Liquefaction of sand and silt is a fairly common effect of large earthquakes. It was well illustrated at Niigata, Japan, during the earthquake of June 16, 1964, and resulted in extensive damage. When part of a sloping soil mass liquefies, the entire mass can undergo catastrophic failure and can flow as a high-density liquid. In southeastern Alaska, deltaic deposits probably would be most susceptible to liquefaction. Sensitive and quick clays, which lose a considerable part of their strength when shaken, commonly fail during an earthquake and become rapid earthflows. Extensive studies were made of the sensitivity of the Bootlegger Cove Clay at Anchorage because of the marked loss of shear strength and dramatic failures of the deposits during the Alaska earthquake of 1964. If similar sensitive clays are present in some places in southeastern Alaska, they most likely are in some of the emergent fine-grained marine deposits; supporting data to confirm their presence, however, are largely lacking. Records of some 50 major earthquakes show that in at least half of the instances water and sediment have been ejected from surficial deposits Water-sediment ejection and associated subsidence and ground fracturing commonly cause extensive damage to the works of man. Ejecta may fill basements and other low-lying parts of buildings. Agricultural land can be covered with a blanket of infertile soils, and small ponds can be filled or made shallow. In southeastern Alaska these phenomena are most likely to occur on valley floors, deltas, tidal flats, alluvial fans, swamps, and lakeshores. Earthquake-induced sliding on land generally is confined to steep slopes but may take place in fine-grained deposits on moderately to nearly flat surfaces if the deposits are subject to liquefaction. A large rockslide triggered by the Lituya Bay, Alaska, earthquake of July 10, 1958, generated a wave that surged up the opposite wall of the inlet to a record height of 1,740 feet. During the Hebgen Lake, Montana, earthquake of August 17, 1959, a spectacular rockslide plunged into the Madison River canyon, buried 28 people, dammed the river, and created a large lake. Earthquake-records are replete with accounts of sliding of surficial deposits during moderate to large earthquakes. Most or all of the general factors that favor subaerial landsliding are present in southeastern Alaska. Earthquake-induced subaqueous slides can produce adverse effects both nearshore and some distance offshore. Nearshore sliding may progress shoreward and destroy harbor facilities and other structures, commonly with substantial loss of life. Disastrous large submarine slides occurred along the fronts of deltas in Seward and Valdez during the Alaska earthquake of 1964. In similar fashion, the largest submarine slides in southeastern Alaska likely will be triggered along the larger delta fronts. Sliding farther offshore can constitute a threat to navigation because of changes in water depths. Also underwater sliding can break communication cables. Glaciers were not greatly affected by the Alaska earthquake of 1964 despite the fact that about 20 percent of the area that underwent strong shaking is covered by ice. In contrast, the cataclysmic avalanche of ice and rock that fell from a high glacier-covered peak in Peru during the earthquake of May 31, 1970, produced devastating effects downvalley on man and his works in the form of mudflows. Most towns in southeastern Alaska are sufficiently distant from glaciers so as not be to directly affected. Both the Alaska earthquake of 1964 and the Hebgen Lake, Montana, earthquake of 1959 significantly affected ground- and surface-water regimens. Water levels in some wells declined whereas in others flow increased. Some springs discharged at a rate three times as much as normal; flow of others decreased or stopped. Discharge of many streams increased