To see the other types of publications on this topic, follow the link: At St. Helena.
Dissertations / Theses on the topic 'At St. Helena'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'At St. Helena.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Manyakanyaka, Anathi. "The variability of retention in St Helena Bay." Master's thesis, University of Cape Town, 2020. http://hdl.handle.net/11427/32519.
Full textAbstract:
The circulation in St Helena Bay and the variability of the retention of the Bay are investigated using seasonal climatologies of the Regional Ocean Modelling System (ROMS). While retention has been studied biologically, the seasonality of the hydrodynamics contributing to the retention have received less attention. In this study we explore how the sea temperature, atmospheric forcing and currents contribute to the seasonal recirculation dynamics in St Helena Bay. Ichthyop, a lagrangian particle tracking method is used to study the spatial variations of local retention rates, with the particles released from the Bay. The circulation on the shelf of the west coast is dominated by upwelling dynamics with the equatorward boundary current, the Benguela Current located just off the shelf. St Helena Bay is protected from the direct impact of the Benguela current by coastal geographical features. A cyclonic circulation pattern is observed in the bay especially in autumn and winter. However, the results suggest that the recirculation patterns are prominent in summer and spring due to the intensification of the Benguela Jet and the nearshore southward current flows along the coast. Similar cyclonic features are observed at 100 m depth in the water column. An analysis of the particle tracking reveals that more drifters are retained in winter than in summer, supported by what is observed in the circulation patterns. Moreover, more drifters are retained in the surface waters than the deep waters.
2
Chaffey, David John. "Characterisation of ocean island basalt sources : St. Helena." Thesis, University of Leeds, 1988. http://etheses.whiterose.ac.uk/625/.
Full textAbstract:
The extrusive and intrusive members of the St. Helena rock suite (SHRS) are formed in an intra-oceanic plate tectonic setting as part of two shield volcanoes. The SHRS vary from picrobasalts to phonofites. The former represent mantle derived melts, whereas the remainder of the suite have undergone differing degrees of crystal fractionation. A stratigraphic framework is developed to illustrate temporal geochemical variations over 2 Ma of subaerial activity. This is accomplished in conjunction with a detailed field study of the SHRS by Baker(1968) which is shown to be largely accurate. It is demonstrated that ascending magma batches are substantially modified by crystal fractionation and subsequent alteration processes. Petrogenetic modelling shows that the genesis of the SHRS is consistent with small degree (1-10%) melting of an olivine - clinopyroxene - orthopyroxene - garnet source containing a residual K-rich phase. Combined Sr-Nd-Pb isotope and fractionation corrected trace element data for fresh rocks enable consideration of changing thermal and chemical fluxes impinging on and interacting with the base of the lithosphere over a period of at least 2 Ma. The existence of two geochemically distinct components in the source region is indicated. A H/MU (high 238U /104Pb)c omponent has extremely radiogenic Pb isotopes (206Pb/104Pb> 20.8) with 143Nd/'44Nd and 87S8r,6 Sr displaced below the mantle array. The complementary depleted component has less radio genic Pb and Sr isotopic compositions and more radio genic Nd compositions. The limited variation of geochemical compositions in the SHRS (caused by mixing of these components) is attributed to the dissimilarity of the components in terms of their trace element abundance and their similarity in terms of ratios of highly incompatible elements. Coupled trace element and isotope variations are evident during the activity of each volcano. During shield development an increase in incompatible trace element enrichment occurs. This is coupled to a decrease in 143Nd/'44Nd, whilst Sr and Pb become progressively more radiogenic. The time dependent variations are thought to be consistent with mixing and melting processes occurring at the base of, or within the lithosphere. A decrease in the signature of the depleted component at the end of activity of the NE volcano and SW volcano is the inferred result of a decreasing thermal flux acting on the base of the lithosphere. With lower heat input less fusion of the depleted component (from the asthenosphere or lithosphere) occurs resulting in an increased H/MU signature in the erupted products through time. Previous explanations for the development of the dominant HIMU component are critically reviewed by considering shared isotope and trace element characteristics for HIMU OIB. U-Th-Pb systematics suggest the HIMU component has remained discrete from other mantle components for approximately 2 Ga. The fractionation event producing the H/MU component is shown to cause an increase in U/Pb and a decrease in Rb/Sr and Th/U.. This is thought to be consistent with a model suggested by Hofmann and White(1980,1982). in which HIMU represents ancient recycled altered oceanic crust. It is demonstrated that other models are less tenable. It is thought that the HIMU characteristics necessitate modification of oceanic crust in subduction zones in addition to the geochemical changes caused by hydrothermal alteration of oceanic crust.
3
Samuels, Damian. "Cape-Helena: An exploration of nostalgia and identity through the Cape Town - St. Helena migration nexus." University of the Western Cape, 2018. http://hdl.handle.net/11394/6542.
Full textAbstract:
Magister Artium - MA (History)In the following two chapters I will attempt to offer a more systemic account of St. Helena immigration to South African between 1838 and 1948. To date, no such study has been undertaken, despite a vibrant oral tradition amongst the descendants of St. Helena immigrants celebrating their St. Helenian heritage and often, in peculiar fashion, romanticise their Island of provenance. The commencement date for my chosen timeframe emerges from a need to authenticate rather tenuous historical accounts of St. Helena’s first mass emigration for the Cape of Good Hope in 1838. Where cases of migration are discussed, these are either incidences of large-scale 41, often aided, migration and settlement, or of those St. Helena migrant workers initially employed under temporary contacts to work in South Africa, specifically within burgeoning industrial sectors of the late-nineteenth or early-twentieth century South Africa.
4
Burns, Fiona E. "Conservation biology of the endangered St. Helena Plover Charadrius sanctaehelenae." Thesis, University of Bath, 2011. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.544502.
Full textAbstract:
Oceanic islands contribute significantly to global biodiversity due to the high levels of endemism they exhibit. Many island species have, however, become extinct following the arrival of humans, and many others remain threatened. This thesis focuses on one of these threatened island species; the St. Helena Plover, Charadrius sanctaehelenae. The objectives of my PhD were threefold: to understand the current status of the St. Helena Plover, to investigate aspects of its environment that may threaten its persistence, and to compare conservation options. Observational data were used to understand how variation in the environment influences the plover’s distribution and demography. This information was used to inform a controlled trial investigating the use of nest exclosures as a way to improve productivity. New understanding of the species’ population ecology was brought together to create a stochastic meta-population model. This model was used to understand the influence of demographic and life history parameters on the population growth rate and to compare alternative conservation options. Indicators of the future status of the St. Helena Plover population appear mixed; with numbers predicted to decline slowly, but with a high chance of species persistence over the timeframe simulated, 50 years. Nest predation by introduced species, predominately cats, was predicted to suppress nest survival and bring productivity at some sites below that required for population stability. The use of nest exclosures did not increase nest survival and led to a decrease in adult survival. Habitat characteristics were more important in determining the species distribution than influencing its demography. The plovers appeared to select breeding habitat to maximise the visibility from the nest and the accessibility of invertebrate prey. Simulations suggested that predator control would have a large beneficial effect on the population growth rate and that concurrent habitat improvement would have greater than additive benefits. Targets for conservation management include Deadwood Plain; predator control as this key site was predicted to lead to the largest increase in the overall population growth rate, and Man and Horse; there may be potential at this site to increase adult survival, which was found to be the most influential demographic parameter.
5
Eastwood, Antonia. "Evolution and conservation of Commidendrum and Elaphoglossum from St. Helena." Thesis, University of Edinburgh, 2002. http://hdl.handle.net/1842/13764.
