Geology Reports⌕ Search

SEARCH · Geology Reports

Results for “Research Paper”

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

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

At least 1,009 records · Page 56Linked to original sources
USGS2024

Hydrodynamic and salinity tesponse to tidal restoration in the Herring River Estuary, MA, considering present and future sea levels

Coastal salt marshes are crucial ecosystems that provide habitat for a variety of species, improve water quality, and play a major role in the global carbon cycle. However, many salt marshes have been severely damaged by human activities such as diking and draining for urban development. Recently, there has been a noticeable shift toward the prioritization of coastal marsh restoration to re-establish their ecosystem services. The removal of anthropogenic barriers such as dikes, sluices, and culverts is a critical component of many projects because it allows for the restoration of tidal flow to support natural hydrologic regimes and salinity conditions, which play a dominant role in determining the ecological and biogeochemical functioning of marshes. This study examines how proposed removal of hydraulic structures will influence the hydrologic potential for marsh restoration in the Herring River Estuary in Cape Cod, Massachusetts, USA. Construction of dikes, roadways, and low-capacity culverts over the last century has substantially restricted tidal flow in the Herring River Estuary, leading to degradation of salt marsh habitat. The estuary is now undergoing the first phase of a restoration project to re-introduce natural hydrologic conditions, increase salinity, and restore salt marsh habitat. To assess how the Herring River Estuary will respond to human- and climate-driven modifications, we develop and apply a validated hydrodynamic model to simulate the complex tidal and salinity dynamics of the estuary under a range of restoration and sea level rise scenarios. We then quantify how salinity and critical hydrologic variables, including tidal range and depth of mean high water, will evolve for various restoration scenarios considering present and future sea levels. The results of this research can inform coastal management and restoration plans that re-create the natural functioning of the system while protecting critical infrastructure and reducing the risk of restoration failure.

Massachusetts↗
USGS1986

Research on polar bears in Alaska, 1983-1985

Research on the ecology and status of polar bear populations in Alaska has continued since 1967. Research was a joint U.S. Fish and Wildlife Service/Alaska Department of Fish and Game effort until passage of the Marine Mammal Protection Act in 1972, and has been largely a Federal effort since then. In 1985, Alaskan polar beer research continues to be carried out by the Research Division of the U.S. Fish and Wildlife Service (DOI). A recent reorganization removed authority for ecological research in Alaska from the Denver Wildlife Research Center, and vested it with the newly created Alaska Office of Fish and Wildlife Research. This new research office is the center for Federal fish and Wildlife related research throughout the state of Alaska and in its coastal waters. Although the responsibility for polar bear research lies with the U.S. Fish and Wildlife Service, numerous other organizations and agencies deserve mention for their cooperation and support of the ongoing research. These include: the U.S. National Oceanic and Atmospheric Administration (DOC), The U.S. Minerals Management Service (DOI), The Canadian Wildlife Service, The Northwest Territories Wildlife Service, the Yukon Wildlife Service, Dome Petroleum Ltd, Gulf Canada, and the Alaska Department of Fish and game.

Alaska↗
USGS2023

Development of small uncrewed aerial systems for multi-instrument geophysical data acquisition in active geothermal systems

Small Uncrewed Aerial Systems (sUAS) serve as critical platforms for geophysical data collection at an intermediate scale between lower resolution, regional datasets collected via crewed aerial surveys, and high resolution, but spatially sparse sampling of ground-based data collection methods. Advances in sensor design and sUAS capabilities have led to rapid advances in the amount and type of geophysical data that can be acquired using sUAS-based survey designs (Gavazzi et al., 2019). Here we showcase the utility of a single sUAS (the Matrice 600 Pro and accompanying sensor package) that collects magnetic, thermal infra-red (TIR) and gas (CO2, SO2, H2S, water vapor) data for use in geothermal resource exploration and monitoring, with case studies in eastern California and Iceland. The work highlights the flexibility of modern sUAS systems for single-team acquisition of multiple independent but coupled geophysical data which allow for a multidisciplinary approach to geothermal systems research. We summarize the workflows involved in collecting each dataset as well as several common issues encountered both during data collection and data processing.

