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USGS1980

A review and evaluation of alternatives for updating U.S. Geological Survey land use and land cover maps

Since 1974, the U.S. Geological Survey has been engaged in a nationwide program of baseline mapping of land use and land cover and associated data at a scale of 1:250,000. As l:100,000-scale bases have become available, they have been used for mapping certain areas and for special applications. These two scales are appropriate for mapping land use and land cover data on a nationwide basis within a practical time frame, and with an acceptable degree of standardization, accuracy, and level of detail. An essential requisite to better use of the land is current information on land use and land cover conditions and on the rates and trends of changes with time. Thus, plans are underway to update these maps and data. The major considerations in planning a nationwide program for updating U.S. Geological Survey land use and land cover maps are as follows: (1) How often should maps be updated? (2) What remotely sensed source materials should be used for detecting and compiling changes in land use and land cover? (3) What base maps should be used for presenting data on land use and land cover changes? (4) What maps or portions of a map should be updated? (5) What methods should be used for identifying and mapping changes? (6) What procedures should be followed for updating maps and what formats should be used? These factors must be considered in developing a map update program that portrays an appropriate level of information, relates to and builds upon the existing U.S. Geological Survey land use and land cover digital and statistical data base, is timely, cost-effective and standardized, and meets the varying needs of land use and land cover data users.

Circular↗

USGS2002

Geologic and isostatic gravity map of the Nenana basin area, central Alaska

The Nenana Basin area is a prospective petroleum province in central Alaska, and this geologic and isostatic gravity map is part of a petroleum resource assessment of the area. The geology was compiled from published sources as shown on the index map (map sheet). Map units are organized and presented according to the scheme of lithotectonic terranes proposed by Jones and others (1987) and Silberling and Jones (1984); we recognize, however, that this terrane scheme is controversial and likely to be revised in the future. In some cases, we combined certain terranes because we were unable to match the terrane boundaries given by Jones and others (1987) and Silberling and Jones (1984) with specific faults shown on existing geologic maps. Postaccretion cover deposits represent overlap assemblages that depositionally overlie accreted terranes. Plutonic igneous rocks shown on this map include several plutons that are clearly postaccretionary, based on isotopic ages and (or) field relations. It is possible that some of the plutons predate accretion, but this has not been demonstrated. According to Jones and others (1982), the terranes in the area of our map were assembled during late Mesozoic or earliest Cenozoic time. The gravity contours are derived from data used in earlier compilations that are supplemented by some National Oceanic and Atmospheric Administration data along the Alaska Pipeline level line. The earlier compilations were used for simple Bouguer maps, prepared primarily by non-digital methods, and are superseded by this map. The present map is the result of digital processing that includes the 1967 Geodetic Reference System, the IGSN-71 datum, digital terrain corrections, and conversion to isostatic gravity so that geologic structures on the margin of the Alaska Range are more clearly portrayed. Computation procedures are described in part by Barnes (1972, 1984), Jachens and Roberts (1981), and Barnes and others (1994). The calculations used a crustal density of 2.67 g/cm 3 , a density contrast at the base of the isostatic root of 0.4 g/cm 3 , and a root thickness at sea level of 25 km. The distribution of data within the map area is uneven and locally controls the shape of the computer-generated contours. Altimetry was used for most of the elevation control and its inconsistency is responsible for many of the small contour irregularities. Ninety percent of the measurements are estimated to have an accuracy of about 1.5 mgal or about a quarter of the 5 mgal contour interval. Data collection and analysis were assisted by R.V. Allen, R.C. Jachens, M.A. Fisher, T.R. Bruns, J.G. Blank, J.W. Bader, Z.C. Valin, J.W. Cady, R.L. Morin, and P.V. Woodward. The most promising area for petroleum exploration is a prominent 25 mgal isostatic gravity low north of Nenana (T. 2 S., R. 8 W.). This gravity low probably corresponds to the deepest part of a sedimentary basin filled by Cenozoic strata that includes nonmarine fluvial and lacustrine deposits of the Eocene to Miocene Usibelli Group. Smaller gravity lows are associated with outcrops of these sedimentary rocks north of Suntrana (T. 12 S., R. 6-9 W.) and Sable Pass (T. 16 S., R. 11 W.). A broad low on the north flank of the Alaska Range east of the Wood River (T. 10 S., R. 1 E.) indicates another basin under the Tanana lowland that extends eastward off the map area towards Delta Junction, where its presence was confirmed by both gravity and seismic data. Gravity modelling suggests that the base of the Usibelli Group in the area north of Nenana (T. 2 S., R. 8 W.) is about 3,000 to 3,350 m beneath the ground surface. Organic geochemical studies indicate that mudstones and coals in the Usibelli Group are potential sources of petroleum; calculations based on borehole temperatures suggest that, in the area of the gravity low, these rocks may have been buried deeply enough to generate oil and gas. Two exploratory wells, the Union Nenana No. 1 and the ARCO Totek Hills No. 11, were drilled some distance away from the gravity low in areas where the Usibelli Group is thin. Mudlogs show that both wells were dry holes that bottomed in schist and had gas shows associated with coal beds in the Usibelli Group, but no reported signs of oil.

