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At least 217 records · Page 12Linked to original sources
USGS1937

Thermal springs in the United States

The earliest extensive studies of thermal springs in the United States were made by physicians. In 1831 Dr. John Bell issued a book entitled "Baths and Mineral Waters" in which he listed 21 spring localities. In the edition of his work published in 1855 the number was increased to 181. The earliest report on a geologic study of thermal springs was that of W. B, Rogers in 1840 on the thermal springs of Virginia. In 1875 G. K. Gilbert published a map and table showing thermal springs in the United States and pointed out that they are present chiefly in the mountainous areas of folded and faulted rocks. Early geologic study of them was principally inspired by the information which they afford at a few places on the deposition of minerals. The relation of hot springs to volcanic action has been studied in the Yellowstone National Park and near Lassen Peak in California. Studies in recent years have been concerned with the source of the water as well as of its heat. All the notable thermal springs in the eastern United States are in the Appalachian Highlands, principally in the region of folded rocks. The Atlantic Coastal Plain contains no appreciably warm springs. In Florida there are large springs whose water rises from a depth of a few hundred feet and is about 5° above the mean annual temperature, but they are not usually classed as thermal. The only warm springs in the great Interior Plains region are at and near Hot Springs, S. Dak., in the vicinity of the Black Hills uplift of crystalline rocks. In the Interior Highlands thermal springs occur only in the Ozark region, the largest group being at Hot Springs, Ark. The Rocky Mountain System includes the Yellowstone National Park, with its world-famous hot springs and geysers (see pis. 7,12), and there are many other hot springs within this great mountainous region. In the Intermontane areas of great lava plains and faulted lava mountains in Utah, Nevada, southern Idaho, and eastern Oregon there are many hot springs, closely associated with the larger faults. In the Pacific Mountain System, including the Cascade Range and Sierra Nevada, there are many warm and hot springs, some of which issue in areas of granite, and others in areas of lava. In the Coast Ranges of California many thermal springs issue from different geologic formations. Of the total of more than 1,000 thermal-spring localities listed in this paper more than half are situated in the three States of Idaho, California, and Nevada, each of which contains more than 150 thermal-spring localities. Wyoming, including the Yellowstone National Park, contains more than 100 hot-spring localities. Oregon, Utah, Colorado, Montana, and New Mexico contain several dozen thermal springs each, of which the principal ones are developed as resorts. The other thermal springs are scattered through 12 States, of which Massachusetts, New York, Pennsylvania, and North Carolina contain one spring or group each. More than half of the total number are developed as resorts or used for irrigation or water supply, but many have remained undeveloped because they are not easily accessible.

Water Supply Paper↗
USGS2003

Hydrologic properties and ground-water flow systems of the Paleozoic rocks in the upper Colorado River basin in Arizona, Colorado, New Mexico, Utah, and Wyoming, excluding the San Juan Basin

