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USGS2021

Connectivity of Mojave Desert tortoise populations—Management implications for maintaining a viable recovery network

Executive Summary The historic distribution of Mojave desert tortoises ( Gopherus agassizii ) was relatively continuous across the range, and the importance of tortoise habitat outside of designated tortoise conservation areas (TCAs) to recovery has long been recognized for its contributions to supporting gene flow between TCAs and to minimizing impacts and edge effects within TCAs. However, connectivity of Mojave desert tortoise populations has become a concern because of recent and proposed development of large tracts of desert tortoise habitat that cross, fragment, and surround designated conservation areas. This paper summarizes the underlying concepts and importance of connectivity for Mojave desert tortoise populations by reviewing current information on connectivity and providing information to managers for maintaining or enhancing desert tortoise population connectivity as they consider future proposals for development and management actions. Maintaining an ecological network for the Mojave desert tortoise, with a system of core habitats (TCAs) connected by linkages, is necessary to support demographically viable populations and long-term gene flow within and between TCAs. There are four points for wildlife and land-management agencies to consider when making decisions that could affect connectivity of Mojave desert tortoise populations (for example, in updating actions in resource management plans or amendments that could help maintain or restore functional connectivity in light of the latest information): Management of all desert tortoise habitat for persistence and connectivity . Desert tortoise populations continue to decline within most TCAs, and it is unlikely that trends are better in populations outside protected areas. Fragmentation exacerbates negative population trends by breaking large continuous populations into smaller isolated populations. Connectivity within large populations can enhance resilience to localized disturbances due to rescue by neighboring individuals. In contrast, smaller fragmented populations are resistant to rescue by their isolation and thus could suffer irreversible declines to extirpation from a variety of threats and stochastic events. Enhanced threat reduction to reverse declines within TCAs and to maintain occupied habitat in the surrounding matrix would help reduce the variability in population growth rates and improve the resilience of protected populations even while implementing efforts to improve connectivity. Each TCA has unique strengths and weaknesses regarding its ability to support minimum sustainable populations based on areal extent and its ability to support population increases based on landscape connection with adjacent populations. Considering how proposed projects (inside or outside of TCAs) affect connectivity and the ability of TCAs to support at least 5,000 adult tortoises (the numerical goal for each TCA) could help managers to maintain the resilience of TCAs to population declines. The same project, in an alternative location, could have very different impacts on local and regional populations. For example, within the habitat matrix surrounding TCAs, narrowly delineated corridors may not allow for natural population dynamics if they do not accommodate overlapping home ranges along most of their widths so that tortoises reside, grow, find mates, and produce offspring that can replace older tortoises. In addition, most habitat outside TCAs may receive more surface disturbance than habitat within TCAs. Therefore, managing the entire remaining matrix of desert tortoise habitat for permeability may be better than delineating fixed corridors. These concepts apply, especially given uncertainty about long-term condition of habitat, within and outside of TCAs under a changing climate. Ultimately, questions such as “ What are the critical linkages that need to be protected ?” could be better framed as “ How can we manage the remaining habitat matrix in ways that sustain ecological processes and habitat suitability for special status species ?” Land-management decisions made in the context of the latter question may be more conducive to maintenance of a functional ecological network. Limitations on landscape-level disturbance across habitat managed for the desert tortoise Clearly delineating habitat linkages and differentiating them from non-delineated areas by the uses that are permitted or prohibited within them by specific management guidelines can help achieve functional connectivity. Such guidelines would be most effective if they considered and accounted for all surface disturbances (for example, temporary disturbances such as fiberoptic lines or off-highway vehicle routes, right-of-ways, utility-scale solar development, urbanization) to the extent possible. A weighted framework that varies with the permanence or severity of the disturbance, and can be additive to quantify cumulative effects, could be useful (Xiong, 2020). For example, minor roads can alter tortoise movements independently of other features (Peaden and others, 2017; Hromada and others, 2020), but if the isolated dirt road is accompanied by a powerline that encourages raven predation (Xiong, 2020), then the two features together may be additive. Ignoring minor or temporary disturbance on the landscape could result in a cumulatively large impact that is not explicitly acknowledged (Goble, 2009); therefore, understanding and quantifying all surface disturbance on a given landscape is prudent. In California, the Bureau of Land Management established 0.1–1.0 percent caps on new surface-disturbance for TCAs and mapped linkages that address the issues described in number 1 of this list. Nevada, Utah, and Arizona currently do not have surface-disturbance limits. Limits comparable to those in the Desert Renewable Energy Conservation Plan (DRECP) would be 0.5 percent within TCAs and 1 percent within the linkages modeled by Averill-Murray and others (2013). Limits in some areas of California within the Desert Renewable Energy Conservation Plan, such as Ivanpah Valley, are more restrictive, at 0.1 percent. Continuity across the state line in Nevada could be achieved with comparable limits in the adjacent portion of Ivanpah Valley, as well as the Greater Trout Canyon Translocation Area and the Stump Springs Regional Augmentation Site. These more restrictive limits would help protect remaining habitat in the major interstate connectivity pathway through Ivanpah Valley and focal areas of population augmentation that provide additional population connectivity along the western flank of the Spring Mountains. In a recent study that analyzed 13 years of desert tortoise monitoring data, nearly all desert tortoise observations were at sites in which 5 percent or less of the surrounding landscape within 1 kilometer was disturbed (Carter and others, 2020a). To help maintain tortoise habitability and permeability across all other non-conservation-designated tortoise habitat, all surface disturbance could be limited to less than 5-percent development per square kilometer because the 5-percent threshold for development is the point at which tortoise occupation drops precipitously (Carter and others, 2020a). However, although individual desert tortoises were observed at development levels up to 5 percent, we do not know the fitness or reproductive characteristics of these individuals. This level of development also may not allow for long-term persistence of healthy populations that are of adequate size needed for demographic or functional connectivity; therefore, a conservative interpretation suggests that, ideally, development could be lower. Lower development levels would be particularly useful in areas within the upper 5th percentile of connectivity values modeled by Gray and others (2019). Reducing ancillary threats in places where connectivity is restricted to narrow strips of habitat, for example, narrow mountain passes or vegetated strips between solar development, could enhance the functionality of these vulnerable linkages. In such areas, maintaining multiple, redundant linkages could further enhance overall connectivity. Minimization of mortality from roads and maximization of passage under roads . Roads pose a significant threat to the long-term persistence of local tortoise populations, and roads of high traffic volume lead to severe population declines, which ultimately fragments populations farther away from the roads. Three points (a.–c.) pertain to reducing direct mortality of tortoises on the many paved roads that cross desert tortoise habitat and to maintaining a minimal level of permeability across these roads: Tortoise-exclusion fencing tied into culverts, underpasses, overpasses, or other passages below roads in desert tortoise habitat, would limit vehicular mortality of tortoises and provide opportunities for movement across the roads. Installation of shade structures on the habitat side of fences installed in areas with narrow population-depletion zones would limit overheating of tortoises that may pace the fence. Passages below highways could be maintained or retrofitted to ensure safe tortoise access, for example, by filling eroded drop-offs or modifying erosion-control features such as rip-rap to make them safer and more passable for tortoises. Wildlife management agencies could work with transportation departments to develop construction standards that are consistent with hydrologic/erosion management goals, while also incorporating a design and materials consistent with tortoise survival and passage and make the standards widely available. The process would be most effective if the status of passages was regularly monitored and built into management plans. Healthy tortoise populations along fenced highways could be supported by ensuring that land inside tortoise-exclusion fences is not so degraded that it leads to degradation of tortoise habitat outside the exclusion areas. For example, severe invasive plant infestations inside a highway exclusion could cause an increase of invasive plants outside the exclusion area and degrade habitat; therefore, invasive plants inside road rights of way could be mown or treated with herbicide to limit their spread into adjacent tortoise habitat and minimize the risk of these plants carrying wildfires into adjacent habitat. Adaptation of management based on new information . Future research will continue to build upon and refine models related to desert tortoise population connectivity and develop new ones. New models could consider landscape levels of development and be constructed such that they share common foundations to support future synthesis efforts. If model development was undertaken in partnership with entities that are responsible for management of desert tortoise habitat, it would facilitate incorporation of current and future modeling results into their land management decisions. There are specific topics that may be clarified with further evaluation: The effects of climate change on desert tortoise habitat, distribution, and population connectivity; The effects of large-scale fires, especially within repeatedly burned habitat, on desert tortoise distribution and population connectivity; The ability of solar energy facilities or similar developments to support tortoise movement and presence by leaving washes intact; leaving native vegetation intact whenever possible, or if not possible, mowing the site, allowing vegetation to re-sprout, and managing weeds; and allowing tortoises to occupy the sites; and The design and frequency of underpasses necessary to maintain functional demographic and genetic connectivity across linear features, like highways.