markedly. Most or all of the effects described above could occur in parts of southeastern Alaska during future large earthquakes. Tsunamis, seiches, and other abnormal water waves associated with large earthquakes commonly cause vast property damage and heavy loss of life. Tsunami effects can be devastating to coastal areas as far as many thousands of miles from their generation source. Seiche effects generally are confined to inland bodies of water or to relatively enclosed coastal bodies of water. Abnormal waves generated by submarine sliding or by subaerial sliding into water generally produce only local effects but may be highly devastating. Tsunami waves resulting from the Chilean earthquake of 1960 inflicted extensive damage and loss of life on coastal communities throughout a large part of southern Chile, and significant runups and damage were recorded in many places throughout the Pacific Ocean area. The tsunami waves generated by the Alaska earthquake of 1964 struck with devastating force along a broad stretch of the Alaska coast and produced heavy property damage and loss of life as far away as Crescent City, Calif. Seiche waves generated by that earthquake reached runup heights of 20-30 feet on some lakes in Alaska, and water-level fluctuations were recorded on streams, reservoirs, lakes, and swimming pools in States bordering the Gulf of Mexico. Waves generated by submarine sliding struck violently at a number of places during or immediately after the quake and were the major cause of loss of life and damage to property. Slide-generated waves probably would have a higher destructive potential in southeastern Alaska than either tsunami waves or seiche waves because of their possibly higher local runups and because they can hit the shores almost without warning during or immediately after an earthquake. Nonearthquake-related geologic hazards, although generally far less dramatic than those related to earthquakes, tend to occur so much more frequently or persistently that their aggregate effects can be significant. Three kinds of geologic hazards of this type are discussed: (1) nonearthquake-induced landsliding and subaqueous sliding, (2) flooding, and (3) land uplift. The potential for nonearthquake-triggered landsliding in southeastern Alaska ranges widely from place to place. Past sliding generally furnishes the clue in the prediction of where and in what materials future sliding will occur. Fast-moving rockslides, debris slides, and mudflows can be expected to occur from time to time on steep slopes and be highly destructive to highways, power plants, pipelines, buildings, and other facilities located on a slope or at its base. Present slow downslope movement of talus can be expected to continue at the same general rate unless conditions are changed by man or there are climatic changes. Snow and debris avalanches can be especially hazardous during winter months. Long-inactive landslides may be triggered into renewed activity or new slides may be created by man-induced modifications. Accelerated slope erosion and debris flows may follow large-scale clearing and cutting of timber. Subaqueous sliding can be expected to occur periodically along fronts of deltas and on other oversteepened underwater slopes. Floods have been common in parts of southeastern Alaska because of heavy precipitation and rapid runoff from steep slopes with resulting heavy damage to roads and other facilities. Continued damage can be expected in the future unless more remedial measures are taken. Current uplift of land in southeastern Alaska, although probably not affecting man significantly in a short period of time, may have some adverse long-term effects. These long-term effects should be borne in mind when facilities such as docks and boat harbors are constructed on or near the shore, where there is a critical relation between height of land and water.