The hydrologic properties and ground-water flow systems of Paleozoic sedimentary rocks in the Upper Colorado River Basin were investigated under the Regional Aquifer-System Analysis (RASA) program of the U.S. Geological Survey in anticipation of the development of water supplies from bedrock aquifers to fulfill the region's growing water demands. The study area, in parts of Arizona, Colorado, New Mexico, Utah, and Wyoming, covers about 100,000 square miles. It includes parts of four physiographic provinces--the Middle Rocky Mountains, Wyoming Basin, Southern Rocky Mountains, and Colorado Plateaus. A variety of landforms, including mountains, plateaus, mesas, cuestas, plains, badlands, and canyons, are present. Altitudes range from 3,100 to 14,500 feet. Precipitation is distributed orographically and ranges from less than 6 inches per year at lower altitudes to more than 60 inches per year in some mountainous areas. Most of the infrequent precipitation at altitudes of less than 6,000 feet is consumed by evapotranspiration. The Colorado and Green Rivers are the principal streams: the 1964-82 average discharge of the Colorado River where it leaves the Upper Colorado River Basin is 12,170 cubic feet per second (a decrease of 5,680 cubic feet per second since construction of Glen Canyon Dam in 1963). On the basis of their predominant lithologic and hydrologic properties, the Paleozoic rocks are classified into four aquifers and three confining units. The Flathead aquifer, Gros Ventre confining unit, Bighorn aquifer, Elbert-Parting confining unit, and Madison aquifer (Redwall-Leadville and Darwin-Humbug zones) make up the Four Corners aquifer system. A thick sequence, composed mostly of Mississippian and Pennsylvanian shale, anhydrite, halite, and carbonate rocks--the Four Corners confining unit (Belden-Molas and Paradox-Eagle Valley subunits)--overlies the Four Corners aquifer system in most areas and inhibits vertical ground-water flow between the Four Corners aquifer system and the overlying Canyonlands aquifer. Composed of the uppermost Paleozoic rocks, the Canyonlands aquifer consists, in ascending order, of the Cutler-Maroon, Weber-De Chelly, and Park City-State Bridge zones. The Paleozoic rocks are underlain by a basal confining unit consisting of Precambrian sedimentary, igneous, and metamorphic rocks and overlain throughout most of the Upper Colorado River Basin by the Chinle-Moenkopi confining unit, which consists of Triassic formations composed mostly of shale. The largest values of porosity, permeability, hydraulic conductivity, transmissivity, and artesian yield are exhibited by the Redwall-Leadville zone of the Madison aquifer and the Weber-De Chelly zone of the Canyonlands aquifer. The former consists almost entirely of Devonian and Mississippian carbonate rocks: the latter consists mostly of Pennsylvanian and Permian quartz sandstone. Unit-averaged porosity in hydrogeologic units composed of Paleozoic rocks ranges from less than 1 to 28 percent. Permeability ranges from less than 0.0001 to 3,460 millidarcies. Unit-averaged hydraulic conductivity ranges from 0.000005 to 200 feet per day. The composite transmissivity of Paleozoic rocks ranges from 0.0005 to 47,000 feet squared per day. Artesian yields to wells and springs (excluding atypical springflows) from these hydrogeologic units range from less than 1 to 10,000 gallons per minute. The permeability and watersupply capabilities of all hydrogeologic units progressively decrease from uplifted areas to structural basins. Recharge to the Paleozoic rocks is provided by direct infiltration of precipitation, leakage from streams, and ground-water inflows from structurally continuous areas west and north of the Upper Colorado River Basin. The total recharge available from ground-water systems in the basin from direct precipitation and stream leakage is estimated to be 6,600,000 acre-feet per year. However, little of this recharge directly enters the Paleozoic rocks

Arizona, Colorado, New Mexico, Utah, Wyoming↗
USGS2011

Groundwater availability of the Denver Basin aquifer system, Colorado

The Denver Basin aquifer system is a critical water resource for growing municipal, industrial, and domestic uses along the semiarid Front Range urban corridor of Colorado. The confined bedrock aquifer system is located along the eastern edge of the Rocky Mountain Front Range where the mountains meet the Great Plains physiographic province. Continued population growth and the resulting need for additional water supplies in the Denver Basin and throughout the western United States emphasize the need to continually monitor and reassess the availability of groundwater resources. In 2004, the U.S. Geological Survey initiated large-scale regional studies to provide updated groundwater-availability assessments of important principal aquifers across the United States, including the Denver Basin. This study of the Denver Basin aquifer system evaluates the hydrologic effects of continued pumping and documents an updated groundwater flow model useful for appraisal of hydrologic conditions.

Colorado↗
USGS2004

Map showing spatial and temporal relations of mountain and continental glaciations on the Northern Plains, primarily in northern Montana and northwestern North Dakota