Conference Paper↗
USGS2013

Integrated environmental modeling: a vision and roadmap for the future

Integrated environmental modeling (IEM) is inspired by modern environmental problems, decisions, and policies and enabled by transdisciplinary science and computer capabilities that allow the environment to be considered in a holistic way. The problems are characterized by the extent of the environmental system involved, dynamic and interdependent nature of stressors and their impacts, diversity of stakeholders, and integration of social, economic, and environmental considerations. IEM provides a science-based structure to develop and organize relevant knowledge and information and apply it to explain, explore, and predict the behavior of environmental systems in response to human and natural sources of stress. During the past several years a number of workshops were held that brought IEM practitioners together to share experiences and discuss future needs and directions. In this paper we organize and present the results of these discussions. IEM is presented as a landscape containing four interdependent elements: applications, science, technology, and community. The elements are described from the perspective of their role in the landscape, current practices, and challenges that must be addressed. Workshop participants envision a global scale IEM community that leverages modern technologies to streamline the movement of science-based knowledge from its sources in research, through its organization into databases and models, to its integration and application for problem solving purposes. Achieving this vision will require that the global community of IEM stakeholders transcend social, and organizational boundaries and pursue greater levels of collaboration. Among the highest priorities for community action are the development of standards for publishing IEM data and models in forms suitable for automated discovery, access, and integration; education of the next generation of environmental stakeholders, with a focus on transdisciplinary research, development, and decision making; and providing a web-based platform for community interactions (e.g., continuous virtual workshops).

Environmental Modelling and Software↗
USGS2011

China's rare-earth industry

Introduction China's dominant position as the producer of over 95 percent of the world output of rare-earth minerals and rapid increases in the consumption of rare earths owing to the emergence of new clean-energy and defense-related technologies, combined with China's decisions to restrict exports of rare earths, have resulted in heightened concerns about the future availability of rare earths. As a result, industrial countries such as Japan, the United States, and countries of the European Union face tighter supplies and higher prices for rare earths. This paper briefly reviews China's rare-earth production, consumption, and reserves and the important policies and regulations regarding the production and trade of rare earths, including recently announced export quotas. The 15 lanthanide elements-lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium (atomic numbers 57-71)-were originally known as the rare earths from their occurrence in oxides mixtures. Recently, some researchers have included two other elements-scandium and yttrium-in their discussion of rare earths. Yttrium (atomic number 39), which lies above lanthanum in transition group III of the periodic table and has a similar 3+ ion with a noble gas core, has both atomic and ionic radii similar in size to those of terbium and dysprosium and is generally found in nature with lanthanides. Scandium (atomic number 21) has a smaller ionic radius than yttrium and the lanthanides, and its chemical behavior is intermediate between that of aluminum and the lanthanides. It is found in nature with the lanthanides and yttrium. Rare earths are used widely in high-technology and clean-energy products because they impart special properties of magnetism, luminescence, and strength. Rare earths are also used in weapon systems to obtain the same properties.

Open-File Report↗
USGS1986

This week?s Citation Classic: 'Stickel, L. F. A comparison of certain methods of measuring ranges of small mammals. J. Mammalogy 35: 1-15, 1954.'

During my first employment as a junior biologist conducting food habits analyses at the Patuxent Research Refuge (now Patuxent Wildlife Research Center) of the US Fish and Wildlife Service, the first station director, Arnold L. Nelson, gave each staff biologist the opportunity to spend a little time conducting field studies on the 2,600-acre research area. These studies were to help in ecological evaluation of the area, but also, no doubt, functioned as a morale builder for biologists daily engaged in difficult, demanding and confining laboratory work. I undertook to measure the population density of small mammals in different habitats. The state-of-the-art methods recommended to me and prevalent in the literature worried me, especially after preliminary field work. Reading the classic, paper by W.H. Burt [Terrioriality and home range concepts as applied to mammals. J. Mammalogy 24:346-352, 1943] was a turning point for me in seeing that knowledge of home-range size was the key to measuring population density. My first papers employed these concepts in field evaluations. However, they could give-only limited attention to the question of how home ranges could be measured. Furthermore, the importance of knowledge of the home range to habitat evaluation and to understanding animal behavior was becoming increasingly apparent. Advocacy of many different methods of measuring home ranges appeared in the literature. It did not seem possible to evaluate them objectively. It occurred to me that artificial populations could be used to help in understanding the mechanisms of measuring home ranges. The effects of random trap-visiting, bias toward central traps, trap-spacing, range shape, and other factors could be considered. So grids of traps were inked onto oversize graph paper, and simulated ranges were cut from plastic to be tossed as randomly as possible on the trap-grids. It was a slow, laborious job. Analysis showed that random captures in artificial populations produced patterns that were similar in many ways to those observed in field studies; the necessity of appropriate trap-spacing in relation to range size became obvious. Some commonly used methods of expressing range size proved to be clearly superior to others. However, the artificial populations could not fully simulate actual populations, where use patterns changed as conditions changed and the ?boundaries? of ranges tended to shift continuously or with time. Progress was made, but problems remained. I suspect that the reasons the paper has been cited frequently rest on the continuing interest in home-range behavior and the continuing difficulty in field evaluations, despite the many advances in observational methodology. The sophisticated techniques that became possible with the use of computers [R.I. Jennrich and F.B. Turner. Measurement of non-circular home range. J. Theor. Biol 23:227-237, 1969] also presented new possibilities for analysis and understanding of home-range characteristics and created a resurgence of interest in home-range behavior and its biological significance.

