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At least 415 records · Page 23Linked to original sources
USGS2025

Using hydrogeologic context and water budgets to evaluate the potential for groundwater contributions to contaminants in Lake Superior

This study presents a synthesis of the hydrogeology in the U.S. Lake Superior watershed and the contribution of groundwater to the water budget of the U.S. Lake Superior basin. Much of the shoreline of Lake Superior in Minnesota and Michigan is composed of hydrogeologic units contributing very little direct groundwater discharge to the lake. Groundwater in watersheds adjacent to the lake typically flows in short, local flow systems characterized by thin glacial sediments with active groundwater flow in fractured bedrock within the top 60–90 m below land surface. The complex groundwater system in Wisconsin’s Bayfield Peninsula has the largest groundwater reservoir near the lake, characterized by thick sand and gravel glacial deposits and underlying sandstone aquifer. Although these thick sandy glacial deposits are not in direct contact with the lake at the shoreline, groundwater discharge may still be significant via subsurface exposures beyond the shoreline or flow through the underlying sandstone aquifer. Overall, most groundwater in the watershed is contributed as indirect base flow in streams around the lakeshore and comprises about 60 percent of the upland water budget. Direct groundwater flow to the shoreline contributes 2 to 9 percent of the inflow. Identifying possible contamination sources through direct sampling of groundwater would be an inefficient way to detect problems if sources are unknown, particularly for some chemicals of concern such as PFAS, pesticides, PCBs, chloride, and nutrients. Evaluating the chemical characteristics of contamination is also important to consider in evaluating how groundwater may contribute to pollution in Lake Superior.

Lake Superior↗
USGS2023

Climate-driven mid- to late Holocene hydrologic evolution of arid wetlands documented by strontium, uranium, and oxygen isotopes from Lower Pahranagat Lake, southern Nevada, USA

Lacustrine carbonates in a 12.4-m-long core from Lower Pahranagat Lake (LPAH), southern Nevada, indicate that radiogenic isotopes of Sr and U ( 87 Sr/ 86 Sr and 234 U/ 238 U) preserve evidence of past variations in water sources and evolving hydrologic conditions. Sr and U isotope compositions in LPAH carbonates fall within the range defined by the three primary groundwater sources in Pahranagat Valley and reflect variable mixtures of those sources since the mid-Holocene. Compositions in the oldest sample (5.78 ka) closely match modern compositions of modern discharge from nearby springs, indicating that LPAH water was derived almost exclusively from the local volcanic aquifer. By ca. 5.3–5.2 ka, LPAH water compositions shifted sharply towards isotopic compositions observed in groundwater from the regional carbonate aquifer, indicating a marked increase in surface flow from high-volume springs discharging from the carbonate aquifer to the north. Sediments deposited between 3.08–1.06 ka indicate reduced contributions from the regional aquifer. A comparison of uranium- and oxygen-isotope values in LPAH carbonates suggests that wetter climate conditions favor increased supply from deeper, regional carbonate aquifers compared to drier conditions when contributions from shallower, local volcanic aquifers were more important.

Nevada↗
USGS2012

Seismicity in the twenty years preceding the Loma Prieta California Earthquake

Persistent seismicity occurred at a low rate during at least the twenty years before the Loma Prieta earthquake along the 60 km-long rupture zone. The depth distribution of this seismicity forms a broad “U”-shape that delineates the previously locked rupture zone. Relocations of seismicity during the ten years before the earthquake relative to the Loma Prieta aftershocks show that this “U”-shaped distribution can be partitioned lengthwise into activity on two adjacent subparallel structures: a vertical fault beneath the San Andreas fault trace and an eastward-dipping blind fault beneath the Sargent fault trace. The 11–18 km deep, southwest-dipping part of the Loma Prieta rupture was not active during at least the preceding ten years. The slip geometry of intersecting fault structures in this zone could contribute to both the preparation process and the complexity of the rupture.