Alaska↗

USGS1979

Geologic map of the greater Denver area, Front Range urban corridor, Colorado

This digital map shows the areal extent of surficial deposits and rock stratigraphic units (formations) as compiled by Trimble and Machette from 1973 to 1977 and published in 1979 under the Front Range Urban Corridor Geology Program. Trimble and Machette compiled their geologic map from published geologic maps and unpublished geologic mapping having varied map unit schemes. A convenient feature of the compiled map is its uniform classification of geologic units that mostly matches those of companion maps to the north (USGS I-855-G) and to the south (USGS I-857-F). Published as a color paper map, the Trimble and Machette map was intended for land-use planning in the Front Range Urban Corridor. This map recently (1997-1999) was digitized under the USGS Front Range Infrastructure Resources Project. In general, the mountainous areas in the western part of the map exhibit various igneous and metamorphic bedrock units of Precambrian age, major faults, and fault brecciation zones at the east margin (5-20 km wide) of the Front Range. The eastern and central parts of the map (Colorado Piedmont) depict a mantle of unconsolidated deposits of Quaternary age and interspersed outcroppings of Cretaceous or Tertiary-Cretaceous sedimentary bedrock. The Quaternary mantle comprises eolian deposits (quartz sand and silt), alluvium (gravel, sand, and silt of variable composition), colluvium, and a few landslides. At the mountain front, north-trending, dipping Paleozoic and Mesozoic sandstone, shale, and limestone bedrock formations form hogbacks and intervening valleys.

Colorado↗

USGS2000

Cruise report R/V Surf Surveyor cruise S1-00-CL, mapping the bathymetry of Crater Lake, Oregon

During the Spring of 1999, the US Geological Survey (USGS) Pacific Seafloor Mapping Project (PSMP) was contacted by the US National Park Service Crater Lake National Park (CLNP) to inquire about the plausibility of producing a high-resolution multibeam bathymetric map of Crater Lake. The purpose was to generate a much higher-resolution and more geographically accurate bathymetric map than was produced in 1959, the last time the lake had been surveyed. Scientific interest in various aspects of Crater Lake (aquatic biology, geochemistry, volcanic processes, etc.) has increased during the past decade but the basemap of bathymetry was woefully inadequate. Funds were gathered during the early part of 2000 and the mapping began in late July, 2000. Crater Lake (see fig. 1 in report) is located in south central Oregon (see fig. 2 in report) within the Cascades Range, a chain of volcanoes that stretches from northern California to southern British Columbia. Crater Lake is the collapsed caldera of Mt. Mazama from a climatic eruption about 7700-yr ago (Nelson et al., 1988; Bacon and Lanphere, 1990; Bacon et al., 1997). The floor of Crater Lake has only been mapped three times since the lake was first stumbled upon by gold prospectors in the 1853. The first survey was carried by out by William G. Steel during a joint USGS-US Army expedition under the direction of Maj. Clarence E. Dutton in 1886 (Dutton, 1889). Steelï¿½s mapping survey collected 186 soundings using a Millers lead-line sounding machine (see fig.3 in report). The resulting map (see fig.4 in report) shows only soundings and no attempts were made to generate contours. The second survey, conducted in 1959 by the US Coast and Geodetic Survey, mapped the bathymetry of Crater Lake with an acoustic echo sounder using radar navigation and collected 4000 soundings. The data were contoured by Williams (1961) and Byrne (1962) and the result is a fairly detailed map of the large-scale features of Crater Lake (see fig. 5 in report). The third mapping survey, the one of this report, was a joint USGS-NPS project carried out under a Cooperative Agreement with the Center for Coastal and Ocean Mapping, University of New Hampshire. The 2000 survey used a Kongsberg Simrad EM1002 high-resolution multibeam mapping system owned and operated by C&C Technologies, Inc. of Lafayette, LA.

Oregon↗

USGS2001

Preliminary lithogeochemical map showing near-surface rock types in the Chesapeake Bay watershed, Virginia and Maryland

This preliminary experimental lithogeochemical map shows the distribution of rock types in the Virginia and Maryland parts of the Chesapeake Bay watershed. The map was produced digitally by classifying geologic-map units according to composition, mineralogy, and texture; rather than by age and stratigraphic relationships as shown on traditional geologic maps. This map differs from most lithologic maps in that the lithogeochemical unit classification distinguishes those rock units having key water-reactive minerals that may induce acid neutralization, or reduction, of hosted water at the weathering interface. The validity of these rock units, however, is independent of water chemistry, because the rock units are derived from geologic maps and rock descriptions. Areas of high soil carbon content, and sulfide metal deposits are also shown. Water-reactive minerals and their weathering reactions yield five lithogeochemical unit classes: 1) carbonate rock and calcareous rocks and sediments, the most acid-neutralizing; 2)carbonaceous-sulfidic rocks and sediments, oxygen-depleting and reducing; 3) quartzofeldspathic rocks and siliciclastic sediments, relatively weakly reactive with water; 4) mafic silicate rocks/sediments, oxygen consuming and high solute-load delivering; and, 5) the rarer calcareous-sulfidic (carbonaceous) rocks, neutralizing and reducing. Earlier studies in some parts of the map area have related solute loads in ground and stream waters to some aspects of bedrock lithology. More recent preliminary tests of relationships between four of the classes of mapped lithogeochemical units and ground water chemistry, in the Mid-Atlantic area using this map, have focused on and verified the nitrate-reducing and acid-neutralizing properties of some bedrock and unconsolidated aquifer rock types. Sulfide mineral deposits and their mine-tailings effects on waters are beginning to be studied by others. Additional testing of relationships among the lithogeochemical units and aspects of ground and surface water chemistry could help to refine the lithogeochemical classification, and this map. The testing could also improve the usefulness of the map for assessing aquifer reactivity and the transport properties of reactive contaminants such as acid rain, and nitrate from agricultural sources, in the Chesapeake Bay watershed.