This report is an overview of glacial limits and glacial history on the plains in northern Montana and northeastern North Dakota (long 102?-114?W.) and also in adjacent southern Alberta and Saskatchewan, Canada. In the Rocky Mountains and on the plains adjacent to the mountains in Montana, the map also depicts spatial relations of valley glaciers and piedmont ice lobes to continental ice sheets. Glacial limits east of 102?, in the United States and also in adjacent Canada, are depicted on published maps of the U.S. Geological Survey Quaternary Geologic Atlas of the United States (I-1420) map series. The limits shown here are from data compiled for the Lethbridge, Regina, Yellowstone, and Big Horn Mountains 4? x 6? quadrangles in the Quaternary Geologic Atlas series. This geospatial database has been prepared with a degree of detail appropriate for viewing at a scale of 1:1,000,000. Because of the degree of generalization required, the map is intended for regional analysis, rather than for detailed analysis in specific areas. It depicts the geographic positions of the limits of mountain and continental glaciations and the limits of selected glacial readvances. That information provides a foundation for reconstruction of geologic history and for reconstruction. The base map is simplified. Selected hydrographic features, selected towns and cities, selected physiographic features, and a grid of 1? x 2? topographic quadrangles are included to aid the reader in location of the glacial limits and other features that are depicted here on other maps at different scales. Most of the geologic data were compiled at 1:250,000 scale. The nominal reading scale of the digitized map data is 1:1,000,000. Enlargement will not restore resolution that was lost by simplification or generalization of data. Accompanying illustrations show regional directions of ice movement from Canada into the United States during maximum Illinoian glaciation, during maximum late Wisconsin glaciation, and during a later regional glacial readvance maximum

Scientific Investigations Map↗
USGS1999

Restoration of bighorn sheep metapopulations in and near 15 national parks: Conservation of a severely fragmented species; Volume I, Planning, problem definition, findings, and restoration

Bighorn sheep ( Ovis canadensis ) were historically a ubiquitous species. Prior to the arrival of Europeans, they were seemingly widespread in nearly all steep habitats in the mountains, foothills, river breaks, and prairie badlands of the western United States. However, since catastrophic declines in the late 1800s and early 1900s, most extant populations have existed as small, isolated groups in a highly fragmented distribution. Stochastic events such as seasonal weather change or population fluctuations render these small populations more prone to extirpation than larger populations. Three different subspecies of bighorn sheep were eliminated from 14 of 18 National Park System (NPS) units in the 6-state Intermountain Region of the western United States (Singer 1994). In 1990, when this restoration was initiated, only 4 (18%) of 22 discrete park populations or metapopulations were considered large enough (300-500 animals) to be secure for long-term management. Five (23%) other populations numbered 100-299 animals and 3 (14%) populations numbered 75-99 animals. But, the remaining 10 populations (45%) were either extirpated (n = 2), remnant populations (n = 5, populations of 7-10 animals), or vulnerable to extirpation (n = 3, populations of less than 50 animals). Restoration prior to 1991-96 was largely completed in one NPS unit, but was incomplete in the remaining units. Most bighorn sheep are not federally listed as endangered or threatened species, although the California peninsular population of desert bighorn sheep was recently listed as endangered. The bighorn sheep is a rare or uncommon species that is declining in many parts of its range but is abundant in other areas and still relatively easy to study and manage. The Secretary of the Department of the Interior, Bruce Babbitt, directed the Biological Resources Division of the U.S. Geological Survey in 1993 (when this agency was still the National Biological Service) to research and recover species that were declining to avoid expensive and controversial federal listing. Because the capture and moving of the species are still relatively uncomplicated and because some source stocks are available, aggressive restoration in 15 National Park System units in the former Rocky Mountain Region was recommended in 1990. This report details the 7-year restoration of bighorn sheep to all currently suitable historic habitats in the national parks of the former Rocky Mountain Region (now the Intermountain and Midwest regions of the National Park Service). The purpose of the first phase of the restoration during 1991-93 was to conduct research and population surveys and to formulate the restoration plans. The purpose of the second phase of the initiative during 1994-97 was to conduct GIS-based habitat and biological assessments of prospective restoration sites, write restoration plans, and restore and monitor the released bighorn sheep.

Colorado, Montana, North Dakota, South Dakota, Uta↗
USGS2012

LiDAR - An emerging tool for geological applications

Over the past five to ten years the use and applicability of light detection and ranging (LiDAR) technology has increased dramatically. As a result, more and more LiDAR data now are being collected across the country for a wide range of applications, and LiDAR currently is the technology of choice for high resolution terrain model creation, 3-D city and infrastructure modeling, forestry, and a wide range of scientific applications. LiDAR is a key technology for geological applications both within and outside the U.S. Geological Survey, and efforts are underway to try to collect high resolution LiDAR data for the entire United States (https://pubs.usgs.gov/fs/2012/3089/pdf/fs2012-3089.pdf).