Arizona, California, Nevada↗

USGS2017

Gallium

Gallium is a soft, silvery metallic element with an atomic number of 31 and the chemical symbol Ga. Gallium is used in a wide variety of products that have microelectronic components containing either gallium arsenide (GaAs) or gallium nitride (GaN). GaAs is able to change electricity directly into laser light and is used in the manufacture of optoelectronic devices (laser diodes, light-emitting diodes [LEDs], photo detectors, and solar cells), which are important for aerospace and telecommunications applications and industrial and medical equipment. GaAs is also used in the production of highly specialized integrated circuits, semiconductors, and transistors; these are necessary for defense applications and high-performance computers. For example, cell phones with advanced personal computer-like functionality (smartphones) use GaAs-rich semiconductor components. GaN is used principally in the manufacture of LEDs and laser diodes, power electronics, and radio-frequency electronics. Because GaN power transistors operate at higher voltages and with a higher power density than GaAs devices, the uses for advanced GaN-based products are expected to increase in the future. Gallium technologies also have large power-handling capabilities and are used for cable television transmission, commercial wireless infrastructure, power electronics, and satellites. Gallium is also used for such familiar applications as screen backlighting for computer notebooks, flat-screen televisions, and desktop computer monitors. Gallium is dispersed in small amounts in many minerals and rocks where it substitutes for elements of similar size and charge, such as aluminum and zinc. For example, gallium is found in small amounts (about 50 parts per million) in such aluminum-bearing minerals as diaspore-boehmite and gibbsite, which form bauxite deposits, and in the zinc-sulfide mineral sphalerite, which is found in many mineral deposits. At the present time, gallium metal is derived mainly as a byproduct of the processing of bauxite ore for aluminum; lesser amounts of gallium metal are produced from the processing of sphalerite ore from three types of deposits (sediment-hosted, Mississippi Valley-type, and volcanogenic massive sulfide) for zinc. The United States is expected to meet its current and expected future needs for gallium through imports of primary, recycled, and refined gallium, as well as through domestic production of recycled and refined gallium. The U.S. Geological Survey estimates that world resources of gallium in bauxite exceed 1 billion kilograms, and a considerable quantity of gallium could be present in world zinc reserves.

Professional Paper↗

USGS2017

Manganese

Manganese is an essential element for modern industrial societies. Its principal use is in steelmaking, where it serves as a purifying agent in iron-ore refining and as an alloy that converts iron into steel. Although the amount of manganese consumed to make a ton of steel is small, ranging from 6 to 9 kilograms, it is an irreplaceable component in the production of this fundamental material. The United States has been totally reliant on imports of manganese for many decades and will continue to be so for at least the near future. There are no domestic reserves, and although some large low-grade resources are known, they are far inferior to manganese ores readily available on the international market. World reserves of manganese are about 630 million metric tons, and annual global consumption is about 16 million metric tons. Current reserves are adequate to meet global demand for several decades. Global resources in traditional land-based deposits, including both reserves and rocks sufficiently enriched in manganese to be ores in the future, are much larger, at about 17 billion metric tons. Manganese resources in seabed deposits of ferromanganese nodules and crusts are larger than those on land and have not been fully quantified. No production from seabed deposits has yet been done, but current research and development activities are substantial and may bring parts of these seabed resources into production in the future. The advent of economically successful seabed mining could substantially alter the current scenario of manganese supply by providing a large new source of manganese in addition to traditional land-based deposits. From a purely geologic perspective, there is no global shortage of proven ores and potential new ores that could be developed from the vast tonnage of identified resources. Reserves and resources are very unevenly distributed, however. The Kalahari manganese district in South Africa contains 70 percent of the world’s identified resources and about 25 percent of its reserves. South Africa, Brazil, and Ukraine together accounted for nearly 65 percent of reserves in 2013. The combination of total import reliance for manganese, the mineral commodity’s essential uses in our industrialized society, and the potential for supply disruptions because of the limited sources of the ore makes manganese among the most critical minerals for the United States. Manganese is the 12th most abundant element in Earth’s crust. Its concentration varies among common types of rocks, mostly in the range of from 0.1 to 0.2 percent. The highest quality manganese ores contain from 40 to 45 percent manganese. The formation of these ores requires specialized geologic conditions that concentrate manganese at several hundred times its average crustal abundance. The dominant processes in forming the world’s principal deposits take place in the oceans. As a result, most important manganese deposits occur in ancient marine sedimentary rocks that are now exposed on continents as a result of subsequent tectonic uplift and erosion. In many cases, other processes have further enriched these manganiferous sedimentary rocks to form some of today’s highest grade ores. Modern seabed resources of ferromanganese nodules cover vast areas of the present ocean floor and are still forming by complex interactions of marine microorganisms, manganese dissolved in seawater, and chemical processes on the seabed. Manganese is ubiquitous in soil, water, and air. It occurs most often in solid form but can become soluble under acidic conditions. Manganese mining, like any activity that disturbs large areas of Earth’s surface, has the potential to produce increases in manganese concentrations that could be harmful to humans or the environment if not properly controlled. Although manganese is an essential nutrient for humans and most other organisms, overexposure can lead to neurotoxicity in humans. Workers at manganese mining and processing facilities have the greatest potential to inhale manganese-rich dust. Without proper protective equipment, these workers may develop a permanent neurological disorder known as manganism. Each manganese mine is unique and presents its own suite of potential hazards and preventative measures. Likewise, various nations have their own sets of standards to ensure safe mining, isolation of mine waste, treatment of mine waters, and mine closure and restoration. Interest in mining trace metals contained in ferromanganese nodules and crusts on the seabed has increased rapidly in the past decade. Prime areas for future research include overcoming the technological challenges presented by mining as deep as 6,500 meters below sea level and understanding and mitigating the potential impacts of seabed mining on marine ecosystems.

