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At least 1,153 records · Page 64Linked to original sources

USGS2007

Distribution, habitat, size, and color pattern of Cnemidophorus lemniscatus (Sauria: Teiidae) on Cayo Cochino Pequeño, Honduras

Cayo Cochino Pequeño is a 0.64-km 2 Caribbean island in the Cayos Cochinos archipelago, Department of Islas de la Bahía, Honduras. One published report noted the presence of the rainbow whiptail ( Cnemidophorus lemniscatus ) on Cayo Cochino Pequeño, but nothing is known about the biology of this insular population. During a part of the dry season in July and August 2004, we used drift fences, pitfall traps, and separate observational transects to elucidate the distribution and habitat use of C. lemniscatus on the island. The only population of this species was located in a narrow coastal zone (width to 60 m and length to 450 m) on the southern half of the eastern windward side of the island. We analyzed the percentage of the canopy cover and the percentage of 4 ground coverage types along 2 transects 200 m long in this area to understand the basis of the suitability of the habitat for C. lemniscatus . Descriptively, the area harboring this species on Cayo Cochino Pequeño consisted of the remnants of a coconut palm grove with low-lying herbaceous vegetation and grasses, in which a mosaic of small, open areas of sandy soil and coral fragments, with or without accumulations of debris, were the foci of lizard activities. Also observed in this habitat were 2 individuals of the brown racer ( Dryadophis melanolomus ), an actively foraging snake and likely predator on C. lemniscatus . Data obtained on rainbow whiptails captured in pitfall traps and subsequently released were used to determine the size and color patterns of hatchlings and adult males and females.

Cayo Cochino Pequeno↗

USGS2020

Pulsed Mesozoic deformation in the Cordilleran hinterland and evolution of the Nevadaplano: Insights from the Pequop Mountains, NE Nevada

Mesozoic crustal shortening in the North American Cordillera’s hinterland was related to the construction of the Nevadaplano orogenic plateau. Petrologic and geochemical proxies in Cordilleran core complexes suggest substantial Late Cretaceous crustal thickening during plateau construction. In eastern Nevada, geobarometry from the Snake Range and Ruby Mountains-East Humboldt Range-Wood Hills-Pequop Mountains (REWP) core complexes suggests that the ~10–12 km thick Neoproterozoic-Triassic passive-margin sequence was buried to great depths (>30 km) during Mesozoic shortening and was later exhumed to the surface via high-magnitude Cenozoic extension. Deep regional burial is commonly reconciled with structural models involving cryptic thrust sheets, such as the hypothesized Windermere thrust in the REWP. We test the viability of deep thrust burial by examining the least-deformed part of the REWP in the Pequop Mountains. Observations include a compilation of new and published peak temperature estimates ( ⁠ n = 60 "> n = 60 n=60 ⁠ ) spanning the Neoproterozoic-Triassic strata, documentation of critical field relationships that constrain deformation style and timing, and new 40 Ar/ 39 Ar ages. This evidence refutes models of deep regional thrust burial, including (1) recognition that most contractional structures in the Pequop Mountains formed in the Jurassic, not Cretaceous, and (2) peak temperature constraints and field relationships are inconsistent with deep burial. Jurassic deformation recorded here correlates with coeval structures spanning western Nevada to central Utah, which highlights that Middle-Late Jurassic shortening was significant in the Cordilleran hinterland. These observations challenge commonly held views for the Mesozoic-early Cenozoic evolution of the REWP and Cordilleran hinterland, including the timing of contractional strain, temporal evolution of plateau growth, and initial conditions for high-magnitude Cenozoic extension. The long-standing differences between peak-pressure estimates and field relationships in Nevadan core complexes may reflect tectonic overpressure.

Nevada↗

USGS2005

Turbulence investigation and reproduction for assisting downstream migrating juvenile salmonids, Part II of II: Effects of induced turbulence on behavior of juvenile salmon, 2001-2005 final report