Maryland, Virginia↗

USGS2003

Preliminary soil-slip susceptibility maps, southwestern California

This group of maps shows relative susceptibility of hill slopes to the initiation sites of rainfall-triggered soil slip-debris flows in southwestern California. As such, the maps offer a partial answer to one part of the three parts necessary to predict the soil-slip/debris-flow process. A complete prediction of the process would include assessments of “where”, “when”, and “how big”. These maps empirically show part of the “where” of prediction (i.e., relative susceptibility to sites of initiation of the soil slips) but do not attempt to show the extent of run out of the resultant debris flows. Some information pertinent to “when” the process might begin is developed. “When” is determined mostly by dynamic factors such as rainfall rate and duration, for which local variations are not amenable to long-term prediction. “When” information is not provided on the maps but is described later in this narrative. The prediction of “how big” is addressed indirectly by restricting the maps to a single type of landslide process—soil slip-debris flows. The susceptibility maps were created through an iterative process from two kinds of information. First, locations of sites of past soil slips were obtained from inventory maps of past events. Aerial photographs, taken during six rainy seasons that produced abundant soil slips, were used as the basis for soil slip-debris flow inventory. Second, digital elevation models (DEM) of the areas that were inventoried were used to analyze the spatial characteristics of soil slip locations. These data were supplemented by observations made on the ground. Certain physical attributes of the locations of the soil-slip debris flows were found to be important and others were not. The most important attribute was the mapped bedrock formation at the site of initiation of the soil slip. However, because the soil slips occur in surficial materials overlying the bedrocks units, the bedrock formation can only serve as a surrogate for the susceptibility of the overlying surficial materials. The maps of susceptibility were created from those physical attributes learned to be important from the inventories. The multiple inventories allow a model to be created from one set of inventory data and evaluated with others. The resultant maps of relative susceptibility represent the best estimate generated from available inventory and DEM data. Slope and aspect values used in the susceptibility analysis were 10-meter DEM cells at a scale of 1:24,000. For most of the area 10-meter DEMs were available; for those quadrangles that have only 30-meter DEMs, the 30-meter DEMS were resampled to 10-meters to maintain resolution of 10-meter cells. Geologic unit values used in the susceptibility analysis were five-meter cells. For convenience, the soil slip susceptibility values are assembled on 1:100,000-scale bases. Any area of the 1:100,000-scale maps can be transferred to 1:24,000-scale base without any loss of accuracy. Figure 32 is an example of part of a 1:100,000-scale susceptibility map transferred back to a 1:24,000-scale quadrangle.

California↗

USGS2006

Preliminary surficial geologic map database of the Amboy 30 x 60 minute quadrangle, California

The surficial geologic map database of the Amboy 30x60 minute quadrangle presents characteristics of surficial materials for an area approximately 5,000 km2 in the eastern Mojave Desert of California. This map consists of new surficial mapping conducted between 2000 and 2005, as well as compilations of previous surficial mapping. Surficial geology units are mapped and described based on depositional process and age categories that reflect the mode of deposition, pedogenic effects occurring post-deposition, and, where appropriate, the lithologic nature of the material. The physical properties recorded in the database focus on those that drive hydrologic, biologic, and physical processes such as particle size distribution (PSD) and bulk density. This version of the database is distributed with point data representing locations of samples for both laboratory determined physical properties and semi-quantitative field-based information. Future publications will include the field and laboratory data as well as maps of distributed physical properties across the landscape tied to physical process models where appropriate. The database is distributed in three parts: documentation, spatial map-based data, and printable map graphics of the database. Documentation includes this file, which provides a discussion of the surficial geology and describes the format and content of the map data, a database 'readme' file, which describes the database contents, and FGDC metadata for the spatial map information. Spatial data are distributed as Arc/Info coverage in ESRI interchange (e00) format, or as tabular data in the form of DBF3-file (.DBF) file formats. Map graphics files are distributed as Postscript and Adobe Portable Document Format (PDF) files, and are appropriate for representing a view of the spatial database at the mapped scale.

Open-File Report↗

USGS2007

Revision of Time-Independent Probabilistic Seismic Hazard Maps for Alaska

We present here time-independent probabilistic seismic hazard maps of Alaska and the Aleutians for peak ground acceleration (PGA) and 0.1, 0.2, 0.3, 0.5, 1.0 and 2.0 second spectral acceleration at probability levels of 2 percent in 50 years (annual probability of 0.000404), 5 percent in 50 years (annual probability of 0.001026) and 10 percent in 50 years (annual probability of 0.0021). These maps represent a revision of existing maps based on newly obtained data and assumptions reflecting best current judgments about methodology and approach. These maps have been prepared following the procedures and assumptions made in the preparation of the 2002 National Seismic Hazard Maps for the lower 48 States. A significant improvement relative to the 2002 methodology is the ability to include variable slip rate along a fault where appropriate. These maps incorporate new data, the responses to comments received at workshops held in Fairbanks and Anchorage, Alaska, in May, 2005, and comments received after draft maps were posted on the National Seismic Hazard Mapping Web Site. These maps will be proposed for adoption in future revisions to the International Building Code. In this documentation we describe the maps and in particular explain and justify changes that have been made relative to the 1999 maps. We are also preparing a series of experimental maps of time-dependent hazard that will be described in future documents.