Full textAbstract:
St Helena is an isolated volcanic island (lat. 15° 56'S, long. 5°42'W) in the South Atlantic Ocean. The endemic flora of St Helena, comprised of 49 plant species, is considered to be one of the most threatened in the world. This thesis investigates the evolution and conservation of two threatened groups of plants endemic to St Helena: i) trees in the genera Commidendrum and Melanodehdron (Asteraceae) and ii) epiphytic and terrestrial elaphoglossoid ferns in the genera Elaphoglossum and Microstaphyla (Lomariopsidaceae)Chapter two investigates species relationships of Commidendrum and Melanodendron using the ITS region of ribosomal DNA. Despite showing a range of morphological and ecological variation the four species of Commidendrum form a closely related monophyletic group. Melanodendron integrfolium is sister to Commidendrum indicating that the two genera evolved from a common ancestor which arrived to St Helena via a single dispersal event. The role of heterochrony in the evolution of Commidendrum is discussed. Chapter three investigates self-incompatibility and hybridisation in two of the most threatened Commidendrum species, C. rotundfolium and C. spurium. RAPD data indicated the presence of hybrids in the seed orchards of C. rotundfolium and C. spurium. Self-incompatibility in C. rotundfolium and C. spurium was investigated using a series of pollination experiments which examined pollen-stigma interaction at the stigma interface. Both C. rotundifolium and C. spurium possess a sporophytic self-incompatibility system, and poor seed viability in C. rotundfolium is due to a paucity of S-alleles. The conservations implications of this and interspecific hybridisation are discussed. Chapter four investigates the evolutionary relationships of the four elaphoglossid ferns, E. dimorphum, E. nervosum, E. conforme and M furcata from St Helena using sequences of the chloroplast trnL intron (partial) and trnL-F intergenic spacer. The investigation revealed the close relationship of E. nervosum, E. dimorphum and Mi furcata, whilst E. conforme was found to be distantly related. Microstaphyla furcata is shown to belong to Elaphoglossum confirming the previous transfer of this species to Elaphoglossum bfurcatum. Species relationships of the endemic Elaphoglossum, and the extent and distribution of population genetic diversity were investigated using allozyme analysis in chapter five. As well as supporting the relationships of the taxa in the molecular phylogeny, the allozyme data suggest a hybrid origin of E. dimorphum between E. nervosum and E. bfurcatum. In addition the allozyme data revealed significant genetic differentiation in populations of E. nervosum and E. bfurcatum which should be taken into consideration in any future conservation programme. To conclude, Chapter 5 is a general discussion on the evolution and conservation of island plants, highlighting my research findings from St Helena and comparing it to other studies.
6
Rowe, Rebecca E. "The population biology of Trochetiopsis : a genus endemic to St Helena." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308742.
Full text
7
Waldron, Howard Neil. "Influences on the hydrology of the Cape Columbine/St. Helena region." Master's thesis, University of Cape Town, 1985. http://hdl.handle.net/11427/21856.
Full textAbstract:
Bibliography: pages 92-101.The overall objective of the thesis is to investigate and interpret hydrological events occurring at the Cape Columbine upwelling site and the adjacent coastal waters, with special reference to St. Helena Bay. The first step in the study involves monitoring the meteorological occurrences which resulted in the prevailing hydrology and thus give a general background to the observed structure. It became necessary to establish two sub-systems in the area which can be distinguished on the basis of the time scales within which they operate. Generally speaking, outside St. Helena Bay the waters have a 3-5 day synoptic variability governed by meteorological conditions, but within the semi-closed system of the Bay itself a longer time span of around 25 days governs the processes in this separate but inextricably linked water body.
8
Schulenburg, Alexander Hugo. "Transient observations : the textualizing of St Helena through five hundred years of colonial discourse." Thesis, University of St Andrews, 1999. http://hdl.handle.net/10023/3419.
Full textAbstract:
This thesis explores the textualizing of the South Atlantic island of St Helena (a British Overseas Territory) through an analysis of the relationship between colonizing practices and the changing representations of the island and its inhabitants in a range of colonial 'texts', including historiography, travel writing, government papers, creative writing, and the fine arts. Part I situates this thesis within a critical engagement with post-colonial theory and colonial discourse analysis primarily, as well as with the recent 'linguistic turn' in anthropology and history. In place of post-colonialism's rather monolithic approach to colonial experiences, I argue for a localised approach to colonisation, which takes greater account of colonial praxis and of the continuous re-negotiation and re-constitution of particular colonial situations. Part II focuses on a number of literary issues by reviewing St Helena's historiography and literature, and by investigating the range of narrative tropes employed (largely by travellers) in the textualizing of St Helena, in particular with respect to recurrent imaginings of the island in terms of an earthly Eden. Part III examines the nature of colonial 'possession' by tracing the island's gradual appropriation by the Portuguese, Dutch and English in the sixteenth and early seventeenth century and the settlement policies pursued by the English East India Company in the late seventeenth and early eighteenth century. Part IV provides an account of the changing perceptions, by visitors and colonial officials alike, of the character of the island's inhabitants (from the late eighteenth to the early twentieth century) and assesses the influence that these perceptions have had on the administration of the island and the political status of its inhabitants (in the mid- to late twentieth century). Part V, the conclusion, reviews the principal arguments of my thesis by addressing the political implications of post-colonial theory and of my own research, while also indicating avenues for further research. A localised and detailed exploration of colonial discourse over a period of nearly five hundred years, and a close analysis of a consequently wide range of colonial 'texts', has confirmed that although colonising practices and representations are far from monolithic, in the case of St Helena their continuities are of as much significance as their discontinuities.
9
Van, Sittert Lance. "Labour, capital and the state in the St. Helena Bay fisheries c.1856 - c.1956." Doctoral thesis, University of Cape Town, 1992. http://hdl.handle.net/11427/21708.
Full textAbstract:
This thesis deals with the history of the St Helena Bay inshore fisheries, 1856-1956. Fishing has long been neglected by social and economic historians and the myths propagated by company and popular writers still hold sway. The thesis challenges these by situating commercial fishing at St Helena Bay in the context of changing regional, national and international economies and showing how it was shaped and conditioned by the struggle for ownership of the marine resource between labour and capital, mediated by the state. The thesis is organised chronologically into three epochs. In each the focus moves from macro to micro, tracing the processes of class formation, capital accumulation and state intervention. The first epoch (c.1856-c.1914) examines the merchant fisheries, the second (c.1914-c.1939) the crayfish canning industry and the third ( c.1939-c.195) secondary industrialisation. It is argued that the common property nature of the marine resource and non-identity between labour and production time in fishing created obstacles to capitalist production, discouraging investment and allowing petty-commodity production to flourish. The latter mediated the vagaries of production through a share system of co-adventuring which enabled owners to avoid paying a fixed wage. This system's impact on the nature and consciousness of fishing labour is examined as is its vulnerability to capture by other capitals through insecure land tenure and credit. Fishing capital, in both its merchant and productive guises was dependent on articulation with petty-commodity production to provide it with commodities or raw material and bear the cost of reproducing labour. Articulation was hampered at St Helena Bay both by the persistence of merchant capital and the rent and labour interests of Sandveld agriculture. The origins and effect of this situation on the fisheries is detailed and discussed, highlighting the importance of agricultural capital's political influence with the colonial and provincial state in blocking or subverting the development of productive capital. The advent of the interventionist central state in the 1930s undermined merchant and farmer dominance of the fisheries and cleared the way for the articulation of petty-commodity primary production with secondary industry during and after the Second World War. This articulation was facilitated by the central state restricting access to the marine · resource and investing heavily in marine research and infrastructure to roll-back the natural constraints on fishing and create the conditions for the establishment of a stable capitalist production regime.
10
Shultz, O. "An ethnography of St Helena Bay - A West Coast Town in the age of neoliberalism." Master's thesis, University of Cape Town, 2010. http://hdl.handle.net/11427/14266.
Full textAbstract:
This dissertation uses ethnography as a means to examine how multiple-scale patterns of interaction between social and ecological systems as they manifest locally in St Helena Bay. The growing integration of the West Coast has brought rapid change in the form of industrial production, urban development and in-migration. The pressure placed on local resources by these processes has been exacerbated by the rationalisation of the local fisheries - there are fewer jobs in the formal industry and small-scale fishing rights have become circumscribed. In the neighbourhood of Laingville, historically-contingent racial categories have become reinvigorated in a context resource scarcity. An autochthonous cultural heritage related to the West Coast has become transposed onto the category of 'real' or 'bona fide' fishers. For those who claim this identity, it serves as a means to legitimate claims to resources while simultaneously excluding the claims of others. A pattern of recurring dichotomies emerges as a defining motif capturing the sense among local people that threatening elements from 'outside' are imposing themselves on the local socio-ecology. For small-scale fishers, the lack of recognition by the state of what they believe is their autochthonous right to access to the marine commons feeds an intense sense of frustration. The act of breaking 'the rules' of the state is perceived by many as an assertion of their rights and thus, of their dignity. In the case of poaching, it is seen by fishers as a means to become an active agent in one's own life, while at the same time making more money than could be made if fishing rules were adhered to. Because of these powerful symbolic and material motivations for breaking the rules, it is something that many people take pride in doing. In contradistinction to this, following the rules of the state is seen as collaborating with the state in undermining one's own socio-economic conditions, and, significantly, in negating one's birthright. For many fishers in Laingville, adhering to the rules is infused stigma
11
Tukwayo, Philiswa P. "Temporal and spatial variability in a copepod community off St Helena Bay in 2000/1." Master's thesis, University of Cape Town, 2004. http://hdl.handle.net/11427/6204.
Full textAbstract:
Bibliography: leaves 34-39.The driving forces behind changes in copepod community structure in the Benguela upwelling region are examined. For this study, monthly changes in copepod size structure and species composition were examined at St Helena Bay in 2000/1 in relation to upwelling, phytoplankton and fish. The copepod assemblage was dominated by large species categories in the early period of recruitment (April) and smaller species categories in the late period of recruitment (August). The reappearance of large species categories and increase in copepod biomass is observed in summer months. This is attributed to both predation and upwelling intensity. Arguments are developed to suggest that the copepod size. structure is consistent with 'wasp-waist' control and 'bottom-up' control was responsible for the copepod increase.