Passage through dams is a major source of mortality of anadromous juvenile salmonids because some populations must negotiate up to eight dams in Columbia and Snake rivers. Dams cause direct mortality when fish pass through turbines, but dams may also cause indirect mortality by altering migration conditions in rivers. Forebays immediately upstream of dams have decreased the water velocity of rivers and may contribute substantially to the total migration delay of juvenile salmonids. Recently, Coutant (2001a) suggested that in addition to low water velocities, lack of natural turbulence may contribute to migration delay by causing fish to lose directional cues. Coutant (2001a) further hypothesized that restoring turbulence in dam forebays may reduce migration delay by providing directional cues that allow fish to find passage routes more quickly (Coutant 2001a). Although field experiments have yielded proof of the concept of using induced turbulence to guide fish to safe passage routes, little is known about mechanisms actually causing behavioral changes. To test hypotheses about how turbulence influences movement and behavior of migrating juvenile salmonids, we conducted two types of controlled experiments at Cowlitz Falls Dam, Washington. A common measure of migration delay is the elapsed time between arrival at, and passage through, a dam. Therefore, for the first set of experiments, we tested the effect of induced turbulence on the elapsed time needed for fish to traverse through a raceway and pass over a weir at its downstream end (time trial experiment). If turbulence helps guide fish to passage routes, then fish should pass through the raceway quicker in the presence of appropriately scaled and directed turbulent cues. Second, little is known about how the physical properties of water movement provide directional cues to migrating juvenile salmonids. To examine the feasibility of guiding fish with turbulence, we tested whether directed turbulence could guide fish into one of two channels in the raceway, and subsequently cause them to pass disproportionately over the weir where turbulent cues were aimed (guidance experiment). Last, we measured and mapped water velocity and turbulence during the experiments to understand water movement patterns and the spatial distribution of turbulence in the raceways.

Report↗

USGS2015

Case 3693 Cryptodacus Hendel, 1914 (Insecta: Diptera: Tephritidae): Proposed suppression of Cryptodacus Gundlach, 1862 (Reptilia, Serpentes, Colubridae)

The purpose of this application, under Article 23.9.3, is to conserve current usage of the well-established genus-group name Cryptodacus Hendel, 1914 for a genus of Neotropical fruit flies by suppression of the earlier, unused name Cryptodacus Gundlach, 1862 , currently a junior synonym of Arrhyton Günther, 1858, a genus of snakes, under the plenary power of the Commission, in the interest of nomenclatural stability. Cryptodacus Gundlach has not been used as a valid name since 1883, whereas Cryptodacus Hendel has been used in a significant body of literature relating to fruit fly systematics, morphology and phylogeny and is the currently used name in various name and molecular databases.

Bulletin of Zoological Nomenclature↗

USGS1999

Long-term prairie falcon population changes in relation to prey abundance, weather, land uses, and habitat conditions

We studied a nesting population of Prairie Falcons ( Falco mexicanus ) in the Snake River Birds of Prey National Conservation Area (NCA) from 1974-1997 to identify factors that influence abundance and reproduction. Our sampling period included two major droughts and associated crashes in Townsend's ground squirrel ( Spermophilus townsendii ) populations. The number of Prairie Falcon pairs found on long-term survey segments declined significantly from 1976-1997. Early declines were most severe at the eastern end of the NCA, where fires and agriculture have changed native shrubsteppe habitat. More recent declines occurred in the portion of canyon near the Orchard Training Area (OTA), where the Idaho Army National Guard conducts artillery firing and tank maneuvers. Overall Prairie Falcon reproductive rates were tied closely to annual indexes of ground squirrel abundance, but precipitation before and during the breeding season was related inversely to some measures of reproduction. Most reproductive parameters showed no significant trends over time, but during the 1990s, nesting success and productivity were lower in the stretch of canyon near the OTA than in adjacent areas. Extensive shrub loss, by itself, did not explain the pattern of declines in abundance and reproduction that we observed. Recent military training activities likely have interacted with fire and livestock grazing to create less than favorable foraging opportunities for Prairie Falcons in a large part of the NCA. To maintain Prairie Falcon populations in the NCA, managers should suppress wildfires, restore native plant communities, and regulate potentially incompatible land uses.

The Condor↗

USGS1998

Influence of habitat on behavior of Towndsend's ground squirrels (Spermophilus townsendii)

Trade-offs between foraging and predator avoidance may affect an animal's survival and reproduction. These trade-offs may be influenced by differences in vegetative cover, especially if foraging profitability and predation risk differ among habitats. We examined above-ground activity of Townsend's ground squirrels ( Spermophilus townsendii ) in four habitats in the Snake River Birds of Prey National Conservation Area in southwestern Idaho to determine if behavior of ground squirrels varied among habitats, and we assessed factors that might affect perceived predation risk (i.e. predator detectability, predation pressure, population density). The proportion of time spent in vigilance by ground squirrels in winterfat ( Krascheninnikovia lanata ) and mosaic habitats of winterfat-sagebrush ( Artemisia tridentata ) was more than twice that of ground squirrels in burned and unburned sagebrush habitats. We found no evidence for the “many-eyes” hypothesis as an explanation for differences in vigilance among habitats. Instead, environmental heterogeneity, especially vegetation structure, likely influenced activity budgets of ground squirrels. Differences in vigilance may have been caused by differences in predator detectability and refuge availability, because ground squirrels in the winterfat and mosaic habitats also spent more time in upright vigilant postures than ground squirrels in burned-sagebrush or sagebrush habitats. Such postures may enhance predator detection in low-growing winterfat.

