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Seismic And Magnetic Constraints On The Structure Of Upper Oceanic Crust At Fast And Slow Spreading Ridges
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Book Synopsis Seismic and Magnetic Constraints on the Structure of Upper Oceanic Crust at Fast and Slow Spreading Ridges by : Stefan Anthony Hussenoeder
Download or read book Seismic and Magnetic Constraints on the Structure of Upper Oceanic Crust at Fast and Slow Spreading Ridges written by Stefan Anthony Hussenoeder and published by . This book was released on 1998 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt: The upper ocean crust contains a comprehensive record of the shallow geological processes active along the world's mid-ocean ridge system. This thesis examines the magnetic and seismic structure of the upper crust at two contrasting ridges-the fast spreading East Pacific Rise (EPR) and the slow spreading Mid-Atlantic Ridge (MAR)-to build a more complete understanding about the roles of volcanic emplacement, tectonic disruption and hydrothermal alteration in the near-ridge environment. A technique that inverts potential field measurements. directly from an uneven observation track is developed and applied to near-bottom magnetic data from the spreading segments north of the Kane transform on the MAR. It is concluded that the central anomaly magnetization high marks the locus of focused volcanic emplacement. A cyclic faulting model is proposed to explain the oscillatory magnetization pattern associated with discrete blocks of crust being transported out of the rift valley between intensely altered fault zones. Seismic waveform and amplitude analyses of the magma sill along the EPR reveal it to be a thin (
Book Synopsis Seismic and Magnetic Constraints on the Structure of Upper Oceanic Crust at Fast and Slow Spreading Ridges by :
Download or read book Seismic and Magnetic Constraints on the Structure of Upper Oceanic Crust at Fast and Slow Spreading Ridges written by and published by . This book was released on 1998 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Seismic and Magnetic Constraints on the Strucutre of Upper Oceanic Crust and Fast and Slow Spreading Ridges by : Stefan Anthony Hussenoeder
Download or read book Seismic and Magnetic Constraints on the Strucutre of Upper Oceanic Crust and Fast and Slow Spreading Ridges written by Stefan Anthony Hussenoeder and published by . This book was released on 1998 with total page 492 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Biogeochemistry of Cobalt in the Sargasso Sea by : Mak A. Saito
Download or read book The Biogeochemistry of Cobalt in the Sargasso Sea written by Mak A. Saito and published by . This book was released on 2001 with total page 832 pages. Available in PDF, EPUB and Kindle. Book excerpt: Processes that enable marine phytoplankton to acquire trace metals are fundamental to our understanding of primary productivity and global carbon cycling. This thesis explored the biogeochemistry of cobalt using analytical chemistry and physiological experiments with the dominant phytoplankton species, Prochlorococcus. A high sensitivity method for Co speciation was developed using hanging mercury drop cathodic stripping voltammetry. Dissolved Co at the Bermuda Atlantic Time Series station (BATS) in the Sargasso Sea was bound by strong organic complexes with a conditional stability constant of logK=16.3 +/- 0.9. Biweekly time series measurements of total cobalt near Bermuda from the MITESS sampler were 0-47pM throughout 1999, and averaged 20 +/- 10pM in 1999. A transect of total cobalt from BATS to American coastal waters ranged from 19-133pM and correlated negatively with salinity (r(sup 2)=0.93). Prochlorococcus strains MED4-Ax and SS120 showed an absolute requirement for Co, despite replete Zn. Co-57 uptake rates and growth rates were enhanced by additions of filtered low Co cultures, suggesting that a ligand is present that facilitates Co uptake. Co-limited Prochlorococcus cultures exhibited an increase in the fraction of cells in G2 relative to other cell cycle stages during exponential growth, and the durations of this stage increased with decreasing cobalt concentrations.
Book Synopsis Mid-Ocean Ridges by : Johnson Robin Cann
Download or read book Mid-Ocean Ridges written by Johnson Robin Cann and published by Cambridge University Press. This book was released on 1999-07-22 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt: Covers the most important problems that arise at mid-ocean ridges; for researchers working in the earth sciences.