California↗
USGS2025

Estimates of global surface water dynamics harnessing near real-time land cover observations and open science geospatial capabilities

Spatio-temporal changes to our world’s surface water resources are escalating. Translating how these changes impact communities and ecosystems requires time-varying data of Global Surface Water Extents (GSWE). Traditionally, GSWE mapping has been limited to static estimates, with recent efforts focusing on annual averages, frequency and occurrence of long-term variations. Building upon these foundational capabilities, we harnessed remotely sensed Sentinel-2 based near real-time Dynamic World (DW) land cover products to produce the first-of-its-kind 10 m resolution GSWE dataset representing 2015–2023. Our dataset estimated 2.5 million km 2 of permanent waters and 8 million km 2 of seasonal waters worldwide. Comparing our Sentinel-2 based data to contemporary Landsat-based GSWE, we observed that our data mapped less water within the >50% probability of occurrence range, suggesting a lower presence of open permanent water especially in high latitudes, deviating from what we previously learnt from Landsat data. Statistical analysis compared to well-established observational products and widely used GSWE datasets across some of the world’s most ecologically significant regions, including Pantanal in South America and Haor in South Asia, supports the overall physical realism of our data in predicting global open surface water dynamics. Our key contribution is a prototype Open Science operational framework that extracts routinely available DW products, runs geospatial analytics, and creates actionable water information for educators, researchers, and stakeholders at any scale of practical interest. We present examples of this operational capability through instant mapping of flood in Spain and drought in Lake Urmia, Central Asia, frequent monitoring of river extent changes at the Ganges–Brahmaputra confluence, and above all, interoperability with other existing GSWE applications.

Environmental Research Letters↗
USGS2025

Three decades of World Recreational Fishing Conferences: What have we learned about the dynamics of recreational fisheries?

Recreational fishing extends beyond catching fish, connecting individuals with nature, generating environmental stewards and contributing significantly to both local, regional and national economies. Assessing potential impacts on ecosystems and social-ecological systems requires dedicated multi- and interdisciplinary research and integrative management and policy approaches. Managing recreational fisheries effectively also necessitates transdisciplinary thinking, yet this poses continued challenges, as researchers and managers balance specialized expertise with innovative, boundary-crossing perspectives in light of limited funding in a rapidly changing social-ecological environment. The World Recreational Fishing Conference (WRFC) serves as the leading global scientific forum for addressing these challenges, fostering interdisciplinary exchange among scientists, managers, policy makers and stakeholders. The papers in this special issue represent the output of the last WRFC in Melbourne, Australia in 2023. By reviewing the content of the papers published in the present special issue, we illustrate the critical role of collaborative spaces, such as the WRFC, in bridging different expertise and approaches and fostering innovation, thereby securing adaptive management and conservation of recreational fisheries in response to global changes. Evaluating the development of the WRFC over three decades highlights how this conference series represents a leading think tank serving the entire network of recreational fisheries professionals globally.

Fisheries Management and Ecology↗
USGS2007

Climate Variability and Change

In 2007, the U.S. Geological Survey (USGS) developed a science strategy outlining the major natural science issues facing the Nation in the next decade. The science strategy consists of six science directions of critical importance, focusing on areas where natural science can make a substantial contribution to the well-being of the Nation and the world. This fact sheet focuses on climate variability and change and how USGS research can strengthen the Nation with information needed to meet the challenges of the 21st century.