Journal of Mammalogy↗

USGS1988

Diel variations in iron chemistry in an acidic stream in the Colorado Rocky Mountains, USA

In the Snake River, an acidic mountain stream in the Colorado Rocky Mountains, the concentration of dissolved iron is apparently unrelated to seasonal changes in hydrologic regime, which strongly influence the concentrations of most other dissolved constituents. Hourly sampling indicated that short-term fluctuations in iron chemistry occur, whereas the concentrations of most other dissolved constituents, including other trace metals, remain stable. During the day, greater concentrations of dissolved total and ferrous iron generally occurred during periods of full sunlight. Photoreduction of hydrous iron oxides, which are abundant in the fine sediment and as coatings on the rocks, may be responsible for these observations. Iron chemistry also varied at night, decreasing in dissolved total and ferrous iron until about midnight and increasing until dawn. Oxidation of ferrous iron, and several microbial processes, may contribute to these nighttime changes. In an on-site batch experiment using rocks and streamwater, an increase in dissolved total and ferrous iron occurred on exposure to sunlight, and ferrous oxidation occurred on return to darkness. Short-term fluctuations in iron chemistry are consistent with the lack of correlation between iron and other constituents in the long-term data, and illustrate the potential importance of complex in-stream processes in such stream systems.

Colorado↗

USGS1949

Wildlife effects of DDT dust used for tick control on a Texas prairie

The effect of DDT dust on wildlife was studied at Camp Bullis, Bexar County, Texas, in the summer of 1947. Studies were made on a 206.6 acre plot that was treated with DDT for experimental control of the Lone Star tick ( Amblyomma americanum ). A dust consisting of one part of DDT to nine parts of pyrophyllite was applied at an average rate of 4.4 pounds of DDT per acre. The limits of DDT concentration that affected wildlife cannot be stated exactly because of a heavy rain that fell near the end of the dusting, and because of irregularity in DDT deposition. Since absolute uniformity of dusting could not be expected in any large scale DDT application, the effects observed in these trials were probably fairly representative. However, continued dry weather would have permitted longer exposure to DDT, possibly with more severe effects than those found in this study. The vegetation of the experimental area was roughly 70 percent ungrazed tall-grass prairie and 30 percent trees and shrubs. Ground and bush feeding birds were severely affected. Cardinals, lark sparrows, field sparrows, Bewick's wrens, Carolina wrens, Kentucky warblers, yellow-breasted chats, blue grosbeaks, and painted buntings were nearly or entirely eliminated from the treated area. Birds affected, but less drastically reduced in numbers, were yellow-billed cuckoo, black and white warbler, yellow-throated vireo, and white-eyed vireo. Birds found dead in the DDT area were 9 cardinals, 2 painted buntings, 2 lark sparrows, 1 yellow-breasted chat, and 1 white-eyed vireo. Bird mortality had begun by the day after dusting and was largely over by the end of the fifth day. Census of deer in DDT and check areas before and after treatment showed no reduction in deer numbers and no diminution in use of the DDT area. No deer or fawns were found dead or affected. Box-trapping of raccoons in DDT and check areas before and after treatment showed no effects that could be attributed to DDT. Limited observations on armadillos, striped skunks, and rabbits gave no indication of pronounced damage to these forms. No mammals of any kind were found dead or affected in or near the DDT area. Four rough green snakes and one Texan spiny lizard were found dead in the DDT area. Mortality was probably high among insectivorous reptiles.