12
Holden, Clive John. "Spatial and temporal scales of the coastal currents in the St. Helena Bay - Cape Columbine Region." Master's thesis, University of Cape Town, 1986. http://hdl.handle.net/11427/22335.
Full textAbstract:
Bibliography: pages 96-103.This thesis presents the results of a current meter experiment performed in the St Helena Bay - Cape Columbine region during winter 1982. The work, which forms part of the shelf dynamics programme undertaken by the Sea Fisheries Research Institute, attempts to identify the important time and spatial scales within the coastal currents and to investigate the relationship between the sub-inertial flow and low frequency variations in the coastal winds.
13
Mushanganyisi, Kanakana S. "Seasonal and spatial variability of pelagic fishes in relation to environmental variability in St Helena Bay." Master's thesis, Faculty of Science, 2019. https://hdl.handle.net/11427/31795.
Full textAbstract:
The St Helena Bay Monitoring Line (SHBML) stretches 197 nautical miles off Elands Bay on the west coast of South Africa. It is an extensive long term project on environmental monitoring, running from 2000 till 2012 on an almost monthly basis but currently running on a quarterly basis. It extends through the nursery grounds and part of the transport zone for hydrology and productivity in areas that are significant to early life history of small pelagic fish. Environmental, acoustic and zooplankton data have been collected along the SHBML to obtain information on ocean environment, pelagic fish abundance and also zooplankton abundance. This study used an interdisciplinary approach, analysing historical data collected during biannual surveys of small pelagic fish, to investigate seasonal and spatial variability of pelagic fishes in relation to environmental variability in St Helena Bay. Surface values from 2000 to 2010 of temperature, salinity, oxygen and chlorophyll were analysed in relation to zooplankton and fish densities. The results show partial / weak seasonality of SST in offshore and also in coastal stations. Zooplankton, chlorophyll and oxygen show limited seasonality only in nearshore stations. Strong cross-shelf patterns of SST, chlorophyll, salinity, oxygen, zooplankton biomass and fish abundance were noted. These were expected results from a coastal upwelling system where primary productivity during summer is increased in the nearshore zone. There was a positive relationship between salinity and SST (r = 0.821, p< 0.0001) and a negative relationship between chlorophyll and SST (r = -0.549, p< 0.001), as would be expected in a coastal upwelling environment. When other variables were examined (also in pairs), there were no relationships between SST and oxygen, fish and zooplankton, fish and chlorophyll, fish and SST, fish and oxygen, and chlorophyll and zooplankton. A GLM was fitted to the data to investigate the relationship of pelagic fish density with zooplankton biovolume, chlorophyll, SST and oxygen; the GLM results showed a negative relationship between zooplankton abundance and pelagic fish (t=-1.980, p=0.049). Based on these results, it appears that the SHBML data were not able to pick up seasonal signals but have shown interannual variability and also some inshore-offshore differences.
14
Crichton, Murray. "Are distinct particle spectra an indication of the state of the phytoplankton community in St Helena Bay?" Master's thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/12104.
Full textAbstract:
Includes abstract.Includes bibliographical references.
The potential of phytoplankton particle spectra to be used as the basis for an indicator of the suitability of feeding habitat for fish recruits in the Southern Benguela was investigated. Phytoplankton samples collected on regular cruises on the St Helena Bay Monitoring Line (SHBML) off Elands Bay on the west coast of South Africa had been analysed with the Coulter Counter and formed the basis of this study. Chlorophyll a content of phytoplankton samples was also measured on monthly cruises and with total particle concentration (determined by the Coulter Counter) showed that overall phytoplankton cells represented a significant portion (76%) of samples collected. Surface particle spectra were constructed for the 12 stations on the SHBML for each of 15 monthly cruises between September 2000 and February 2007.
15
Essex, Corinda Sebastiana Stuart. "Class teacher attrition : an investigation of self-reported job satisfaction and commitment amongst teachers on St. Helena island." Thesis, University of Bristol, 2000. http://hdl.handle.net/1983/9d4b9539-742e-4735-8371-7919c8ad045a.
Full textAbstract:
This study investigated levels of job satisfaction and commitment reported by the population of class teachers on St. Helena Island (N = 76), and was set in the context of burgeoning turnover that threatens local educational provision. It explored possible determinants, correlates and implications of these constructs and their interrelationship, drawing comparisons with findings from other cultural environments. The investigation aimed to obtain high quality data that could inform policy decisions designed to reduce attrition, and to test established theories relating to job satisfaction and commitment within a small, developing state setting. A model of possible influences upon the constructs in question and their effect upon career decisions was developed. A three-phase research design was used, involving both qualitative and quantitative approaches to data collection. A purpose-built survey instrument, containing both scale and open-ended items, was constructed and administered. Non-participant observations and interviews were also undertaken. The findings reveal that although most St. Helenian class teachers were moderately satisfied with their jobs and committed to these, all found certain aspects of their role dissatisfying, and a quarter (N = 19) wished to cease teaching. Job satisfaction and commitment were found to possess a weak, positive relationship. Significant differences existed between responses of class teachers within different school sectors, and of those having disparate lengths of teaching experience. These appeared influenced by contextual and personal demographic factors. Similarities between challenges and constraints facing local class teachers and those in both developed, and other developing, states emerged strongly. Emanating from the results, recommendations for changes at strategic and operational levels that may reduce class teacher attrition were formulated, and areas for further research identified. The investigation, thus, sheds light upon the job satisfaction and commitment of St. Helenian class teachers and contributes to international literature pertaining to the theoretical aspects of these constructs
16
Schultz, Oliver John. "Belonging to the West Coast : an ethnography of St Helena Bay in the context of marine resource scarcity." Master's thesis, University of Cape Town, 2010. http://hdl.handle.net/11427/13040.
Full textAbstract:
Includes bibliographical references (leaves 87-96).This dissertation uses ethnography as a means to examine how multiple-scale patterns of interaction between social and ecological systems as they manifest locally in St Helena Bay. The growing integration of the West Coast has brought rapid change in the form of industrial production, urban development and in-migration. The pressure placed on local resources by these processes has been exacerbated by the rationalisation of the local fisheries - there are fewer jobs in the formal industry and small-scale fishing rights have become circumscribed. In the neighbourhood of Laingville, historically-contingent racial categories have become reinvigorated in a context resource scarcity.
17
Ismail, Hassan Ebrahiem. "Seasonal variability and the relationship between dissolved inorganic nutrients and selected environmental parameters inshore and offshore of St. Helena Bay." Thesis, Cape Peninsula University of Technology, 2017. http://hdl.handle.net/20.500.11838/2550.
Full textAbstract:
Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2017.The purpose of the present study was to apply data collected monthly over a 6-year period along the almost 200 km long St. Helena Bay Monitoring Line in the Southern Benguela upwelling system to investigate co-variation between an upwelling index calculated from nearby wind records and physical and chemical properties along the transect. The extent to which the well-documented seasonal upwelling cycles is manifested at the surface along an inshore-offshore variation was investigated in the context of implications for the validity of remote sensing as a monitoring tool in this ocean area and to improve understanding of the physical drivers of biological processes in St. Helena Bay. This study shows that surface temperature and nutrient concentrations exhibit very poor seasonality and weak correlation with the upwelling index. This is, despite clear evidence for spatial inshore-offshore gradients in temperature, nutrients, and chlorophyll-a, consistent with an upwelling regime. The upper ocean temperature gradient shows a much better correspondence to the upwelling index but at the same time demonstrates that surface heating, and not vertical mixing related to upwelling, controls the upper ocean temperature gradient. In this study linear lagged correlations were also examined and discussed to gain insight into the effect upwelling has on the surface waters in St. Helena Bay with the view of determining the following: (1) Does upwelling lead to an increase or decrease of the water properties? (2) What is the characteristic lag between an upwelling event and its effect on these water properties? (3) Is the effect and/or lag different for the different seasons? and (4) Is the effect and/or lag different for stations inside the bay and those outside the bay?. A combination of surface turbulent cooling through upwelling occurred after a lag of 8 to 10 days in winter and early summer, but less than half in late summer, similar to results obtained with salinity. However, the rest of the salinity results fit in poorly with the temperature results. The only significant correlation obtained with the inshore stations during late summer is the inexplicable positive correlation at a lag of 7 days. For all three seasons virtually none of the oxygen results fit the expected pattern. All three nutrients showed a more positive correlation coefficient and significance than the negative ones. Significant negative correlations occurred mainly during late summer at lags of 7 to 9 days caused by planktonic depletion of nutrients. Also, in this season, significant positive correlations between south-north wind and nutrients only occurred at short lags. This observation supports the earlier temperature-based conclusion that the influence of upwelling develops most rapidly at this time of the year. A rapid increase in chlorophyll-a levels followed by nutrient enrichment of the surface layers are evident. iii The results suggest that remote sensing techniques would be inadequate tools to monitor upwelling events in the Southern Benguela. Secondly, the incidence of phytoplankton blooms is more likely triggered by stratified conditions associated with surface heating than relaxation of upwelling winds. Finally, these results also emphasise the importance of validating lagged outputs against real-time measurements in supporting a simpler hydrological model in narrowing down these significant uncertainties.