Book Synopsis Seismology and Structure of the Earth by : Barbara Romanowicz
Download or read book Seismology and Structure of the Earth written by Barbara Romanowicz and published by Elsevier. This book was released on 2010-04-20 with total page 873 pages. Available in PDF, EPUB and Kindle. Book excerpt: Treatise on Geophysics: Seismology and Structure of the Earth, Volume 1, provides a comprehensive review of the state of knowledge on the Earths structure and earthquakes. It addresses various aspects of structural seismology and its applications to other fields of Earth sciences. The book is organized into four parts. The first part principally covers theoretical developments and seismic data analysis techniques from the end of the nineteenth century until the present, with the main emphasis on the development of instrumentation and its deployment. The second part reviews the status of knowledge on the structure of the Earths shallow layers, starting with a global review of the Earth's crustal structure. The third part focuses on the Earth's deep structure, divided into its main units: the upper mantle, the transition zone and upper-mantle discontinuities, the D region at the base of the mantle, and the Earth's core. The fourth part comprises two chapters which discuss constraints on Earth structure from fields other than seismology: mineral physics and geodynamics. Self-contained volume starts with an overview of the subject then explores each topic with in depth detail Extensive reference lists and cross references with other volumes to facilitate further research Full-color figures and tables support the text and aid in understanding Content suited for both the expert and non-expert
Download or read book Igneous Petrogenesis written by m Wilson and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 476 pages. Available in PDF, EPUB and Kindle. Book excerpt: courses more petrogenesis-orientated are im My main objective in writing this book has been to mediately confronted with a basic problem; the review the processes involved in present-day mag ma generation and their relationship to global average student does not have a strong enough tectonic processes. Clearly, these are fundamental background in geochemistry to understand the to our understanding of the petrogenesis of ancient finer points of most of the relevant publications in volcanic and plutonic sequences, the original tec scientific journals. It is virtually impossible to fmd tonic setting of which may have been obscured by suitable reading material for such students, as most subsequent deformation and metamorphism. authors of igneous petrology textbooks have de Until fairly recently, undergraduate courses in liberately steered clear of potentially controversial igneous petrology tended to follow rather classical petrogenetic models. Even the most recent texts lines, based on the classification of igneous rocks, place very little emphasis on the geochemistry of descriptive petrography, volcanic landforms, types magmas erupted in different tectonic settings, of igneous intrusions and regional petrology . despite extensive discussions of the processes re However, the geologist of the late 1980s requires, in sponsible for the chemical diversity of magmas.
Book Synopsis The Mid-oceanic Ridges by : Adolphe Nicolas
Download or read book The Mid-oceanic Ridges written by Adolphe Nicolas and published by Copernicus. This book was released on 1995 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt: Contains the most recent oceanographic data with ophiolites, representing fossil ocean crust, abducted onto the continents by tectonic processes.
Book Synopsis Dynamics of Freshwater Plumes by : Derek Allen Fong
Download or read book Dynamics of Freshwater Plumes written by Derek Allen Fong and published by . This book was released on 1998 with total page 618 pages. Available in PDF, EPUB and Kindle. Book excerpt: A freshwater plume often forms when a river or an estuary discharges water onto the continental shelf. Freshwater plumes are ubiquitous features of the coastal ocean and usually leave a striking signature in the coastal hydrography. The present study combines both hydrographic data and idealized numerical simulations to examine how ambient currents and winds influence the transport and mixing of plume waters. The first portion of the thesis considers the alongshore transport of freshwater using idealized numerical simulations. In the absence of any ambient current, the downstream coastal current only carries a fraction of the discharged fresh water; the remaining fraction recirculates in a continually growing "bulge" of fresh water in the vicinity of the river mouth. The fraction of fresh water transported in the coastal current is dependent on the source conditions at the river mouth. The presence of an ambient current augments the transport in the plume so that its freshwater transport matches the freshwater source. For any ambient current in the same direction as the geostrophic coastal current, the plume will evolve to a steady-state width. A key result is that an external forcing agent is required in order for the entire freshwater volume