Professional Paper↗

USGS1964

Geology and ground-water conditions of Clark County, Washington, with a description of a major alluvial aquifer along the Columbia River

This report presents the results of an investigation of the ground-water resources of the populated parts of Clark County. Yields adequate for irrigation can be obtained from wells inmost farmed areas in Clark County, Wash. The total available supply is sufficient for all foreseeable irrigation developments. In a few local areas aquifers are fine-grained, and yields of individual wells are low. An enormous ground-water supply is available from a major alluvial aquifer underlying the flood plain of the Columbia River in the vicinity of Vancouver, Camas, and Washougal, where the aquifer is recharged, in part, by infiltration from the river. Yields of individual wells are large, ranging to as much as 4,000 gpm (gallons per minute). Clark County lies along the western flank of the Cascade Range. in the structural lowland (Willamette-Puget trough) between those mountains and the Coast Ranges to the west. The area covered by the report includes the urban, the suburban, and most of the agricultural lands in the county. These lands lie on a Series of nearly fiat plains and benches which rise steplike from the level of the Columbia River (a few feet above sea level) to about 800 feet above sea level. Clark County is-drained by the Columbia River (the trunk stream of the Pacific Northwest) and its tributaries. The Columbia River forms the southern and western boundaries of the county. Although the climate of the county is considered to be humid, the precipitation ranging from about 37 to more than 110 inches annually in various parts of the county, the unequal seasonal distribution (about 1.5 inches total for ;July and August in the agricultural area) makes irrigation highly desirable for most .crops and essential for some specialized crops. Consolidated rocks of Eocene to Miocene age, chiefly volcanic lava flows and pyroclastics but including some sedimentary strata, crop out in the foothills of the Cascades in the eastern part of the county and underlie the younger, unconsolidated rocks in the lowlands to the west At most places small to moderate quantities of water can be obtained from fractures in the older consolidated rocks. However, in the populated parts of the county, these rocks generally are overlain by considerable thicknesses of more permeable materials, and few wells have been drilled in them. Springs and dug wells yield an ample domestic supply at a number of outlying farms in the foothills. The younger (Pliocene to Recent) unconsolidated materials were deposited chiefly by streams in the basin formed by downwarping of the older rocks. However, some lake deposits and glacial drift also are included. The oldest unit of this group, the lower member of the Troutdale formation of Pliocene age, consists chiefly of clay, silt, and fine sand but includes lenses of coarser sand and, rarely, gravel. The maximum known thickness of the lower member of the Troutdale formation is about 660 feet. This unit is not a good aquifer because most of the strata are fine grained. However, at a few places drilled wells have penetrated lenses of coarser grained materials in these deposits and have obtained small to moderate amounts of water from them. The upper member of the Troutdale formation consists almost entirely of lightly to moderately cemented gravel, of which the most striking feature is the presence of a considerable percentage of quartzite pebbles. The average thickness of the upper member of the Troutdale may originally have been 300 to 400 feet. The member crops out over considerable areas in the county and, where conditions of topography and exposure are optimum, has beer very deeply weathered. It is suggested that the upper member of the Troutdale formation may prove to be of early Pleistocene age.

Washington↗

USGS1959

Geology of Glacier National Park and the Flathead Region, Northwestern Montana

This report summarizes available data on two adjacent and partly overlapping regions in northwestern Montana. The first of these is Glacier National Park plus small areas east and west of the park. The second is here called, for convenience, the Flathead region; it embraces the mountains from the southern tip of Glacier Park to latitude 48 deg north and between the Great Plains on the east and Flathead Valley on the west. The fieldwork under the direction of the writer was done in 1948, 1949, 1950, and 1951, with some work in 1952 and 1953. The two regions together include parts of the Swan, Flathead, Livingstone, and Lewis Ranges. They are drained largely by branches of the Flathead River. On the east and north, however, they are penetrated by tributaries of the Missouri River and in addition by streams that flow into Canada. Roads and highways reach the borders of the regions; but there are few roads in the regions and only two highways cross them. The principal economic value of the assemblage of mountains described in the present report is as a collecting ground for snow to furnish the water used in the surrounding lowlands and as a scenic and wildlife recreation area. A few metallic deposits and lignitic coal beds are known, but these have not proved to be important and cannot, as far as can now be judged, be expected to become so. No oil except minor seeps has yet been found, and most parts of the two regions covered do not appear geologically favorable to the presence of oil in commercial quantities. The high, Hungry Horse Dam on which construction was in progress during the fieldwork now floods part of the Flathead region and will greatly influence the future of that region. The rocks range in age from Precambrian to Recent. The thickest units belong to the Belt series of Precambrian age, and special attention was paid to them. As a result, it is clear that at least the upper part of the series shows marked lateral changes within short distances. This fact introduces complexities into stratigraphic correlation and should be remembered wherever the series is studied. The stromatolites, or fossil algae, in the Belt series, although still imperfectly understood, give clues with respect to problems of ecology and stratigraphy. The subdivisions of the Belt series within the areas covered by the present report are, in ascending order, Altyn limestone, Appekunny argillite, Grinnell argillite, Siyeh limestone, and Missoula group. Local subdivisions of the Missoula group are possible in certain areas, and all the units just named are expected to be subdivided when detailed studies are undertaken. In the Glacier National Park and Flathead regions together, it is probable that between 25,000 and 30,000 feet of beds belonging to the Belt series, possibly more, are present. These consist largely of quartzitic argillite, quartzite, and carbonate rocks, mostly dolomitic. Small gabbroic and diabasic intrusive bodies and, at one horizon, basaltic lava are associated with the Belt series. Above the Belt series is a thick sequence of Cambrian, Devonian, and Carboniferous strata, in which limestone is dominant, followed by strata of Jurassic and Cretaceous age, largely limestone and shale and partly of terrestrial origin. Slightly consolidated gravel, sand, and silt of Tertiary age are preserved in some valleys and as erosional remnants on the plains close to the mountain border. Pleistocene and Recent glacial and fluviatile deposits are plentiful in mountain valleys and on the plains east of the mountains. Sufficient crustal movements took place during the latter part of Belt time to produce tension cracks that permitted some intrusion and related extrusion to occur. Broad crustal warping probably took place at intervals during the Paleozoic era, but these successive movements left little record other than the absence of sedimentary rock units that might otherwise have been deposited. The same can be said of much of the Me

Professional Paper↗

USGS1956

Sedimentation and chemical quality of surface waters in the Wind River basin, Wyoming

This report gives results of an investigation by the U. S. Geological Survey of chemical quality of surface waters and sedimentation in the Wind River Basin, Wyo. The sedimentation study was begun in 1946 to determine the quantity of sediment that is transported by the streams in the basin; the probable sources of the sediment; the effect of large irrigation projects on sediment yield, particularly along Fivemile Creek; and the probable specific weight of the sediment when initially deposited in a reservoir. The study of the chemical quality of the water was begun in 1945 to obtain information on the sources, nature, and amounts of dissolved material that is transported by streams and on the suitability of the waters for different uses. Phases of geology and hydrology pertinent to the sedimentation and chemical quality were studied. Results of the investigation through September 30, 1952, and some special studies that were made during the 1953 and 1954 water years are reported. The rocks in the Wind River Basin are granite, schist, and gneiss of Precambrian age and a thick series of sedimentary strata that range in age from Cambrian to Recent. Rocks of Precambrian and Paleozoic age are confined to the mountains, rocks of Mesozoic age crop out along the flank of the Wind River and Owl Creek Mountains and in denuded anticlines in the floor of the basin, and rocks of Tertiary age cover the greater part of the floor of the basin. Deposits of debris from glaciers are in the mountains, and remnants of gravel-capped terraces of Pleistocene age are on the floor of the basin. The lateral extent and depth of alluvial deposits of Recent age along all the streams are highly variable. The climate of the floor of the basin is arid. The foothills probably receive a greater amount of intense rainfall than the areas at lower altitudes. Most precipitation in the Wind River Mountains falls as snow. The foothill sections, in general, are transitional zones between the cold, humid climate of the high mountains and the warmer, drier climate of the basin floor. Average annual runoff in the basin is about 3.6 inches on the basis of adjusted streamflow records for the Bighorn River near Thermopolis. Runoff from the mountains is high and is mostly from melting of snow and from spring and early summer rains. It does not vary greatly from year to year because annual water losses are small in comparison to annual precipitation. In the areas on the floor of the basin, where runoff is low, the runoff is mostly the result of storms in late spring and early summer. The annual water losses nearly equal the annual precipitation; therefore, runoff is extremely variable, in terms of percentage changes, from year to year and from point to point during any 1 year.