Current Contents / Agriculture, Biology & Environm↗
USGS2014

Report of Committee on Runoff, 1942–43

The Committee on Runoff was not formally constituted until February 6, 1943, when the members of the Section, as listed above, were asked to serve. At the suggestion of President CHURCH the Committee has been so selected that there is Nation‐wide geographic distribution from West to East with the majority of the Committee composed of younger men. If the 33 papers prepared for discussion at the regular sessions of the Section of Hydrology at the annual meeting of 1943 can be used as a measure, war instead of curtailing the activities of the Section has acted as an impetus. Also in the field of hydrology as a whole, war activities have apparently not resulted in a decrease of activities. There has been, however, a gradual decrease of activities in the field of research and an increase of activities in the field of applied hydrology. The enormous expansion of our industrial machine and the great concentration of armies and industrial workers into restricted areas; the demands for water, for power, for food and for municipal use; and operations underlying many of our war efforts, secret and otherwise—all these have created problems requiring the full‐time effort of hydrologists, both in private and governmental service. It is with some degree of satisfaction that each one of us can feel that either as a result of our past research or in our present positions we have been or are doing our bit to win the war.

Eos, Transactions, American Geophysical Union↗
USGS2010

Modeling downstream fining in sand-bed rivers. I: Formulation

In this paper a numerical modeling formulation is presented for simulation of the development of the longitudinal profile and bed sediment distribution in sand-bed rivers. The objective of the model application, which is presented in the companion paper (Wright and Parker, 2005), is to study the development of two characteristics of large, low-slope, sand-bed rivers: (1) a downstream decrease in bed slope (i.e. concave upward longitudinal profile) and (2) a downstream decrease in characteristic bed sediment diameter (e.g. the median bed surface size D 50 ). Three mechanisms that lead to an upward concave profile and downstream fining are included in the modeling formulation: (1) a delta prograding into standing water at the downstream boundary, (2) sea-level rise, and (3) tectonic subsidence. In the companion paper (Wright and Parker, 2005) the model is applied to simulate the development of the longitudinal profile and downstream fining in sand-bed rivers flowing into the ocean during the past 5000 years of relatively slow sea-level rise.

Journal of Hydraulic Research↗
USGS2019

Measuring settling velocity in a strongly tidal estuary

Predicting sediment transport in estuarine systems requires understanding sediment settling velocity, its range of fluctuations, and the shortcomings of the tools to measure it. Previous studies have used Laser In-Situ Scattering and Transmissometry (LISST) instruments to measure particle size and Acoustic Doppler Velocimeters (ADV) to return estimates of settling velocity. We deployed both instruments over a 4-week period in summer 2016 in San Pablo Bay, CA, and observed conflicting results from the two instruments. The LISST indicated the settling velocity decreased with increasing bed shear stress, while the ADV showed that settling velocity increased. Comparing the experimental conditions from this study with previous research reveals that the ADV method requires steady state conditions that were not achieved. Although the ADV method uses easily measured quantities to return the settling velocity, it relies on assumptions that are not always valid in estuarine settings.