Open-File Report↗

USGS2007

Geologic Map of the Goleta Quadrangle, Santa Barbara County, California

This map depicts the distribution of bedrock units and surficial deposits and associated deformation underlying those parts of the Santa Barbara coastal plain and adjacent southern flank of the Santa Ynez Mountains within the Goleta 7 ?? quadrangle at a compilation scale of 1:24,000 (one inch on the map = 2,000 feet on the ground) and with a horizontal positional accuracy of at least 20 m. The Goleta map overlaps an earlier preliminary geologic map of the central part of the coastal plain (Minor and others, 2002) that provided coverage within the coastal, central parts of the Goleta and contiguous Santa Barbara quadrangles. In addition to new mapping in the northern part of the Goleta quadrangle, geologic mapping in other parts of the map area has been revised from the preliminary map compilation based on new structural interpretations supplemented by new biostratigraphic data. All surficial and bedrock map units are described in detail in the accompanying map pamphlet. Abundant biostratigraphic and biochronologic data based on microfossil identifications are presented in expanded unit descriptions of the marine Neogene Monterey and Sisquoc Formations. Site-specific fault-kinematic observations (including slip-sense determinations) are embedded in the digital map database. The Goleta quadrangle is located in the western Transverse Ranges physiographic province along an east-west-trending segment of the southern California coastline about 100 km (62 mi) northwest of Los Angeles. The Santa Barbara coastal plain surface, which spans the central part of the quadrangle, includes several mesas and hills that are geomorphic expressions of underlying, potentially active folds and partly buried oblique and reverse faults of the Santa Barbara fold and fault belt (SBFFB). Strong earthquakes have occurred offshore within 10 km of the Santa Barbara coastal plain in 1925 (6.3 magnitude), 1941 (5.5 magnitude) and 1978 (5.1 magnitude). These and numerous smaller seismic events located beneath and offshore of the coastal plain, likely occurred on reverse-oblique-slip faults that are similar to, or continuous with, Quaternary reverse faults crossing the coastal plain. Thus, faults of the SBFFB pose a significant earthquake hazard to the approximately 200,000 people living within the major coastal population centers of Santa Barbara and Goleta. In addition, numerous Quaternary landslide deposits along the steep southern flank of the Santa Ynez Mountains indicate the potential for continued slope failures and mass movements in developed areas. Folded, faulted, and fractured sedimentary rocks in the subsurface of the coastal plain and adjacent Santa Barbara Channel are sources and form reservoirs for economic deposits of oil and gas, some of which are currently being extracted offshore. Shallow, localized sedimentary aquifers underlying the coastal plain provide limited amounts of water for the urban areas, but the quality of some of this groundwater is compromised by coastal salt-water contamination. The present map compilation provides a set of uniform geologic digital coverages that can be used for analysis and interpretation of these and other geologic hazards and resources in the Goleta region.

Open-File Report↗

USGS2012

Preliminary surficial geologic map of the Newberry Springs 30' x 60' quadrangle, California

The Newberry Springs 30' x 60' quadrangle is located in the central Mojave Desert of southern California. It is split approximately into northern and southern halves by I-40, with the city of Barstow at its western edge and the town of Ludlow near its eastern edge. The map area spans lat 34°30 to 35° N. to long -116 °to -117° W. and covers over 1,000 km 2 . We integrate the results of surficial geologic mapping conducted during 2002-2005 with compilations of previous surficial mapping and bedrock geologic mapping. Quaternary units are subdivided in detail on the map to distinguish variations in age, process of formation, pedogenesis, lithology, and spatial interdependency, whereas pre-Quaternary bedrock units are grouped into generalized assemblages that emphasize their attributes as hillslope-forming materials and sources of parent material for the Quaternary units. The spatial information in this publication is presented in two forms: a spatial database and a geologic map. The geologic map is a view (the display of an extracted subset of the database at a given time) of the spatial database; it highlights key aspects of the database and necessarily does not show all of the data contained therein. The database contains detailed information about Quaternary geologic unit composition, authorship, and notes regarding geologic units, faults, contacts, and local vegetation. The amount of information contained in the database is too large to show on a single map, so a restricted subset of the information was chosen to summarize the overall nature of the geology. Refer to the database for additional information. Accompanying the spatial data are the map documentation and spatial metadata. The map documentation (this document) describes the geologic setting and history of the Newberry Springs map sheet, summarizes the age and physical character of each map unit, and describes principal faults and folds. The Federal Geographic Data Committee (FGDC) compliant metadata provides detailed information about the digital files and file structure of the spatial data.

California↗

USGS2014

Preliminary geologic map of the eastern Willapa Hills, Cowlitz, Lewis, and Wahkiakum Counties, Washington

This digital map database and the PDF derived from the database were created from the analog geologic map: Wells, R.E. (1981), “Geologic map of the eastern Willapa Hills, Cowlitz, Lewis, and Wahkiakum Counties, Washington.” The geodatabase replicates the geologic mapping of the 1981 report with minor exceptions along water boundaries and also along the north and south map boundaries. Slight adjustments to contacts along water boundaries were made to correct differences between the topographic base map used in the 1981 compilation (analog USGS 15-minute series quadrangle maps at 1:62,500 scale) and the base map used for this digital compilation (scanned USGS 7.5-minute series quadrangle maps at 1:24,000 scale). These minor adjustments, however, did not materially alter the geologic map. No new field mapping was performed to create this digital map database, and no attempt was made to fit geologic contacts to the new 1:24,000 topographic base, except as noted above. We corrected typographical errors, formatting errors, and attribution errors (for example, the name change of Goble Volcanics to Grays River Volcanics following current State of Washington usage; Walsh and others, 1987). We also updated selected references, substituted published papers for abstracts, and cited published radiometric ages for the volcanic and plutonic rocks. The reader is referred to Magill and others (1982), Wells and Coe (1985), Walsh and others (1987), Moothart (1993), Payne (1998), Kleibacker (2001), McCutcheon (2003), Wells and others (2009), Chan and others (2012), and Wells and others (in press) for subsequent interpretations of the Willapa Hills geology.