Water Supply Paper↗

USGS1964

Water resources of the Hartford-New Britain area, Connecticut

The Hartford-New Britain area includes the metropolitan areas of Hartford and New Britain and parts of several adjoining towns. Water used in the area is withdrawn from the principal streams and aquifers at an average rate of 463.5 mgd (million gallons per day). Sufficient water is available from these sources to meet present requirements and those for many years to come, although local shortages may develop in some areas as the result of problems of distribution and treatment. About 98 percent of all water used in 1957 was from surface sources. More than 425 mgd was required by industry, and about 23 mgd was for domestic water supply. The Farmington River upstream from Collinsville is the chief source of water for public supply in the Hartford-New Britain area, whereas the Connecticut River is the chief source of water for industry. An average of about 40 mgd is withdrawn from the upper Farmington River for public supply, and about 404 mgd is withdrawn by industry from the Connecticut River for nonconsumptive use and returned directly to the stream. The Connecticut River is the source of the largest quantity of water in the area. The flow of the stream at Thompsonville may be expected to equal or exceed about 2,000 mgd 95 percent of the time, and the flow should not be less than this amount for periods longer than 12 days. The flow below Thompsonville is increased by additions from the Scantic, Farmington, Park, and Hockanum Rivers and from numerous smaller tributary streams. The available streamflow data for the aforementioned rivers have been summarized graphically in the report. The chemical quality of water in the Connecticut River is good, except for short periods when the iron concentration is high. In addition to the removal of iron some other treatment may be necessary if water from the Connecticut River is used for special purposes. The chemical quality of the tributary streams is good, except the quality of the Park River, which is poor. Thus the Connecticut River in the vicinity of Hartford offers an almost unlimited source of water of good chemical quality to the Hartford, New Britain area. The Connecticut River and many of its tributaries, however, are polluted to some degree, and the cost of treatment for pollution and of delivery of water to the area presents an economic problem in the further development of these sources. The Hartford-New Britain area in the vicinity of Hartford has been plagued by floods since the time of its settlement. Most of the damage to property and loss of life in the Hartford area has been caused by flooding of the Connecticut and Park Rivers. Floods have occurred on the Connecticut River and its tributaries in every month of the year, but the most severe floods occur in the spring and fall. The most devastating flood on the Connecticut River occurred on March 21, 1986, when the stage at Hartford reached 37.0 feet above mean sea level. The maximum flood on the Park River occurred on August 19, 1955, when the stage reached 43.5 feet above mean sea level. Floods on the other tributaries have been frequent and some have been large, but damage has not been as great because the streams flow mostly through rural areas. Small to moderate supplies of water suitable for domestic use and for small municipalities and industries are available from wells in the Hartford-New Britain area. Moderate supplies are obtainable from five definable sand-and-gravel aquifers and from widespread consolidated sedimentary rocks. Yields to individual wells range from 15 to 400 gpm (gallons per minute) for wells penetrating sand and gravel and from 1 to 578 gpm for wells penetrating consolidated sedimentary rocks. Sand and gravel deposits bordering the Connecticut River downstream from Rocky Hill afford the greatest potential for the development of large supplies of ground water. Small supplies ranging from 1 to 40 gpm are obtainable from glacial till and from consolidated crystalline rocks.

Connecticut↗

USGS1976

Hydrologic evaluation of salinity control and reclamation projects in the Indus Plain, Pakistan--A summary

This report summarizes the observations and findings of a team of four specialists from the U.S. Geological Survey assigned to Pakistan under the auspices of the U.S. Agency for International Development during May to August 1972 for a hydrologic evaluation of Salinity Control and Reclamation Projects in the Indus Plain Individual members of the team undertook comprehensive studies related to climatology, surface-water hydrology, and the canal system; streamflow and sediment yields of the rivers; computer applications to hydrologic data; aquifer characteristics; hydrologic evaluation of Salinity Control and Reclamation Projects (SCARPs); tubewell performance; hydrology of shallow versus deep tubewells; well and well-screen design in the Indus Plain; evaluation of observed and anticipated trends in both private and public tubewell development; evaluation of water-quality programs, data analysis, and records, and computer coding of special water-quality data; and evaluation of water-level data, well discharge and specific-capacity tests and aquifer tests. The reclamation program, by pumping from tubewells, has been notably successful in lowering the water table, in providing supplemental water for irrigation and for leaching of salinized soils, and in improving crop production. Some changes in water quality have been observed in SCARP-I and the Mona Scheme of SCARP-II, but these have not as yet (1972) significantly affected the utility of the water for irrigation. Problems associated with reclamation include control of deterioration in performance of tubewells and their rehabilitation, local brackish or saline-water encroachment, and maintenance of a favorable salt balance in the ground-water system. Rapid and as yet (1972) unregulated growth of shallow private tubewell development in the past decade has introduced complicating factors to the reclamation planning of the early 1960's which had emphasized public tubewell development through the SCARP program. In comparing shallow (0-200 feet) with deep (200-400 feet} tubewell development, it is concluded that long-term response of the water table is the same, whether many shallow wells of small capacity or fewer deeper wells of large capacity pump the same total volume of water in the same area. Moreover, it is concluded that there is no definite advantage for either type of pumping regime with respect to water quality. Utilization of the Punjab aquifer could be greatly enhanced by recharge of high-quality water diverted from the Chenab and Jhelum Rivers to the Ravi and Sutlej Rivers by way of the link and irrigation canals during periods of surplus flow. Recharge to the aquifer could also be improved by diversion of high-quality water from the Chenab and the Jhelum to natural nalas and other surface drainageways during periods of surplus flow. Such recharge would be of much better quality than water leaching downward from irrigated fields. Continued monitoring of the hydrologic system and research on problems engendered by reclamation are essential to the viability of the SCARP program and related water-resources development in the Indus River Basin.