Texas↗

USGS1997

Distribution of black-tailed jackrabbit habitat determined by GIS in southwestern Idaho

We developed a multivariate description of black-tailed jackrabbit (Lepus californicus) habitat associations from Geographical Information Systems (GIS) signatures surrounding known jackrabbit locations in the Snake River Birds of Prey National Conservation Area (NCA), in southwestern Idaho. Habitat associations were determined for characteristics within a 1-km radius (approx home range size) of jackrabbits sighted on night spotlight surveys conducted from 1987 through 1995. Predictive habitat variables were number of shrub, agriculture, and hydrography cells, mean and standard deviation of shrub patch size, habitat richness, and a measure of spatial heterogeneity. In winter, jackrabbits used smaller and less variable sizes of shrub patches and areas of higher spatial heterogeneity when compared to summer observations (P < 0.05). During the low population phase, jackrabbits also used agricultural regions more during winter than summer. The association with agricultural regions was emphasized spatially in a GIS map contrasting winter and summer periods. Multivariate habitat means (P < 0.001), but not individual GIS variables (P > 0.05), differed significantly between high and low population phase. We used the Mahalanobis distance statistic to rank all 50-m cells in a 440,000-ha region relative to the multivariate mean habitat vector. On verification surveys to test predicted models, we sighted jackrabbits in areas ranked close to the mean habitat vector. Areas burned by large-scale fires between 1980 and 1992 or in an area repeatedly burned by military training activities had greater Mahalanobis distances from the mean habitat vector than unburned areas and were less likely to contain habitats used by jackrabbits.

Journal of Wildlife Management↗

USGS1997

Use of burrow entrances to indicate densities of Townsend's ground squirrels

Counts of burrow entrances have been positively correlated with densities of semi-fossorial rodents and used as an index of densities. We evaluated their effectiveness in indexing densities of Townsend's ground squirrels ( Spermophilus townsendii ) in the Snake River Birds of Prey National Conservation Area (SRBOPNCA), Idaho, by comparing burrow entrance densities to densities of ground squirrels estimated from livetrapping in 2 consecutive years over which squirrel populations declined by >75%. We did not detect a consistent relation between burrow entrance counts and ground squirrel density estimates within or among habitat types. Scatter plots indicated that burrow entrances had little predictive power at intermediate densities. Burrow entrance counts did not reflect the magnitude of a between-year density decline. Repeated counts of entrances late in the squirrels' active season varied in a manner that would be difficult to use for calibration of transects sampled only once during this period. Annual persistence of burrow entrances varied between habitats. Trained observers were inconsistent in assigning active-inactive status to entrances. We recommend that burrow entrance counts not be used as measures or indices of ground squirrel densities in shrubsteppe habitats, and that the method be verified thoroughly before being used in other habitats.

Idaho↗

USGS1997

Spatial use and habitat selection of golden eagles in southwestern Idaho

We measured spatial use and habitat selection of radio-tagged Golden Eagles ( Aquila chrysaetos ) at eight to nine territories each year from 1992 to 1994 in the Snake River Birds of Prey National Conservation Area. Use of space did not vary between years or sexes, but did vary among seasons (home ranges and travel distances were larger during the nonbreeding than during the breeding season) and among individuals. Home ranges were large, ranging from 190 to 8,330 ha during the breeding season and from 1,370 to 170,000 ha outside of the breeding season, but activity was concentrated in small core areas of 30 to 1,535 ha and 485 to 6,380 ha during the breeding and nonbreeding seasons, respectively. Eagles selected shrub habitats and avoided disturbed areas, grasslands, and agriculture. This resulted in selection for habitat likely to contain their principal prey, black-tailed jackrabbits ( Lepus californicus ). Individuals with home ranges in extensive shrubland (n = 3) did not select for shrubs in the placement of their core areas or foraging points, but individuals in highly fragmented or dispersed shrublands (n = 5) concentrated their activities and foraged preferentially in jackrabbit habitats (i.e. areas with abundant and large shrub patches). As home ranges expanded outside of the breeding season, individuals selected jackrabbit habitats within their range. Shrubland fragmentation should be minimized so that remaining shrub patches are large enough to support jackrabbits.

The Auk↗

USGS2012

Bird populations on the Island of Tinian: persistence despite wholesale loss of native forests

Bird habitat on the island of Tinian, Mariana Islands, has been substantially altered, and only around 5% of the island has native forest today. The modern bird fauna is likely to be a subset of the original avifauna where only species tolerant to native forest loss and human disturbance have survived. Avian surveys were conducted on the island in 2008 by the U.S. Fish and Wildlife Service to provide current densities and abundances of the remaining species, and assess population trends using data collected from previous surveys. During the three surveys (1982, 1996, and 2008), 18 species were detected, and abundances and trends were assessed for 11 species. Five of the nine native species and one alien bird have increased since 1982. Three native birds—Mariana Fruit-Dove ( Ptilinopus roseicapilla ), Micronesian Honeyeater ( Myzomela rubratra ), and Tinian Monarch ( Monarcha takatsukasae )—have decreased since 1982. Trends for the remaining two birds (one native and one alien) were considered relatively stable. Only five birds, including the Tinian Monarch, showed significant differences among regions of Tinian by year. Increased development on Tinian may result in increases in habitat clearing and expansion of human-dominated habitats, and declines in some bird populations would likely continue or be exacerbated with these actions. Expanded development activities on Tinian would also mean increased cargo movement between Guam and Tinian, elevating the probability of transporting the Brown Tree Snake ( Boiga irregularis ) to Tinian, which would lead to precipitous decreases and extinctions.