Washington↗

USGS2014

California State Waters Map Series — Offshore of Half Moon Bay, California

In 2007, the California Ocean Protection Council initiated the California Seafloor Mapping Program (CSMP), designed to create a comprehensive seafloor map of high-resolution bathymetry, marine benthic habitats, and geology within the 3-nautical-mile limit of California’s State Waters. The CSMP approach is to create highly detailed seafloor maps through collection, integration, interpretation, and visualization of swath sonar data, acoustic backscatter, seafloor video, seafloor photography, high-resolution seismic-reflection profiles, and bottom-sediment sampling data. The map products display seafloor morphology and character, identify potential marine benthic habitats, and illustrate both the surficial seafloor geology and shallow (to about 100 m) subsurface geology. The Offshore of Half Moon Bay map area is located in northern California, on the Pacific coast of the San Francisco Peninsula about 40 kilometers south of the Golden Gate. The city of Half Moon Bay, which is situated on the east side of the Half Moon Bay embayment, is the nearest significant onshore cultural center in the map area, with a population of about 11,000. The Pillar Point Harbor at the north edge of Half Moon Bay offers a protected landing for boats and provides other marine infrastructure. The map area lies offshore of the Santa Cruz Mountains, part of the northwest-trending Coast Ranges that run roughly parallel to the San Andreas Fault Zone. The Santa Cruz Mountains lie between the San Andreas Fault Zone and the San Gregorio Fault system. The flat coastal area, which is the most recent of numerous marine terraces, was formed by wave erosion about 105 thousand years ago. The higher elevation of this same terrace west of the Half Moon Bay Airport is caused by uplift on the Seal Cove Fault, a splay of the San Gregorio Fault Zone. Although originally incised into the rising terrain horizontally, the ancient terrace surface has been gently folded into a northwest-plunging syncline by compression related to right-lateral strike-slip movement along the San Gregorio Fault Zone. The lowest elevation coincides with the deepest part of Half Moon Bay; the terrace surface rises both to the north and to the south. Uplift in this map area has resulted in relatively shallow water depths within California’s State Waters and, thus, little accommodation space for sediment accumulation. Sediment is observed in the shelter of Half Moon Bay and on the outer half of the California’s State Waters shelf. Sediment in the area is mobile, often forming dunes and sand waves. A westward bend in the San Andreas Fault Zone, southeast of the map area, coupled with right-lateral movement along the Seal Cove Fault, which comes ashore in Pillar Point Harbor, has resulted in the folding and uplifting of sedimentary rocks of the Purisima Formation in the offshore. Differential erosion of these folded and faulted layers of the Purisima Formation has exposed the parallel curved-rock ridges that are visible on the seafloor from the headland at Pillar Point. During the winter, strong North Pacific storms generate large, long-period waves that shoal and break over this bedrock reef at the world-famous surfing location known as Mavericks. The Offshore of Half Moon Bay map area lies within the cold-temperate biogeographic zone that is called either the “Oregonian province” or the “northern California ecoregion.” This biogeographic province is maintained by the long-term stability of the southward-flowing California Current, an eastern limb of the North Pacific subtropical gyre that flows from Oregon to Baja California. At its midpoint off central California, the California Current transports subarctic surface (0–500 m deep) waters southward, about 150 to 1,300 km from shore. Seasonal northwesterly winds that are, in part, responsible for the California Current, generate coastal upwelling. The south end of the Oregonian province is at Point Conception (about 365 km south of the map area), although its associated phylogeographic group of marine fauna may extend beyond to the area offshore of Los Angeles in southern California. The ocean off central California has experienced a warming over the last 50 years that is driving an ecosystem shift away from the productive subarctic regime towards a depopulated subtropical environment. Seafloor habitats in the Offshore of Half Moon Bay map area, which lies within the Shelf (continental shelf) megahabitat, range from significant rocky outcrops that support kelp-forest communities nearshore to rocky-reef communities in deep water. Biological productivity resulting from coastal upwelling supports populations of sea birds such as Sooty Shearwater, Western Gull, Common Murre, Cassin’s Auklet, and many other less populous bird species. In addition, an observable recovery of Humpback and Blue Whales has occurred in the area; both species are dependent on coastal upwelling to provide nutrients. The large extent of exposed inner shelf bedrock supports large forests of “bull kelp,” which is well adapted for high wave-energy environments. Common fish species found in the kelp beds and rocky reefs include lingcod and various species of rockfish and greenling.