18
Crom, Helena [Verfasser], Hans-Joachim [Gutachter] Trappe, and Christian [Gutachter] Perings. "Haarcortisol als chronischer Stressparameter bei Patienten mit akutem ST-Strecken-Hebungsinfarkt / Helena Crom ; Gutachter: Hans-Joachim Trappe, Christian Perings ; Medizinische Fakultät." Bochum : Ruhr-Universität Bochum, 2020. http://d-nb.info/1214443141/34.
Full text
19
Rose, Juliet. "The Role of Strategic Partnerships, Policy and Funding Mechanisms in Strategic Management Planning for the Crown Wastes on St Helena Island, South Atlantic." Thesis, University of Reading, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485348.
Full textAbstract:
St Helena in the South Atlantic has undergone centuries ofdegradation, followed by decades ofunmanaged re-vegetation. The island's landscape is dominated by the Crown Wastes: wastelands ofbare soil and sparse mainly exotic scrub which accounts for over 60% ofthe island's land area. The Crown Wastes need a managed recovery programme that can meet the island's needs through a range ofdifferent objectives that include endemic plant conservation, agriculture, forestry, tourism and housing. Implementing an environmental management approach with complex and varied objectives carnes with it a considerable management responsibility, and a requirement for sufficient and consistent technical, financial and human capacity. However, extremely limited hmnan, technical and financial resources are available for environmental management on St Helena due a range ofpolitical, social and economic issues associated with the island. This study looks specifically at three ofthe obstacles integral to effective environmental management and recovery on St Helena and the Crown Wastes in particular: b~ding capacity; resources; and guidance and explores the role ofstrategic partnerships. (Government and NGO), funding and policy mechanisms in helping to overcome them. These three areas are explored uSing a combination ofstakeholder and documentary analysis methodologies. A semi-structured interview technique was chosen for stakeholder consultation and the results displayed as role- and conceptually-ordered matrices.This study concludes that while the island faces a complex range of challenges to environmental management, there is a no less daunting array ofopportunities that will require considerable effort to-exploit effectively. Strategic partnerships, policy and funding mechanisms all have specific and important roles to play in the development ofa . strategic environmental management plan for the Crown Wastes.
20
Grove, R. "Conservation and colonial expansion : a study of the evolution of environmental attitudes and conservation policies on St. Helena, Mauritius and in India, 1660-1860." Thesis, University of Cambridge, 1988. https://www.repository.cam.ac.uk/handle/1810/272256.
Full textAbstract:
The approach adopted in this thesis is essentially chronological. The first chapter aims to provide a fairly superficial survey of the development of European perceptions of the environment in the early phases of mercantilist expansion, before much in the way of colonial settlement was undertaken. It highlights the connections between expansion and changes in perception with regard to the symbolic importance of islands, botanic gardens and early state responses to timber shortage. It also draws attention to the importance of medical perceptions of the extra-European environment. In the second chapter a comparison is drawn between Dutch and English approaches to the tropical environment in the early years of expansion. Considerable space is devoted to the case of St Helena. This is because it was the first location in which European colonists first acquired a notion of the full environmental implications of their rule and for which detailed documentary evidence is available. The story of the developing ecological crisis on St Helena emphasises how inadequate European precedents were in the encounter between the early colonial state and the tropical environment. It demonstrates, too, the early divergence in perceptions between colonists and the metropolitan power. Early attempts at counteracting the process of ecological deterioration on St Helena underlined the contradictions between the European image of the tropical island and the reality of capital investment in plantation agriculture and 'improvement'. The experience of St Helena was also important in a longer-term way. Many scientists important in the later development of conservation ideas in other parts of the world were specifically influenced by their knowledge of the problematic history of land-use on St Helena and the attempts made there to impede ecological degradation. These included Alexander Beatson, J.R. Forster, Joseph Hooker, F.A. Dalzell and G.P. Marsh. In the third chapter much attention is devoted to the history of eighteenth century Mauritius, partly for comparative purposes and partly to emphasise the attitude of the French state to scientific information and its greater readiness to intervene in environmental matters. The development of an environmental consciousness on Mauritius was significant both as a phenomenon on its own and because of the example which it set. The role of the colonial government naturalist was pioneered there. Concepts of species extinction also emerged clearly, for the first time, on Mauritius and the island also saw the emergence of a legislative conservation policy rooted in a desiccation theory which linked deforestation and soil erosion to hydrological and climatic conditions. Notions of environmental moral economy and the significance of the tropical island are also explored in the chapter, in the context of the emergence of pre-Revolutionary radicalism, Physiocracy and early Romantic thinking. Chapter Four attempts to deal in some depth with the intellectual background to the early nineteenth century response of the British to ecological change in India. The importance of German science and a German 'romanticist' critique of ecological change is outlined and some emphasis is given to the emergence of a 'global' approach to the interactions between people (especially Europeans) and the environment. In particular the significance of the intellectual links between the Cook Voyages and the careers of J.R. Forster, Sir Joseph Banks and Alexander Von Humboldt is stressed. A beginning is also made in the task of surveying the way in which German professional naturalists and doctors deliberately sought out British colonial employ, a phenomenon that was to be important in the emergence of state conservation in India, the Cape, Australia and in other colonies. The chapter makes clear the continuing importance of small island environments during the nineteenth century in stimulating an awareness of environmental vulnerability, particularly for Alexander Beatson, William Burchell and J.B. Boussingault.
21
Fawcett, Alexandra. "Multi-sensor mooring development and its use to characterise physical processes relevant to harmful algal bloom dynamics in the St Helena Bay area, South Africa." Master's thesis, University of Cape Town, 2006. http://hdl.handle.net/11427/6470.
Full textAbstract:
Word processed copy.Includes bibliographical references.
Harmful algal blooms (HABs), typically attributed to dinoflagellate species, occur along the west coast of South Africa, particularly during the latter part of the upwelling season. As part of the Benguela Current Large Marine Ecosystem (BCLME) programme, a buoy has been developed locally for monitoring the development and occurrence of HABs. The mooring is situated three and a half kilometres offshore from Lambert's Bay, downstream from the Cape Columbine upwelling cell, on the west coast of South Africa, and collects high frequency time series data, available in real time. The instrument package on the buoy provides bio-optical data analogous to remote sensing reflectance, temperature and current profile data, and fluorescence. The locally developed mooring and observing system is the only real-time, bio-optical mooring in southern Africa. Its development, and configuratoin of the instruments, data collection and telecommunications systems, are fully documented in this thesis.
22
Russell, Daniel Lee Jr. "The development of New Life Christian Academy: a resourceful K-5 to twelfth grade christian school established in a rural setting on St. Helena Island, South Carolina." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2013. http://digitalcommons.auctr.edu/dissertations/2782.
Full textAbstract:
This dissertation will address the implementation of New Life Christian Academy (NLCA), a Christian Education School, produced out of New Life Deliverance Temple (NLDT), in St. Helena Island, South Carolina. The desire was to target students who have a desire in educational and spiritual achievements regardless of race, creed or religion. Parents who have become disillusioned with the Beaufort County public school system will be presented the progress of the current students at NLCA, who have transferred from the public school setting. The researcher founded the school by merging a homeschool run by a parent of NLDT and a new school which had never been operational. The advantage the researcher has concerning this project is that he was responsible for the grassroots implementation orchestrating every step from changing the county code allowing a school to locating modular buildings to house the school.
NLDT is not considered a ‘mega ministry’ (2,000 or more membership) nor is the church located in a major metropolis, but on a dirt road in a rural section of St. Helena Island. Though the church possessed meager funds, this lack of capital did not prevent the pursuit of building a Christian school on church property. The researcher formed a board to assist in searching for rules and regulations so that the school will be in compliance. The first teacher hired by NLCA was Mrs. Mary Bolles who started her homeschool and was very well versed in Christian and secular education. NLCA has formed relationships between parent, teacher and student resulting in increased communication. The empirical data to assist in developing the foundation for the school will include: (a) Surveys conducted showing how the children have transitioned into the Christian/ Secular educational setting, (b) Showing how other Christian Schools operate within Beaufort Schools, (c) Data which will confirm the weaknesses of area county schools, and (d) surveys which will aid in satisfying the needs of students, staff and parents.