Fact Sheet↗
USGS2002

Human-health pharmaceutical compounds in Lake Mead, Nevada and Arizona, and Las Vegas Wash, Nevada, October 2000-August 2001

The U.S. Geological Survey and the National Park Service conducted a reconnaissance study to investigate the occurrence of selected human-health pharmaceutical compounds in water samples collected from Lake Mead on the Colorado River and Las Vegas Wash, a waterway used to transport treated wastewater from the Las Vegas metropolitan area to Lake Mead. Current research indicates many of these compounds can bioaccumulate and may adversely affect aquatic organisms by disrupting physiological processes, impairing reproductive functions, increasing cancer rates, contributing to the development of antibiotic-resistant strains of bacteria, and acting in undesirable ways when mixed with other substances. These compounds may be present in effluent because a high percentage of prescription and non-prescription drugs used for human-health purposes are excreted from the body as a mixture of parent compounds and degraded metabolite compounds; also, they can be released to the environment when unused products are discarded by way of toilets, sinks, and trash in landfills. Thirteen of 33 targeted compounds were detected in at least one water sample collected between October 2000 and August 2001. All concentrations were less than or equal to 0.20 micrograms per liter. The most frequently detected compounds in samples from Las Vegas Wash were caffeine, carbamazepine (used to treat epilepsy), cotinine (a metabolite of nicotine), and dehydronifedipine (a metabolite of the antianginal Procardia). Less frequently detected compounds in samples collected from Las Vegas Wash were antibiotics (clarithromycin, erythromycin, sulfamethoxazole, and trimethoprim), acetaminophen (an analgesic and anti-inflammatory), cimetidine (used to treat ulcers), codeine (a narcotic and analgesic), diltiazem (an antihypertensive), and 1,7-dimethylxanthine (a metabolite of caffeine). Fewer compounds were detected in samples collected from Lake Mead than from Las Vegas Wash. Caffeine was detected in all samples collected from Lake Mead. Other compounds detected in samples collected from Lake Mead were acetaminophen, carbamazepine, cotinine, 1,7-dimethylxanthine, and sulfamethoxazole.

Nevada, Arizona↗
USGS2022

Human-cougar interactions: A literature review related to common management questions

Interactions between humans and cougars ( Puma concolor ) present unique challenges for wildlife managers; reducing occurrences that lead to conflict is a priority for state and provincial wildlife agencies throughout western North America, including Washington. With an increase in management emphasis of human-wildlife conflict resolution, a growing body of scientific literature related to cougar wildland-urban ecology and the factors that contribute to interactions between cougars and people has developed. Based on discussions with the Fish and Wildlife Commission, our 10-member Human-Cougar Interaction Science Review Team assessed both the analytical and ecological merits of current literature, focusing on data and methods, to summarize the current state of knowledge on human-cougar interactions and factors affecting these interactions. We did not use our review findings to provide management recommendations or evaluate/suggest policy alternatives, but we did highlight important information gaps, research needs, and proposed strategies for conducting scientific investigations to benefit managers and policy makers in the future. We used bibliographic lists, keyword searches in research databases, and new literature encountered as citations within papers we reviewed to identify 96 potential studies for review. We evaluated 41 studies that aligned with eight commonly asked questions regarding how various factors contribute to cougar proximity to, and interactions with people. Our review concluded that the roles of cougar removals (Question 1), cougar population size or trajectory (Question 2), the abundance or diversity of prey (Question 3), human population size, distribution, or recreation levels (Question 6), human attitudes (Question 7), and competition with other large carnivores (Question 8) in cougar interactions with people remain uncertain. We found the studies evaluating the efficacy of nonlethal deterrents (Question 4) provided some evidence that these methods reduce conflict, most notably that flashing lights can reduce interactions in specific situations. Our review of papers investigating the role of landscape characteristics (Question 5) revealed spatial ecology to be the most reliably studied and best understood facet of cougar wildland-urban ecology; study designs in these investigations were also the most rigorous. Most cougar use, and subsequent interactions with people, occur at the wildland-urban interface or in exurban and rural residential settings immediately adjacent because these habitats provide both abundant native prey (deer) and stalking cover, or they retain enough native landcover, connectivity, and prey to support cougar use, but with a human presence at a level that does not substantially deter cougars. We identified only a limited number of informative studies in our review, primarily because many studies did not collect data to specifically address relevant management questions after developing testable hypotheses. Much of the literature we reviewed was derived from ad hoc mining of pre-existing data that had been collected for other routine reasons, data were often not assessed for accuracy, and confounding factors were inadequately addressed. Consequently, many factors theorized to contribute to cougar interactions with people require more rigorous investigation. Because wildland-urban systems are complex, and interactions encompass both human and cougar behavior, we recommend the use of long-term studies that incorporate both ecological and anthropogenic factors within a control-treatment design with replicate study sites to address questions with direct management relevance.