California↗

USGS2015

California State Waters Map Series — Offshore of San Francisco, California

In 2007, the California Ocean Protection Council initiated the California Seafloor Mapping Program (CSMP), designed to create a comprehensive seafloor map of high-resolution bathymetry, marine benthic habitats, and geology within California’s State Waters. The CSMP approach is to create highly detailed seafloor maps through collection, integration, interpretation, and visualization of swath sonar data, acoustic backscatter, seafloor video, seafloor photography, high-resolution seismic-reflection profiles, and bottom-sediment sampling data. The map products display seafloor morphology and character, identify potential marine benthic habitats, and illustrate both the surficial seafloor geology and shallow (to about 100 m) subsurface geology. The Offshore of San Francisco map area is centered on the City of San Francisco and the Golden Gate channel, a waterway that connects the Pacific Ocean to the San Francisco Bay between the Marin Headlands and San Francisco Peninsula. The San Francisco Bay Area is the second-largest urban area on the U.S. West Coast with a combined population of over seven million. The bay supports several major cargo ports and the Port of San Francisco’s Fisherman’s Wharf is a major center for Northern California’s commercial and sport fishing fleets. The coastal part of the map area predominantly consists of high bluffs and vertical sea cliffs shaped by uplift and erosion of the Marin Headlands and San Francisco Peninsula east of the San Andreas and San Gregorio Fault Zones. The seafloor in the map area extends from the shoreline and western end of the Golden Gate channel to water depths of about 30 to 50 m, except for the San Andreas graben area, where water depths reach 75 m. Sea-level rise, tidal currents, and tectonics have shaped bathymetry in the map area. During the Last Glacial Maximum, Sea level was about 125 m lower than present day and the shoreline was more than 45 km west of San Francisco near the Farallon Islands. At that time, the map area was part of a large alluvial plain connected to a drainage basin that included much of California’s Central Valley. A river system flowed westward through the narrows of the Golden Gate channel and an alluvial valley bounded to the north and south by bedrock highlands, including the present-day Pacifica-Pescadero and Bolinas shelves. Rising seas entered the Golden Gate about 11,000 to 10,000 years ago and subsequent marine flooding led to progressive growth of the San Francisco Bay. Strong tidal currents, accelerating through the relatively narrow Golden Gate, have scoured the bedrock channel to a depth of 113 m. East and west of the channel, tidal currents decelerate and form large fields of sand waves. Offshore of the Marin Headlands, eastward transfer of right-lateral fault slip in a complex of faults northwest of the map area has caused extension and the formation of a sediment basin called the San Andreas graben on the continental shelf. The accommodation space created by extension on the shelf and the proximity to sediment transported to the ocean through San Francisco Bay results in a sand-dominated offshore shelf environment. Seafloor habitats in the Offshore of San Francisco map area comprise significant sand-dominated sediment habitat with sand wave and ripple bedforms indicative of high wave and current energy. North of the Golden Gate, biological productivity resulting from coastal upwelling supports populations of Sooty Shearwater, Western Gull, Common Murre, Cassin’s Auklet, and many other less populous bird species. In addition, an observable recovery of Humpback and Blue Whales has occurred in the area; both species are dependent on coastal upwelling to provide nutrients. For the first time in 65 years, Pacific Harbor Porpoise returned to San Francisco Bay in 2009. On the coast north of the Golden Gate, the large extent of exposed inner shelf bedrock supports large forests of “bull kelp,” which is well adapted for high wave-energy environments. Common fish species found in the kelp beds and rocky reefs include painted greenling, kelp greenling, lingcod, and several varieties of rockfish. Circulation over the continental shelf in the Offshore of San Francisco map area is dominated by the southward-flowing California Current, an eastern limb of the North Pacific Gyre that flows from Oregon to Baja California. At its midpoint offshore of central California, the California Current transports subarctic surface waters southeastward, about 150 to 1,300 km from shore. Seasonal northwesterly winds that are, in part, responsible for the California Current, generate coastal upwelling. Ocean temperatures offshore of central California have increased over the past 50 years, driving an ecosystem shift from the productive subarctic regime towards a depopulated subtropical environment.

California↗

USGS1999

Digital Map of Surficial Geology, Wetlands, and Deepwater Habitats, Coeur d'Alene River Valley, Idaho

The Coeur d'Alene (CdA) River channel and its floodplain in north Idaho are mostly covered by metal-enriched sediments, partially derived from upstream mining, milling and smelting wastes. Relative to uncontaminated sediments of the region, metal-enriched sediments are highly enriched in silver, lead, zinc, arsenic, antimony and mercury, copper, cadmium, manganese, and iron. Widespread distribution of metal-enriched sediments has resulted from over a century of mining in the CdA mining district (upstream), poor mine-waste containment practices during the first 80 years of mining, and an ongoing series of over-bank floods. Previously deposited metal-enriched sediments continue to be eroded and transported down-valley and onto the floodplain during floods. The centerpiece of this report is a Digital Map Surficial Geology, Wetlands and Deepwater Habitats of the Coeur d'Alene (CdA) River valley (sheets 1 and 2). The map covers the river, its floodplain, and adjacent hills, from the confluence of the North and South Forks of the CdA River to its mouth and delta front on CdA Lake, 43 linear km (26 mi) to the southwest (river distance 58 km or 36 mi). Also included are the following derivative theme maps: 1. Wetland System Map; 2. Wetland Class Map; 3. Wetland Subclass Map; 4. Floodplain Map; 5. Water Regime Map; 6. Sediment-Type Map; 7. Redox Map; 8. pH Map; and 9. Agricultural Land Map. The CdA River is braided and has a cobble-gravel bottom from the confluence to Cataldo Flats, 8 linear km (5 mi) down-valley. Erosional remnants of up to four alluvial terraces are present locally, and all are within the floodplain, as defined by the area flooded in February of 1996. High-water (overflow) channels and partly filled channel scars braid across some alluvial terraces, toward down-valley marshes and (or) oxbow ponds, which drain back to the river. Near Cataldo Flats, the river gradient flattens, and the river coalesces into a single channel with a large friction-dominated central sand bar at Cataldo Landing. Metal-enriched sediments that were dredged from the central sand bar were deposited on Cataldo Flats, to form extensive dredge-spoil deposits. From the central sand bar to CdA Lake, thick deposits of metal-enriched sand partially fill the middle of the pre-mining-era channel along straight reaches, and form point-bars along the inside margins of meander bends. Metal-enriched sand and silt form oxidized bank-wedge deposits along riverside margins of pre-mining-era levees of gray silty mud. Metal-enriched levee sand deposits extend across bank wedges and natural levees, generally thinning and fining away from the river, toward lateral marshes and lakes, where dark gray metal-enriched silt and mud overlie silty peat, deposited before the mining era. Distributary streams and man-made canals locally diverge from the river, connecting it to lateral marshes and lakes, and metal-enriched sand splays locally fan out across the floodplain. At the mouth of the river, a bouyancy-dominated river-mouth bar crests beyond the ends of the emergent levees. Thick delta-front deposits of metal-enriched sand slope from the river-mouth bar to the bottom of CdA Lake.