Alaska↗
USGS2024

Special topic—Eruption plumes and clouds

Introduction Explosive eruptions create plumes of volcanic ash and gas that can rise more than 30,000 feet (9.1 kilometers [km]) above sea level within minutes of eruption onset. The resulting clouds disperse under prevailing winds and may cause hazardous conditions hundreds to thousands of kilometers from the volcano, including in international airspace. Rapid detection and characterization of explosive activity is vital to mitigate the wide-ranging effects of volcanic ash. Ashfall thicknesses as small as a millimeter or so on the ground can affect infrastructure, agriculture, and air quality, requiring extensive clean-up procedures (Schuster, 1981; Warrick and others, 1981, U.S. Geological Survey, 2022). Volcanic clouds also pose substantial threats to aircraft. Since 1953, 88 encounters between airplanes and ash clouds have been documented worldwide (International Civil Aviation Organization, 2015, appendix F), resulting in aircraft damage and, in 9 cases, engine failure (Guffanti and others, 2010). In 1982, two large passenger planes suffered complete engine failure owing to eruptions in Indonesia (Global Volcanism Program, 1982) and a similar incident occurred over Alaska in 1989 (Casadevall, 1994). In all three cases, they were able to restart some engine capability and land safely once they emerged from the ash clouds, although with substantial damage (Guffanti and others, 2010). The clear threat to aviation has led to establishment of nine Volcanic Ash Advisory Centers (VAAC) around the world to monitor and rapidly disseminate information about volcanic eruptions to the aviation community. U.S. Geological Survey (USGS) volcano observatories issue the Volcano Observatory Notice for Aviation that informs of preeruptive unrest or eruptive activity. When ash-producing eruptions do occur, volcano observatories work closely with their regional VAAC to ensure consistency and accuracy in eruption onset time, cloud altitude, ash production, and duration as reported in Volcanic Ash Advisories. Explosive volcanism in the United States and Commonwealth of the Northern Mariana Islands prompts 50–100 such advisories in any given year (table J1). This collaborative effort is greatly aided by USGS detection and monitoring of eruption clouds to ensure a timely and coordinated response. To support these efforts to provide guidance on ash transport and fallout, the USGS developed the Ash3d volcanic ash dispersion model ( https://vsc-ash.wr.usgs.gov/ash3d-gui ) (Schwaiger and others, 2012). Automated simulations are run daily by the USGS for volcanoes that are in elevated states of unrest, and in response mode when eruptions occur. During eruptions, the model output is provided to local National Weather Service Weather Forecast Offices to guide them in the issuance of their information products (such as special weather statements, ashfall advisories, or ashfall warnings), as well as to State and local governments and the public. Characterization of the eruption source is needed to estimate the parameters used to initialize the Ash3d model, and by the Anchorage and Washington VAACs to initialize other dispersion models that inform forecasts for the airborne volcanic cloud. The source parameters that can be provided by observation during an eruption include eruption start time, eruption cloud height over time, and eruption duration. Other, nonobservable source parameters, such as mass eruption rate and grain-size distribution, are based on empirical correlations and study of historical deposits. The goal is to provide a time series of cloud heights, mass eruption rates, and particle-size distributions that accurately reflects current conditions. When feasible, the USGS also provides guidance on the nature of ongoing eruptions and forecasts future activity using petrologic monitoring of collected tephra samples. The aims of providing accurate observable parameters are achieved through analysis of (1) near-real-time meteorological satellite data, (2) ground-based cameras (see of Flinders, A.F., Lowenstern, J.B., Coombs, M.L., and Poland, M.P., eds., Recommended capabilities and instrumentation for volcano monitoring in the United States: U.S. Geological Survey Scientific Investigations Report 2024–5062–G, 11 p., https://doi.org/10.3133/sir20245062g.">chapter G , this volume; Orr and others, 2024), (3) weather radar, (4) volcanic lightning detection, and (5) ground-based ash sensors and sampling. Explosive eruptions can be detected by a variety of geophysical monitoring, including infrasound (see of Flinders, A.F., Lowenstern, J.B., Coombs, M.L., and Poland, M.P., eds., Recommended capabilities and instrumentation for volcano monitoring in the United States: U.S. Geological Survey Scientific Investigations Report 2024–5062–C, 11 p., https://doi.org/10.3133/sir20245062c.">chapter C , this volume; Lyons and others, 2024) and seismicity (see of Flinders, A.F., Lowenstern, J.B., Coombs, M.L., and Poland, M.P., eds., Recommended capabilities and instrumentation for volcano monitoring in the United States: U.S. Geological Survey Scientific Investigations Report 2024–5062–B, 9 p., https://doi.org/10.3133/sir20245062b.">chapter B , this volume; Thelen and others, 2024). However, those methods cannot quantify the altitude, ash content, and dispersal dynamics of resulting volcanic clouds. Ideally, all available sources of monitoring data are synthesized to develop a coherent understanding of eruptive activity. The guidance summarized here provides a framework for characterizing volcanic clouds in the atmosphere and tracking the evolution of explosive eruption dynamics.