Report↗
USGS2003

An overview on current fluid-inclusion research and applications

This paper provides an overview of some of the more important developments in fluid-inclusion research and applications in recent years, including fluid-inclusion petrography, PVTX studies, and analytical techniques. In fluid-inclusion petrography, the introduction of the concept of 'fluid-inclusion assemblage' has been a major advance. In PVTX studies, the use of synthetic fluid inclusions and hydrothermal diamond-anvil cells has greatly contributed to the characterization of the phase behaviour of geologically relevant fluid systems. Various analytical methods are being developed and refined rapidly, with the Laser-Raman and LA-ICP-MS techniques being particularly useful for volatile and solute analyses, respectively. Ore deposit research has been and will continue to be the main field of application of fluid inclusions. However, fluid inclusions have been increasingly applied to other fields of earth science, especially in petroleum geology and the study of magmatic and earth interior processes.

Acta Petrologica Sinica↗
USGS2017

Cooperative science to inform Lake Ontario management: Research from the 2013 Lake Ontario CSMI program

Since the mid-1970s, successful Lake Ontario management actions including nutrient load and pollution reductions, habitat restoration, and fish stocking have improved Lake Ontario. However, several new obstacles to maintenance and restoration have emerged. This special issue presents management-relevant research from multiple agency surveys in 2011 and 2012 and the 2013 Cooperative Science and Monitoring Initiative (CSMI), that span diverse lake habitats, species, and trophic levels. This research focused on themes of nutrient loading and fate; vertical dynamics of primary and secondary production; fish abundance and behavior; and food web structure. Together these papers identify the status of many of the key drivers of the Lake Ontario ecosystem and contribute to addressing lake-scale questions and management information needs in Lake Ontario and the other Great Lakes and connecting water bodies.

Lake Ontario↗
USGS2021

Scientific contributions of the Mangrove Macrobenthos and Management (MMM) conference series, 2000-2019

The conservation of mangrove forests has become an important international policy priority in recent decades, and is mirrored by a large increase in research interest. Multiple disciplines now use mangroves as a study system, from molecular biology to social science. The variety of research conducted in mangroves is exemplified by the Mangrove Macrobenthos & Management (MMM) conference series, the world's largest gathering of researchers and practitioners dedicated to the science and conservation of the mangrove ecosystem. Established in 2000, MMM is a useful barometer with which to identify and measure research trends over the last 20 years. This study describes the history of the MMM conference series, and analyses the research presented in this series as a potential proxy of how the broader mangrove research field has changed through time. Presentations in early MMM conferences were dominated by macrobenthos studies, reflective of the origins of MMM as a forum specifically for mangrove macrobenthos research. However, later conferences have come to reflect the broader interests of the mangrove research field, and have tracked the emergence of blue carbon and other ecosystem services. Mangrove forests continue to be a rich and diverse ecosystem of study, and future MMM conferences will continue to provide a platform for impactful research and management.