Open-File Report↗

USGS2015

Flood Map for the Winooski River in Waterbury, Vermont, 2014

From August 28 to 29, 2011, Tropical Storm Irene delivered rainfall ranging from approximately 4 to more than 7 inches in the Winooski River Basin in Vermont. The rainfall resulted in severe flooding throughout the basin and significant damage along the Winooski River. In response to the flooding, the U.S. Geological Survey (USGS), in cooperation with the Federal Emergency Management Agency, conducted a new flood study to aid in flood recovery and restoration and to assist in flood forecasting. The study resulted in two sets of flood maps that depict the flooding for an 8.3-mile reach of the Winooski River from about 1,000 feet downstream of the Waterbury-Bolton, Vermont, town line upstream to about 2,000 feet upstream of the Waterbury-Middlesex, Vt., town line. The first set of maps consists of flood-recovery maps depicting the boundaries of floodwaters at the 10-, 4-, 2-, 1-, and 0.2-percent annual exceedance probability (AEP) discharges, the boundaries of the floodway, and the boundaries of floodwaters from Tropical Storm Irene as estimated by a hydraulic model. The second set of maps consists of flood-inundation maps depicting the areal extent and depth of flooding corresponding to selected water levels (stages) at the USGS Winooski River above Crossett Bk at Waterbury, VT (04288040) streamgage. The maps correspond to streamgage water levels ranging from 417.0 to 431.0 feet in 2-foot increments. The availability of these flood-inundation maps along with current stage from the USGS streamgage obtained from a USGS Web site will provide emergency management personnel and residents with information that is critical for flood response activities such as evacuations and road closures, as well as for post-flood recovery efforts. These flood inundation maps can be accessed through the USGS Flood Inundation Mapping Science Web site ( http://water.usgs.gov/osw/flood_inundation/ ). To generate the maps, flood profiles for the Winooski River were developed. The U.S. Army Corps of Engineers one-dimensional step-backwater Hydrologic Engineering Center River Analysis System model (HEC–RAS), was used to compute the water-surface profiles along the study reach. The simulated water-surface profiles were then combined with a geographic information system digital elevation model derived from light detection and ranging (lidar) data with a vertical accuracy that meets or exceeds vertical national map accuracy standards for 2-foot contour mapping to delineate the area flooded for each water-surface profile. High-water marks from Tropical Storm Irene were available for seven locations along the study reach. The highwater marks were used to estimate water-surface profiles and discharges resulting from Tropical Storm Irene throughout the study reach. From a comparison of the estimated water-surface profile for Tropical Storm Irene with the water-surface profiles for the 1- and 0.2-percent annual exceedance probability (AEP) floods, it was determined that the high-water elevations resulting from Tropical Storm Irene exceeded the estimated 1-percent AEP flood throughout the Winooski River study reach but did not exceed the estimated 0.2-percent AEP flood at any location within the study reach.

Vermont↗

USGS2014

Standard for the U.S. Geological Survey Historical Topographic Map Collection

This document defines the digital map product of the U.S. Geological Survey (USGS) Historical Topographic Map Collection (HTMC). The HTMC is a digital archive of about 190,000 printed topographic quadrangle maps published by the USGS from the inception of the topographic mapping program in 1884 until the last paper topographic map using lithographic printing technology was published in 2006. The HTMC provides a comprehensive digital repository of all scales and all editions of USGS printed topographic maps that is easily discovered, browsed, and downloaded by the public at no cost. Each printed topographic map is scanned “as is” and captures the content and condition of each map. The HTMC provides ready access to maps that are no longer available for distribution in print. A new generation of topographic maps called “US Topo” was defined in 2009. US Topo maps, though modeled on the legacy 7.5-minute topographic maps, conform to different standards. For more information on the HTMC, see the project Web site at: http://nationalmap.gov/historical/ .