Hawai'i↗

USGS2013

Amphibians and reptiles of Guyana, South America: illustrated keys, annotated species accounts, and a biogeographic synopsis

Guyana has a very distinctive herpetofauna. In this first ever detailed modern accounting, based on voucher specimens, we document the presence of 324 species of amphibians and reptiles in the country; 148 amphibians, 176 reptiles. Of these, we present species accounts for 317 species and color photographs of about 62% (Plates 1–40). At the rate that new species are being described and distributional records are being found for the first time, we suspect that at least 350 species will be documented in a few decades. The diverse herpetofauna includes 137 species of frogs and toads, 11 caecilians, 4 crocodylians, 4 amphisbaenians, 56 lizards, 97 snakes, and 15 turtles. Endemic species, which occur nowhere else in the world, comprise 15% of the herpetofauna. Most of the endemics are amphibians, comprising 27% of the amphibian fauna. Type localities (where the type specimens or scientific name-bearers of species were found) are located within Guyana for 24% of the herpetofauna, or 36% of the amphibians. This diverse fauna results from the geographic position of Guyana on the Guiana Shield and the isolated highlands or tepuis of the eastern part of the Pantepui Region, which are surrounded by lowland rainforest and savannas. Consequently, there is a mixture of local endemic species and widespread species characteristic of Amazonia and the Guianan Region. Although the size of this volume may mislead some people into thinking that a lot is known about the fauna of Guyana, the work has just begun. Many of the species are known from fewer than five individuals in scientific collections; for many the life history, distribution, ecology, and behavior remain poorly known; few resources in the country are devoted to developing such knowledge; and as far as we are aware, no other group of animals in the fauna of Guyana has been summarized in a volume such as this to document the biological resources. We briefly discuss aspects of biogeography, as reflected in samples collected at seven lowland sites (in rainforest, savanna, and mixed habitats below 500 m elevation) and three isolated highland sites (in montane forest and evergreen high-tepui forest above 1400 m elevation). Comparisons of these sites are preliminary because sampling of the local faunas remains incomplete. Nevertheless, it is certain that areas of about 2.5 km2 of lowland rainforest can support more than 130 species of amphibians and reptiles (perhaps actually more than 150), while many fewer species (fewer than 30 documented so far) occur in a comparable area of isolated highlands, where low temperatures, frequent cloudiness, and poor soils are relatively unfavorable for amphibians and reptiles. Furthermore, insufficient study has been done in upland sites of intermediate elevations, where lowland and highland faunas overlap significantly, although considerable work is being accomplished in Kaieteur National Park by other investigators. Comparisons of the faunas of the lowland and isolated highland sites showed that very few species occur in common in both the lowlands and isolated highlands; that those few are widespread lowland species that tolerate highland environments; that many endemic species (mostly amphibians) occur in the isolated highlands of the Pakaraima Mountains; and that each of the isolated highlands, lowland savannas, and lowland rainforests at these 10 sites have distinctive faunal elements. No two sites were identical in species composition. Much more work is needed to compare a variety of sites, and especially to incorporate upland sites of intermediate elevations in such comparisons. Five species of sea turtles utilize the limited areas of Atlantic coastal beaches to the northwest of Georgetown. All of these are listed by the International Union for the Conservation of Nature as being of global concern for long-term survival, mostly owing to human predation. The categories of Critically Endangered or Endangered are applied to four of the local sea turtles (80%). It is important to protect the few good nesting beaches for the sea turtles of Guyana. We have documented each of the species now known to comprise the herpetofauna of Guyana by citing specimens that exist in scientific collections, many of which were collected and identified by us and colleagues, including students of the University of Guyana (UG). We also re-identified many old museum specimens collected by others in the past (e.g., collections of William Beebe) and we used documented publications and collection records of colleagues, most of whom have been working more recently. We present dichotomous keys for identifying representatives of the species known to occur in Guyana, and we present brief annotated species accounts. The accounts provide the current scientific name, original name (with citation of the original description, which we personally examined in the literature), some outdated names used in the recent past, type specimens, type localities, general geographic distribution, examples of voucher specimens from Guyana, coloration in life (and often a color photograph), and comments pointing out interesting subjects for future research.