Estuarine, Coastal and Shelf Science↗
USGS2008

Report on the Aseismic Slip, Tremor, and Earthquakes Workshop

This report summarizes the discussions and information presented during the workshop on Aseismic Slip, Tremor, and Earthquakes. Workshop goals included improving coordination among those involved in conducting research related to these phenomena, assessing the implications for earthquake hazard assessment, and identifying ways to capitalize on the education and outreach opportunities presented by these phenomena. Research activities of focus included making, disseminating, and analyzing relevant measurements; the relationships among tremor, aseismic or 'slow-slip', and earthquakes; and discovering the underlying causative physical processes. More than 52 participants contributed to the workshop, held February 25-28, 2008 in Sidney, British Columbia. The workshop was sponsored by the U.S. Geological Survey, the National Science Foundation?s Earthscope Program and UNAVCO Consortium, and the Geological Survey of Canada. This report has five parts. In the first part, we integrate the information exchanged at the workshop as it relates to advancing our understanding of earthquake generation and hazard. In the second part, we summarize the ideas and concerns discussed in workshop working groups on Opportunities for Education and Outreach, Data and Instrumentation, User and Public Needs, and Research Coordination. The third part presents summaries of the oral presentations. The oral presentations are grouped as they were at the workshop in the categories of phenomenology, underlying physical processes, and implications for earthquake hazards. The fourth part contains the meeting program and the fifth part lists the workshop participants. References noted in parentheses refer to the authors of presentations made at the workshop, and published references are noted in square brackets and listed in the Reference section. Appendix A contains abstracts of all participant presentations and posters, which also have been posted online, along with presentations and author contact information at http://www.earthscope.org/science/cascadia.

Open-File Report↗
USGS2024

Genetic origins of a resurging lake whitefish, Coregonus clupeaformis, population in the Detroit River, Laurentian Great Lakes

The Detroit River connects Lake Huron and Lake Erie of the Laurentian Great Lakes. The river once supported a substantial lake whitefish ( Coregonus clupeaformis ) fishery until the early 1900s, when habitat loss, pollution, and overfishing contributed to the collapse of the fishery and loss of spawning populations in the river. In the early 1970s, efforts were initiated to improve water and habitat quality, and in December 2005 a spawning male lake whitefish and viable eggs were collected; the first documented evidence of spawning since 1916. Researchers have tracked the spawning magnitude of the lake whitefish population in the Detroit River since 2005 by assessing the number of eggs deposited on egg mats. Genetic analysis of larval fish hatched from eggs collected in the field between 2005 and 2018 was used to determine the relative contributions of Lake Erie and Lake Huron to the resurging population. Over 80% of the hatched larvae had parents originating from Lake Erie in all the years sampled. The estimated number of full-sibling families sampled at Belle Isle was the same in 2010 and 2014 and varied between 2009 and 2016 at Fighting Island. The estimated number of lake whitefish parents at Fighting Island decreased in the most recent collections possibly due to loss of habitat on spawning reefs due to sedimentation. Our results provide additional evidence that restored spawning habitat in the Detroit River is again being used by lake whitefish and continued reproduction at these sites may improve the Great Lakes portfolio of ecological and genetic diversity.

Detroit River↗
USGS2020

Life history structure of westslope cutthroat trout: Inferences from otolith microchemistry

Life history diversity is important for population stability and is dependent on connectivity to habitat that supports all life stages and life history strategies for a species. Westslope Cutthroat Trout Oncorhynchus clarkii lewisi (WCT) exhibit plasticity in life history strategies in response to environmental variability, but fisheries managers have been challenged with evaluating the life history structure of WCT populations. The goals of this research were to use strontium isotopes (i.e., 87 Sr/ 86 Sr) derived from ambient water and sagittal otoliths to assess spatial variability and describe the life history structure of WCT. Water samples ( n = 49) and WCT ( n = 571) sagittal otoliths were collected throughout the Coeur d’Alene Lake basin in Idaho and analyzed for Sr isotopes. Model-based discriminant function analysis was used to assign WCT to natal tributaries and to infer maternal origins. Life history structure was inferred from maternal signatures and indicated that fluvial (68% of all fish), resident (27%), and adfluvial (5%) life history strategies were present. Connectivity in lotic systems and from lotic to lentic environments supports WCT life history diversity and contributes to a broad distribution of the species.

