Thesis advisor: John E. Ebel / The seismicity of the mid Atlantic Ridge (MAR) was compared in space and time with the seismicity along the Atlantic continental margins of Europe, Africa, North America, the Carribean and South America in a bid to appraise the level of influence of the ridge push force at the MAR on the Atlantic coastal seismicity. By analyzing the spatial and temporal patterns of many earthquakes (along with the patterns in their stress directions) in diverse places with similar tectonic settings, it is hoped that patterns that might be found indicate some of the average properties of the forces that are causing the earthquakes. The spatial analysis of the dataset set used shows that areas with higher seismic moment release along the north MAR spatially correlate with areas with relatively lower seismic moment release along the north Atlantic continental margins (ACM) and vice versa. This inverse spatial correlation observed between MAR seismicity and ACM seismicity might be due to the time (likely a long time) it takes stress changes from segments of the MAR currently experiencing high seismic activity to propagate to the associated passive margin areas presently experiencing relatively low seismic activity. Furthermore, the number of Atlantic basin and Atlantic coast earthquakes occurring away from the MAR is observed to be independent of the proximity of earthquake’s epicenters from the MAR axis. The effect of local stress as noted by Wysession et al. (1995) might have contributed to the independence of Atlantic basin and Atlantic coast earthquake proximity from the MAR. The Latchman (2011) observation of strong earthquakes on a specific section of the MAR being followed by earthquakes on Trinidad and Tobago was tested on other areas of the MAR and ACM. It was found that that the temporal delay observed by Latchman does not exist for the seismicity along other areas along the MAR and ACM. Within the time window used for this study, it appears that seismicity is occurring randomly in space away from the MAR. The weak anticorrelations between ACM and MAR seismicity show that the ridge push force probably has some level of influence on the ACM seismicity. However, as revealed from previous research on the study area, the forces resulting from lateral density contrasts related to topographic features and lateral density variations between oceanic and continental crust also appear to significantly influence the seismicity of the Atlantic coastal margins. / Thesis (MS) — Boston College, 2015. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Geology and Geophysics.

In thin-film mixtures of alcohol and water, differences in evaporation rates and surface tensions between the two liquids can cause what is known as Marangoni convection within the fluid. This can lead to the formation of interesting instabilities on the surface of the film, such as the commonly observed “wine tears” phenomenon. Similar instabilities are observed when an inclined plate is immersed in a water alcohol reservoir. In addition to the tears, small ridges can be observed where the thin-film along the side of the plate rejoins the larger reservoir. These ridges slowly drift to the side and merge with other ridges, coarsening into larger ones. Using lubrication theory, Hosoi and Bush developed a one-dimensional model of the ridge instability which takes into account gravity, capillarity and Marangoni stresses at the surface of the film and results in a fourth-order non-linear partial differential equation describing the height of the ridges as a function of time and position along the plate. Two different but complementary numerical models were implemented to solve their equation. Both models are able to show development of ridges from random initial conditions as well as lateral ridge movement and coarsening. In addition to the numerical approaches some analysis was done on the equation to gain further insight into the nature of the ridge coarsening.

Recent high-resolution seismic imaging has allowed detailed reconstruction of the relationship between fold development and crestal faulting of the Chinook and Cascade folds in the deepwater Gulf of Mexico. Using 3-D seismic and biostratigraphic data, we have found that (1) short wavelength (~2300m), small amplitude folds (~540m) within the upper Cretaceous and upper Jurassic stratigraphic sequences took place no later than the late Jurassic, (2) large wavelength and amplitude fold growth, starting in the early Cretaceous, was produced by salt withdrawal, and (3) periods of increased sedimentation, fold growth, and fault slip occurred during the middle Miocene and late Miocene. Although the dominant stage of long wavelength, large amplitude fold growth started around early Cretaceous, the development of the Cascade and Chinook structures was continuous, punctuated by episodes of accelerated growth during the middle Miocene at rates of 337 and 235 m/Ma in the Cascade and 203 and 230 m/Ma in the Chinook. A later event of accelerated growth occurred during the late Miocene at rates of 1038 m/Ma in the Cascade and 1189 m/Ma in the Chinook. Accompanying fold growth was sedimentation, which was highest at 1949 m/Ma in the Cascade and 2585 m/Ma in the Chinook. Although limb tilt rates varied through fold growth, the highest rates also occurred during the middle Miocene at 0.330 and 0.196 degree/Ma for the Cascade and Chinook, respectively with the development of crestal faults at maximum slip rates of 88 and 90 m/Ma.