Scientific Investigations Report↗
USGS2021

Historical changes in bed elevation and water depth within the Nehalem Bay, Oregon, 1891–2019

Estuaries, at the nexus of rivers and the ocean, are depositional areas that respond to changes in streamflow, tides, sea level, and inputs of sediment from marine and watershed sources. Understanding changes in bed elevations, deposited and eroded sediment, and water depth throughout estuaries is relevant for understanding their present-day status and long-term evolution, identifying potential hazards to human communities, and informing estuarine conservation. In response to observations of sedimentation in the Nehalem Bay, northwestern Oregon, by the Port of Nehalem, the magnitudes and patterns of bathymetric change in the Bay were documented and described by two approaches. The first approach compared changes in bed elevation with estimated volumes of erosion and deposition from overlapping survey data acquired in 1957 and 2019 for the area of the Nehalem Bay from upstream of the Highway 101 bridge to downstream of Fishery Point. The second approach examined changes in water depth for seven zones from the confluence of the North Fork and Nehalem Rivers to the mouth of the Nehalem River using nautical charts (1891, 1947, 1970, 1990, and 2004). These two approaches were used because the bathymetric surveys from 1957 and 2019 could be tied to a common vertical datum, allowing for a direct comparison of changes in bed elevations, whereas the nautical charts could not be tied to a common vertical datum, which limited the analyses to a comparison of changes in water depths over a broader time frame. Bed elevation changes from 1957 to 2019 were assessed from upstream of the Highway 101 bridge to downstream of Fishery Point where the two surveys overlapped (2 square kilometers) using thalweg longitudinal profiles, channel cross sections, and digital elevation models (DEMs) showing the elevation differences between the two surveys (or DEMs of difference). The most prominent change between 1957 and 2019 was the migration of the thalweg (or deepest part of the channel) between the downstream end of Lazarus Island and downstream of Fishery Point; this migration resulted in sediment deposition in the former thalweg and sediment erosion in formerly shallow areas to form the new thalweg. Bed elevation changes in the thalweg also varied longitudinally between 1957 and 2019. The bed elevation of the thalweg in both surveys, however, was generally less than 1 meter (m). The thalweg in the area of overlapping surveys shortened from about 7.0 to 6.7 kilometers in length over that same period. The bed elevation changes between the DEMs showed that maximum erosion and deposition was 4.3 and 4.5 m, respectively. In this same time period, the net change in sediment volume was 230,000 cubic meters (m 3 ), indicating net deposition. However, the error estimated for the 95 percent confidence interval analyses is ±315,000 m 3 , and therefore does not preclude the possibility that net erosion may have occurred. Historical changes in water depth from soundings depicted on nautical charts from 1891, 1947, 1970, 1990, and 2004 were evaluated by assessing spatial and temporal changes for seven zones of the Nehalem Bay. Across all years and zones, water depths ranged from about 0.2 to 9.4 m, whereas median water depths ranged from 0.3 to 6.4 m. Median depths and the range of water depths did not systematically increase or decrease throughout all zones during the same periods. In all nautical charts, the zone at the mouth of the Nehalem River consistently had the deepest soundings (7.9 to 9.4 m) and the greatest range of water depths (7.3 to 8.8 m). Qualitative evaluation of the nautical charts showed minimal changes in the overall shape of the Nehalem Bay. The exception to this observation was at the mouth of the Bay, where two historical outlets to the Pacific Ocean depicted in the 1891 nautical chart were reduced to one outlet following the construction of jetties (1916 and 1918). The results of this study emphasize that bed elevations and water depths within the Nehalem Bay have varied between 1891 and 2019, as illustrated by the lateral and vertical changes in the thalweg and changes in water depths over time. Changes in thalweg position and related patterns of sediment erosion and deposition are expected in the future as the Nehalem Bay continues to respond to changes in tides, sea level, streamflow, and sediment inputs from watershed and marine sources. The results of this study and the surveys from 1957 and 2019 provide a foundation for documenting and evaluating future changes in the Nehalem Bay and prioritizing actions to manage and protect natural resources and recreational access to the Nehalem Bay.