Theologically, the Biblical basis for the school was discovered in Daniel the first chapter, showing four youths who had been forcibly removed from their native land and were successful in enemy territory, not compromising their Jewish values. The objective remains to parallel this Biblical past into a current motif which will allow the student to experience holistic curriculums of education, enabling them to meet life’s challenges, utilizing a Christian perspective.
23
Toefy, Rashieda. "Extant benthic Foraminifera from two bays along the SW coast of South Africa, with a comment about their use as indicators of pollution." Thesis, University of the Western Cape, 2010. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_8713_1307079132.
Full textAbstract:
The results of the multivariate analyses suggest that most of the variation in the composition of the samples was of an intra-sample nature, illustrating large scale patchiness in foraminiferal distribution. There were, however, definite differences between communities around Robben Island and in St Helena Bay, and least variation was found between the control and pipeline sites, and between the stations of each site. When the trace metal concentrations and the percentage nitrogen increased, the richness, diversity and abundance of foraminifera tended to decrease. Sediment grain size positively affected abundance but negatively affected diversity and richness. In both areas mean grain size did not, however, appear to play a very large role in influencing diversity. Cadmium, copper, chromium, the percentage nitrogen and the mean grain size were identified as the most important variables influencing the community structure by the BIOENV BEST routine in PRIMER. The trace metals and percentage nitrogen only had negative effects on the diversity and abundance as well as on the abundance of the dominant genera, whereas the mean grain size had variable effects.
24
Baker, Cynthia Fay. "Phytoplankton in Mt. St. Helens Lakes, Washington." PDXScholar, 1995. https://pdxscholar.library.pdx.edu/open_access_etds/5017.
Full textAbstract:
Phytoplankton communities in fifteen lakes in the Mt. St. Helens area were surveyed to assess the abundance and species present. Eleven of the lakes were inside the blast zone of the 1980 eruption and four were located outside the blast zone as a comparison. The hypothesis is that lakes will cluster together based on the algal species present and that some algae will be correlated with certain environmental conditions. A cluster analysis was performed to determine if the lakes would group together based on algal abundance. There did not appear to be any distinct clustering among the study lakes, but this analysis did help to sort out some similarities of algal species present between lakes. It demonstrated that the lakes outside the blast zone were not functional as control lakes because they were very different from the blast-zone lakes. They had different assemblages of algae and their origin was so different from the blast-zone lakes that there was little overlap between them. The factor analysis was applied to determine the relationships between environmental variables and phytoplankton. The hypothesis is that certain algae are associated with each other and with identifiable environmental factors. Factor analysis should detect these patterns. The factors represent some condition in the environment but the analysis would be virtually meaningless unless these conditions can be recognized and the factors named. From the factor analysis alone, I could not name the factors but returned to the task after the canonical correlation analysis was performed. The canonical correlation analysis gave some clues to identify the environmental conditions that exert control on these algae. The most useful statistical technique used in this study was the canonical correlation analysis. This analysis is a useful tool in community ecology studies where species-environment relationships can be inferred from community composition and environmental data. The environmental data used was nutrient and light attenuation present at the time the phytoplankton samples were taken. From this analysis I summarized a list of algae and with what environmental conditions that they are associated. Trophic state categories were assigned to the lakes from a trophic state index based on phytoplankton biovolume.
25
Spake, Phillip. "Geothermal Exploration North of Mount St. Helens." Master's thesis, Temple University Libraries, 2019. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/585881.
Full textAbstract:
GeologyM.S.
Active seismicity and volcanism north of Washington state’s Mount St. Helens provide key ingredients for hydrothermal circulation at depth. This broad zone of seismicity defines the St. Helens Seismic Zone, which extends well north of the volcanic edifice below where several faults and associated fractures in outcrop record repeated slip, dilation, and alteration indicative of localized fluid flow. Candidate reservoir rocks for a geothermal system include marine metasediments overlain by extrusive volcanics. The colocation of elements comprising a geothermal system at this location is tested here by analysis of the structures potentially hosting a reservoir, their relationship to the modern stress state, and temperature logs to a depth of 250 m. Outcrop mapping and borehole image log analysis down to 244 m document highly fractured volcaniclastic deposits and basalt flows. Intervening ash layers truncate the vertical extent of most structures. However, large strike slip faults with well-developed fault cores and associated high fracture density cross ash layers; vein filling and alternation of the adjacent host rock in these faults suggest they act as vertically extensive flow paths. These faults and associated fractures record repeated slip, dilation, and healing by various dolomite, quartz, and hematite, as well as clay alteration, indicative of long-lived, localized fluid flow. In addition, where these rocks are altered by igneous intrusion, they host high fracture density that facilitated heat transfer evidenced by associated hydrothermal alteration. Breakouts in image logs indicate the azimuth of SHmax in the shear zone is broadly consistent with both the GPS plate convergence velocity field as well as seismically active strike slip faults and strike-slip faults mapped in outcrop and borehole image logs. However, the local orientation of SHmax varies by position relative to the edifice and in some cases with depth along the borehole making a simple regional average SHmax azimuth misleading. Boreholes within the seismic zone display a wider variety of fracture attitudes than those outside the shear zone, potentially promoting permeability. Temperature profiles in these wells all indicate isothermal conditions at average groundwater temperatures, consistent with rapidly flowing water localized within fractures. Together, these results indicate that the area north of Mount Saint Helens generates and maintains porosity and permeability suggesting that conditions necessary for a geothermal system are present, although as yet no modern heat source or hydrothermal circulation was detected at shallow depth.
Temple University--Theses
26
Schneider, Andrew Daniel 1982. "Constraints on Eruption Dynamics, Mount St. Helens, WA, 2004-2008." Thesis, University of Oregon, 2009. http://hdl.handle.net/1794/10026.
Full textAbstract:
xi, 114 p. : ill. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.Different models have been proposed for the "drumbeat" earthquakes that accompanied recent eruptive behavior at Mount St. Helens. Debate continues as to whether seismicity is related to brittle failure during the extrusion of solid dacite spines or is the result of hydrothermal fluids interacting with a crack buried in the volcanic edifice. My model predictions of steady-state conduit flow confirm the strong control that degassing exerts on eruptive behavior. I discuss the necessary role of degassing for extruded material to attain the high density (low vesicularity) of the observed spine material and discuss the implications for generating seismicity. A brittle-failure source of seismicity requires that the gouge elastic properties accommodate some strain, since the magma compressibility in the upper conduit is too low to do so on its own. I also report on a novel method for generating high-resolution digital elevation models of fault surface textures.
Committee in Charge: Dr. Alan Rempel, Chair; Dr. Katharine Cashman; Dr. David Schmidt
27
Hall, Arthur Lewis. "The representation of aspects of Afrikaner and British masculinity in the first season of Arende (1989) by Paul C Venter and Dirk de Villiers : a critical analysis." Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/33360.
Full textAbstract:
This study performs a critical analysis of the representation of Afrikaner and
British masculinity in the first season of the South African War (1899-1902)
television series Arende (1989-1993). The study first identifies key concepts in
both western identity and masculinity and then moves on to build an historical
theoretical base from which season one is analysed. This theoretical base is
created through the assimilation of historical sources dealing with masculinity and
masculine events from both the Afrikaners and the British.
In order to provide a suitable foundation for the investigation into masculinity, the
study first briefly explores the concept of identity and how it manifests in both the
Afrikaner and British society represented in the first season of Arende. This was
done by using a psychological model designed by Roy F Baumeister (1986) which
involves both individual and societal identity. Identity as a social construct is also
investigated, and the question why identity matters in society is discussed
Arguments for a structuralist semiotic approach to identity in a particular society
are presented.
In dealing with the overview of dominant western masculinity a number of key
terms were identified and discussed. These include patriarchy, the female body
and masculine control, social labelling, gender order and ‘women watching,’ the
family unit, division of labour and public and private space, hegemonic masculinity
and the male hero. After this overview, the study conducted an assimilation
exercise into historic Afrikaner and British masculinity during the time before and
after the South African War. This discussion centres on a number of points
dealing with both societies, namely the model male, male military tradition,
masculine rebels/outcasts and other masculine issues, and male relations with
women.
The final part of this study involves the analysis of the masculine theory,
generated in the previous chapter, on the Arende text. This was done by selecting six characters from each of the two societies in season one and describing how
they represent themselves in a masculine manner (or not).Dissertation (MA)--University of Pretoria, 2013.
gm2014
Visual Arts
unrestricted
28
Berlo, Kim. "Time scales of magma evolution at Mount St. Helens." Thesis, University of Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432346.
Full text
29
Kelly, Valerie Jean. "Limnology of two new lakes, Mount St. Helens, WA." PDXScholar, 1991. https://pdxscholar.library.pdx.edu/open_access_etds/3576.
