Part 1 The viscosity of silicate melts is a fundamental physical property that determines the mobility and transport behaviour of magma on the surface and in planetary interiors. The viscosity of liquid fayalite (Fe2SiO4), the Fe-rich end-member of the abundant upper mantle mineral olivine, was determined up to 9.2 GPa and 1850 °C using in situ falling sphere viscometry and X-ray radiography imaging. The viscosity of liquid fayalite was found to decrease with pressure both along the melting curve and an isotherm, with temperature having very little influence on viscosity at high pressure. This work is the first to determine the viscosity of a highly depolymerized silicate melt at high pressure as only recent advances in experimental techniques have allowed the difficulties associated with studying depolymerized liquids at high pressure to be overcome. The results are in contrast with previous studies on moderately depolymerized silicate melts such as diopside and peridotite which found viscosity to initially increase with pressure. In accordance with recent in situ structural measurements on liquid fayalite, the viscosity decrease is likely a result of the increase in Fe-O coordination with pressure. The results show that the behaviour of silicate melts at depth is strongly dependent on the melt structure and composition. Part 2 The magnitude of the thermal anomaly at hotspot locations has a fundamental influence on the dynamics of mantle melting and therefore has an important role in shaping the surface of our planet. The North Atlantic Igneous Province (NAIP) is the surface expression of a major mantle plume and is unique in the fact that it has a complete magmatic history. The highest 3He/4He volcanic rocks on Earth are found in the early NAIP picrites of West Greenland and Bafin Island and high 3He/4He rocks are still erupted on Iceland today. However, the relationship between 3He/4He and mantle plumes has remained enigmatic. The main aim of this work is to use the ideal opportunity provided by the NAIP to investigate the relationship between temperature, mantle melting dynamics and helium isotopes within a mantle plume. The magmatic temperatures of a suite of picrites and primitive basalts spanning the spatial and temporal range of the NAIP was determined using traditional olivine-melt thermometry, a forward mantle melting model and the newly developed Al-in-olivine thermometer. This study is the first to provide a detailed petrologic approach to investigating the mantle temperature of the NAIP throughout its magmatic history and is the first to compare all three techniques in detail. The Al-in-olivine thermometer was found to be the most robust proxy for mantle temperature. The early stage of volcanic activity in the NAIP is associated with the arrival of the ancestral Iceland plume head and resulted in a uniform temperature anomaly with Al-in-olivine temperatures 250-300° above that of ambient MORB across an area 2000 km in diameter. In addition, the temperature of the plume is shown to have been subject to large temperature fluctuations on a timescale of 107 years and is currently increasing, which has had profound effects on the melting dynamics and bathymetry of the North Atlantic region. Using existing and new 3He/4He measurements, no clear relationship between 3He/4He and temperature is observable. However, it is noted that the maximum 3He/4He of primitive basalts from the NAIP has decreased through time. These relationships are explicable if the high 3He/4He reservoir is located in either the core or the core-mantle boundary (CMB), from which helium diffuses into the lower mantle. The high 3He=4He signature is incorporated into a plume when it breaks away from the base of the mantle and over the lifetime of the plume, the 3He/4He source is gradually depleted. The temperature of the plume can vary independently in responses to heat flow at the CMB, which is in turn related to changes in mantle convection. Global plate tectonics and mantle processes are therefore intricately linked with melting dynamics at hotspot locations.

"Review of the literature shows that the reported correlation between predictions and experimental data of flame spread vary greatly. The discrepancies displayed by the models are generally attributed to inaccurate input parameters, user effects, and inadequacy of the model. In most experiments, the metric to which the model is deemed accurate is based on the prediction of the heat release rate, but flame spread is a highly complex phenomenon that should not be simplified as such. Moreover, fire growth models are usually made up of distinctive groups of calculation on separate physical phenomena to predict processes that drive fire growth. Inaccuracies of any of these “sub-models” will impact the overall flame spread prediction, hence identifying the sources of error and sensitivity of the subroutines may aid in the development of more accurate models. Combating this issue required that the phenomenon of flame spread be decomposed into four components to be studied separately: turbulent fluid dynamics, flame temperature, flame heat transfer, and condensed phase pyrolysis. Under this framework, aspects of a CFD model may be validated individually and cohesively. However, a lack of comprehensive datasets in the literature hampered this process. Hence, three progressively more complex sets of experiments, from free plume fires to fires against an inert wall to combustible wall fires, were conducted in order to obtain a variety of measurements related to the four inter-related components of flame spread. Multiple permutations of the tests using different source fuels, burner size, and source fire heat release rate allowed a large amount of comparable data to be collected for validation of different fire configurations. FDS simulations using mostly default parameters were executed and compared against the experimental data, but found to be inaccurate. Parametric study of the FDS software shows that there are little definitive trends in the correlation between changes in the predicted quantities and the modeling parameters. This highlights the intricate relationships shared between the subroutines utilized by FDS for calculations related to the four components of flame spread. This reveals a need to examine the underlying calculation methods and source code utilized in FDS."