Techniques and Methods↗

USGS1987

Map showing the distribution and characteristics of plutonic rocks in the Tonopah 1 degree by 2 degrees Quadrangle, central Nevada

Plutonic rocks, mostly granite and granodiorite, are widely distributed in the west two-thirds of the Tonopah 1 degree by 2 degree quadrangle, Nevada. These rocks were systematically studied as part of the Tonopah CUSMAP project. Studies included field mapping, petrographic and modal analyses, geochemical studies of both fresh and altered plutonic rocks and altered wallrocks, and K-Ar and Rb-Sr radiometric dating. Data collected during this study were combined with previously published data to produce a 1:250,000-scale map of the Tonopah quadrangle showing the distribution of individual plutons and an accompanying table summarizing composition, texture, age, and any noted hydrothermal alteration and mineralization effects for each pluton. The main areas mapped as part of this study, mapped along with collaborators listed in parentheses, were the Paradise Range (N.J. Silberling), north Cedar Mountain (R.A. Armin), the east side of the Toiyabe Range (G. F. Brem and R. A. Armin), and the south end of the Toquima Range (R.A. Armin). Most mapping was done at a scale of 1:24,000. These maps were combined with previously published maps and other maps of the Tonopah CUSMAP project to produce this pluton map The accompanying table includes the name (if any) of the pluton and its location, the age of the pluton (either a radiometric age or an age inferred from field relations), modal composition, texture, mineralogy, hydrothermal alteration and mineralization related to the pluton, the source of mapping shown on this map, and published references on the pluton. Radiometric ages are either published K-Ar and fission track ages or new whole-rock Rb-Sr ages determined by A. C. Robinson on samples collected either for this study or as part of regional Sr-isotope studies by R.W. Kistler and A.C. Robinson. K-Ar ages published prior to 1977 are corrected using the new I.U.C.S. constants (Steiger and Jager, 1977). Muscovite alteration ages are reported for several plutons and represent minimum ages for emplacement of these plutons. Compositional classification follows the T. J. G.S. system (“Streckeisen, 1976) and is based either on modal analyses of slabs or estimates from hand specimens. All modes, unless otherwise noted, were measured in this study. The number of modes determined is shown in parentheses, and the range in volume percent of major minerals is given. Where no modal data are available, the color index (percentage of mafic minerals) and major mafic minerals are given for most plutons. Data tabulated on hydrothermal alteration and mineralization related to plutons are based on observations made during field studies for this project. Clear genetic relation between granitic plutonism and several mineral deposits previously attributed to granitic plutonism were not substantiated, and these inconsistencies are noted in the table.

Miscellaneous Field Studies Map↗

USGS2003

Geologic map of the Horse Mountain Quadrangle, Garfield County, Colorado

New 1:24,000-scale geologic map of the Horse Mountain 7.5' quadrangle, in support of the USGS Western Colorado I-70 Corridor Cooperative Geologic Mapping Project, summarizes available geologic information for the quadrangle. It provides new interpretations of the stratigraphy, structure, and geologic hazards in the area of the southwest flank of the White River uplift. Bedrock strata include the Paleocene and early Eocene Wasatch Formation down through Ordovician and Cambrian units into Precambrian hornblende tonalite. The Wasatch Formation includes the Shire, Molina and Atwell Gulch Members which are mapped separately. The underlying Upper Cretaceous Mesaverde Group is subdivided into the Willams Fork and Iles Formations. The Cameo-Fairfield clinker zone within the Williams Fork Formation is mapped separately. The Iles Formation includes the Rollins Sandstone Member at the top, mapped separately, and the Cozzette Sandstone and Corcoran Sandstone Members, which are undivided. The Mancos Shale consists of four members, an upper member, the Niobrara Member, the Juana Lopez Member, and a lower member, undivided. The Lower Cretaceous Dakota Sandstone, the Upper Jurassic Morrison Formation, and Jurassic Entrada Sandstone are mapped separately. The Lower Jurassic and Upper Triassic Glen Canyon Sandstone is mapped with the Entrada in the Horse Mountain Quadrangle. The upper Triassic Chinle Formation and the Lower Permian and Triassic(?) State Bridge Formation are present. The Pennsylvanian and Permian Maroon Formation is undivided. All the exposures of the Middle Pennsylvanian Eagle Valley Evaporite are diapiric, intruded into the Middle Pennsylvanian Eagle Valley Formation, which includes locally mappable limestone beds. The Lower and Middle Pennsylvanian Belden Formation and the Lower Mississippian Leadville Limestone are present. The Upper Devonian Chaffee Group consists of the Dyer Dolomite and the underlying Parting Quartzite, undivided. Locally, the Lower Ordovician Manitou Formation is mapped separately beneath the Chaffee. Elsewhere, Ordovician through Cambrian units, the Manitou and Dotsero Formations, underlain by the Sawatch Quartzite, are undivided. The southwest flank of the White River uplift is a late Laramide structure that is represented by the steeply southwest-dipping Grand Hogback, which is only present in the southwestern corner of the map area, and less steeply southwest-dipping older strata that flatten to nearly horizontal attitudes in the northern part of the map area. Between these two are a complex of normal faults, the largest of which dips southward placing Chafee dolostone and Leadville Limestone adjacent to Eagle Valley and Maroon Formations. Diapiric Eagle Valley Evaporite intruded close to the fault on the down-thrown side. Removal of evaporite by either flow or dissolution from under younger parts of the strata create structural benches, folds, and sink holes on either side of the normal fault. A prominent dipslope of the Morrison-Dakota-Mancos part of the section forms large slide blocks and mass movement deposits consisting of a chaos of admixed Morrison and Dakota lithologies. The major geologic hazard in the area consists of large landslides both associated with dip-slope slide blocks and the steep slopes of the Eagle Valley Formation and Belden Formation in the northern part of the map. Abandoned coal mines are present along the north face of the Grand Hogback in the lower part of the Mesaverde Group

Miscellaneous Field Studies Map↗