Full textAbstract:
Coldwater Lake and Castle Lake are two new lakes which were formed in the aftermath of the volcanic eruption of Mount St . Helens, WA in May, 1980. This research describes the limnology of these lakes ten years later, and includes physical, chemical, and biological parameters. The two lakes are compared and contrasted. Previous research on the eruption and its aftermath, as well as earlier studies of the lakes are described.
30
Scharnberg, Larry Duane. "Zooplankton Community Structure in Lakes Near Mt. St. Helens, WA." PDXScholar, 1995. https://pdxscholar.library.pdx.edu/open_access_etds/5050.
Full textAbstract:
Eighteen lakes around Mt. St. Helens (MSH) were sampled for zooplankton from September '92 until September '94. Samples were enumerated and identified to the species level in most cases. Standard deviation and t-tests were performed to determine the precision of enumeration methods and replication of duplicate tows. Palatability indexes based upon predator preferences were developed and coupled with length-frequency analyses as indicators of predation pressure. The weighted means of the summer samples were then subjected to cluster analysis in an attempt to categorize lakes with respect to zooplankton community structure. Lastly, the community compositions and abundances of MSH lakes were compared to those in lakes on Mt. Rainier and Mt. Hood in an attempt to assess recovery of MSH lakes from the 1980 eruption. Results of analyses indicate the presence of three distinct groups of lakes: 1) A group of lakes with heavy predation resulting in simplified zooplankton communities dominated by Keratella, Ke/licottia, and sometimes cyclopoid species. Predation in these instances can be attributed to extremely high fish or Chaoborus abundance. 2) A second group of lakes characterized by great depth, high transparency, significant abundances of Diaptomus kenai, and moderate to light fish predation. These lakes support balanced zooplankton communities with substantial proportions of Daphnid and calanoid specimens attaining large size. Significant indications of size-specific niche differentiation among the cladocerans are notably absent from these first two groups. 3) A third group consists of lakes which appear to be more productive than the other two groups. This group has higher biovolumes of zooplankton in general, coexistence of several different sized cladoceran species, the highest diversity indices of all the lakes sampled, and moderate predation as indicated by length-frequency analysis. Two conclusions are drawn from the data. First, it appears that predation and primary productivity are both significant factors affecting the abundance and composition of MSH zooplankton communities. Additionally, these data document a significant overlap in zooplankton species in lakes near Mt. Rainier and Mt. Hood, suggesting that the zooplankton communities in lakes around MSH have recovered from the effects of the 1980 eruption.
31
Menting, Victor Lee. "The Biogeochemistry of Lakes in the Mount St. Helens Blast Zone." PDXScholar, 1995. https://pdxscholar.library.pdx.edu/open_access_etds/4927.
Full textAbstract:
Dilution and ash weathering are the most important processes controlling the ion chemistry of lakes in the Mount St. Helens blast zone. Gibbs' models indicated total dissolved solids were decreasing as a result of dilution from high precipitation and runoff and the lakes plot in the rock weathering dominated region. Plots of theoretical dilution curves indicated a decline in ion concentrations as a result of dilution. Ion concentrations followed the exponential decline predicted by the dilution curve, although concentrations were higher than predicted by the curve. Increased concentrations were a result of the rapid weathering of ash in basins and on lake bottoms. Rapid weathering of ash in lake watersheds and on lake bottoms continues to influence the ionic concentrations of the lakes. In general, sodium and potassium have declined at a much faster rate than calcium or magnesium. Slower relative declines in concentrations of calcium and magnesium were a result of more rapid rate of leaching of calcium and magnesium from the ash. Ash in the watersheds will continue to be a major contributor to the overall ion chemistry of the lakes until such time as the watersheds are stabilized by vegetation and a permanent soil layer. Ash on lake bottoms will be unavailable as sources of ionic constituents when it becomes buried within deep sediment layers. Ion concentrations observed in study lakes affected by the eruption were similar to those observed in control lakes with few exceptions. Although ion concentrations in affected lakes have declined to values observed in control lakes, most were at higher concentrations than the regional means. Several functions of the ion chemistry were used to correlate planktonic community structure to lake ion chemistry. The data suggested ion chemistry was not influencing biological community structures as no patterns emerged. Analysis of diatom populations with respect to monovalent:divalent cation ratios showed no correlation.
32
Schneider, Andrew Daniel. "Constraints on eruption dynamics, Mount St. Helens, WA, 2004-2008 /." Connect to title online (Scholars' Bank), 2009. http://hdl.handle.net/1794/10026.
Full text
33
Mellors, Robin Anthony. "Studies of volcanism on Santorini, Greece and Mount St. Helens U.S.A." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.256454.
Full text
34
Williams, Trevor David. "Surviving Catastrophe: Resource Allocation and Plant Interactions Among the Mosses of Mount St. Helens Volcano." PDXScholar, 2016. https://pdxscholar.library.pdx.edu/open_access_etds/3373.
Full textAbstract:
Mosses are some of the first colonizers to disturbed sites, yet their roles in early plant community structuring are not well understood. The primary succession zones of volcanoes provide opportunities to conduct natural experiments into how mosses contribute to early plant community formation, as well as how the unique environments found in such zones affect plant traits, particularly those associated with stress tolerance. Though plant community changes have been well-documented since Mount St. Helens (MSH) volcano erupted in 1980, the volcano's moss assemblages, their influence on other plants, and their potential roles in chemical-mediated competition and biogeochemical cycling have garnered little attention. Using a natural stress gradient from primary to secondary succession zones on MSH, and in control and nutrient manipulated test plots, I sought to elucidate how populations of three dominant moss species, Polytrichum juniperinum, Ceratodon purpureus, and Racomitrium canescens, respond to abiotic stress, as well as to provide life history and interaction data on establishment stages of these stress tolerant taxa.
I first analyzed possible tradeoffs in survival strategies of four moss communities in test plots along an abiotic stress gradient. In P. juniperinum, seta specific density (mg/mm) increased significantly in response to nitrogen (N) addition. Differences in both vegetative and sexual reproductive morphological measurements were dependent on site and did not correlate with abiotic stress. In C. purpureus, the percentage of total spores germinated increased with N addition. Site dependent responses in nutrient allocation to vegetative and reproductive structures may be a result of phenotypic plasticity alone or may be a result of local adaptation. In mosses adapted to environmental stress, the allocation of nitrogen must be balanced between growth and survival. Efficient nitrogen uptake confers a competitive advantage if allocated to the higher dispersal of quickly germinating spores.
Second, my results show the moss R. canescens may be able to inhibit the germination rate of co-occurring moss spores when spores were germinated in moss gametophyte infusions. R. canescens may also inhibit the germination of the co-occurring vascular plant Lupinus lepidus when seeds are germinated within intact moss patches. By uncovering chemical-mediated interactions between mosses on the germination and initial growth of neighboring mosses and vascular plants we can gain a better understanding of the mechanisms stress tolerant plants may use to limit resource competition. Such advantages offer insight into how mosses effectively colonize and affect primary succession landscapes.
35
Paul, Anne. "Modélisation numérique des déformations d'un édifice volcanique application au Mont St Helens /." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb376002854.
Full text
36
Paul, Anne. "Modélisation numérique des déformations d'un édifice volcanique : applications au Mont St Helens." Grenoble 1, 1986. http://www.theses.fr/1986GRE10006.
Full textAbstract:
La mesure des déplacements de surface liés â l'activité volcanique est une méthode très utilisée dans la surveillance et l'étude des volcans actifs. De nombreux modèles mécaniques ont été réalisés pour tenter de déduire la structure interne de ces données de déplacements, et notamment pour localiser les chambres magmatiques. Mais ils négligent tous le caractère fortement hétérogène et discontinu des édifices volcaniques. Un nouveau modèle permettant précisément l'étude des milieux hétérogènes et fracturés est utilisé. Son hypothèse de base est que l'édifice se comporte comme s'il était constitué d'un assemblage de blocs se déplaçant les uns par rapport aux autres. L'éruption très bien documentée du Mont St Helens (1980) sert de test pour cette méthode de blocs, en permettant de comparer déplacements calculés et déplacements mesurés. Quatre modèles bi-dimensionnels de ce volcan sont construits à partir d'une coupe géologique nord-sud. Chacun d'eux permet de tester l'effet d'un paramètre du modèle (géométrie, conditions aux limites, coefficient de frottement entre blocs, chemin de sollicitation). L'intrusion d'un dôme de lave à l'intérieur du flanc nord est simulée par l'application d'une montée en pression incrémentale puis les modèles sont soumis à une accélération horizontale simulant un séisme. Les résultats de cette modélisation mettent en évidence la dépendance des modes de déformation et de rupture vis à vis du coefficient de frottement entre les blocs. On obtient un assez bon accord avec les observations pour la plus faible des deux valeurs de ce coefficient testées (O. S). La rupture du flanc nord en grand glissement de terrain se produit aussi bien sous la seule influence de la montée en pression que sous pression et séisme combinés. Mais le second type de chargement donne un meilleur accord des résultats avec la réalité, et confirme ainsi qu'un séisme était bien à l'origine de l'éruption. Enfin, on discute, à la lumière de ces résultats, de la possibilité d'appréhender les structures internes et les mouvements du magma, à partir des mesures de déplacements de surface
37
Hansen, S. M., B. Schmandt, A. Levander, E. Kiser, J. E. Vidale, G. A. Abers, and K. C. Creager. "Seismic evidence for a cold serpentinized mantle wedge beneath Mount St Helens." NATURE PUBLISHING GROUP, 2016. http://hdl.handle.net/10150/622112.