Abstract We use InGaAlAs and InGaAsP as materials of 1.55mm multi-quantum-well spot-size converter ridge waveguide lasers. On lateral conversion, we fabricate a taper ridge waveguide. On vertical conversion, we add guard layers on each side of active layer. For InGaAlAs ridge waveguide lasers, simulation results show a far field 16o ¡Ñ 27o¡]lateral ¡Ñ vertical¡^at guard layer width S = 0.1 mm with 300-150-50 mm narrow-tapered waveguide structure. Due to large Zn background contamination in the MOCVD growth chamber, we did not fabricate the InGaAlAs lasers successfully. For the InGaAsP ridge waveguide lasers, we measure a far field 18o ¡Ñ 28o and a threshold current 23 mA for the 200-250-50 mm narrow-tapered waveguide structure; a far field 20o ¡Ñ 26o and a threshold current 22 mA for the 200-250-50 mm wide-tapered waveguide structure.

Carnegie Ridge is a prominent bathymetric feature of the Gal??pagos Volcanic Province originated from the interaction of the Gal??pagos Hot Spot and the Cocos - Nazca Spreading Center. Our present knowledge regarding its crustal structure is limited to ridge transects along which wide-angle refraction seismic experiments have been conducted. In this study, the long-wavelength crustal structure of Carnegie Ridge between ~81?? W and 89?? W was determined by employing 2-D forward gravity modeling as the primary analytical technique. Model structures were built by assuming Airy isostasy and crustal layers of constant density. The geometry and density structure of the thickened oceanic crust beneath the ridge was constrained based on available seismic velocity models. Except for regions near the Ecuador Trench, the gravity modeling solution along the different transects examined in this study accounted adequately for the observed gravity anomaly field over the ridge. Crustal overthickening mainly accommodated in oceanic layer 3 and the asymmetry of the crustal root geometry characterize the estimated long-wavelength crustal structure. The asymmetry on eastern Carnegie Ridge is thought to be related to a ridge-related rifting whereas the origin and nature of that estimated on western Carnegie Ridge remain uncertain. Crustal volume fluxes were calculated at Carnegie Ridge and the Gal??pagos Archipelago, and at Cocos Ridge in order to explain the along-axis variations of the estimated crustal thickness. Along-axis crustal thickness variations on eastern Carnegie Ridge, and the formation of its bathymetric saddle were found to be related to the decline in the total volume output of the Gal??pagos Hot Spot. According to my results, this decay started soon after the spreading center shifted to the south of the hotspot (i.e., ~15 Ma) and continued for ~4.5 m.y. Since ~10 Ma the volume output of the GHS started to increase again, giving rise to the formation of western Carnegie Ridge and the Gal??pagos Archipelago. This increase continued until ~2 Ma, when the hotspot intensity started a new decrease that continues until the present time.

Thesis (M.S.)--Northern Michigan University, 2009. / Bibliography: leaf 79.

The interaction of tidal currents with Fraser Ridge in the Strait of Georgia, B.C., generates an internal lee-wave on each strong flood but, due to the ridge's asymmetry, not during ebbs. Just prior to lee-wave formation, a strong accelerated bottom jet forms with magnitudes up to 0.7 m s^-1 forms during barotropic tidal flows reaching 0.2 m s^-1. On the steepest slope, this jet forms directly above a rare glass sponge reef, and may prevent the sponges from being smothered in sediment by periodically resuspending and carrying it away. Both the accelerated jet and lee-wave remove tidal energy. At peak flood tide, the lee-wave has energy dissipation rates reaching 10^-5 W kg^-1 that removes energy at a rate of ~611 W m^-1, while the bottom boundary layer at the time of the accelerated jet has energy dissipation rates reaching 10^-4 W kg^-1 that removes energy at a rate of ~525 W m^-1. / Graduate

Thesis (Ph. D.)--University of Hawaii at Manoa, 1995. / Includes bibliographical references (leaves 77-86). / Microfiche. / ix, 86 leaves, bound ill. (some col.) 29 cm