Oregon↗
USGS2011

High geologic slip rates since early Pleistocene Initiation of the San Jacinto and San Felipe fault zones in the San Andreas fault system: southern California, USA

The San Jacinto right-lateral strike-slip fault zone is crucial for understanding plate-boundary dynamics, regional slip partitioning, and seismic hazards within the San Andreas fault system of southern California, yet its age of initiation and long-term average slip rate are controversial. This synthesis of prior and new detailed studies in the western Salton Trough documents initiation of structural segments of the San Jacinto fault zone at or slightly before the 1.07-Ma base of the Jaramillo subchron. The dextral faults changed again after ca. 0.5–0.6 Ma with creation of new fault segments and folds. There were major and widespread basinal changes in the early Pleistocene when these new faults cut across the older West Salton detachment fault. We mapped and analyzed the complex fault mesh, identified structural segment boundaries along the Clark, Coyote Creek, and San Felipe fault zones, documented linkages between the major dextral faults, identified previously unknown active strands of the Coyote Creek fault 5 and 8 km NE and SW of its central strands, and showed that prior analyses of these fault zones oversimplify their complexity. The Clark fault is a zone of widely distributed faulting and folding SE of the Santa Rosa Mountains and unequivocally continues 20–25 km SE of its previously inferred termination point to the San Felipe Hills. There the Clark fault zone has been deforming basinal deposits at an average dextral slip rate of ≥10.2 +6.9/−3.3 mm/yr for ~0.5–0.6 m.y. Five new estimates of displacement are developed here using offset successions of crystalline rocks, distinctive marker beds in the late Cenozoic basin fill, analysis of strike-slip–related fault-bend folds, quantification of strain in folds at the tips of dextral faults, and gravity, magnetic, and geomorphic data sets. Together these show far greater right slip across the Clark fault than across either the San Felipe or Coyote Creek faults, despite the Clark fault becoming “hidden” in basinal deposits at its SE end as strain disperses onto a myriad of smaller faults, strike-slip ramps and flats, transrotational systems of cross faults with strongly domain patterns, and a variety of fault-fold sets. Together the Clark and Buck Ridge–Santa Rosa faults accumulated ~16.8 +3.7/−6.0 km of right separation in their lifetime near Clark Lake. The Coyote Ridge segment of the Coyote Creek fault accumulated ~3.5 ± 1.3 km since roughly 0.8–0.9 Ma. The San Felipe fault accumulated between 4 and 12.4 km (~6.5 km preferred) of right slip on its central strands in the past 1.1–1.3 Ma at Yaqui and Pinyon ridges. Combining the estimates of displacement with ages of fault initiation indicates a lifetime geologic slip rate of 20.1 +6.4/−9.8 mm/yr across the San Jacinto fault zone (sum of Clark, Buck Ridge, and Coyote Creek faults) and about ~5.4 +5.9/−1.4 mm/yr across the San Felipe fault zone at Yaqui and Pinyon ridges. The NW Coyote Creek fault has a lifetime slip rate of ~4.1 +1.9/−2.1 mm/yr, which is a quarter of that across the Clark fault (16.0 +4.5/−9.8 mm/yr) nearby. The San Felipe fault zone is not generally regarded as an active fault in the region, yet its lifetime slip rate exceeds those of the central and southern Elsinore and the Coyote Creek fault zones. The apparent lower slip rates across the San Felipe fault in the Holocene may reflect the transfer of strain to adjacent faults in order to bypass a contractional bend and step at Yaqui Ridge. The San Felipe, Coyote Creek, and Clark faults all show evidence of major structural adjustments after ca. 0.6–0.5 Ma, and redistribution of strain onto new right- and left-lateral faults and folds far removed from the older central fault strands. Active faults shifted their locus and main central strands by as much as 13 km in the middle Pleistocene. These changes modify the entire upper crust and were not localized in the thin sedimentary basin fill, which is only a few kilometers thick in most of the western Salton Trough. Steep microseismic alignments are well developed beneath most of the larger active faults and penetrate basement to the base of the seismogenic crust at 10–14 km. We hypothesize that the major structural and kinematic adjustments at ca. 0.5–0.6 Ma resulted in major changes in slip rate within the San Jacinto and San Felipe fault zones that are likely to explain the inconsistent slip rates determined from geologic (1–0.5 m.y.; this study), paleoseismic, and geodetic studies over different time intervals. The natural evolution of complex fault zones, cross faults, block rotation, and interactions within their broad damage zones might explain all the documented and implied temporal and spatial variation in slip rates. Co-variation of slip rates among the San Jacinto, San Felipe, and San Andreas faults, while possible, is not required by the available data. Together the San Jacinto and San Felipe fault zones have accommodated ~25.5 mm/yr since their inception in early Pleistocene time, and were therefore slightly faster than the southern San Andreas fault during the same time interval. If the westward transfer of plate motion continues in southern California, the southern San Andreas fault in the Salton Trough may change from being the main plate boundary fault to defining the eastern margin of the growing Sierra Nevada microplate, as implied by other workers.

