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 17 of 17 for “"Seafloor spreading"”.
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Oblique Seafloor Spreading, the Malpelo Plate Hypothesis, and Cocos-Nazca-Pacific Plate Motion Circuit
We show that oblique seafloor spreading occurs in several regions where obliquity, α, was not recognized before. These include the slow spreading centers of the Red Sea (α≈20°), intermediate spreading centers of the Cocos-Nazca plate boundary between 91°W and 94°W (α≈9°), and superfast spreading …
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Tectonics of the West Iberia continental margin from seismic reflection data
… that has been serpentinized. This implies that seafloor spreading does not immediately follow continental breakup. Where the peridotite ridge is well-developed, it parallels a deeply-penetrating, west-dipping normal fault. Hydrodynamic circulation drove seawater down this fault close to the …
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Novel Insights into the Palaeomagnetism of Serpentinized Peridotites from the Troodos and Oman Ophiolites
… rotation that began shortly after it formed by seafloor spreading. The timing of this rotation is well-constrained by palaeomagnetic analysis of the sedimentary rocks that were deposited continuously while the underlying oceanic crust rotated. In this context, different magnetization directions …
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Tectonic and magmatic processes during extension in planetary lithospheres : rifting, spreading, delamination, and recycling on Earth and Venus
… the transition from continental rifting to seafloor spreading. The study finds that the transition is controlled by high temperature shear zones in the mantle and by a change in stress from gravitational collapse to buoyant upwelling of a melt-rich mantle. On Venus, extensional systems form …
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Seismic imaging and thermal modeling of active continental rifting processes in the Salton Trough, Southern California
… the Colorado River. Unlike the southern Gulf, seafloor spreading has not initiated. Instead, seismicity, high heat flow, and minor volcanoes attest to ongoing rifting of thin, transitional crust. Recently acquired controlled-source seismic refraction and wide-angle reflection data in the Salton …
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Quantification of Permeability-Porosity Relationships in Seafloor Vent Deposits: Dependence on Pore Evolution Processes
Hydrothermal mineral deposits formed along seafloor spreading centers help regulate the transfer of heat and mass from Earth's interior to the oceans. Aqueous fluids circulate within the seafloor and are emitted through vent deposits, formed from interaction between vent fluids and seawater. These …
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North-south variations in structure, topography, and melting regime along the ultra-slow spreading Red Sea Ridge
The Red Sea rift is a nascent ultra-slow spreading ridge superimposed on the Afar plume. Based on high-resolution seismic data, the southernmost (south of the Danakil rift at 17.05°N), southern (17.05-19.75°N), and central (19.75-23.8°N) segments display seafloor spreading that is anomalously …
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Diffuse flow from hydrothermal vents
… flow under typical environmental conditions at seafloor spreading centers. A laboratory simulation was conducted to test an analytic model of diffuse plume rise. The results showed that diffuse plumes are likely to remain near the seafloor, with their maximum rise height scaled with the diameter …
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Structure and evolution of an oceanic megamullion on the Mid-Atlantic ridge at 27°N
Megamullions in slow-spreading oceanic crust are characterized by smooth "turtle-back" morphology and are interpreted to be rotated footwalls of long-lived detachment faults. Megamullions have been analyzed in preliminary studies, but many questions remain about structural and tectonic details of …
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Structure and Accretion at Mid-Ocean Ridges With High Magma Supply: Perspectives From Seafloor Escarpments and Iceland
… about processes operating at mid-ocean ridge spreading centers and the generation of oceanic lithosphere that covers approximately 2/3 of Earth's surface. In particular, geologist are uncertain about specific details of magmatic and tectonic processes beneath these divergent plate boundaries …
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A 3D Analysis of the Indo-Australian Slab Subducting Beneath Sumatra
… of the Wharton Basin, which preserves an fossil seafloor spreading ridge offset by north-south trending fracture zones. Currently, the subducted plate geometry is not well-constrained and is debated between authors. This study models the geometry and spatial extent of the subducted …
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Compressible Convection and Subduction: Kinematic and Dynamic Modeling
… of the subducting slab explain time-dependent seafloor spreading at the mid-ocean ridge, convergence rate of the oceanic plate at trench and arc-normal migration of arc volcanoes.
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Crustal accretion and evolution at slow and ultra-slow spreading mid-ocean ridges
Half of the ocean crust is formed at spreading centers with total opening rates less than 40 km/Myr. The objective of this Thesis is to investigate temporal variations in active ridge processes and crustal aging at slow-spreading centers by comparing axial crustal structure with that on conjugate …
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The origin of the ninetyeast ridge and the northward motion of India, based on DSDP paleolatitudes
This thes is is a collection of papers on the paleomagnetics of samples from several Deep Sea Drilling Project (DSDP) sites in the Indian Ocean. These papers present the basic paleomagnetic data, discuss the statistical methods for analyzing such data from DSDP cores, and examine the implications …
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Crustal structure of rifted and convergent margins : the U.S. East Coast and Aleutian margins
… by 50 to 80% within this interval and then seafloor spreading began with an unusually large volume of igneous crust production. The initial volcanic extrusives were emplaced subaerially and are now present beneath the sediments in a thick seaward-dipping wedge. We use post-stack depth …
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Modelling plate kinematics in the Scotia sea
… continental crustal blocks and the signatures of seafloor spreading are defined semi-automatically using gravity and total field magnetic anomalies and some of their residuals, transformations and derivatives. This study is the first of the region to integrate gridded magnetic and gravity data in …
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Temporal and petrological constraints of ultrahigh-pressure metamorphism and exhumation of crustal material from mantle depths to Earth's surface: Insights from a large and small ultrahigh-pressure terrane
… of hot asthenospheric fluids related to westward seafloor spreading in the Woodlark Rift from ca. 6.0 to 5.2 Ma. Subsequently, the partially-molten (U)HP rocks rose as diapirs that underwent rapid near-vertical exhumation to the base of the crust, resulting in the generation of abundant partial …