An unusual turtle fauna from Lightning Ridge, New South Wales (Albian) reveals that Australian turtles had a more extensive Mesozoic history than previously indicated. Reevaluation of several primitive groups provides novel information on turtle evolution in the southern hemisphere. Seven turtle taxa are identified at Lightning Ridge. Two are Testudines indet. and two indeterminate chelid groups are evinced by isolated elements. Three new taxa are assigned to the new family Spoochelyidae in the superfamily Meiolanoidea. Spoochelys ormondea n. fam., gen. et sp., Sunflashemys bartondracketti n. gen. et sp. and Opalania baagiwayamba n. gen. et sp. are predominantly land-living turtles with high-domed shells and short manus and pes. The sister-group relationship with the Meiolaniidae, supported by a suite of cranial and postcranial synapomorphies, increases the stratigraphic range of the horned turtles by around ~ 50 my. Primitive structures in Spoochelys (postparietal, supratemporal and interpterygoid vacuity), occur with derived features that are variably developed across Triassic and Jurassic turtles. Phylogenetic analysis precariously resolves the meiolanoids as sister group to a clade containing Palaeochersis and Proterochersis. Limited pleurodiran attributes suggest that meiolanoids may be pleurodiromorphs, closer to primitive pleurodires than to cryptodires. As basal ‘side-necked’ turtles, the Lightning Ridge meiolanoids permit first insights into cranial and postcranial progressions in pleurodiran stem taxa. Evidence of diverse meiolanoids in Early Cretaceous Australia and ancient radiations of meiolanoid-like turtles in southern Pangea, suggest that the horned turtles are a Triassic group and that the dichotomy between Pleurodira and Cryptodira occurred well before the Late Triassic. Early Cretaceous chelids at Lightning Ridge occur at higher palaeolatitude than in South America. The temporal range of Australian chelids is extended by ~ 50 my, demonstrating that chelids had a Jurassic history in Australia, with broad diversifications across the polar supercontinent. The palaeoecological setting of Lightning Ridge is comprehensively described for the first time. Diverse invertebrates and vertebrates include terrestrial, freshwater aquatic and rare marine forms that are anomalous at this near-polar palaeolatitude (~65-70oS). The anachronistic occurrence in Early Cretaceous Australia of distinctive radiations of ‘Triassic-type’ turtles, and other relic groups, implies prolonged intervals of biogeographic isolation in the eastern provinces of Pangea.

An unusual turtle fauna from Lightning Ridge, New South Wales (Albian) reveals that Australian turtles had a more extensive Mesozoic history than previously indicated. Reevaluation of several primitive groups provides novel information on turtle evolution in the southern hemisphere. Seven turtle taxa are identified at Lightning Ridge. Two are Testudines indet. and two indeterminate chelid groups are evinced by isolated elements. Three new taxa are assigned to the new family Spoochelyidae in the superfamily Meiolanoidea. Spoochelys ormondea n. fam., gen. et sp., Sunflashemys bartondracketti n. gen. et sp. and Opalania baagiwayamba n. gen. et sp. are predominantly land-living turtles with high-domed shells and short manus and pes. The sister-group relationship with the Meiolaniidae, supported by a suite of cranial and postcranial synapomorphies, increases the stratigraphic range of the horned turtles by around ~ 50 my. Primitive structures in Spoochelys (postparietal, supratemporal and interpterygoid vacuity), occur with derived features that are variably developed across Triassic and Jurassic turtles. Phylogenetic analysis precariously resolves the meiolanoids as sister group to a clade containing Palaeochersis and Proterochersis. Limited pleurodiran attributes suggest that meiolanoids may be pleurodiromorphs, closer to primitive pleurodires than to cryptodires. As basal ‘side-necked’ turtles, the Lightning Ridge meiolanoids permit first insights into cranial and postcranial progressions in pleurodiran stem taxa. Evidence of diverse meiolanoids in Early Cretaceous Australia and ancient radiations of meiolanoid-like turtles in southern Pangea, suggest that the horned turtles are a Triassic group and that the dichotomy between Pleurodira and Cryptodira occurred well before the Late Triassic. Early Cretaceous chelids at Lightning Ridge occur at higher palaeolatitude than in South America. The temporal range of Australian chelids is extended by ~ 50 my, demonstrating that chelids had a Jurassic history in Australia, with broad diversifications across the polar supercontinent. The palaeoecological setting of Lightning Ridge is comprehensively described for the first time. Diverse invertebrates and vertebrates include terrestrial, freshwater aquatic and rare marine forms that are anomalous at this near-polar palaeolatitude (~65-70oS). The anachronistic occurrence in Early Cretaceous Australia of distinctive radiations of ‘Triassic-type’ turtles, and other relic groups, implies prolonged intervals of biogeographic isolation in the eastern provinces of Pangea.