Proceedings of the Biological Society of Washingto↗

USGS1871

Report of the Geological Exploration of the Fortieth Parallel, Volume V: Botany

The territory within which botanical collections have been nmade in connection with the United States Geological Survey of the 40th Parallel lies wholly within the limits of Northern Nevada and Utah. It forms a narrow tract at no point exceeding seventy miles in width, between the meridians of 111° and 120°, and extending frorn the parallel of 39° at the southwestern limit to that of 42° at the northeastern. This region constitutes the northern portion of what was at first designated as the "Great Basin" the high plateau, without outlet for its waters, separated on the north by low divides from the valley of the Snake River and continuing southward until it merges into the desert of the Lower Colorado. Geologically considered, however, as well as botanically, the term is now properly made to include the whole similar arid stretch of country northward to the plains of the Columbia in latitude 48°.

Nevada;Utah↗

USGS1963

Crustal structure in the western United States; study of seismic propagation paths and regional traveltimes in the California-Nevada region

The U.S. Geological Survey, with the assistance of United ElectroDynamics, Inc., completed ten weeks of seismic-refraction field work during the summer of 1962 in the southwestern part of the United States. This work was a continuation of a program initiated in 1961 to study traveltimes and seismic propagation paths in the earth?s crust and upper mantle in the western United States. A total of 761 seismograms were recorded along 10 profiles from 86 explosions at 18 shotpoints. Analysis of the data is continuing, but a few conclusions can be made from a preliminary study: (1) Variations in traveltimes in the Basin and Range province are large but measurable, and perhaps predictable. (2) Traveltimes of seismic waves in adjacent geologic provinces are usually significantly different. (3) The velocity of P g along all of the profiles recorded in 1962 ranges from 5.0 to 6.5 km/sec, and averages 6.0 km/sec. (4) The average velocity of P g in extreme northern Nevada and southern Idaho is 5.6 km/sec, and it is 6.1 km/sec in most of Nevada and California. (5) The average velocity of P n is 7–9 km/ sec and ranges from 7.85 to 7.95 km/sec on reversed profiles where the true P n velocity could be computed. (6) A shallow "intermediate" layer with a velocity of approximately 6.8 km/sec was found in the Snake River Plain. (7) Refraction arrivals from the mantle (P n ) were recorded in the Sierra Nevada. They indicate that the thickness of the crust in the Sierra Nevada is much greater than that in the Basin and Range province. (8) Many refinements in field techniques were made during the 1962 field season.

California;Nevada;Idaho↗

USGS1965

The Black Canyon of the Gunnison: Today and Yesterday

Since the early visit of Captain John William Gunnison in the middle of the last century, the Black Canyon of the Gunnison has stirred mixed apprehension and wonder in the hearts of its viewers. It ranks high among the more awesome gorges of North America. Many great western canyons are as well remembered for their brightly colored walls as for their airy depths. Not so the Black Canyon. Though it is assuredly not black, the dark-gray tones of its walls and the hazy shadows of its gloomy depths join together to make its name well deserved. Its name conveys an impression, not a picture. After the first emotional impact of the canyon, the same questions come to the minds of most reflective viewers and in about the following order: How deep is the Black Canyon, how wide, how does it compare with other canyons, what are the rocks, how did it form, and how long did it take? Several western canyons exceed the Black Canyon in overall size. Some are longer; some are deeper; some are narrower; and a few have walls as steep. But no other canyon in North American combines the depth, narrowness, sheerness, and somber countenance of the Black Canyon. In many places the Black Canyon is as deep as it is wide. Between The Narrows and Chasm View in the Black Canyon of the Gunnison National Monument (fig. 15) it is much deeper than wide. Average depth in the monument is about 2,000 feet, ranging from a maximum of about 2,700 feet, north of Warner Point (which also is the greatest depth anywhere in the canyon), to a minimum of about 1,750 feet at The Narrows. The stretch of canyon between Pulpit Rock and Chasm View, including The Narrows, though the shallowest in the monument, is also the narrowest, has some of the steepest walls, and is, therefore, among the most impressive segments of the canyon (fig. 3). Profiles of several well-known western canyons are shown in figure 1. Deepest of these by far is Hells Canyon of the Snake, on the Idaho-Oregon border. Clearly, it dwarfs the Black Canyon in the immensity of its void, though its flaring walls lack the alarming verticality of the Black Canyon. Arizona's Grand Canyon of the Colorado is acknowledged as the greatest of them all; it is not as deep as Hells Canyon, but it is wider, longer, more rugged, and far more colorful. Its depth is two to three times that of the Black Canyon. Zion Canyon, Utah, combines depth, sheerness, serenity, and color in a chasm that ranges from capacious to extremely narrow. Its Narrows have a depth-to-width ratio unmatched by any other major American canyon. California's Yosemite Valley, in a setting of sylvan verdure, is unique among the gorges shown in profile in figure 1 in being the only glacial trough; its monolithic walls bear witness to the abrasive power of moving ice. Few cliffs in the world match the splendor of its El Capitan. Lodore Canyon, on the Green River in Dinosaur National Monument, Colorado, is best known, perhaps, for its noisy splashy rapids, first made famous by John Wesley Powell. Lodore Canyon also features towering cliffs of deep-red quartzite. Grand Canyon of the Yellowstone River, Wyoming, is noted for its great waterfalls, dashing river, and bright coloration. The Royal Gorge of the Arkansas River, Colorado, features the 'world's highest suspension bridge'. The profiles shown in figure 1 afford some basis for comparing one canyon with another. They cannot abstract in two dimensions the overall impression that each canyon makes. Color, vegetation, outcrop habit, vantage point, season of year, length of visit - even the roar of the river or lack thereof - all contribute to this highly personal effect. For a river of its size, the Gunnison has an unusually steep gradient through the Black Canyon. The river falls about 2,150 feet from the head of the canyon at Sapinero to the mouth at its junction with North Fork - a distance of about 50 miles and an average rate of fall of about 43 feet per mile. By comparison, the Green