Water Supply Paper↗

USGS2020

Groundwater characterization and effects of pumping in the Death Valley regional groundwater flow system, Nevada and California, with special reference to Devils Hole

Groundwater flow and development were characterized in four groundwater basins of the Death Valley regional flow system in Nevada and California with calibrated, groundwater-flow models. Natural groundwater discharges in the Furnace Creek, Lower Amargosa, and Saratoga Spring areas were defined and distributed consistently with a revised hydrogeologic framework. This simplified hydrogeologic framework was limited to four hydraulically unique, hydrogeologic units: (1) basin fill; (2) carbonate rocks; (3) volcanic rocks; and (4) low-permeability granitic and siliciclastic rocks. Hydrogeologic units and division of carbonate and volcanic rocks between shallow and deep were supported by results from 271 aquifer tests and specific-capacity estimates. Greater than 90 percent of field-estimated transmissivity occurred within 1,600 feet (ft) of the water table. Pumping in the study area from 1960 to 2010 averaged 46,000 acre-feet per year (acre-ft/yr), which is 80 percent of the predevelopment discharge. The central Amargosa Desert and Pahrump Valley were the two primary pumping centers and measurably affected water levels across 900 square miles in 2018. Water levels in Devils Hole were a special focus because endangered Devils Hole pupfish ( Cyprinodon diabolis ) are affected by water-level declines. Pumping 42,100 acre-ft by Cappaert Enterprises, formerly Spring Meadows, Inc., caused a 2.3-ft water-level decline in Devils Hole , which temporarily reduced habitat of Devils Hole pupfish by 85 percent in 1972. If no pumping occurred, water levels in Devils Hole would have risen naturally about 1 ft between 1973 and 2018 from temporal variations in recharge. The 2.6-ft range of measured water-level changes in Devils Hole was simulated with a root-mean-square error of 0.2 ft during the 70-year period of record. Simulated water-level declines from pumping totaled 1.4 ft in 2018, with 25 and 34 percent attributed to pumping by Cappaert Enterprises and the central Amargosa Desert, respectively. Water levels in Devils Hole will decline at rates of 0.1–0.2 ft per decade if pumping from Ash Meadows groundwater basin and the central Amargosa Desert continue at current rates. Effects of future natural water-level fluctuations remain unknown. Ash Meadows and Alkali Flat–Furnace Creek Ranch groundwater basins are hydraulically connected near well AD-4 , about 5 miles south of the town of Amargosa Valley, Nevada. About 40 percent of the discharge from the Furnace Creek area is recharged in the Ash Meadows groundwater basin. Basin fill in the central Amargosa Desert hydraulically connects carbonate rocks east of well AD-4 with saturated carbonate rocks in the Funeral Range. About 7 percent of the 960,000 acre-ft pumped from Ash Meadows and Alkali Flat–Furnace Creek Ranch groundwater basins prior to 2019 was captured discharge from springs and phreatophytes. Greater than 40 percent of the 2,080,000 acre-ft pumped from Pahrump Valley between 1910 and 2019 was capture that primarily discharged from Bennetts and Manse Springs. Simulated advective-flow distances and velocities from underground nuclear tests are within the range of advective transport calculations from tritium data and previous radionuclide transport investigations. Boundary conditions and flow rates from the regional model in this study are plausible for local-scale flow and radionuclide transport models. Simulated 165-year groundwater-flow paths do not extend into pumping areas and effects of regional pumping on advective transport are negligible.

California, Nevada↗

USGS2009

Preparing a population for an earthquake like Chi-Chi: The Great Southern California ShakeOut

The Great Southern California ShakeOut was a week of special events featuring the largest earthquake drill in United States history. On November 13, 2008, over 5 million southern Californians pretended that a magnitude-7.8 earthquake had occurred and practiced actions that could reduce its impact on their lives. The primary message of the ShakeOut is that what we do now, before a big earthquake, will determine what our lives will be like after. The drill was based on a scenario of the impacts and consequences of such an earthquake on the Southern San Andreas Fault, developed by over 300 experts led by the U.S. Geological Survey in partnership with the California Geological Survey, the Southern California Earthquake Center, Earthquake Engineering Research Institute, lifeline operators, emergency services and many other organizations. The ShakeOut campaign was designed and implemented by earthquake scientists, emergency managers, sociologists, art designers and community participants. The means of communication were developed using results from sociological research on what encouraged people to take action. This was structured around four objectives: 1) consistent messages – people are more inclined to believe something when they hear the same thing from multiple sources; 2) visual reinforcement – people are more inclined to do something they see other people doing; 3) encourage “milling” or discussing contemplated action – people need to discuss an action with others they care about before committing to undertaking it; and 4) focus on concrete actions – people are more likely to prepare for a set of concrete consequences of a particular hazard than for an abstract concept of risk. The goals of the ShakeOut were established in Spring 2008 and were: 1) to register 5 million people to participate in the drill; 2) to change the culture of earthquake preparedness in southern California; and 3) to reduce earthquake losses in southern California. All of these goals were met. The final registration at www.shakeout.org for the 2008 ShakeOut was 5.47 million people, or one-quarter of the population of the region. A survey conducted with the registered participants showed that the messages they took from the ShakeOut were the concepts intended, including the importance of “Drop, Cover, Hold On”, the interdependency of earthquake risk (“We are all in this together”) and the possibility of reducing losses through preparation and mitigation. Sales data from the Home Depot hardware stores in southern California showed a 260% increase in the sale of earthquake safety products during the month of the ShakeOut, November 2008.

California↗

USGS1994

Stratigraphy of the Mississippi-Alabama shelf and the Mobile River incised-valley system

The Mobile River incised-valley system located in the northern Gulf of Mexico occupies an area from southern Alabama through Mobile Bay to the outer Mississippi-Alabama continental shelf. During the Wisconsinan regression, this incised-valley system was fluvially eroded and extended across the exposed shelf to a shelf-margin delta complex. The last postglacial transgression drowned the entrenched alluvial valleys and reworked the alluvial fill and estuarine deposits to form shoals on the middle shelf. As the postglacial transgression slowed. Mobile Bay was formed. Mobile Bay is a large estuarine system protected by barrier islands. This paper documents the late Quaternary history of the Mobile River incised valley and fill. Mobile Bay is a large (> 1000 km 2 ) microtidal estuary in southern Alabama that receives drainage through the Mobile River system. The Mobile River catchment is the fourth largest in the United States and terminates at the bayhead delta of Mobile Bay. The bay is a classic example of a wave-dominated, drowned, fluvial incised valley. During the middle-late Wisconsinan, glacial maximum, relative sea level was approximately 120 m lower than present. The Mobile River incised valley was a conduit for drainage from the catchment to the shelf margin. The sediment carried by the fluvial system during this lowstand passed through the Mobile River incised valley, across the exposed shelf and was deposited on the shelf margin as deltaic lobes. Rapid sea-level rise forced coastal-plain shorelines landward across the present mid-continental shelf. Transgression of the estuary mouth left a series of estuary-mouth-bar deposits that were reworked and overlie alluvial fill. These sand-rich deposits were submerged by the continuing transgression and reworked to form shoals As the Holocene sea-level rise slowed, the Mobile River incised valley became an estuarine depocenter. In the present alluvial valley, lowstand deposits are overlain by estuarine sediments deposited during the initial flooding of the valley and subsequent formation of Mobile Bay. During the present highstand, longshore sediment transport formed a spit across much of the bay mouth, creating a restricted estuary into which a bayhead delta has prograded. Late Holocene deposits in Mobile Bay consists predominantly or lagoonal sediments with bayhead-delta deposits encroaching into the northern end of the bay. The Holocene incised-valley fill (estuarine facies) underlying Mobile Buy fit well into the conceptual facies model of a microtidal wave-dominated estuary. The model does not fit as well, however, with the rapidly transgressed shelf portion of the incised valley. The down dip section does not contain a clearly identifiable (from seismic profiles) estuarine facies; the valley fill is primarily fluvial and is overlain by marine shoals. In the Mobile River incised valley, the distal portion of the valley was rapidly drowned, allowing the thin estuarine facies to be reworked. The proximal portion was drowned more slowly, leaving the estuarine facies intact. Thus, the single incised valley contains two very different types of fill.