California↗
USGS1970

Propagation of captive American kestrels

A colony of kestrels ( Palco sparverius ) was established at the Patuxent Wildlife Research Center in 1964 in connection with work on pesticides. The kestrels were acquired from the wild, both as nestlings and as full-grown birds, and were housed in several rows of outdoor pens. Each 50 x 20 ft pen was covered with wire netting and had its long sides in common with adjacent pens. During the first two reproductive seasons, untreated parent birds (dosed birds are not included in this paper) ate eggs and young. Cannibalism virtually ceased after the diet was changed from ground beef or horsemeat supplemented with liver, vitamins, and minerals to one containing a finely ground mixture of laboratory rodents, chicken heads, skinned chicken necks, and supplements; hatching success thereafter generally equaled that of a wild population. In 1967, 16 pairs of untreated hawks (3-year-old females) laid clutches averaging 4.9 eggs, hatched 88 percent of their eggs, and fledged 88 percent of their young. In 1968, 10 pairs of this group (4-year-old females) laid clutches averaging 4.9 eggs, hatched 51 percent of their eggs, and fledged 85 percent of their young. Nine yearling pairs (hatched in captivity) laid clutches in 1968 averaging 5.1 eggs, hatched 87 percent of their eggs, and fledged all of their young.

Maryland↗
USGS2012

Improving scientific communication through the use of U.S. Geological Survey Video Podcasts

It is crucial that scientist find innovative ways of effectively communicating research to resource managers, public officials, and the general public. New technologies, such as video podcasts, are being used as an outreach tool to communicate results from the U.S Geological Survey (USGS) National Water-Quality Assessment (NAWQA) program. The purpose of these podcasts is to summarize scientific research and methods from the NAWQA program. Video podcasts are audio podcasts that incorporate video clips to illustrate ideas presented in simple, concise language with brief 3 to 5-minute films. The process of creating concise podcast messages expands the potential audience for communicating research findings, but the production of video podcasts requires adequate allocation of time and resources. Audience responses to NAWQA podcasts thus far indicate that video is an effective means of sharing scientific information with a broader audience.

Conference Paper↗
USGS1976

A simplified slope-area method for estimating flood discharges in natural channels

Discharge of a stream may be computed from the slope of the water surface, the cross-sectional area, and an estimate of channel roughness. This, the slope-area method, is widely used to compute flood peak discharges from high-water marks. Reliability of a computed discharge depends largely on the roughness coefficient, which must be estimated. This paper shows that results of comparable accuracy can be obtained from area and slope alone in natural channels; a roughness coefficient is not needed because roughness and slope are related. The estimating equation and suggestions for application of the simplified method are included.

Journal of Research of the U.S. Geological Survey↗
USGS2006

The potential roles of biological soil crusts in dryland hydrologic cycles

Biological soil crusts (BSCs) are the dominant living cover in many drylands of the world. They possess many features that can influence different aspects of local hydrologic cycles, including soil porosity, absorptivity, roughness, aggregate stability, texture, pore formation, and water retention. The influence of biological soil crusts on these factors depends on their internal and external structure, which varies with climate, soil, and disturbance history. This paper presents the different types of biological soil crusts, discusses how crust type likely influences various aspects of the hydrologic cycle, and reviews what is known and not known about the influence of biological crusts on sediment production and water infiltration versus runoff in various drylands around the world. Most studies examining the effect of biological soil crusts on local hydrology are done by comparing undisturbed sites with those recently disturbed by the researchers. Unfortunately, this greatly complicates interpretation of the results. Applied disturbances alter many soil features such as soil texture, roughness, aggregate stability, physical crusting, porosity, and bulk density in ways that would not necessarily be the same if crusts were not naturally present. Combined, these studies show little agreement on how biological crusts affect water infiltration or runoff. However, when studies are separated by biological crust type and utilize naturally occurring differences among these types, results indicate that biological crusts in hyperarid regions reduce infiltration and increase runoff, have mixed effects in and regions, and increase infiltration and reduce runoff in semiarid cool and cold drylands. However, more studies are needed before broad generalizations can be made on how biological crusts affect infiltration and runoff. We especially need studies that control for sub-surface soil features such as bulk density, micro- and macropores, and biological crust structure. Unlike the mixed effects of biological crusts on infiltration and runoff among regions, almost all studies show that biological crusts reduce sediment production, regardless of crust or dryland type.