Idaho↗
USGS1988

Three decades of geochronologic studies in the New England Appalachians

Over the past 30 years, both isotope geochronology and plate tectonics grew from infancy into authoritative disciplines in the geological sciences. Previously, mountain systems like the Appalachians had been viewed almost entirely in the context of the classical geosyncline, implying a gradualism in stratigraphic and structural change throughout the orogen. Age control, determined largely from distant fossiliferous strata, was unabashedly carried to high-grade metamorphic rocks based only on lithological correlations. With the new concepts in tectonics came the realization that abrupt breaks in stratigraphy and structure occur in many cases at the boundaries of lithotectonic zones. Fortunately, the new techniques of isotope geochronology could be brought to bear directly on the rocks of the immediate study area. This paper chronicles some of the major contributions to the geology of the New England Appalachians that resulted from these efforts during the past three decades. In tracing the history of geochronologic research, one encounters an increasingly sophisticated approach to the analytical and interpretive aspects of the discipline. Today, the geochronologist can, under optimum conditions, constrain the age of stratigraphic units, igneous activity, deformation, and metamorphism with accuracy that is capable of resolving fine structure within individual orogenic pulses. He participates in full partnership with other colleagues of the science in unravelling the mysteries of mountain building. Several of the topical problems of New England geology in which geochronology played a key role include (1) the recognition and delineation of Avalonia as a Late Proterozoic eastern basement distinct from more western terranes, (2) the dating of the White Mountain Plutonic-Volcanic Suite, a Mesozoic igneous event spanning 100 m.y., and (3) the temporal and spatial separation of structural and metamorphic features imprinted by the Taconic and Acadian orogenies. The existing geochronology is summarized into a map and table emphasizing the temporal construction of the New England Appalachians. By using lithotectonic zones as the building blocks of the orogen, seven such zones are defined in terms of pre-, syn-, and post-assembly geologic history. From west to east, these lithotectonic zones are (1) Berkshire-Green Mountain, (2) Rowe-Hawley, (3) Connecticut Valley, (4) Bronson Hill, (5) Kearsarge-Central Maine, (6) Tatnic Hill-Nashoba, and (7) Avalonia. Avalonia is further divided into three subzones, Hope Valley, Esmond-Dedham, and Penobscot Bay, which themselves may have had distinct origins and assembly histories. The boundaries between these zones are faults in most cases, some of which may have had recurring movement to further complicate any plate-tectonic scenario. A delineation of underlying Grenvillian, Chain Lakes, and Avalonian basement is also attempted, which now can make use of isotopes in igneous rocks as petrogenetic indicators to supplement the rare occurrences of basement outcrop within mobile zones of the orogen. The belt of Permian thermal disturbance within the Kearsarge-Central Maine zone is hypothesized to reflect rapid rebound following compressional thickening of underlying Avalonian basement during the Alleghanian orogeny.

Geological Society of America Bulletin↗
USGS2021

Time to refine mercury mass balance models for fish

Mercury mass balance models (MMBMs) for fish are powerful tools for understanding factors affecting growth and food consumption by free-ranging fish in rivers, lakes, and oceans. Moreover, MMBMs can be used to predict the consequences of global mercury reductions, overfishing, and climate change on mercury (Hg) concentration in commercially and recreationally valuable species of fish. Such predictions are useful in decision-making by resource managers and public health policy makers, because mercury is a neurotoxin and the primary route of exposure of mercury to humans is via consumption of fish. Recent evidence has emerged to indicate that the current-day version of MMBMs overestimates the rate at which fish eliminate mercury from their bodies. Consequently, MMBMs overestimate food consumption by fish and underestimate Hg concentration in fish. In this perspective, we explore underlying reasons for this overestimation of Hg-elimination rate, as well as consequences and implications of this overestimation. We highlight emerging studies that distinguish species and sex as contributing factors, in addition to body weight and water temperature, that can play an important role in how quickly Hg is eliminated from fish. Future research directions for refining MMBMs are discussed.