California↗
USGS2018

Northeast

The distinct seasonality of the Northeast’s climate supports a diverse natural landscape adapted to the extremes of cold, snowy winters and warm to hot, humid summers. This natural landscape provides the economic and cultural foundation for many rural communities, which are largely supported by a diverse range of agricultural, tourism, and natural resource-dependent industries (see Ch. 10: Ag & Rural, Key Message 4) . The recent dominant trend in precipitation throughout the Northeast has been towards increases in rainfall intensity, with increases in intensity exceeding those in other regions of the contiguous United States. Further increases in rainfall intensity are expected, with increases in total precipitation expected during the winter and spring but with little change in the summer. Monthly precipitation in the Northeast is projected to be about 1 inch greater for December through April by end of century (2070–2100) under the higher scenario (RCP8.5). Ocean and coastal ecosystems are being affected by large changes in a variety of climate-related environmental conditions. These ecosystems support fishing and aquaculture, tourism and recreation, and coastal communities. Observed and projected increases in temperature, acidification, storm frequency and intensity, and sea levels are of particular concern for coastal and ocean ecosystems, as well as local communities and their interconnected social and economic systems. Increasing temperatures and changing seasonality on the Northeast Continental Shelf have affected marine organisms and the ecosystem in various ways. The warming trend experienced in the Northeast Continental Shelf has been associated with many fish and invertebrate species moving northward and to greater depths. Because of the diversity of the Northeast’s coastal landscape, the impacts from storms and sea level rise will vary at different locations along the coast. Northeastern cities, with their abundance of concrete and asphalt and relative lack of vegetation, tend to have higher temperatures than surrounding regions due to the urban heat island effect. During extreme heat events, nighttime temperatures in the region’s big cities are generally several degrees higher than surrounding regions, leading to higher risk of heat-related death. Urban areas are at risk for large numbers of evacuated and displaced populations and damaged infrastructure due to both extreme precipitation events and recurrent flooding, potentially requiring significant emergency response efforts and consideration of a long-term commitment to rebuilding and adaptation, and/or support for relocation where needed. Much of the infrastructure in the Northeast, including drainage and sewer systems, flood and storm protection assets, transportation systems, and power supply, is nearing the end of its planned life expectancy. Climate-related disruptions will only exacerbate existing issues with aging infrastructure. Sea level rise has amplified storm impacts in the Northeast (Key Message 2), contributing to higher surges that extend farther inland, as demonstrated in New York City in the aftermath of Superstorm Sandy in 2012. Service and resource supply infrastructure in the Northeast is at increasing risk of disruption, resulting in lower quality of life, economic declines, and increased social inequality. Loss of public services affects the capacity of communities to function as administrative and economic centers and triggers disruptions of interconnected supply chains (Ch. 16: International, Key Message 1) . Increases in annual average temperatures across the Northeast range from less than 1°F (0.6°C) in West Virginia to about 3°F (1.7°C) or more in New England since 1901. Although the relative risk of death on very hot days is lower today than it was a few decades ago, heat-related illness and death remain significant public health problems in the Northeast. For example, a study in New York City estimated that in 2013 there were 133 excess deaths due to extreme heat. These projected increases in temperature are expected to lead to substantially more premature deaths, hospital admissions, and emergency department visits across the Northeast. For example, in the Northeast we can expect approximately 650 additional premature deaths per year from extreme heat by the year 2050 under either a lower (RCP4.5) or higher (RCP8.5) scenario and from 960 (under RCP4.5) to 2,300 (under RCP8.5) more premature deaths per year by 2090. Communities, towns, cities, counties, states, and tribes across the Northeast are engaged in efforts to build resilience to environmental challenges and adapt to a changing climate. Developing and implementing climate adaptation strategies in daily practice often occur in collaboration with state and federal agencies (e.g., New Jersey Climate Adaptation Alliance 2017, New York Climate Clearinghouse 2017, Rhode Island STORMTOOLS 2017, EPA 2017, CDC 2015 ). Advances in rural towns, cities, and suburban areas include low-cost adjustments of existing building codes and standards. In coastal areas, partnerships among local communities and federal and state agencies leverage federal adaptation tools and decision support frameworks (for example, NOAA’s Digital Coast, USGS’s Coastal Change Hazards Portal, and New Jersey’s Getting to Resilience). Increasingly, cities and towns across the Northeast are developing or implementing plans for adaptation and resilience in the face of changing climate (e.g., EPA 2017 ). The approaches are designed to maintain and enhance the everyday lives of residents and promote economic development. In some cities, adaptation planning has been used to respond to present and future challenges in the built environment. Regional efforts have recommended changes in design standards when building, replacing, or retrofitting infrastructure to account for a changing climate.