Hydrological Processes↗
USGS2015

Moving environmental DNA methods from concept to practice for monitoring aquatic macroorganisms

The discovery that macroorganisms can be detected from their environmental DNA (eDNA) in aquatic systems has immense potential for the conservation of biological diversity. This special issue contains 11 papers that review and advance the field of eDNA detection of vertebrates and other macroorganisms, including studies of eDNA production, transport, and degradation; sample collection and processing to maximize detection rates; and applications of eDNA for conservation using citizen scientists. This body of work is an important contribution to the ongoing efforts to take eDNA detection of macroorganisms from technical breakthrough to established, reliable method that can be used in survey, monitoring, and research applications worldwide. While the rapid advances in this field are remarkable, important challenges remain, including consensus on best practices for collection and analysis, understanding of eDNA diffusion and transport, and avoidance of inhibition in sample collection and processing. Nonetheless, as demonstrated in this special issue, eDNA techniques for research and monitoring are beginning to realize their potential for contributing to the conservation of biodiversity globally.

Biological Conservation↗
USGS2003

The National Map: from geography to mapping and back again

When the means of production for national base mapping were capital intensive, required large production facilities, and had ill-defined markets, Federal Government mapping agencies were the primary providers of the spatial data needed for economic development, environmental management, and national defense. With desktop geographic information systems now ubiquitous, source data available as a commodity from private industry, and the realization that many complex problems faced by society need far more and different kinds of spatial data for their solutions, national mapping organizations must realign their business strategies to meet growing demand and anticipate the needs of a rapidly changing geographic information environment. The National Map of the United States builds on a sound historic foundation of describing and monitoring the land surface and adds a focused effort to produce improved understanding, modeling, and prediction of land-surface change. These added dimensions bring to bear a broader spectrum of geographic science to address extant and emerging issues. Within the overarching construct of The National Map, the U.S. Geological Survey (USGS) is making a transition from data collector to guarantor of national data completeness; from producing paper maps to supporting an online, seamless, integrated database; and from simply describing the Nation’s landscape to linking these descriptions with increased scientific understanding. Implementing the full spectrum of geographic science addresses a myriad of public policy issues, including land and natural resource management, recreation, urban growth, human health, and emergency planning, response, and recovery. Neither these issues nor the science and technologies needed to deal with them are static. A robust research agenda is needed to understand these changes and realize The National Map vision. Initial successes have been achieved. These accomplishments demonstrate the utility of The National Map to the Nation and give confidence in evolving its future applications.

Photogrammetric Engineering and Remote Sensing↗
USGS2016

Measuring distance “as the horse runs”: Cross-scale comparison of terrain-based metrics

Distance metrics play significant roles in spatial modeling tasks, such as flood inundation (Tucker and Hancock 2010), stream extraction (Stanislawski et al. 2015), power line routing (Kiessling et al. 2003) and analysis of surface pollutants such as nitrogen (Harms et al. 2009). Avalanche risk is based on slope, aspect, and curvature, all directly computed from distance metrics (Gutiérrez 2012). Distance metrics anchor variogram analysis, kernel estimation, and spatial interpolation (Cressie 1993). Several approaches are employed to measure distance. Planar metrics measure straight line distance between two points (“as the crow flies”) and are simple and intuitive, but suffer from uncertainties. Planar metrics assume that Digital Elevation Model (DEM) pixels are rigid and flat, as tiny facets of ceramic tile approximating a continuous terrain surface. In truth, terrain can bend, twist and undulate within each pixel. Work with Light Detection and Ranging (lidar) data or High Resolution Topography to achieve precise measurements present challenges, as filtering can eliminate or distort significant features (Passalacqua et al. 2015). The current availability of lidar data is far from comprehensive in developed nations, and non-existent in many rural and undeveloped regions. Notwithstanding computational advances, distance estimation on DEMs has never been systematically assessed, due to assumptions that improvements are so small that surface adjustment is unwarranted. For individual pixels inaccuracies may be small, but additive effects can propagate dramatically, especially in regional models (e.g., disaster evacuation) or global models (e.g., sea level rise) where pixels span dozens to hundreds of kilometers (Usery et al 2003). Such models are increasingly common, lending compelling reasons to understand shortcomings in the use of planar distance metrics. Researchers have studied curvature-based terrain modeling. Jenny et al. (2011) use curvature to generate hierarchical terrain models. Schneider (2001) creates a ‘plausibility’ metric for DEM-extracted structure lines. d’Oleire- Oltmanns et al. (2014) adopt object-based image processing as an alternative to working with DEMs; acknowledging the pre-processing involved in converting terrain into an object model is computationally intensive, and likely infeasible for some applications. This paper compares planar distance with surface adjusted distance, evolving from distance “as the crow flies” to distance “as the horse runs”. Several methods are compared for DEMs spanning a range of resolutions for the study area and validated against a 3 meter (m) lidar data benchmark. Error magnitudes vary with pixel size and with the method of surface adjustment. The rate of error increase may also vary with landscape type (terrain roughness, precipitation regimes and land settlement patterns). Cross-scale analysis for a single study area is reported here. Additional areas will be presented at the conference.