Facets↗
USGS2005

Ecological science and sustainability for the 21st century

Ecological science has contributed greatly to our understanding of the natural world and the impact of humans on that world. Now, we need to refocus the discipline towards research that ensures a future in which natural systems and the humans they include coexist on a more sustainable planet. Acknowledging that managed ecosystems and intensive exploitation of resources define our future, ecologists must play a greatly expanded role in communicating their research and influencing policy and decisions that affect the environment. To accomplish this, they will have to forge partnerships at scales and in forms they have not traditionally used. These alliances must act within three visionary areas: enhancing the extent to which decisions are ecologically informed; advancing innovative ecological research directed at the sustainability of the planet; and stimulating cultural changes within the science itself, thereby building a forward-looking and international ecology. We recommend: (1) a research initiative to enhance research project development, facilitate large-scale experiments and data collection, and link science to solutions; (2) procedures that will improve interactions among researchers, managers, and decision makers; and (3) efforts to build public understanding of the links between ecosystem services and humans.

Frontiers in Ecology and the Environment↗
USGS1922

Guidebook of the western United States: Part E - The Denver & Rio Grande Western route

The United States of America comprise an area so vast in extent and so diverse in natural features as well as in characters due to human agency that the American citizen who knows thoroughly his own country must have traveled widely and observed wisely. To 'know America first' is a patriotic obligation, but to meet this obligation the railroad traveler needs to have his eyes directed toward the more important or essential things within his field of vision and then to have much that he sees explained by what is unseen in the swift passage of the train. Indeed, many things that attract his attention are inexplicable except as the story of the past is available to enable him to interpret the present. Herein lie the value and the charm of history, whether human or geologic. The present stimulus given to travel in the home country will encourage many thousands of Americans to study geography at first hand. To make this study most profitable the traveler needs a handbook that will answer the questions that come to his mind so readily along the way. Furthermore, the aim of such a guide should be to stimulate the eye in the selection of the essentials in the scene that so rapidly unfolds itself in the crossing of the continent. In recognition of the opportunity to render service of this kind to an unusually large number of American citizens, as well as to visitors from other countries, the United States Geological Survey has published a series of guidebooks covering four of the older railroad routes west of the Mississippi. The present volume is an addition to this series and covers one of the finest scenic routes of the continent. These books are educational in purpose, but the method adopted is to entertain the traveler by making more interesting what he sees from the car window. The plan of the series is to present authoritative information that may enable the reader to realize adequately the scenic and material resources of the region he is traversing, to comprehend correctly the basis of its development, and above all to appreciate keenly the real value of the country he looks out upon, not as so many square miles of territory represented on the map in a railroad folder by meaningless spaces, but rather as land - real estate, if you please - varying widely in present appearance because differing largely in its history, and characterized by even greater variation in values because possessing diversified natural resources. One region may be such as to afford a livelihood for only a pastoral people; another may present opportunity for intensive agriculture; still another may contain hidden stores of mineral wealth that may attract large industrial development; and, taken together, these varied resources afford, the promise of long-continued prosperity for this or that State. Items of interest in civic development or references to significant epochs in the record of discovery and settlement may be interspersed. with explanations of mountain and valley or statements of geologic history. In a broad way the story of the West is a unit, and every chapter should be told in order to meet fully the needs of the tourist who aims to understand all that he sees. To such a traveler-reader this series of guidebooks is addressed. To this interpretation of our own country the United States Geological Survey brings the accumulated data of decades of pioneering investigation, and the present contribution is only one type of return to the public which has supported this scientific work under the Federal Government - a by-product of research. In the preparation of the description of the country traversed by the Denver & Rio Grande Western Route the geographic and geologic information already published as well as unpublished material in the possession of the Geological Survey has been utilized, but to supplement this material Mr. Campbell made a field examination of the entire route in 1915-1916. Information has been furnished by others,

Bulletin↗