Report↗
USGS2023

Arsenic, chromium, uranium, and vanadium in rock, alluvium, and groundwater, Mojave River and Morongo Areas, western Mojave Desert, southern California

Trace elements within groundwater that originate from aquifer materials and pose potential public-health hazards if consumed are known as geogenic contaminants. The geogenic contaminants arsenic, chromium, and vanadium can form negatively charged ions with oxygen known as oxyanions. Uranium complexes with bicarbonate and carbonate to form negatively charged ions having aqueous chemistry similar to oxyanions. The concentrations of arsenic, chromium, uranium, and vanadium in groundwater result from the combined effects of (1) geologic abundance within aquifer materials; (2) the fraction of these elements that have weathered from and sorbed to the surfaces of mineral grains and are potentially available to groundwater; and (3) the aqueous chemistry of dissolved oxyanions in groundwater during different redox conditions and pH, both of which are affected by hydrogeology, including the length of time groundwater has been in contact with aquifer materials. Concentrations of arsenic, chromium, uranium, and vanadium were measured in samples of (1) rock, surficial alluvium, and drill cuttings using portable (handheld) X-ray fluorescence (pXRF); (2) operationally defined fractions extractable from these materials; and (3) water from wells sampled between 2000 and 2018 within the 3,500 square mile Mojave River area and Morongo area of the western Mojave Desert, southern California. Regionally, rock and surficial alluvium in the Mojave River and Morongo areas are high in arsenic, low in chromium and uranium, and near the average bulk continental crust concentration for vanadium. Locally, high chromium concentrations are present in mafic rock within the San Gabriel Mountains; high uranium concentrations are present in felsic rock within the San Bernardino Mountains; and high arsenic, uranium, and vanadium concentrations are present in extrusive (volcanic) felsic rock within uplands surrounding groundwater basins along the Mojave River downstream from Barstow, California. Elemental assemblages identified using principal component analyses (PCA) of pXRF data were used to characterize felsic, mafic, and felsic volcanic source terranes in rock, surficial alluvium, and in geologic material penetrated by selected monitoring wells drilled between 1994 and 2018. Highly felsic alluvium associated with recent deposition from the Mojave River was identified along the 90-mile length of the floodplain aquifer along the river. The thickness of these highly felsic alluvial deposits ranged from 200 feet (ft) near Victorville and near Barstow to a thin veneer about 30 ft thick downstream from Victorville and downstream portions of the floodplain aquifer within the Mojave Valley. Groundwater in the Mojave River and Morongo areas was generally oxic and alkaline (pH≥7.5). Maximum concentrations of arsenic, hexavalent chromium [Cr(VI)], uranium, and vanadium in water from as many as 498 wells sampled between 2000 and 2018 were 360, 140, 1,470, and 690 micrograms per liter (μg/L), respectively. Water from 22 percent of sampled wells exceeded the U.S. Environmental Protection Agency (EPA) maximum contaminant level (MCL) for arsenic of 10 μg/L, with arsenic concentrations commonly exceeding the MCL in water from wells east of Barstow, deep wells in the Victorville fan, and in suboxic or reduced groundwater within the floodplain aquifer. Water from about 1 percent of sampled wells had Cr(VI) concentrations greater than the California MCL for total chromium of 50 μg/L, whereas 13 percent of sampled wells had Cr(VI) concentrations greater than the former California MCL of 10 μg/L. Hexavalent chromium concentrations were highest in water from wells in the