Bulletin↗

USGS2001

The geology and mineral deposits of part of the western half of the Hailey 1 degree x 2 degrees quadrangle, Idaho

Rocks in the western half of the Hailey 1°x2° quadrangle of south-central Idaho include various units of the Atlanta lobe of the Idaho batholith (biotite granodiorite to two-mica granite) of Cretaceous age and plutons and dikes of Tertiary (Eocene to Miocene) age that intrude the batholith. Eocene plutonic rocks consist of a bimodal suite of anorogenic granite and tonalite-granodiorite and hypabyssal rhyolite and rhyodacite dikes. Rocks of the Eocene Challis Volcanics are scarce in the map area but are widespread to the east. Rhyolite ash flows of the Miocene Idavada Volcanics and basalt of the Snake River Plain crop out in the southern part of the area. Lacustrine rocks of probable Eocene to Holocene age are present in the vicinity of Anderson Ranch Reservoir. Quaternary basalts and gravels are widespread on the South Fork of the Boise River, and alluvial deposits are common along active drainages. Metasedimentary rocks of unknown age crop out on House Mountain, Chimney Peak, and on the ridges east of Anderson Ranch Reservoir. Older structures in the Idaho batholith include a major fault beneath House Mountain that may be a decollement for one of the large thrust sheets in eastern Idaho or part of an extensional core complex. The southern part of the Atlanta lobe of the Idaho batholith is cut by northeast-striking faults (parallel with the Trans-Challis fault system) that are related to Eocene extension and by northwest-oriented faults that formed during basin and range extension in the Miocene. The basin and range faults have prominent scarps typical of basin and range topography. The combination of northeast and northwest faults has broken the batholith into a series of rhomboid blocks. Some of these northeast and northwest faults are older structures that were reactivated in the Eocene or Miocene, as indicated by Ar 40 /Ar 39 dates on mineralized rock contained in some of the structures. The Idaho batholith and associated rocks in the map area host several hundred mines and prospects in 18 mining districts. The deposits range in age from Cretaceous to Eocene, and many were developed for precious metals. Most of the deposits are in quartz veins in shear zones in granitic rocks of the batholith. Several districts were actively being explored for low-grade, bulk-minable, precious-metal deposits in the late 1980s and early 1990s.