Full textAbstract:
Mount St Helens is the most active volcano within the Cascade arc; however, its location is unusual because it lies 50 km west of the main axis of arc volcanism. Subduction zone thermal models indicate that the down-going slab is decoupled from the overriding mantle wedge beneath the forearc, resulting in a cold mantle wedge that is unlikely to generate melt. Consequently, the forearc location of Mount St Helens raises questions regarding the extent of the cold mantle wedge and the source region of melts that are responsible for volcanism. Here using, high-resolution active-source seismic data, we show that Mount St Helens sits atop a sharp lateral boundary in Moho reflectivity. Weak-to-absent PmP reflections to the west are attributed to serpentinite in the mantle-wedge, which requires a cold hydrated mantle wedge beneath Mount St Helens (V similar to 700 degrees C). These results suggest that the melt source region lies east towards Mount Adams.
38
Olson, Keith Vinton. "Inventory and Initiation Zone Characterization of Debris Flows on Mount St. Helens, Washington Initiated during a Major Storm Event in November, 2006." PDXScholar, 2012. https://pdxscholar.library.pdx.edu/open_access_etds/929.
Full textAbstract:
The heavy precipitation event of November 3-8, 2006 dropped over 60 cm of rain onto the bare southern slopes of Mount St. Helens and generated debris flows in eight of the sixteen drainages outside the 1980 debris avalanche zone. Debris flows occurred on the upper catchments of the Muddy River, Shoestring Glacier, Pine Creek, June Lake, Butte Camp Dome, Blue Lake, Sheep Creek, and South Fork Toutle River. Debris flows were clustered on the west and south-east sides of the mountain. Of the eight debris flows, three were initiated by landslides, while five were initiated by headward or channel erosion. Six debris flows were initiated in deposits mapped as Holocene volcaniclastic deposits, while two were in 1980 pyroclastics on andesite flows. The largest (~975,000 m2) and longest (~8,900 m) debris flow was initiated by landslides in the upper South Fork Toutle River Drainage. The average debris flow initiation zone elevation was 1,750 m, with clusters around 1,700 m and 2,000 m elevation. The lower cluster is associated with basins that host modern or historic glaciers, while the upper is possibly associated with recent pyroclastic deposits. Upper drainages with debris flows averaged 41% slopes steeper than 33 degrees, while those without debris flows averaged 34%. The upper basins with debris flows averaged 6% snow and ice cover, 21% consolidated bedrock, and 74% unconsolidated deposits. Basins without debris flows averaged 3% snow and ice cover, 27% bedrock, and 67% unconsolidated deposits. Drainages with debris flows averaged an 89% loss of glacier area between 1998 and 2009, while those without debris flows lost 68%. Further comparing glacier coverage during that period found that only five of ten glaciers still existed in 2009. On average, the glaciers had reduced in area by 67%, decreased in length by 36%, and retreated by an average of 471 m during that period. Basin attributes were measured or calculated in order to construct a predictive debris flow model based on that of Pirot (2010) using multiple logistic regression. The most significant factors were the percentage of slopes steeper than 33 degrees, unconsolidated deposits in the upper basin, and average annual rainfall. These factors predicted the 2006 debris flows with an accuracy of 94% in a debris flow susceptibility map for Mount St. Helens.
39
Vogel, Michael, and Eberhard Blücher. "Bundesfördermittel helfen Flutfolgeschäden zu beseitigen." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-66269.
Full textAbstract:
Seit mehreren Jahren steht die Landesstelle für Bestandserhaltung der Bibliothek des Klosters Marienthal in Ostritz beratend zur Seite. Folgerichtig ergaben sich während und nach dem Hochwasser der Neiße im August 2010 besonders intensive fachliche Kontakte (siehe auch Thomas Bürger; Michael Vogel: Kulturgutschutz und Notfallverbünde. – In: BIS. – 3(2010)4, S. 223 – 224). Zwar war die im ersten Stock gelegene barocke Saalbibliothek nicht unmittelbar von den Fluten betroffen, jedoch waren verschiedene im Erdgeschoss aufbewahrte Objekte durchnässt worden und die sehr ungünstigen raumklimatischen Bedingungen nach der Flut führten auch zu Gefährdungen vor allem durch Schimmel in höher gelegenen Räumen.
40
Wood, David M. "Pattern and process in primary succession in high elevation habitats on Mount St. Helens /." Thesis, Connect to this title online; UW restricted, 1987. http://hdl.handle.net/1773/5234.
Full text
41
McDaniel, Priscilla. "Trans-Atlantic mothers : the migratory experiences of St Helenian working women." Thesis, University of Bristol, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.573399.
Full textAbstract:
Trans-Atlantic mothers are separated from their families by the vast Atlantic Ocean because they work off-shore. The unique history, culture, and economic circumstances of St Helena contribute a different dimension to developing migration theory. Disparate characteristics such as the remote location geographical location, the small community setting, nationality and the absence of immigration barriers, as well as the historical aspects of British colonisation all make up a distinct context for migration. Whilst some St Helenians are domestic workers in Britain, most work for the British military support services. The militarisation of the South Atlantic after the Falklands War, and the restoration of British citizenship shape mother migration and the feminisation of increased migration outflows. Using qualitative in-depth interviews with a purposive sample of22 migratory working mothers, this 'insider' researcher used a phenomenological approach to analyse their detailed accounts of their migration experiences. The findings show that income differentials, family needs and relative deprivation fuel mother migration. Evidently Trans-Atlantic motherhood is constrained by socio-cultural ideologies but the findings reinforce that mothers who are physically absent, can be emotionally available. The research reveals that regardless of costs and inconvenience, emotional intimacy can be maintained across the distance. Although migratory work transforms the meaning of St Helenian mothering, the study argues that this group of mothers did not 'trade- in' motherhood - they redefined it. Clearly Trans-Atlantic mothers changed the structure of the nuclear family, but strengthened the extended family. The value of kin networks is strong but there is confirmation of matriarchal conflict and the significance of the role of estranged fathers.
42
Proctor, Sarah. "Fluvial Biogeomorphic Evolution of the Upper South Fork Toutle River, WA After the 1980 Eruption of Mount St. Helens." Thesis, University of Oregon, 2017. http://hdl.handle.net/1794/22293.
Full textAbstract:
The eruption of Mount St. Helens in 1980 severely impacted the woody vegetation within the geomorphic floodplain as well as the morphology of the Upper South Fork Toutle River. Historic aerial imagery and LiDAR data were used in combination to create snapshots of the channel and vegetation in 1980, 1983, 1996, 2003, and 2014. This data was mapped and analyzed using GIS, with the primary focus on 2D channel change, vegetation change, and channel-vegetation interactions from 1980 to 2014. No vegetation was discernable in 1980-83 but the vegetation present in 1996 increased in area and in density from 1996 to 2014. The number of channels locations were dependent on vegetation density and presence while vegetation growth occurred predominately in areas previously occupied by the channel.
43
Riker, Jenny Michelle. "Experimental constraints on volatile-driven crystallisation in volcanic systems: A case study at Mount St. Helens." Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.629006.
Full textAbstract:
Degassing and crystallisation are concomitant processes in volcanic systems that together modulate the physico-chemical properties of magmas. The compositions and textures of crystal-bearing volcanic rocks therefore preserve valuable information about the degassing paths experienced by their host magmas. Accurate interpretation of the rock record, however, requires a detailed interpretive framework. This thesis presents the results of high-temperature, high-pressure experiments designed to clarify the mechanisms and manifestations of volatile-driven crystallisation in natural magmas. The well-characterised :Mount St. Helens volcanic system is taken as a case study. Isothermal phase equilibria experiments in P- XH20 space establish the fluid-composition dependence of phase relations in Mount St. Helens (Sugar Bowl) rhyodacite. Parameterisation of experimentally derived data enables simulation of magmatic properties across a wide range of parameter space. This approach has been applied to investigate the equilibrium evolution of phase assemblages, abundances, and compositions along different H20 - C02 degassing trajectories. Experimental decompression of magmas saturated with H20 and H20 -C0 2 fluids further demonstrates that plagioclase textures are strongly modulated by the isothermal decompression (PH20 - t) path. The presence of CO2 increases crystal nucleation rates relative to the pure-water case, while growth on pre-existing crystals contributes significantly to added crystallisation at a range of decompression conditions. Comparison of crystal textures in experimental samples and natural pyroclasts are used to interpret changing magma storage conditions during the summer 1980 explosive- effusion transition at Mount St. Helens. Finally, the behaviour of magmatic volatiles in the shallow crust is ultimately modulated by the nature and abundance of vapour exsolved at depth. To this end, this research presents new constraints on water solubility in silicic melts at lower crustal pressures, where experimental determinations are sparse. Together with data from lower pressures, these experiments define a continuous solubility curve in the Sugar Bowl rhyodacite from 0.1- 1.1 GPa. Saturation water contents suggest that the presence of fluid-saturated, evolved melts is likely in the deep crust.