Outcrop: The Newsletter of the Rocky Mountain Asso↗
USGS2001

Coal bed sequestration of carbon dioxide

Geologic sequestration of CO 2 generated from fossil fuel combustion may be an environmentally attractive method to reduce the amount of greenhouse gas emissions. Of the geologic options, sequestering CO 2 in coal beds has several advantages. For example, CO 2 injection can enhance methane production from coal beds; coal can trap CO 2 for long periods of time; and potential major coal basins that contain ideal beds for sequestration are near many emitting sources of CO 2 . One mission of the Energy Resources Program of the U.S. Geological Survey is to maintain assessment information of the Nation’s resources of coal, oil, and gas. The National Coal Resources Assessment Project is currently completing a periodic assessment of 5 major coal-producing regions of the US. These regions include the Powder River and Williston and other Northern Rocky Mountain basins (Fort Union Coal Assessment Team, 1999), Colorado Plateau area (Kirschbaum and others, 2000), Gulf Coast Region, Appalachian Basin, and Illinois Basin. The major objective of this assessment is to estimate available coal resources and quality for the major producing coal beds of the next 25 years and produce digital databases and maps. Although the focus of this work has been on coal beds with the greatest potential for mining, it serves as a basis for future assessments of the coal beds for other uses such as coal bed methane resources, in situ gasification, and sites for sequestration of CO 2 . Coal bed methane production combined with CO 2 injection and storage expands the use of a coal resource and can provide multiple benefits including increased methane recovery, methane drainage of a resource area, and the long-term storage of CO 2 .

Conference Paper↗
USGS1970

Aquilapollenites (Rouse) Funkhouser — Selected Rocky Mountain taxa and their stratigraphic ranges

The genus Aquilapollenites and its type species, A. quadrilobus, are redescribed, and the latter is illustrated. This report summarizes our present information on stratigraphic ranges of selected Rocky Mountain species and varieties of Aquilapollenites. Of the 17 taxa included in this report, 10 are previously named species, 4 are new species, and 3 are new varieties. One species is transferred from the genus Mancicorpus and another from the genus Parviprojectus. The stratigraphic data concerning Aquilapollenites incorporate available information from U.S. Geological Survey pollen collections.

Alaska, Colorado, Montana, North Dakota, South Dak↗
USGS1979

Altered volcanic ash partings in Wasatch Formation coal beds of the northern Powder River basin: composition and geologic applications

In contrast to the coal-bearing rocks of the Appalachian and Eastern Interior Basins, those of the northern Powder River Basin exhibit more complex stratigraphic and facies relationships, and regional correlations of coal beds are, therefore, more difficult to establish. Recently, however, several coal beds in the Powder River Basin, as well as coal beds in several other coal basins of the Rocky Mountain region, have been found to contain thin but persist·ent layers. of altered volcanic ash described as kaolinitic bentonites (Bohor, 1976, 1977, 1978, Bohor and others, 1976, 1978, Bohor and Pillmore, 1976). These layers serve as isochronous marker horizons which aid in correlating coal beds over broad areas.

