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Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.
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A magnetic observatory is a specially designed ground-based facility that supports time-series measurement of the Earth’s magnetic field. Observatory data record a superposition of time-dependent signals related to a fantastic diversity of physical processes in the Earth’s core, mantle, lithosphere, ocean, ionosphere, magnetosphere, and, even, the Sun and solar wind.
Are you a gardener? Then you know that certain species and varieties of species grow best in certain growing zones related to climate. This growing zone concept also applies to species in natural ecosystems. One threat of climate change to wetland biodiversity is that some species may be losing the ability to track an appropriate season for flowering, seed production and growth, impairing their ability to regenerate. Based on genetic constraints, such species may have a limited ability to adjust to changing climates. For biodiversity conservation to be successful in the future, the first order of business is to formulate the goals of such projects regardless of philosophical differences in approaches. If the real goal is to conserve species, then conservation planners may need to put all management options on the table. Despite the uncertainties, with the risk of species losses so imminent, the best strategy may be to throw any dogmatism out the window and use multiple approaches.
Describes the impact of USGS scientist David Parkhurst's influential contributions to the fields of aqueous geochemistry and hydrogeology. Parkhurst is the recipient of the 2012 O.E. Meinzer award of the Geological Society of America's Hydrogeology Division.
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As part of our DOE-funded proposal to characterize gas hydrate in the Gulf of Mexico using marine electromagnetic methods, a collaboration between SIO, LLNL, and USGS with the goal of measuring the electrical properties of lab-created methane (CH 4 ) hydrate and sediment mixtures was formed. We examined samples with known characteristics to better relate electrical properties measured in the field to specific gas hydrate concentration and distribution patterns. Here we discuss first-ever electrical conductivity (σ) measurements on unmixed CH 4 hydrate (Du Frane et al., 2011): 6 x 10-5 S/m at 5 °C, which is ~5 orders of magnitude lower than seawater. This difference allows electromagnetic (EM) techniques to distinguish highly resistive gas hydrate deposits from conductive water saturated sediments in EM field surveys. More recently, we performed measurements on CH 4 hydrate mixed with sediment and we also discuss those initial findings here. Our results on samples free of liquid water are important for predicting conductivity of sediments with pores highly saturated with gas hydrate, and are an essential starting point for comprehensive mixing models.
Seismic reflection images from the deep-water Aleutian and Bowers Basins of the Bering Sea contain many hundreds of acoustic Velocity-AMPlitude (VAMP) anomalies, each of which may represent a large accumulation of natural gas hydrate. Against a backdrop of essentially horizontal sedimentary reflections, the VAMP anomalies stand out as both high-amplitude bright spots and zones of vertically aligned horizon distortions. The VAMPs are interpreted as natural gas chimneys overlain by concentrated hydrate caps.
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Studies by Warner in the 1950’s and van Riper in the 1970’s identified disease as a potential limiting factor in the distribution and abundance of Hawaii’s native forest birds. Mosquito-transmitted protozoan and viral infections caused by malarial parasites and pox virus were especially significant. Both organisms were introduced to the islands after the arrival of Europeans and are thought to have affected avian communities the same way that measles devastated native Hawaiian peoples.
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No abstract available.