United States Geological Survey

About: United States Geological Survey is a government organization based out in Reston, Virginia, United States. It is known for research contribution in the topics: Population & Groundwater. The organization has 17899 authors who have published 51097 publications receiving 2479125 citations. The organization is also known as: USGS & US Geological Survey.

Pan-African microplate accretion of the Arabian Shield

Abstract: The late Proterozoic Arabian Shield is composed of at least five geologically distinct terranes (microplates) separated by four ophiolite-bearing suture zones. Three ensimatic island-arc terranes occur in the western shield, whereas the two terranes in the eastern shield have continental affinities. The western two sutures are island-arc-island-arc joins, whereas the eastern two sutures collectively form a major coilisional orogenic belt. Accretion of the five terranes to form an Arabian neocraton occurred from 715 to 630 Ma. After accretion, intracratonic deformation and magmatism related to collision continued and resulted in the formation of molasse, intermediate to silicic volcanic rocks, peralka-line to peraluminous granites (640-570 Ma), and a major left-lateral wrench fault system (∼630-550 Ma) which displaced the northern part of the Arabian neocraton ∼250 km to the northwest. These tectonic events represent the accretion of the Arabian portion of Gondwanaland during the Pan-African event.

Tree mortality from drought, insects, and their interactions in a changing climate

Abstract: Climate change is expected to drive increased tree mortality through drought, heat stress, and insect attacks, with manifold impacts on forest ecosystems. Yet, climate-induced tree mortality and biotic disturbance agents are largely absent from process-based ecosystem models. Using data sets from the western USA and associated studies, we present a framework for determining the relative contribution of drought stress, insect attack, and their interactions, which is critical for modeling mortality in future climates. We outline a simple approach that identifies the mechanisms associated with two guilds of insects - bark beetles and defoliators - which are responsible for substantial tree mortality. We then discuss cross-biome patterns of insect-driven tree mortality and draw upon available evidence contrasting the prevalence of insect outbreaks in temperate and tropical regions. We conclude with an overview of tools and promising avenues to address major challenges. Ultimately, a multitrophic approach that captures tree physiology, insect populations, and tree-insect interactions will better inform projections of forest ecosystem responses to climate change.

Comparing Examples of Modern and Ancient Turbidite Systems: Problems and Concepts

Abstract: A useful comparison of modern and ancient submarine fans can be based only on well-understood and thoroughly mapped systems. In addition, the examples selected for comparison must represent depositional systems similar in such characteristics as type of basin, size of sediment source, physical and temporal scales, and stage of development. Many fan sedimentation models presently in use do not meet these criteria.

Removal of Antibiotics from Surface and Distilled Water in Conventional Water Treatment Processes

Abstract: Conventional drinking water treatment processes were evaluated under typical water treatment plant conditions to determine their effectiveness in the removal of seven common antibiotics: carbadox, sulfachlorpyridazine, sulfadimethoxine, sulfamerazine, sul- famethazine, sulfathiazole, and trimethoprim. Experiments were conducted using synthetic solutions prepared by spiking both distilled/ deionized water and Missouri River water with the studied compounds. Sorption on Calgon WPH powdered activated carbon, reverse osmosis, and oxidation with chlorine and ozone under typical plant conditions were all shown to be effective in removing the studied antibiotics. Conversely, coagulation/flocculation/sedimentation with alum and iron salts, excess lime/soda ash softening, ultraviolet irra- diation at disinfection dosages, and ion exchange were all relatively ineffective methods of antibiotic removal. This study shows that the studied antibiotics could be effectively removed using processes already in use in many water treatment plants. Additional work is needed on by-product formation and the removal of other classes of antibiotics.

On the flow of water in an elastic artesian aquifer

Abstract: Slichter showed in 1898 that a solution may be obtained for a given problem in the steady motion of ground-water by solving the familiar Laplace equation and that therefore in steady-state conditions a problem in the motion of ground-water is mathematically analogous to a problem in the steady flow of heat or electricity [see 1 of “References” at end of paper]. More recently it has been recognized that the analogy holds also for the non-steady-state flow of compressible liquids, in elastic systems as well as in rigid systems. In studying the effect of the discharge of flowing wells on the head in the Dakota sandstone, Meinzer [2, 3] concluded that the water discharged by the wells had largely been derived locally from storage. It was found that the amount of water withdrawn from storage could not be accounted for on the basis of the compressibility of water alone but that it might be accounted for on the basis of the probable compressibility of the sandstone itself. Prior to that time, estimates of water-supplies from artesian aquifers had been based upon the assumption that artesian aquifers are perfectly incompressible and inelastic However, as Meinzer states [2, p. 289], “artesian aquifers are apparently all more or less compressible and elastic though they differ widely in the degree and relative importance of these properties. In general, the properties of compressibility and elasticity are of the most consequence in aquifers that have low permeability, slow recharge, and high head.”