Wyoming↗
USGS1906

Geology and underground waters of the Arkansas Valley in eastern Colorado

In the valley of Arkansas River in southeastern Colorado there is an area of considerable extent in which artesian flows are available. During the last ten years numerous wells have been sunk to develop this important resource and, in most cases in the lower lands, abundant water supplies have been obtained. The principal water-bearing bed is the "Dakota" formation, which consists of two sheets of porous sandstone separated by a small body of clay and overlain in the greater portion of the area by a mass of impervious shales. The sandstones receive their waters from, rainfall and from the sinking of streams along the foothills of the Rocky Mountains and on some of the higher slopes south of the Arkansas Valley. In the passage of this sandstone underground, the waters which it contains are held down by the overlying shales, but, as some of the sandstone outcrops are at relatively low levels to the east only a moderate head or pressure is sustained. On account of this low head, artesian flows are available only in the lower lands, and one of the principal objects of this investigation has been the determination of the area in which flows are to be expected. The "Dakota" sandstone and associated formations do not lie level, or even slope regularly to the east, but are flexed into low arches and shallow troughs of considerable complexity of configuration. Accordingly, in investigating this source of water supply, it has been necessary to ascertain the structure and distribution of the various formations in order to indicate the variations in depth to the water-bearing stratum. The principal results of these investigations are set forth: (1) In the geologic map (Pl. VI), which shows the distribution of the formations on the surface; (2) in the map, Pl. XXV, which shows the depth to the water-bearing horizon, the area in which flows are expected, the head of the underground waters, and other features, and (3) in the cross sections (Pls. VII and XXIII), which show the principal underground features. The investigation has been in progress for several years and is an extension of the preliminary examination of the region by G. K. Gilbert in 1894 and 1895. For the western portion of the area the maps and texts of the Pueblo, Elmoro, Walsenburg, Spanish Peaks, and Pikes Peak folios have been utilized as far as practicable. For the central and eastern portions the larger features of the geology have been specially mapped, and considerable detailed mapping has been done in the region south and southeast of Canyon and Colorado Springs. In the field work I have been assisted by Mr. C. A. Fisher, who has examined in detail the Nepesta quadrangle and contributed numerous other data. Dr. W. S. Tangier Smith and Messrs. C. E. Sicbenthal and W. T. Lee have made observations in certain areas. Much valuable information respecting wells has been furnished by Mr. William Archer, of the Atchison, Topeka and Santa Fe Railway Company, and Mr. C. H. McVay, well driller at Rocky Ford.

Colorado↗
USGS2007

Subsurface stratigraphic cross sections of cretaceous and lower tertiary rocks in the Wind River Basin, central Wyoming: Chapter 9 in Petroleum systems and geologic assessment of oil and gas resources in the Wind River Basin Province, Wyoming

The stratigraphic cross sections presented in this report were constructed as part of a project conducted by the U.S. Geological Survey to characterize and evaluate the undiscovered oil and gas resources of the Wind River Basin (WRB) in central Wyoming. The primary purpose of the cross sections is to show the stratigraphic framework and facies relations of Cretaceous and lower Tertiary rocks in this large, intermontane structural and sedimentary basin, which formed in the Rocky Mountain foreland during the Laramide orogeny (Late Cretaceous through early Eocene time). The WRB is nearly 200 miles (mi) long, 70 mi wide, and encompasses about 7,400 square miles (mi 2 ) (fig. 1). The basin is structurally bounded by the Owl Creek and Bighorn Mountains on the north, the Casper arch on the east, the Granite Mountains on the south, and the Wind River Range on the west.

Wyoming↗
USGS1891

Altitudes between Lake Superior and the Rocky Mountains

In the survey of Lake Agassiz, a preliminary report of which forms Bulletin No. 39, it was found necessary to ascertain the altitudes determined within its area by railroad surveys as the basis for leveling along the shore lines of that glacial lake, and learning their relations in height to each other, to the great lakes of the St. Lawrence and Nelson Rivers, and to the ocean. From the time of the first observations and description of the upper beaches of Lake Agassiz by the author in 1879 and 1881, for the Geological Survey of Minnesota, and especially since the work was extended in 1885, under the U. S. Geological Survey, to include both sides of this lacustrine area in Minnesota and North Dakota now drained by the Red River of the North, much attention has been given to this collection of altitudes, and to the means of referring them to the sea level. The greater part of Lake Agassiz, however, was in Manitoba and adjacent British Territory, stretching north to the Saskatchewan; and in 1887, jointly for the Geological Surveys of the United States and of Canada, the author continued his examination of the beaches and deltas on the west side of the lake along a distance of a hundred miles north from the international boundary, across the prairie region of southwestern Manitoba, the leveling in this work being based on the altitudes of the Canadian Pacific Railway and its branches and connecting railways.