discharged by a river to be transported as a coastal current. The next section of the thesis addresses the wind-induced advection of a river plume, using hydrographic data collected in the western Gulf of Maine. The observations suggest that the plume's cross-shore structure varies markedly as a function of fluctuations in alongshore wind forcing. Consistent with Ekman dynamics, upwelling favorable winds spread the plume offshore, at times widening it to over 50 km in offshore extent, while downwelling favorable winds narrow the plume width to a few Rossby radii. Near-surface current meters show significant correlations between cross-shore currents and alongshore wind stress, consistent with Ekman theory. Estimates of the terms in the alongshore momentum equation calculated from moored current meter arrays also indicate an approximate Ekman balance within the plume. A significant correlation between alongshore currents and alongshore wind stress suggests that interfacial drag may be important. The final section of the thesis is an investigation of the advection and mixing of a surface-trapped river plume in the presence of an upwelling favorable wind stress, using a three-dimensional model in a simple, rectangular domain. Model simulations demonstrate that the plume thins and is advected offshore by the cross shore Ekman transport. The thinned plume is susceptible to significant mixing due to the vertically sheared horizontal currents. The first order plume response is explained by Ekman dynamics and a Richardson number mixing criterion. Under a sustained wind event, the plume evolves to a quasi-steady, uniform thickness. The rate of mixing slowly decreases for longer times as the stratification in the plume weakens, but mixing persists under a sustained upwelling wind until the plume is destroyed. Mixing is most intense at the seaward plume front due to an Ekman straining mechanism in which the advection of cross-shore salinity gradients balances vertical mixing. The mean mixing rate observed in the plume is consistent with the mixing power law suggested by previous studies of 1-D mixing, in spite of the two-dimensional dynamics driving the mixing in the plume
Book Synopsis Faulting and Magmatism at Mid-Ocean Ridges by : W. Roger Buck
Download or read book Faulting and Magmatism at Mid-Ocean Ridges written by W. Roger Buck and published by American Geophysical Union. This book was released on 1998-02-04 with total page 349 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book can benefit the nonspecialist who wants to keep up with work on magmatism and tectonics, as well as researchers working on mid-ocean ridges."--BOOK JACKET.
Download or read book Treatise on Geophysics written by and published by Elsevier. This book was released on 2015-04-17 with total page 5604 pages. Available in PDF, EPUB and Kindle. Book excerpt: Treatise on Geophysics, Second Edition, is a comprehensive and in-depth study of the physics of the Earth beyond what any geophysics text has provided previously. Thoroughly revised and updated, it provides fundamental and state-of-the-art discussion of all aspects of geophysics. A highlight of the second edition is a new volume on Near Surface Geophysics that discusses the role of geophysics in the exploitation and conservation of natural resources and the assessment of degradation of natural systems by pollution. Additional features include new material in the Planets and Moon, Mantle Dynamics, Core Dynamics, Crustal and Lithosphere Dynamics, Evolution of the Earth, and Geodesy volumes. New material is also presented on the uses of Earth gravity measurements. This title is essential for professionals, researchers, professors, and advanced undergraduate and graduate students in the fields of Geophysics and Earth system science. Comprehensive and detailed coverage of all aspects of geophysics Fundamental and state-of-the-art discussions of all research topics Integration of topics into a coherent whole
Book Synopsis Seismic Constraints on Shallow Crustal Processes at the East Pacific Rise by : Gail L. Christeson
Download or read book Seismic Constraints on Shallow Crustal Processes at the East Pacific Rise written by Gail L. Christeson and published by . This book was released on 1994 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis is concerned with understanding how oceanic crust is emplaced at mid-ocean ridges. The emphasis is upon fast-spreading ridges, and the use of seismic techniques to image the uppermost several hundred meters of the crust. We present the results of nine on-bottom seismic refraction experiments carried out over young East Pacific Rise (EPR) crust. The experiments are unusual in that both the source and receiver are located within a few meters of the seafloor, allowing high-resolution determinations of shallow crustal structure. Three experiments were located within the axial summit caldera (ASC), over 'zero-age' crust. The seismic structure at these three locations is fundamentally the same, with a thin (60 m) surficial low-velocity (
Book Synopsis A Study of the Seismic Structure of Ocean Crust Formed at Slow-spreading, Mid-ocean Ridges by : Caroline Louise Scott