Alabama↗

USGS1944

Exploratory water-well drilling in the Houston District, Texas

In the spring and summer of 1939 a program of exploratory drilling wad undertaken in the Houston district, Tx., in conjunction with a general initiation of the water resources of the district. The main purposes of the program were to determine the thickness and character of water-bearing sands down to a maximum depth of 2,000 feet, the chemical character of the water at different depths, and the artesian pressure and to provide additional observation wells for studying fluctuations in artesian pressure and possibilities of intrusion of salt water from the direction of the Gulf. Thirteen deep test wells, 5? inches in diameter and ranging in depth from 360 to 2,000 feet, were put down with a hydraulic rotary drill by the city of Houston. The combined drilling footage of all of the wells amounted to 17,460 feet, and their averse depth was 1,246 feet. All were electrically logged. Samples of cuttings were collected from the drilling mud after every 20 feet of drilling. In 6 of the wells sand samples were obtained by core drilling in beds at selected horizons, about 230 feet being recovered. A total of 15 samples of sand and water were obtained in 8 wells by the drill-stem method. Side-wall sampling was attempted. Six of the test holes were cased with 3? casing (inside diameter) and equipped with screens so that water-level measurements could be made and samples of water collected for chemical analyses , Selected sand samples were analyzed and tested in a field laboratory for mechanical composition, permeability, and porosity. The field and laboratory data were studied with special reference to the significance of the electrical logs. A comparison of the electrical logs of the test wells with the driller's logs shows that, on the whole, they agree remarkably well in fixing the upper and lower limits of the thicker beds of sand and clay, but that the agreement is not so close where the beds are thin. Variable results were obtained from attempts to correlate the second curve of the electrical log with the permeability and mechanical composition of the sand samples obtained by core drilling and drill-stem sampling. In the case of the core samples there was no apparent relationship between any of the three characteristics in well 3, but in well 5 a slight but distinct increase in the resistivity was accompanied by a large increase in permeability. In well 6 the resistivity in nearly every case varied with the permeability and coarseness of the samples. In well 6 the drilling mud was local clay enriched with Aquagel, whereas in wells 3 and 5 only local clay was used; the data obtained, however, are too meager to be used on a basis for even a tentative conclusion as to the effect of artificial mud on the correlations. In the 15 drill-stem sand samples the data show that, in general, the resistivity of sands having fluid content varies with but is not proportional to the permeability, but there seems to be little or no relationship between the coarseness of the sands and either the resistivity or the permeability. Studies of the relationship of the electrical logs to the salinity of the water indicate that increasing chloride is accompanied by decreasing resistivity. They suggest .that changes in the chloride content are accompanied by large changes in resistivity when the water contains less than 100 parts per million of chloride and by relatively small changes when the chloride content is over 100 parts per million. On the whole, the results of the test drilling from Houston tend to show that, although electrical logs give much information that is useful in the development of water wells, for the present at least these logs should be used in conjunction with driller's logs and drill-stem sampling of both sand and water in all the more promising sand horizons. The tests indicate that an average of 600 feet of .water-bearing sands occurs between the surface and a depth of 1,500 feet along the line of test wells we

Water Supply Paper↗

USGS1905

Economic geology of the Bingham mining district, Utah

The field work of which this report represents the final results was first undertaken in the summer of the year 1900. This district had long been selected by the writer as worthy of special economic investigation, as well on account of the importance of its products as because of its geological structure and the peculiar relations of its ore deposits. It was not, however, until the summer mentioned above that the means at the disposal of the Survey, both pecuniary and scientific, justified its undertaking. As originally planned, the areal or surface geology was to have been worked out by Mr. Keith, who had already spent many years in unraveling the complicated geological structure of the Appalachian province, while Mr. Boutwell, who had more recently become attached to the Survey, was to have charge of the underground geology, or a study of the ore deposits, under the immediate supervision of the writer. When the time came for actually taking the field, it was found that the pressure of other work would not permit Mr. Keith to carry out fully the part allotted to him, and in consequence a part of his field work has fallen to Mr. Boutwell. Field work was commenced by the writer and Mr. Boutwell early in July, 1900. Mr. Keith joined the party on August 10, but was obliged to leave for other duties early in September. Mr. Boutwell carried on his field work continuously from July until December, taking up underground work after the snowfall had rendered work on the surface geology impracticable. The geological structure had proved to be unexpectedly intricate and complicated, so that, on the opening of the field season of 1901, it was found necessary to make further study in the light of results already worked out, and Mr. Boutwell spent some weeks in the district in the early summer of 1901. His field work that year, partly in California and partly in Arizona, as assistant to Mr. Waldemar Lindgren, lasted through the summer and winter and well into the spring of 1902, so that but little time , was left before he was obliged to take the field again in his study of the Park City district of Utah. Mr. Keith had been too closely occupied with his Appalachian work to complete his part,' and thus the publication of this report has been unusually delayed. While the delay is a cause for regret, this regret is much tempered by the consideration that had the report been published earlier many facts brought to light during the vigorous development of the region in late years, which have an important bearing upon the structure and genesis of the ore deposits, could not have been used in its preparation.

Utah↗

USGS1975

Geochemical Exploration Techniques Applicable in the Search for Copper Deposits

Geochemical exploration is an important part of copper-resource evaluation. A large number of geochemical exploration techniques, both proved and untried, are available to the geochemist to use in the search for new copper deposits. Analyses of whole-rock samples have been used in both regional and local geochemical exploration surveys in the search for copper. Analyses of mineral separates, such as biotite, magnetite, and sulfides, have also been used. Analyses of soil samples are widely used in geochemical exploration, especially for localized surveys. It is important to distinguish between residual and transported soil types. Orientation studies should always be conducted prior to a geochemical investigation in a given area in order to determine the best soil horizon and the best size of soil material for sampling in that area. Silty frost boils, caliche, and desert varnish are specialized types of soil samples that might be useful sampling media. Soil gas is a new and potentially valuable geochemical sampling medium, especially in exploring for buried mineral deposits in arid regions. Gaseous products in samples of soil may be related to base-metal deposits and include mercury vapor, sulfur dioxide, hydrogen sulfide, carbon oxysulfide, carbon dioxide, hydrogen, oxygen, nitrogen, the noble gases, the halogens, and many hydrocarbon compounds. Transported materials that have been used in geochemical sampling programs include glacial float boulders, glacial till, esker gravels, stream sediments, stream-sediment concentrates, and lake sediments. Stream-sediment sampling is probably the most widely used and most successful geochemical exploration technique. Hydrogeochemical exploration programs have utilized hot- and cold-spring waters and their precipitates as well as waters from lakes, streams, and wells. Organic gel found in lakes and at stream mouths is an unproved sampling medium. Suspended material and dissolved gases in any type of water may also be useful media. Samples of ice and snow have been used for limited geochemical surveys. Both geobotanical and biogeochemical surveys have been successful in locating copper deposits in many parts of the world. Micro-organisms, including bacteria and algae, are other unproved media that should be studied. Animals can be used in geochemical-prospecting programs. Dogs have been used quite successfully to sniff out hidden and exposed sulfide minerals. Tennite mounds are commonly composed of subsurface material, but have not as yet proved to be useful in locating buried mineral deposits. Animal tissue and waste products are essentially unproved but potentially valuable sampling media. Knowledge of the location of areas where trace-element-associated diseases in animals and man are endemic as well as a better understanding of these diseases, may aid in identifying regions that are enriched in or depleted of various elements, including copper. Results of analyses of gases in the atmosphere are proving valuable in mineral-exploration surveys. Studies involving metallic compounds exhaled by plants into the atmosphere, and of particulate matter suspended in the atmosphere are reviewed these methods may become important in the future. Remote-sensing techniques are useful for making indirect measurements of geochemical responses. Two techniques applicable to geochemical exploration are neutron-activation analysis and gamma-ray spectrometry. Aerial photography is especially useful in vegetation surveys. Radar imagery is an unproved but potentially valuable method for use in studies of vegetation in perpetually clouded regions. With the advent of modern computers, many new techniques, such as correlation analysis, regression analysis, discriminant analysis, factor analysis, cluster analysis, trend-surface analysis, and moving-average analysis can be applied to geochemical data sets. Selective use of these techniques can provide new insights into the interpretatio