Bulletin↗
USGS2011

Lithosphere-asthenosphere interaction beneath the western United States from the joint inversion of body-wave traveltimes and surface-wave phase velocities

The relation between the complex geological history of the western margin of the North American plate and the processes in the mantle is still not fully documented and understood. Several pre-USArray local seismic studies showed how the characteristics of key geological features such as the Colorado Plateau and the Yellowstone Snake River Plains are linked to their deep mantle structure. Recent body-wave models based on the deployment of the high density, large aperture USArray have provided far more details on the mantle structure while surface-wave tomography (ballistic waves and noise correlations) informs us on the shallow structure. Here we combine constraints from these two data sets to image and study the link between the geology of the western United States, the shallow structure of the Earth and the convective processes in mantle. Our multiphase DNA10-S model provides new constraints on the extent of the Archean lithosphere imaged as a large, deeply rooted fast body that encompasses the stable Great Plains and a large portion of the Northern and Central Rocky Mountains. Widespread slow anomalies are found in the lower crust and upper mantle, suggesting that low-density rocks isostatically sustain part of the high topography of the western United States. The Yellowstone anomaly is imaged as a large slow body rising from the lower mantle, intruding the overlying lithosphere and controlling locally the seismicity and the topography. The large E-W extent of the USArray used in this study allows imaging the 'slab graveyard', a sequence of Farallon fragments aligned with the currently subducting Juan de Fuca Slab, north of the Mendocino Triple Junction. The lithospheric root of the Colorado Plateau has apparently been weakened and partly removed through dripping. The distribution of the slower regions around the Colorado Plateau and other rigid blocks follows closely the trend of Cenozoic volcanic fields and ancient lithospheric sutures, suggesting that the later exert a control on the locus of magmato-tectonic activity today. The DNA velocity models are available for download and slicing at http://dna.berkeley.edu. ?? 2011 The Authors Geophysical Journal International ?? 2011 RAS.

Geophysical Journal International↗
USGS2003

Water quality and trend analysis of Colorado-Big Thompson system reservoirs and related conveyances, 1969 through 2000

The U.S. Geological Survey, in an ongoing cooperative monitoring program with the Northern Colorado Water Conservancy District, Bureau of Reclamation, and City of Fort Collins, has collected water-quality data in north-central Colorado since 1969 in reservoirs and conveyances, such as canals and tunnels, related to the Colorado–Big Thompson Project, a water-storage, collection, and distribution system. Ongoing changes in water use among agricultural and municipal users on the eastern slope of the Rocky Mountains in Colorado, changing land use in reservoir watersheds, and other water-quality issues among Northern Colorado Water Conservancy District customers necessitated a reexamination of water-quality trends in the Colorado–Big Thompson system reservoirs and related conveyances. The sampling sites are on reservoirs, canals, and tunnels in the headwaters of the Colorado River (on the western side of the transcontinental diversion operations) and the headwaters of the Big Thompson River (on the eastern side of the transcontinental diversion operations). Carter Lake Reservoir and Horsetooth Reservoir are off-channel water-storage facilities, located in the foothills of the northern Colorado Front Range, for water supplied from the Colorado–Big Thompson Project. The length of water-quality record ranges from approximately 3 to 30 years depending on the site and the type of measurement or constituent. Changes in sampling frequency, analytical methods, and minimum reporting limits have occurred repeatedly over the period of record. The objective of this report was to complete a retrospective water-quality and trend analysis of reservoir profiles, nutrients, major ions, selected trace elements, chlorophyll- a , and hypolimnetic oxygen data from 1969 through 2000 in Lake Granby, Shadow Mountain Lake, and the Granby Pump Canal in Grand County, Colorado, and Horsetooth Reservoir, Carter Lake, Lake Estes, Alva B. Adams Tunnel, and Olympus Tunnel in Larimer County, Colorado. This report summarizes and assesses: Water-quality and field-measurement profile data collected by the U.S. Geological Survey and stored in the U.S. Geological Survey National Water Information System, Time-series trends of chemical constituents and physical properties, Trends in oxygen deficits in the hypolimnion of the reservoirs in the late summer season by the seasonal Kendall trend test method, Nutrient limitation and trophic status indicators, and Water-quality data in terms of Colorado water-quality standards. Water quality was generally acceptable for primary uses throughout the Colorado–Big Thompson system over the site periods of record, which are all within the span of 1969 to 2000. Dissolved solids and nutrient concentrations were low and typical of a forested/mountainous/crystalline bedrock hydrologic setting. Most of the more toxic trace elements were rarely detected or were found in low concentrations, due at least in part to a relative lack of ore-mineral deposits within the drainage areas of the Colorado–Big Thompson Project. Constituent concentrations consistently met water-quality standard thresholds set by the State of Colorado. Trophic-State Index Values indicated mesotrophic conditions generally prevailed at reservoirs, based on available Secchi depth, total phosphorus concentrations, and chlorophyll- a concentrations. Based on plots of time-series values and concentrations and seasonal Kendall nonparametric trends testing, dissolved solids and most major ions are decreasing at most sites. Many of the nutrient data did not meet the minimum criteria for time-series testing; but for those that did, nutrient concentrations were generally stable (no statistical trend) or decreasing (ammonia plus organic nitrogen and total phosphorus). Iron and manganese concentrations were stable or decreasing at most sites that met testing criteria. Chlorophyll- a data were only collected for 11 years but generally indicated quasi-stable or downward temporal trends.