44
Bishop, John G. "Demographic and population genetic variation during colonization by the herb Lupinus lepidus on Mount St. Helens /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/5177.
Full text
45
Bakkegard, Kristin Ann. "The Genetics of Colonization in Two Amphibian Species After the 1980 Eruption of Mount St. Helens." DigitalCommons@USU, 2008. https://digitalcommons.usu.edu/etd/77.
Full textAbstract:
The genetics of colonization is understudied in salamanders but has large conservation implications as new habitats are formed or restored to their previous condition. The 1980 eruption of Mount St. Helens provided a natural experiment to study the genetic effects of a large infrequent environmental disturbance on two species of salamander, Taricha granulosa (Rough-skinned newt) and Ambystoma gracile (Northwestern salamander). Both these species breed in ponds, and are thought to exhibit high breeding site fidelity and low vagility. I designated three treatments based on the effects of the eruption: new ponds (created by the eruption, immigrants only), recovery lakes (in blast zone, survivors plus immigrants), and reference lakes (unaffected by eruption, assumed to represent pre-eruption genetic diversity measures). Salamanders took at least nine years to colonize the new ponds. I studied the population genetics of colonization and recovery using microsatellites and AFLPs (amplified fragment length polymorphisms) to measure genetic diversity, gene flow, and population substructure at Mount St. Helens National Volcanic Monument. Based on population genetics theory and the life history characteristics of these pond-breeding amphibians, I predicted that genetic diversity would be lower in newly colonized ponds compared to recovery or reference sites. I also expected significant levels of population substructuring. Finally, I predicted that because of their lower vagility and large number of neotenes, that A. gracile would have less gene flow and a greater degree of population substructuring than T. granulosa. My predictions were not supported by my data. There was no loss of genetic diversity in new or recovery populations in either species. There was no strong evidence for population substructure by either AMOVA, isolation by distance or principal components analysis. Gene flow (Fst) was high in both species. Taricha granulosa and A. gracile were found to be resistant to a large infrequent environmental disturbance. Loss of genetic variability in new populations cannot automatically be assumed. Predicting dispersal and colonization ability based on the broad category of pond-breeding amphibian is not always reliable.
46
Meadows, Tim. "Forecasting long-term sediment yield from the upper North Fork Toutle River, Mount St. Helens, USA." Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/27800/.
Full textAbstract:
The Toutle-Cowlitz River system experienced dramatic landscape disturbance during the catastrophic eruption of Mount St Helens on May 18, 1980. The eruption was triggered by a 2.5 km3 debris avalanche which buried the upper 60 km2 of the North Fork Toutle River catchment to an average depth of 45 m and obliterated the surface drainage network. Subsequent channel response on the debris avalanche, dominated by incision and widening, has delivered significant quantities of sediment to downstream reaches where resultant deposition has reduced channel capacity and heightened flood risk. Estimates of future sediment yield from the upper North Fork Toutle River are therefore required to inform development of sustainable options for long-term flood risk mitigation. Previous estimates have been based on extrapolation of post-eruption trends in sediment yield and channel network evolution, but the divergent predictions reported in a number of studies have clouded effective decision-making regarding long-term sediment management. This study therefore uses a numerical, landscape evolution model (CAESAR-Lisflood) to make long-term forecasts of sediment yield based on process simulation rather than extrapolation. A suite of forecasts of cumulative catchment sediment yields up to 2100 are produced using scenario-based model runs designed to account for uncertainty associated with the hydrological impacts of climate change and the model coefficient for lateral mobility. The forecasts fall in a narrow band +/-20% of the mean that lies between two previous estimates derived from the extrapolation of post-eruption trends. Importantly, predicted trends in future annual sediment yield are predominantly linear, although some limited decay is evident for runs in which modelled channel lateral mobility is lower. Sustained sediment production in the upper North Fork Toutle River is found to result from persistent bank erosion and channel widening. These findings cast doubt on the applicability of negative exponential decay functions based on the rate law to characterise post-disturbance sediment yield when lateral rather than vertical adjustments dominate channel evolution. Moreover, forecast trends in future sediment yield suggest that it may not be possible to manage future sediment-related flood risk along the lower Cowlitz solely by retaining sediment in the upper North Fork Toutle River catchment.
47
Parker, Charlotte. "'An island between' : multiple migrations and the repertoires of a St Helenian identity." Thesis, University of Warwick, 2012. http://wrap.warwick.ac.uk/51501/.
Full textAbstract:
The small Island of St Helena is a British Overseas Territory. In 1981 the British Nationality Act denied the islanders their British citizenship rights and in 2002 their rights as British citizens were fully restored. As a consequence of the return of British citizenship, a new wave of migration has occurred whereby many islanders are migrating to the UK. Embedded within an ethnographic framework, the thesis draws upon 68 interviews undertaken with St Helenians both on and off the island. Drawing upon the islanders stories, narratives and repertoires, this thesis oscillates between the two fields of Social Anthropology and Cultural Studies. The analysis combines the anthropological truth claims of the community, as well as utilizes a post-structuralist approach that investigates the data for a micro understanding of discourse, ideology, identity, nuance and complexity, that demonstrates the paradoxical investments for the islanders. For cultural analytical triangulation, the theoretical concepts of Althusser, Bourdieu, Plummer and Bakhtin have been drawn upon, to investigate the feelings, emotions, cultural values and symbolic practices as demonstrated by the St Helenian community themselves. This thesis is a study of St Helenianness alongside Britishness and Islandness. Migration, identity, Diaspora, transnationalism and citizenship are common themes within this thesis, but the contribution is specifically to island studies.
48
Friedlander, Elizabeth Anne. "The nature and evolution of conduit faults in the 2004-2008 Mount St. Helens lava dome eruption." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/40473.
Full textAbstract:
Mount St. Helens reawakened 24 years after erupting in the 1980’s. This effusive eruption produced 95 million cubic meters of dacite in the form of 7 discrete, competent spines or domes of lava between September 2004- June 2008. The spines comprise low-porosity dacite that is inferred to have crystallized at a depth of about 1 km and are enveloped by a 1-3 meter carapace of fault gouge. The rate of linear extrusion of the spines peaked at 11 m/day in November 2004 and subsequently slowed to < 0.5 m/day. Dome growth was accompanied by a “drumbeat” seismicity that was sourced from 1-0.5 km below the vent.
Here, field, petrographic, and microstructural observations on the nature of deformation attending the extrusion of Spines 4, 5 and 7 at Mount St. Helens (2004-2006) are presented. The enveloping fault zones provide a static view of the cumulative strain produced by shear along the conduit wall. The conduit faults narrow from Spine 4 to Spine 7 and exhibit fewer macroscopic brittle features. Strain accommodation is achieved through a scale-dependent ductility.
The subsurface ascent velocities for each packet of magma are reconstructed using surface observed extrusion rates. Computed shear strain rates for the margins of the conduit range from 1x10⁻⁴ to 7.9x10⁻⁵ s⁻¹. As ascent rate decreases, fault zone width also decreases maintaining an average shear strain rate of 4.3x10⁻⁵ s⁻¹. Intense strain localization within each fault zone is expressed by 0.001 m thick slickensides implying very high (co-seismic) transient shear-strain rates of 1x10⁻¹s⁻¹ (Spines 4-5) to 2.2x10⁻²s⁻¹ (Spine 7).
I conclude with a time and space model for the evolution of the fault zone as magma ascends the conduit, and how the fault zones evolve through time. The factors that contribute to the differences in conduit fault zone width and nature throughout the eruption are: 1) differences in ascent rates at the onset and origin of brittle failure, 2) variations in shear strain rates, 3) and the increasing residence time throughout the eruption that the damaged fault rocks experienced at high temperatures within the conduit.
49
Hawes, Richard Anthony. "The paradise of every nuisance : the development of municipal public health services in St. Helens, 1868-1914." Thesis, University of Liverpool, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316149.
Full text
50
Beattie, Maureen A. "The effect of natural disasters on tourism : a study of Mount St. Helens and Yellowstone National Park /." Online version of thesis, 1992. http://hdl.handle.net/1850/11110.
Full text