Professional Paper↗

USGS2007

The Yellowstone hotspot, Greater Yellowstone ecosystem, and human geography

Active geologic processes associated with the Yellowstone hotspot are fundamental in shaping the landscapes of the greater Yellowstone ecosystem (GYE), a high volcanic plateau flanked by a crescent of still higher mountainous terrain. The processes associated with the Yellowstone hotspot are volcanism, faulting, and uplift and are observed in the geology at the surface. We attribute the driving forces responsible for the northeastward progression of these processes to a thermal plume rising through the Earth’s mantle into the base of the southwest-moving North American plate. This progression began 16 million years ago (Ma) near the Nevada-Oregon border and arrived at Yellowstone about 2 Ma. Before arrival of the hotspot, an older landscape existed, particularly mountains created during the Laramide orogeny about 70–50 Ma and volcanic terrain formed by Absaroka andesitic volcanism mostly between 50–45 Ma. These landscapes were more muted than the present, hotspot-modified landscape because the Laramide-age mountains had worn down and an erosion surface of low relief had developed on the Absaroka volcanic terrain. The Yellowstone Plateau was built by hotspot volcanism of rhyolitic lavas and caldera-forming rhyolite tuffs (ignimbrites). Streams eroding back into the edges of this plateau have created scenic waterfalls and canyons such as the Grand Canyon of the Yellowstone and Lewis Canyon. Rhyolite is poor in plant nutrients and forms sandy, well-drained soils that support the monotonous, fire-adapted lodgepole pine forests of the Yellowstone Plateau. Non-rhyolitic rocks surround this plateau and sustain more varied vegetation, including spruce, fir, and whitebark pine forests broken by grassy meadows. Heat from the hotspot rises upward and drives Yellowstone’s famed geysers, hot springs, and mudpots. These thermal waters are home to specialized, primitive ecosystems, rich in algae and bacteria. The rock alteration associated with hydrothermal systems creates the bright colors of Yellowstone’s Grand Canyon. Basin-and-range-style faulting has accompanied migration of the hotspot to Yellowstone and formed the linear mountains and valleys that occur north and south of the hotspot track, which is the present-day eastern Snake River Plain. High rates of basin-and-range faulting occurred adjacent to the migrating Yellowstone hotspot, creating distinctive landscapes within the GYE such as the Teton Range/Jackson Hole, with characteristic rugged, forested ranges and adjacent flat-floored grassy valleys. The difference in altitude between the mountains and valleys provides a topographic gradient in which vegetation maturation advances with altitude; animal-migration patterns also follow this trend. The valleys provide natural meadows, agricultural land, town sites, and corridors for roads. Uplift of the GYE by as much as 1 km (3,000 ft) during the last 5 million years has resulted in ongoing erosion of deep, steep-walled valleys. Many prominent ecological characteristics of Yellowstone derive from this hotspot-induced uplift, including the moderate- to high- altitude terrain and associated cool temperatures and deep snowfall. Modern and Pleistocene climate and associated vegetation patterns strongly relate to the topography created by the hotspot and its track along the eastern Snake River Plain. Winter air masses from the moist northern Pacific Ocean traverse the topographic low of the Snake River Plain to where orographic rise onto the Yellowstone Plateau and adjacent mountains produces deep snow. A winter precipitation shadow forms on the lee (eastern) sides of the GYE. During Pleistocene glacial times, this moisture conduit provided by the hotspot-track-produced ice-age glaciers that covered the core of the present GYE. These glaciers sculpted bedrock and produced glacial moraines that are both forested and unforested, sand and gravel of ice-marginal streams and outwash gravels that are commonly covered with sagebrush-grassland, and silty lake sediments that are commonly covered by lush grassland such as Hayden Valley. The effects of the Yellowstone hotspot also profoundly shaped the human history in the GYE. Uplift associated with the hotspot elevates the GYE to form the Continental Divide, and streams drain radially outward like spokes from a hub. Inhabitants of the GYE 12,000–10,000 years ago, as well as more recent inhabitants, followed the seasonal green-up of plants and migrating animals up into the mountain areas. During European immigration, people settled around Yellowstone in the lower parts of the drainages and established roads, irrigation systems, and cultural associations. The core Yellowstone highland is too harsh for agriculture and inhospitable to people in the winter. Beyond this core, urban and rural communities exist in valleys and are separated by upland areas. The partitioning inhibits any physical connection of communities, which in turn complicates pursuit of common interests across the whole GYE. Settlements thus geographically isolated evolved as diverse, independent communities

Idaho, Montana, Utah, Wyoming↗

USGS1996

Direct temperature measurements of deposits, Mount St. Helens, Washington, 1980-1981

A program of temperature studies of the eruptive products of Mount St. Helens was established May 20, 1980, 2 days after the catastrophic eruption of May 18. Temperature-depth profiles were measured by thermocouple to determine the emplacement temperatures of deposits of the debris avalanche and blast of May 18 and of deposits of the pyroclastic flows of May 18, May 25, June 12, July 22, August 7, and October 17, 1980. At some of the localities where deposits had cooled appreciably before measurement, emplacement temperatures were recovered mathematically from data gathered from observations of the cooling histories of the deposits. In addition, methodologies and specialized temperature-measuring equipment were developed to maximize efficiency in data collection and to minimize risk to personnel. In general, the more recent eruptive deposits were emplaced at higher temperatures than the earlier ones. Emplacement temperatures of deposits of the debris avalanche ranged from about 70 to 100°C. Temperatures of deposits of the blast ranged from about 100 to 325°C and varied with the azimuth of the measurement site from the vent; the higher temperatures were measured in the northeast sector. Emplacement temperatures of the later pumiceous pyroclastic-flow deposits ranged from about 300 to 680°C, and temperatures in nearvent facies were about 750 to 850°C. The most important features shown by the data obtained from the deposits produced by the blast are (1) their generally lower temperature relative to deposits emplaced by the subsequent pumiceous pyroclastic flows, attributed to relatively low temperatures of the cryptodome and admixing of significant amounts of accidental material and air; (2) an azimuthal variation of emplacement temperatures, hotter toward the east, attributed to thermal inhomogeneities in the source material and differential cooling associated with differing grain sizes and terrains over which the blast traveled; (3) emplacement temperatures that exhibited little change with distance from the vent to distances as great as 20 km, attributed to little cooling along the path, preferential elutriation of the cooler, finer particles, preferential interaction between air and the blast material at the head of the flow, and production of heat during the flow, possibly by friction; (4) thermal stratigraphy observed in some of the ponded pyroclastic-flow deposits in major valleys, attributed in part to a grain-size effect (finer upward) and in part to longer residence of the younger deposits as veneer deposits on the adjacent ridges before their secondary mobilization into the valleys; and (5) temperatures in the veneer deposits and moving blast cloud that were possibly higher than emplacement temperatures of the ponded pyroclastic-flow deposits. The most important features shown by the data obtained from the postblast, pumiceous pyroclastic-flow deposits are (1) generally hotter deposits in the later eruptions than in the earlier ones, attributed to less admixing of the pyroclastic material with air because of the observed progressive decrease in vigor of the successive eruptions; (2) little heat loss (100-200°C) of near-vent material during eruption, as predicted by simple adiabatic expansion; (3) little downflow cooling in the deposits after the first several hundred meters of travel, attributed to the same factors proposed for the blast deposits; (4) multiple flow units that were emplaced at different temperatures by most of the eruptions, attributed to differential cooling through differing amounts of admixed air in accordance with the vigor of the individual eruptive pulses; and (5) cooler material in the ash-cloud deposits than in the source pyroclastic flows because of more effective cooling of the elutriated finer material by the admixed air. Descriptions of the materials and methods we used, and the tabular data and temperature-depth profiles that support our findings, are included as appendices.