Colorado↗
USGS1980

The geologic story of the Great Plains

The Great Plains! The words alone create a sense of space and a feeling of destiny a challenge. But what exactly is this special part of Western America that contains so much of our history? How did it come to be? Why is it different? Geographically, the Great Plains is an immense sweep of country; it reaches from Mexico far north into Canada and spreads out east of the Rocky Mountains like a huge welcome mat. So often maligned as a drab, featureless area, the Great Plains is in fact a land of marked contrasts and limitless variety: canyons carved into solid rock of an arid land by the waters of the Pecos and the Rio Grande; the seemingly endless grainfields of Kansas; the desolation of the Badlands; the beauty of the Black Hills. Before it was broken by the plow, most of the Great Plains from the Texas panhandle northward was treeless grassland. Trees grew only along the floodplains of streams and on the few mountain masses of the northern Great Plains. These lush prairies once were the grazing ground for immense herds of bison, and the land provided a bountiful life for those Indians who followed the herds. South of the grasslands, in Texas, shrubs mixed with the grasses: creosote bush along the valley of the Pecos River; mesquite, oak, and juniper to the east. The general lack of trees suggests that this is a land of little moisture, as indeed it is. Nearly all of the Great Plains receives less than 24 inches of rainfall a year, and most of it receives less than 16 inches. This dryness and the strength of sunshine in this area, which lies mostly between 2,000 and 6,000 feet above sea level, create the semiarid environment that typifies the Great Plains. But it was not always so. When the last continental glacier stood near its maximum extent, some 12,000-14,000 years ago, spruce forest reached southward as far as Kansas, and the Great Plains farther south was covered by deciduous forest. The trees retreated northward as the ice front receded, and the Great Plains has been a treeless grassland for the last 8,000-10,000 years. For more than half a century after Lewis and Clark crossed the country in 1805-6, the Great Plains was the testing ground of frontier America here America grew to maturity (fig. 1). In 1805-7, explorer Zebulon Pike crossed the southcentral Great Plains, following the Arkansas River from near Great Bend, Kans., to the Rocky Mountains. In later years, Santa Fe traders, lured by the wealth of New Mexican trade, followed Pike's path as far as Bents Fort, Colo., where they turned southwestward away from the river route. Those pioneers who later crossed the plains on the Oregon Trail reached the Platte River near the place that would become Kearney, Nebr., by a nearly direct route from Independence, Mo., and followed the Platte across the central part of the Great Plains.

