Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 16 of 16 for “"Joint Program in Marine Geology and Geophysics."”.
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Investigation of the effect of a circular patch of vegetation on turbulence generation and sediment deposition using four case studies
… the spatial distribution of sediment deposition in the wake of a circular patch of model vegetation and the effect of the patch on turbulence and mean flow. Two difference types pf vegetation were used along with two different stem densities totaling four different case studies. The spatial …
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The marine biogeochemistry of molybdenum
Prevailing wisdom holds that the vertical distribution of molybdenum (Mo) in the open ocean is conservative, despite Mo's important biological role and association with Mn oxides and anoxic sediments. Mo is used in both nitrogenase, the enzyme responsible for N2 fixation, and nitrate reductase, …
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Climate controls on coral growth in the Caribbean
… limited by a lack of knowledge of the dominant environmental controls on coral growth. Corals exhibit significant responses to environmental variability occurring on multi-annual to decadal timescales, which are significantly longer than the duration of typical laboratory and field-based …
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Chemical, isotopic, and temporal variations during crustal differentiation : insights from the Dariv Igneous Complex, Western Mongolia
… basaltic melts is a critical process in producing a compositionally stratified continental crust characterized by a silicic upper crust and a mafic lower crust. This thesis explores outstanding questions associated with fractional crystallization through detailed field, petrological, …
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Syn-eruptive degassing of a single submarine lava flow : constraints on MORB CO₂ variability, vesiculation, and eruption dynamics
… a wide range of CO2 concentrations, reflecting saturation to supersaturation (and rarely undersaturation) relative to their emplacement depths. In this study, we explore the mechanisms of CO2 degassing and the implications this has for estimating the advance rates and durations of seafloor …
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Basalt petrogenesis beneath slow- and ultraslow-spreading Arctic mid-ocean ridges
To explore the ability of melting mafic lithologies to produce alkaline ocean-island basalts (OIB), an experimental study was carried out measuring clinopyroxene (Cpx)melt and garnet (Gt)-melt partition coefficients during silica-poor garnet pyroxenite melting for a suite of trace elements, …
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Trace element proxies and mineral indicators of hydrothermal fluid composition and seafloor massive sulfide deposit formation processes
… of seafloor massive sulfide (SMS) deposits and related hydrothermal vent fluids to identify proxies of reaction zone conditions (host-rock lithology, hydrothermal fluid temperature and chemistry). Chapter 2 investigates the morphology, mineralogy, and geochemistry of SMS deposits from six …
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Geochemical and rheological constraints on the dynamics of the oceanic upper mantle
I provide constraints on mantle convection through observations of the rheology and composition of the oceanic upper mantle. Convection cannot be directly observed, yet is a fundamental part of the plate tectonic cycle. Relative motion among plates is accommodated by localized deformation at their …
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The CAFE experiment : a joint seismic and MT investigation of the Cascadia subduction system
In this thesis we present results from inversion of data using dense arrays of collocated seismic and magnetotelluric stations located in the Cascadia subduction zone region of central Washington. In the migrated seismic section, we clearly image the top of the slab and oceanic Moho, as well as a …
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The effect of a shallow low viscosity zone on mantle convection and its expression at the surface of the earth
… features of the oceanic plates cannot be explained by conductive cooling with age. A number of these anomalies require additional convective thermal sources at depths below the plate: mid-plate swells, the evolution of fracture zones, the mean depth and heat flow relationships with age and the …
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Quaternary morphology and paleoenvironmental records of carbonate islands
… that the present-day morphology of carbonate islands has developed largely in response to late Pleistocene sea level oscillations in addition to variable vertical motion and reef accretion rates. In particular, large amplitude 'ice-house' sea-level variability resulted in long lagoonal …
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Seismic and gravitational studies of melting in the mantle's thermal boundary layers
… geophysical tools to the task of better understanding mantle melting phenomena at the upper and lower boundaries of the mantle. The first study uses seafloor bathymetry and small variations in the gravitational acceleration over the Hawaii-Emperor seamount chain to constrain the changes in the …
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Determining timescales of natural carbonation of peridotite in the Samail Ophiolite, Sultanate of Oman
Determining timescales of the formation and preservation of carbonate alteration products in mantle peridotite is important in order to better understand the role of this potentially important sink in the global carbon cycle and also to evaluate the feasibility of using artificially-enhanced, in …
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Plagioclase preferred orientation in the layered mylonites : evaluation of flow laws for the lower crust
We evaluate the applicability of plagioclase and gabbro flow laws by comparing predicted and observed deformation mechanisms in gabbroic shear zones. Gabbros and layered gabbro mylonites were collected from the Southwest Indian Ridge (SWIR), ODP Hole 735B. Deformation temperatures are constrained …
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Structure and mechanics of the subducted Gorda Plate : constrained by afterslip simulations and scattered seismic waves
… zones host the greatest earthquakes on earth and pose great threat to human society. The largest slip in megathrust earthquakes often occurs in the 10-50 km depth range, yet seismic imaging of the material properties in this region has proven difficult. This thesis focuses on developing …
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A radiocarbon method and multi-tracer approach to quantifying groundwater discharge to coastal waters
Groundwater discharge into estuaries and the coastal ocean is an important mechanism for the transport of dissolved chemical species to coastal waters. Because many dissolved species are present in groundwater in concentrations that are orders of magnitude higher than typical river concentrations, …