Magmatic volatiles from subglacial edifices offer useful insights into palaeo-ice thicknesses and during subaerial eruptions are a strong influence on eruptive behaviour. However, pre-eruptive volatile concentrations and degassing paths are lacking from subglacially erupted edifices and thus the role of volatiles in determining the explosivity of subglacial eruptions remains unclear. The eruptive mechanisms of subglacial rhyolite are particularly poorly understood as such an eruption has not occurred during recent history and therefore has never been observed. Furthermore, the pre-eruptive volatile content of Icelandic rhyolite is poorly constrained. I have measured the volatile content of melt inclusions and matrix glasses from five subglacial rhyolitic edifices in Iceland, which formed through contrasting eruptive behaviour. I provide the first chamber to surface degassing profiles for subglacial volcanism and used their residual volatile contents to reconstruct quenching pressures and thus palaeo-ice thicknesses. Volatile-based estimates of the palaeo-ice surfaces for Bláhnúkur (1,000 m a.s.l.), Dalakvísl, (1,020 m a.s.l.) and Angel Peak (1,120 m a.s.l.) are broadly consistent with estimates made from the subglacial-subaerial transition of tuyas thought to have formed at a similar time (1,090 m a.s.l.). Relative differences between samples have been interpreted as showing intrusive formation for some of the facies at Bláhnúkur, and a syn-eruptive jökulhlaup during the formation of Dalakvísl, thus offering useful insight into edifice construction and the associated hazards. Pre-eruptive volatiles contents reveal that effusive magma had relatively low pre-eruptive H2O contents (up to 2.9 wt.%), slow ascent rates and experienced open-system degassing, whereas explosive magma had up to 4.8 wt.% H2O, fast ascent rates and closed-system degassing. Thus the role of volatiles in subglacial systems seems similar to the role played in subaerial eruptions in terms of influencing eruptive behaviour. Furthermore, measured H2O contents are much higher than was expected of Icelandic rhyolite, which is generally considered to be ‘dry’.

The earliest ice flow for which there is evidence originated from between south and south-south-east. Following this ice flowed from the south-east and then from between east-south-east and east. These flows occurred within a single ice sheet. There is no evidence that the ice had its origins in Scandinavia. Throughout Orkney much of the material eroded by the ice sheet was finally deposited only a short distance down-ice$ Approximately three-quarters of the erratics (>25mm.) and of the gravel fragments (2.8 - 19mm.) has probably been transported less than 10 km. Variations in the grain size composition of the till and in its colour can also be systematically related to the nature of the bedrock lithologies in the path of the ice flow after allowance has been made for similarly linlited down-ice transport. A number of sequences of till units were discovered. These built up at sites in areas containing outcrops of contrasting lithologies where, as the ice flow direction changed through time, the nature of the' lithologies traversed by the later flow differed substantially from that of the lithologies traversed during the earlier flow and where conditions were favourable for the preservation of the deposits of both flows. It is proposed that the characteristics (lithological composition of the gravel fraction, grain size composition, colour) of the till at any point in Orkney in either the horizontal or vertical plane can b.e considered as a function of ice flow direction during the period of genesis of the till and of the bedrock lithologies occurring within 10 km. in an up-ice direction. Aa the ice thinned deflections of the flow occurred due to the interaction of the underlying relief with the ice surface slope. Finally hummocky drift features formed beneath stagnant ice and from debris accumulated on the ice surface So its margin. Subsequent to the retreat of the ice sheet, ice reoccupied parts of Hoy. In northern Hoy an end moraine and a kame terrace have been identified. A radiocarbon date of )44,300 B.Po obtained from shell material in the till l.aid down by the main ice sheet ia used to suggest that this may have last crossed Orkney prior to the late Devensian glaciation ( 25 - 13,000 B.P.)