Conference Paper↗
USGS2000

Fish stocking in protected areas: Summary of a workshop

Native and nonnative sport fish have been introduced into the majority of historically fishless lakes in wilderness, generating conflicts between managing wilderness as natural ecosystems and providing opportunities for recreation. Managers faced with controversial and difficult decisions about how to manage wilderness lakes may not always have ready access to research relevant to these decisions. To address this problem, and to expose scientists to the concerns and constraints of managers and wilderness users, a workshop was held in October 1998 at the Flathead Lake Biological Station in Polson, Montana. Participants included 43 scientists, state and federal managers, wilderness users and advocates and students. Four subject areas were addressed: federal, state, tribal and user perspectives, community and ecosystem effects, species effects and management recommendations. Papers from the workshop are being developed for an issue of the journal Ecosystems.

Proceedings↗
USGS2004

Coastal-change and glaciological maps of Antarctica

Changes in the area and volume of polar ice sheets are intricately linked to changes in global climate, and the resulting changes in sea level may severely impact the densely populated coastal regions on Earth. Melting of the West Antarctic part alone of the Antarctic ice sheet could cause a sea-level rise of approximately 6 meters (m). The potential sea-level rise after melting of the entire Antarctic ice sheet is estimated to be 65 m (Lythe and others, 2001) to 73 m (Williams and Hall, 1993). In spite of its importance, the mass balance (the net volumetric gain or loss) of the Antarctic ice sheet is poorly known; it is not known for certain whether the ice sheet is growing or shrinking. In a review paper, Rignot and Thomas (2002) concluded that the West Antarctic part of the Antarctic ice sheet is probably becoming thinner overall; although the western part is thickening, the northern part is thinning. Joughin and Tulaczyk (2002), based on analysis of ice-flow velocities derived from synthetic aperture radar, concluded that most of the Ross ice streams (ice streams on the east side of the Ross Ice Shelf) have a positive mass balance. The mass balance of the East Antarctic is unknown, but thought to be in near equilibrium. Measurement of changes in area and mass balance of the Antarctic ice sheet was given a very high priority in recommendations by the Polar Research Board of the National Research Council (1986), in subsequent recommendations by the Scientific Committee on Antarctic Research (SCAR) (1989, 1993), and by the National Science Foundation's (1990) Division of Polar Programs. On the basis of these recommendations, the U.S. Geological Survey (USGS) decided that the archive of early 1970s Landsat 1, 2, and 3 Multispectral Scanner (MSS) images of Antarctica and the subsequent repeat coverage made possible with Landsat and other satellite images provided an excellent means of documenting changes in the coastline of Antarctica (Ferrigno and Gould, 1987). The availability of this information provided the impetus for carrying out a comprehensive analysis of the glaciological features of the coastal regions and changes in ice fronts of Antarctica (Swithinbank, 1988; Williams and Ferrigno, 1988). The project was later modified to include Landsat 4 and 5 MSS and Thematic Mapper (TM) (and in some areas Landsat 7 Enhanced Thematic Mapper Plus (ETM+)), RADARSAT images, and other data where available, to compare changes over a 20- to 25- or 30-year time interval (or longer where data were available, as in the Antarctic Peninsula). The results of the analysis are being used to produce a digital database and a series of USGS Geologic Investigations Series Maps consisting of 24 maps at 1:1,000,000 scale and 1 map at 1:5,000,000 scale, in both paper and digital format (Williams and others, 1995; Williams and Ferrigno, 1998; and Ferrigno and others, 2002).

IMAP↗