Download or read book A Study of the Seismic Structure of Ocean Crust Formed at Slow-spreading, Mid-ocean Ridges written by Caroline Louise Scott and published by . This book was released on 2004 with total page 49 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Thermal Structure of Mid-Ocean Ridges (Lucky Strike, Mid-Atlantic Ridge) and Magma Chambers by : Doga Dusunur
Download or read book Thermal Structure of Mid-Ocean Ridges (Lucky Strike, Mid-Atlantic Ridge) and Magma Chambers written by Doga Dusunur and published by . This book was released on 2008 with total page 163 pages. Available in PDF, EPUB and Kindle. Book excerpt: Modeling the thermal state of the oceanic crust is an important task to understand the construction of oceanic crust which covers two thirds of the surface of our planet. The interplays among magma delivery to the axis and cooling of the oceanic lithosphere as a function of both space and time are key factors to understand the creation of the oceanic crust, which is primarily determined by the overall thermal structure of mid-ocean ridges. Classical thermal models do not predict steady state axial magma chambers (AMCs) along mid-ocean ridges at spreading rates less than 30 mm/year. The identification and seismic imaging of an axial magma chamber underlying the Lucky Strike central volcano and hydrothermal field at the Mid-Atlantic Ridge provides a unique opportunity to study the thermal structure of slow spreading ridges. Here we present coupled microseismic data and thermal modeling to provide insight on the nature of ephemeral magma chambers at slow-spreading ridges, to constrain the timescales associated with changes in melt supply and the parameters that can create them, and to shed light on the different mechanisms that can result on the cooling and disappearance of these structures. Both the coupled microseismic and thermal modeling results, and the time-constraints derived from the geological constraints put forward, suggest that focused melt supply to the segment center is required regularly, and that this supply is maintained over extended periods of time, that can lead to a durable magma chamber. This thesis, while focusing on the processes occurring at the Lucky Strike, provide a more general template to both understand and study other slow-spreading ridge segments, and to gain insight on how the oceanic crust is formed along them.
Book Synopsis Crustal Accretion and Evolution at Slow and Ultra-slow Spreading Mid-ocean Ridges by :
Download or read book Crustal Accretion and Evolution at Slow and Ultra-slow Spreading Mid-ocean Ridges written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Funding was provided by the National Science Foundation through Contract No. OCE-9300450 and by the Joint Oceanographic Institutions through Subcontract No. JSC1-00.
Book Synopsis Crustal Structure in Areas of Active Crustal Accretion by : Leonard Dale Bibee
Download or read book Crustal Structure in Areas of Active Crustal Accretion written by Leonard Dale Bibee and published by . This book was released on 1979 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Upper Crustal and Lithosphere-Asthenosphere Boundary Seismic Structure of 0-75 Ma Old Normal Oceanic Lithosphere in the Equatorial Atlantic Ocean by : Pranav Audhkhasi
Download or read book Upper Crustal and Lithosphere-Asthenosphere Boundary Seismic Structure of 0-75 Ma Old Normal Oceanic Lithosphere in the Equatorial Atlantic Ocean written by Pranav Audhkhasi and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Previous studies on upper oceanic crust have been limited to young lithosphere and wide-angle seismic data, which lacks resolution in the upper crust. The oceanic lithosphere-asthenosphere boundary (LAB) has been studied extensively by seismological studies, but also suffers from low vertical resolution. The TransAtlantic ILAB experiment collected multi-channel seismic reflection data over oceanic lithosphere aged 0-75 Ma formed at the slow-spreading Mid-Atlantic Ridge in the Equatorial Atlantic Ocean. Analysis of upper crust by means of seismic imaging and high-resolution tomography indicates the top of the crust (Layer 2A) is never sealed from 0-75 Ma and hydrothermal systems continue in older oceanic crust. Most of the evolution happens within the first 4 Myr, beyond which intensity of hydrothermal circulation reduces and sediment cover increases. Layer 2A/2B boundary is a lava/dyke contact at the ridge-axis and a hydrothermal alteration front away from the ridge-axis. Co-located heatflow data from the LITHOS experiment supports the possibility of large hydrothermal cells in older oceanic crust. The LAB is imaged throughout on lithosphere aged 2-75 Ma. From 2-47 Ma, there is evidence of a LAB channel decoupling the lithospheric mantle from the asthenospheric mantle with the lithosphere being 25 km thick at 2 Myr and 72 km thick at 47 Myr. However from 49-75 Myr, a single LAB reflection is imaged implying possible disruption of the base of the channel due to adjacent Cameroon Volcanic Line. Strong evidence of mantle thermal anomaly comes from the LAB being shallower and an uplifted lithosphere.