Bulletin↗
USGS1952

Late quaternary geology and frost phenomena along Alaska Highway, Northern British Columbia and Southeastern Yukon

Reconnaissance field work along the Alaska Highway in northern British Columbia and southeastern Yukon furnishes preliminary data on the later Quaternary history of the region, and on the processes and results of intensive frost action. Extensive erosion surfaces were developed prior to glaciation, such as the Alberta Plateau of northeastern British Columbia and the Yukon Plateau in southern Yukon . In the region from Dawson Creek to Fort Nelson, British Columbia , the drift is dominantly a slightly weathered bouldery clay till of Wisconsin age, deposited by ice that came from the east. In the northern Rocky Mountains, the last eastward advance of the Wisconsin glaciers to the mountain front preceded the maximum westward advance of the ice sheets. In the foothills belt west of the Highway , the tills of these two advances are separated by lake deposits. Much of the drift is probably pre-Altamont in age and was subjected to vigorous frost action during the Altamont substage. The climate ameliorated perhaps with the advent of the post-glacial optimum and possibly coincident with the development of prairies. A recent change from prairie to forest perhaps indicates a slight cooling in recent time. In the northern Rocky Mountains, four substages of Wisconsin glaciation are recognized tentatively on the basis of morainal deposits and outwash terraces. The upper Liard basin is characterized by extensive pitted outwash plains, probably of late Wisconsin age. From Teslin Lake to Whitehorse, the Highway is bordered by extensive terraces of gravel and sand deposited in ice-marginal streams and lakes. Intensive frost action has modified pre-existing land forms and has produced a wide variety of features, such as talus, blockfields, stone rings, stone stripes, and terraces. Long smooth slopes, chiefly due to mass movements such as solifluction, are characteristic of the landscapes. These slopes and ancient soil structures extend down into forested areas and probably developed prior to the advent of forests, doubtless prior to the post-glacial optimum. Phenomena resulting from intensive frost action at the present time are restricted largely to areas above timber line.

Alaska, Yukon, British Columbia↗
USGS1999

1999 Resource assessment of selected Tertiary coal beds and zones in the northern Rocky Mountains and Great Plains region

The USGS has assessed resources of selected coal of the Fort Union Formation and equivalent units in the Northern Rocky Mountains and Great Plains region. The assessment focused on coal in the Powder River, Williston, Hanna-Carbon, and Greater Green River basins most likely to be utilized in the next few decades. In other basins in the region Tertiary coal resources are summarized but not assessed. Disc 1, in PDF files, includes results of the assessment and chapters on coal geology, quantity and quality, and land use and ownership. Disc 2 provides GIS files for land use and ownership maps and geologic maps, and basic GIS data for the assessed basins. ArcView shapefiles, PDF files for cross sections and TIFF files are included along with ArcView Datapublisher software for Windows-based computer systems.

Colorado, Montana, Wyoming↗
USGS1995

Data on selected herbicides and two triazine metabolites in precipitation of the Midwestern and Northeastern United States, 1990-91

Weekly precipitation (rain and snow) samples were collected from 81 National Atmospheric Deposition Program/National Trends Network sites in the Midwestern and Northeastern United States for the analysis of herbicides. In addition, five high- elevation background sites along the Rocky Mountains and in Alaska were sampled to provide data on herbicides in precipitation at sites far from the study area. The study began in March 1990 and continued through September 1991. The precipitation samples were shipped to the Central Analytical Laboratory operated by the Illinois State Water Survey for analyses of inorganic compounds. Subsamples of the precipitation were shipped to the U.S. Geological Survey laboratory in Lawrence, Kansas, for the analysis of 11 herbicides and 2 triazines metabolites. This report provides descriptions of the study area, sample-collection methods, laboratory methods, and quality assurance. The report also includes a compilation of herbicide concentration data from both enzyme-linked immunosorbent assay and gas chromatography/mass spectrometry methods. Laboratory analyses consisted of 6,230 samples that were analyzed by enzyme-linked immunosorbent assay using alachlor and atrazine microtiter plates and 2,341 samples that were confirmed by gas chromatography/mass spectrometry analysis. Graphical and statistical comparisons of the two analytical methods are given in this report. Data from this study have been useful in determining the spatial and temporal distribution of herbicide concentrations and deposition in precipitation of over a 26-State area of the Midwestern and Northeastern United States. The data also provide evidence of long-range atmospheric transport of herbicides and triazine metabolites.

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