Idaho↗

USGS2020

Estimated groundwater withdrawals from principal aquifers in the United States, 2015

In 2015, about 84,600 million gallons per day (Mgal/d) of groundwater were withdrawn in the United States for various uses including public supply, self-supplied domestic, industrial, mining, thermoelectric power, aquaculture, livestock, and irrigation. Of this total, about 94 percent (79,200 Mgal/d) was withdrawn from principal aquifers, which are defined as regionally extensive aquifers or aquifer systems that have the potential to be used as sources of water of suitable quality and quantity to meet various needs. The remaining 6 percent (5,400 Mgal/d) was withdrawn from other, nonprincipal aquifers in the United States. Sixty-six principal aquifers belonging to 5 major lithologic groups have been identified and delineated in the United States, including Puerto Rico and the U.S. Virgin Islands. Of the water withdrawn from principal aquifers in 2015, 81 percent (63,900 Mgal/d) was from the unconsolidated and semiconsolidated sand and gravel lithologic group, 7.1 percent (5,630 Mgal/d) was from the igneous and metamorphic-rock lithologic group, 6.8 percent (5,360 Mgal/d) was from the carbonate-rock lithologic group, 3.4 percent (2,680 Mgal/d) was from the sandstone lithologic group, and 2.2 percent (1,710 Mgal/d) was from the sandstone and carbonate-rock lithologic group. The most heavily pumped of the 24 principal aquifers and aquifer systems within the unconsolidated and semiconsolidated sand and gravel lithologic group were the High Plains aquifer (12,300 Mgal/d), Mississippi River Valley alluvial aquifer (12,100 Mgal/d), Central Valley aquifer system (11,100 Mgal/d), and Basin and Range basin-fill aquifers (7,390 Mgal/d). Withdrawals for irrigation were 48,100 Mgal/d and accounted for 75 percent of the total withdrawals from this lithologic group. Although unconsolidated sand and gravel aquifers are widely distributed and were used as sources of water in all States except Hawaii and the U.S. Virgin Islands, 56 percent of the total withdrawn from unconsolidated and semiconsolidated sand and gravel aquifers was in just four States: California (15,600 Mgal/d), Arkansas (9,560 Mgal/d), Nebraska (5,570 Mgal/d), and Texas (4,830 Mgal/d). The most heavily pumped of the seven principal aquifers within the igneous and metamorphic-rock lithologic group were the Snake River Plain (2,930 Mgal/d) and Columbia Plateau basaltic-rock aquifers (1,080 Mgal/d), which are located in the northwestern United States and together accounted for 71 percent of the water withdrawn from this lithologic group. Withdrawals for irrigation were 4,190 Mgal/d and accounted for more than 74 percent of the total withdrawals from this lithologic group. Seventy-eight percent of the withdrawals from igneous and metamorphic-rock aquifers were in three States: Idaho (3,230 Mgal/d), Washington (614 Mgal/d), and Oregon (528 Mgal/d). The most heavily pumped of the 15 principal aquifers and aquifer systems within the carbonate-rock lithologic group were the Floridan aquifer system (3,180 Mgal/d) and the Biscayne aquifer (679 Mgal/d), which are in the southeastern United States and together accounted for almost 72 percent of the withdrawals from this lithologic group. Withdrawals for public supply (2,440 Mgal/d) and irrigation (1,610 Mgal/d) together accounted for almost 76 percent of the total withdrawals from this lithologic group. Although water was withdrawn from carbonate-rock aquifers in 35 States, 71 percent of the total withdrawn was in Florida (3,020 Mgal/d) and Georgia (785 Mgal/d). The most heavily pumped of the 15 principal aquifers within the sandstone lithologic group was the Cambrian-Ordovician aquifer system (921 Mgal/d), which is in the north-central United States and accounted for 34 percent of the water withdrawn from this lithologic group. Withdrawals for public supply were 1,030 Mgal/d and accounted for 38 percent of the total withdrawals from this lithologic group. Although sandstone aquifers were used as sources of water in 32 States, 45 percent of the total withdrawn from sandstone aquifers was in five States: Minnesota (321 Mgal/d), Wisconsin (319 Mgal/d), Kansas (193 Mgal/d), Illinois (187 Mgal/d), and Pennsylvania (179 Mgal/d). The most heavily pumped of the five principal aquifers and aquifer systems within the sandstone and carbonate-rock lithologic group were the Edwards-Trinity aquifer system (661 Mgal/d) in the south-central United States and the Valley and Ridge aquifers (551 Mgal/d) of the eastern United States, which together accounted for 71 percent of total withdrawals from this lithologic group. Withdrawals from sandstone and carbonate-rock aquifers for public-supply (713 Mgal/d), irrigation (469 Mgal/d), and self-supplied domestic (253 Mgal/d) uses accounted for about 84 percent of the total withdrawals from this lithologic group. Although water was withdrawn from sandstone and carbonate-rock aquifers in 25 States, 65 percent of the total withdrawn was in Texas (651 Mgal/d), Pennsylvania (238 Mgal/d), and Florida (223 Mgal/d).

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