This research contributes to the debate on glacier dynamics, which have a significant effect on global climate change and sea-level changes. Glacier advances and retreats have great effects which can be viewed not only from their influence upon human and habitats within their immediate locality but their much more pervasive influence on all global habitats due to the effect of modern ice masses on global climate and sea-level. One of the most fundamental characteristics of glaciers and ice sheets is their ability to move. In the early models adopted to simulate glacier flow, glaciers were thought to rest on clean bedrock. However, borehole studies in different glacial areas revealed the presence of a bed of deformable sediment underneath some glaciers. Although the old common model assumed that glacier movement is generated by sliding processes, recent research proved that a high percentage of glacier movement is attributed to the shearing process of the saturated bed sediment. In the glacial environment, sediment production, deformation and deposition cannot be separated conceptually. Sediments produced by the direct erosion of lithified material by glacier ice typically contain particles spanning a large size distribution. Frequent interaction, between particles and between particles and the rigid bed, results in their substantial modification during transport. Inter-particle stresses are often high enough to cause fracture and abrasion of particles. The grain size distribution of sediments is a fundamental control on sediment deformation properties. The evolution of particle size distribution of glacial sediment, due to glacier movement, would result in an increase in the fine modes of their particles with the increase of transport distance, but there appears to be a lower size limit beyond which no further particle crushing occurs, regardless of transport distance. This complies with those findings which studied breakage potentials of some granular soils. Tests carried out on samples of a glacial sediment which were collected from Langjokull-Iceland, indicated that this sediment had been subjected to pervasive deformation underneath glaciers, which involved sediment particle breakage, resulting in this sediment reaching a terminal grading state such that no further significant particle breakage could be achieved under any further pressure or strains. The sediment behaviour accordingly was completely different to that expected for granular soils which follow a Critical State (CS) framework. The sediment exhibited a stiff behaviour represented by the lack of a clear yielding point in its compression curves, and no unique Normal Compression Line was observed, indicating that a transitional behaviour can be obtained from this sediment which has reached its terminal grading. On the other hand, a differently graded sample from the same sediment exhibited a behaviour similar to granular soils which deform following a CS framework, in which a clear yielding point, which is associated with particle breakage, and a tendency to form a unique Normal Compression Line is observed, an implication that the grading of the sediment is a key factor in defining the mechanical behaviour of the sediment. The research also addresses the rheology of glacial sediment deformation by investigating the influence of strain rate on its mechanical behaviour, and comparing the results obtained from Langjokull sediment with existing data of tests which were carried out on another glacial sediment which was collected from Ice Stream B-West Antarctica.

Over the last 50 years a significant increase in the atmospheric and upper ocean temperatures in the Antarctic Peninsula (AP) region has been observed. As a result major ice-shelves have retreated during the 20th century. In connection, glaciers have accelerated and an increased dynamic ice mass loss is observed, especially over the last decade. Despite these major changes, an exact quantification of ice mass changes of the AP, with its roughly 1000 glaciers, is not available. Almost no long-term (multi-decadal) glacier mass balance records for the AP exist and in-situ measurements are rare. On the other hand, the United States Geological Survey (USGS) and British Antarctic Survey (BAS) archives hold a large number of historic aerial stereo-photographs of the AP, dating back to the early 1940s. These images contain a valuable source of information and have been used to demonstrate widespread retreat of glaciers in this region. Less effort has been made so far to use this stereo-photography for the extraction of elevation data to compare it with recent elevation information to determine glacier volume change from which mass changes may be estimated. This dissertation seeks to close this research gap and to extend the number of mass balance records for the AP, by investigating, measuring, and analysing historical glacier elevation change in the AP using digital elevation models (DEMs) derived from USGS and BAS airborne (1948-2005) and ASTER spaceborne (2001-2010) stereo imagery. To ensure reliable and accurate measurements of surface elevation change, extracted DEMs need to be registered in a precise manner. The lack of ground control information in the AP is a major obstacle for this and can result in inaccurate absolute orientations of DEMs. If uncorrected, possible offsets between DEMs introduce significant error and i can lead to an over- or underestimation of glacier change. Thus, in order to precisely co-register corresponding historic and modern DEMs an iterative robust least squares surface matching algorithm was applied. The underlying surface matching approach was previously developed for small-scale coastal erosion studies at Newcastle University. Within the context of this work it has been successfully modified and improved to enable large scale glacier change assessment in areas of steep topography which is typical for the AP. For a total of 12 glaciers in the AP, located along the western coast between 64° and 71° S, DEMs from the historic archive stereo-imagery were successfully extracted and combined with DEMs derived from modern aerial and ASTER satellite imagery. The improved surface matching approach allowed precise co-registration of these DEMs and enabled the accurate measurement of glacier surface mass balance at the lower portion of the glaciers. Widespread frontal glacier surface lowering, of up to 50 m, has been observed on 12 glaciers with a mean lowering rate of 0.28 ± 0.03 m/yr over a period of 37 years (1970-2007). Higher rates, of up to 0.6 m/yr, were observed in the north-western Peninsula. Two glaciers which have multi-epoch coverage show a significantly larger-than-average lowering since about 1990. These results are in close correspondence with an increase in positive degree days over the last four decades and suggest that much of this lowering can be attributed to atmospheric forcing. However, the observed spatial and temporal variations in the lowering rates suggests that the pattern of surface change is not a simple one and that a regional upscaling is not straight forward. The glaciers represent only 1.2 % of all estimated glaciers in the AP and only the glacier fronts (~20 % of each glacier) were studied. Observations also show an elevation increase at some higher altitude locations within a few km of the glacier fronts, raising the potential that the lowering may have been at least partially compensated for by increased high-altitude accumulation.