Sheep Creek alluvial fan, eroded from mafic rock in the San Gabriel Mountains, although Cr(VI) concentrations greater than the former California MCL also were present elsewhere in the study area where mafic materials or older groundwater were present. Water from about 9 percent of sampled wells exceeded the EPA MCL for uranium of 30 μg/L, with concentrations exceeding the MCL commonly associated with irrigation return from agricultural land overlying the floodplain aquifer. Water from about 7 percent of sampled wells had vanadium concentrations greater than the California notification level of 50 μg/L; most of these wells were in the Victorville fan within the Mojave River area. In general, arsenic concentrations were higher in suboxic or reduced water; chromium concentrations were higher in oxic, alkaline (pH≥7.5) water; uranium concentrations were higher in circumneutral to slightly alkaline water (pH≤7.4); and vanadium concentrations were higher in highly alkaline (pH≥8.0) water, independent of redox status. Concentrations within geologic source terranes are not the sole factor controlling the concentrations of geogenic elements in groundwater. Differences in mineral weathering, pH-dependent sorption to surface-exchange sites on mineral grains, and aqueous geochemistry (especially redox status and pH) affect geogenic element concentrations in groundwater. Consequently, the relative abundances of arsenic, Cr(VI), uranium, and vanadium in groundwater differ from their relative abundances in the average bulk continental crust and their regional abundances in rock and surficial alluvium within groundwater basins of the western Mojave Desert. Processes that control the concentrations of arsenic, chromium, uranium, and vanadium in groundwater operate at the mineral-grain and aquifer scale. At the mineral-grain scale, sequential chemical extraction data show arsenic and uranium are more available to groundwater (under specific geochemical conditions) than chromium or vanadium, which largely are unavailable within unweathered mineral grains. Additionally, chromium and vanadium form few aqueous complexes and bind tightly with iron minerals within surface coatings on mineral grains making them less available to groundwater, whereas complexation with other dissolved ions enhances the solubility of uranium and, to a lesser extent, arsenic. Complexation also increases the valence (less negative charge) and increases the size of dissolved oxyanions and uranium complexes with bicarbonate and carbonate making them less readily sorbed to aquifer materials. At the aquifer scale, hydrogeology (including isolation of water in aquifers from surface sources of recharge, older groundwater age, and long contact times between groundwater and aquifer materials) combined with geochemical processes (such as silicate weathering) to produce alkaline groundwater. Desorption from sorption sites on the surfaces of mineral grains with increasing pH increases arsenic, chromium, and vanadium concentrations in water from wells and increases Cr(VI) concentrations as long as water remains oxic. Aqueous geochemistry and concentrations of geogenic contaminants also are affected by anthropogenic activities including (1) discharge of treated municipal wastewater, which may change the redox status of groundwater; (2) return from irrigated agriculture, which may alter the chemistry of groundwater and increase the solubility of trace elements such as uranium; and (3) groundwater pumping and subsequent water-level declines, which may change the source of water yielded by wells. The quality of water imported from northern California and infiltrated from ponds for groundwater recharge may be altered by naturally present trace elements, especially uranium in areas of agricultural land use or chromium within mafic alluvium.

California↗