Professional Paper↗

USGS1955

Water resources of southeastern Florida, with special reference to the geology and ground water of the Miami area

The circulation of water, in any form, from the surface of the earth to the atmosphere and back again is called the hydrologic cycle. A comprehensive study of the water resources of any area must, therefore, include data on the climate of the area. The humid subtropical climate of southeastern Florida is characterized by relatively high temperatures, alternating semi-annual wet and dry seasons, and usually light but persistent winds. The recurrence of drought in an area having relatively large rainfall such as southeastern Florida indicates that the agencies that remove water are especially effective. Two of the most important of the agencies associated with climate are evaporation and transpiration, or "evapotranspiration". Evaporation losses from permanent water areas are believed to average between about 40 and 45 inches per year. Over land areas indirect methods must be used to determine losses by evapotranspiration; necessarily, these values are not precise. Because of their importance in the occurrence and movement of both surface and ground waters, detailed studies were made of the geology and geomorphology of southern Florida. As a result of widespread crustal movements, southern Florida emerged from the sea in late Pliocene time and probably was slightly tilted to the west. At the beginning of the Pleistocene the continent emerged still farther as a result of the lowering of sea level attending the first widespread glaciation. During this epoch, southern Florida may have stood several hundred feet above sea level. During the interglacial ages the sea repeatedly flooded southern Florida. The marine members of the Fort Thompson formation in the Lake Okeechobee-Everglades depression and the Caloosahatchee River Valley apparently are the deposits of these interglacial invasions by the sea. The fresh-water marls, sands, and organic deposits of the Fort Thompson formation appear to have accumulated during glacial ages when sea level was low and the area was a land surface partly occupied by fresh-water lakes and marshes. Elsewhere in southern Florida the deposits are mainly marine limestones and sandy terrace deposits. The Pliocene surface upon which these Pleistocene sediments were deposited was highest to the north and west of the present Everglades and Kissimmee River basin, and it sloped gently to the south, southeast, and east. On this slightly sloping floor, alternately submerged and emerged, the later materials were built; these materials modified by wind, rain, and surface and ground waters, have largely determined the present topographic and ecologic character of southern Florida. The most important aquifer in southern Florida, and the one in which most of the wells are developed, is the Biscayne aquifer. It is composed of parts of the Tamiami formation (Miocene), Caloosahatchee marl (Pliocene), Fort Thompson formation, Anastasia formation, Key Largo limestone, Miami oolite, and Pamlico sand (Pleistocene). In some parts of southern Florida, the Pamlico sand and the Anastasia formation are not a part of the Biscayne aquifer; however, they are utilized in the development of small water supplies. Most of the Caloosahatchee marl and the Fort Thompson formation in the Lake Okeechobee area is of very low permeability. In the northern Everglades their less permeable parts contain highly mineralized waters, which appear to have been trapped since the invasions by the Pleistocene seas. These waters have been modified by dilution with fresh ground water and by chemical reactions with surrounding materials. Sea-level fluctuations, starting at the close of the Pliocene with the highest levels and progressing toward the Recent with successively lower levels, have built a series of nearly flat marine terrances abutting against one another much like a series of broad stearsteps. Erosion and solution have defaced and, in places, have obliterated the original surficial forms of these old sea bottoms, shores, and shoreline features, but their remnants today are widespread and, in some places, are easily recognizable.

Florida↗

USGS1960

Geology and ground-water resources of the lower Little Bighorn River Valley, Big Horn County, Montana, with special reference to the drainage of waterlogged lands

The lower Little Bighorn River valley, Montana, is in the unglaciated part of the Missouri Plateau section of the Great Plains physiographic province. The river and its principal tributaries rise in the Bighorn Mountains, and the confluence of this northward-flowing stream with the Bighorn River is near the east edge of Hardin, Mont. The normal annual precipitation ranges from about 12 inches in the northern part of the area to 15 inches in the southern part. The economy of the area is founded principally on farming, much of the low-lying land adjacent to the river being irrigated. The irrigated land is within the Crow Indian Reservation, although a part is privately owned. The bedrock formations exposed in the area are of Cretaceous age and include the Parkman sandstone, Claggett shale, Eagle sandstone, Telegraph Creek shale, and Cody shale. The Cloverly formation, Tensleep sandstone, and Madison limestone, which underlie but are not exposed in the area, and the Parkman sandstone in the southern half of the area appear to be the principal bedrock aquifers. All except the Parkman lie at depths ranging from a few feet to several thousand feet, and all appear to be capable of yielding water in commercial quantities. Some of the other formations arc capable of yielding enough water for domestic and stock needs. The river alluvium of Recent age and the Pleistocene terrace deposits are the principal unconsolidated formations in the area with respect to water supply and drainage. Wells yielding as much as 100 gallons per minute may be developed in favorable areas. Pumping tests reveal that the transmissibility of the coarser unconsolidated materials probably ranges from about 15,000 to 30,000 gallons per day per foot. Two tests of the Parkman sandstone showed transmissibilities of 6,000 and 20,000 gallons per day per foot. Although a test of the Cloverly formation showed a transmissibility of only 3,000 gallons per day per foot, the high artesian pressure--80 pounds per square inch at the land surface--in the Cloverly caused the tested well to yield about 200 gallons per minute by natural flow; this is greater than the yield of any other single well in the area. Textural properties were compared with the hydraulic properties determined by laboratory tests to show the relation between different types of waterbearing materials. Materials classified as heavy soils-normally somewhat dense and impervious-had an average permeability of 7.2 gallons per day per square foot, which was more than expected. One sample of very coarse alluvial material had a permeability of 6,000 gallons per day per square foot. The depth to water beneath irrigation units was mapped, thus showing the waterlogged areas. Waterlogging is not a serious problem where the water table is more than 6 feet below the land surface. For the drainage studies the unconsolidated deposits are classified in two zones-coarse-grained sediments resting on the relatively impermeable bedrock floor and overlying fine-grained sediments which extend to the land surface. The transmissibility of the coarse-sediment zone generally is many times greater than that of the fine-sediment zone. Because in many places drains could not be economically dug deep enough to enter the coarse zone, the study of the effectiveness of drainage completed in the fine zone received much attention. The studies showed that, despite a considerable thickness of fine-grained sediments between the bottom of the drain and the top of the coarse zone, drainage ditches frequently were effective in relieving waterlogging of fields nearby. Pilot relief wells installed in existing drains showed that the effectiveness of some drains could be increased appreciably by installing a series of relief wells. Records of fluctuations of water levels in 196 observation wells and water-level contour maps were studied to show the principal areas of recharge and discharge in the irrigable areas.

Montana↗