Slope failures in infrastructure assets across the UK and Ireland have been observed in recent years. These failures can in many cases be attributed to progressive failure. The mechanisms which cause progressive failure are not understood and research is ongoing in many areas to understand them. One process under investigation is strength reduction by strain softening due to seasonal cycles in pore water pressure. The research presented here has incorporated field investigations, laboratory testing and numerical analysis to assess the geomechanical response of glacial till cuttings to climatically driven pore water pressure cycles. Three research sites were selected and their geotechnical and hydrogeological properties characterised through field investigation and laboratory testing. Alternative methods of in situ stiffness measurement have been used to establish the small strain stiffness to the formation for use in numerical simulations. A pore water pressure monitoring programme has been established across three study sites and provides a comprehensive dataset for use in this and future analyses. Pore water pressures are seen to be driven by climate controlled recharge. Advanced stress path testing was carried out in the laboratory to assess the possibility of strain softening. Reconstituted samples of glacial till were taken through extension and compression loading, followed by controlled pore water pressure cycles to simulate seasonal changes. From these tests shear strain was observed to continue with no increase in deviator load, indicating that strain softening maybe possible in this soil deposit. Validated numerical models of coupled stress-strain and pore water pressure have been compiled which represent the overconsolidated glacial till cuttings in this area. From this base climatically driven pore water pressure cycles were simulated. Shear strains are recorded as increasing with time with the greatest magnitude of change occurring at the toe of excavations.

'Large cut slopes (excavations) in glacial tillare a common occurrence along road and rail networks in Northern Ireland, due to unique drumlin topography in the province. Despite observed occurrences of delayed slope failures within till cuttings, their long-term performance is not well understood. Decreases in the stability of overconsolidated clay till slopes with time have been shown to be in response to pore water pressure (PWP) cycles induced by soil-climate interactions. This research has developed and presented an understanding of the mechanisms controlling PWP fluctuations within till slopes in response to climatic factors. Three cut slopes in till were instrumented to measure PWP variations, surface soil water content, suction, and shallow water table fluctuations. Field and laboratory tests were carried out to characterise the geotechnical and hydraulic properties of the till. The field instrumentation facilitated the identification of a number of characteristic controls on PWP variations, including the seasonal soil water balance and more rapid PWP responses due to gravity driven recharge and stress changes. A numerical soil water storage model was used to estimate the temporal variability in recharge to the till. This water balance accounts for PWP variation, in-situ hydraulic conductivity and fracture porosity within the till. The outputs from the water balance model were subsequently used as a boundary condition in a transient seepage model. This is coupled with a limit equilibrium analyses to assess variability in the factor of safety of the cuttings. Furthermore, a generic model was used to explore how variations in climatic and hydrogeologic conditions will affect long-term slope stability. The research highlights the control of the hydrogeologic setting and climatic conditions on PWP dynamics, and makes suggestions for how this understanding can be used in design, management and remediation measures of cut slopes to protect these assets in the future.

Glaciers are a major component of the global climate system, adjusting to changes in climate over a range of timescales. Knowledge of the dynamics of contemporary glaciated landscapes will allow accurate reconstruction of glacier margin fluctuations within the landform and sedimentary record as well as predictions of the response of ice-marginal landscapes to future glacier margin fluctuations. Existing models of ice-marginal, proglacial landscape evolution focus primarily on landforms generated in response to single, relatively short-lived, highmagnitude large-scale events such as glacier surges or glacier outburst floods (jökulhlaups). Observations of these events have frequently been restricted to short time windows (days to several years) or inferred from stratigraphic sections and are therefore subject to misinterpretation. Relatively little research has been undertaken on the development of icemarginal and proglacial landscapes over decadal time-scales (101-102 years). This study examines the controls on the evolution of the ice-marginal landscape of Skeiðarárjökull over a decadal timescale. Skeiðarárjökull is a temperate, surge-type, piedmont outlet glacier located in south-east Iceland. Skeiðarárjökull, and its outwash plain Skeiðarársandur, have been subject to numerous surges and jökulhlaups and post-depositional modification due to the melt out of buried glacier ice, providing a valuable modern process-form analogue for landscape evolution at Pleistocene ice sheet margins. Digital Elevation Models (DEMs) were extracted from the aerial photographs taken at intervals over the past six decades to quantify the rate of landscape change over decadal time periods. This data, when combined with observations from aerial photographs of numerous suites of large-scale sub- and englacial features exposed by the glacier's recession permits models of the long-term response of proglacial regions to surges, jökulhlaups and glacier margin recession to be tested. This study developed a holistic model to describe the interdependence of glacier margin fluctuations, jökulhlaups and post-depositional modification and their impact on sandur evolution.

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