evidence for multiphase sedimentation and deformation during hydrofracturing Keywords: micromorphology, hydrofractures, subglacial to ice marginal environments Hydrofracture systems are being increasingly recognised within subglacial to ice marginal settings and represent a visible expression of the passage of pressurised meltwater through these glacial environments. Such structures provide a clear record of fluctuating hydrostatic pressure, leading to brittle fracturing of the host sediment/bedrock, and penecontemporaneous liquefaction and introduction of the sediment-fill. A detailed macro and microstructural study of a hydrofracture system cutting Devonian sandstone bedrock exposed at the Meads of St. John, near Inverness (NE Scotland) has revealed that this complex multiphase system was active over a prolonged period and accommodated several phases of fluid flow. The main conduits which fed the hydrofracture system are located along bedding within the sandstone, with the site of the wider, steeply inclined to subvertical, transgressive linking sections being controlled by the contemporaneous development of high-angle fractures and normal faults; the latter occurring in response to localised extension within the bedrock. A comparison with published engineering hydraulic fracturing data indicates that the various stages of sediment-fill deposited during a flow event can be directly related to the fluctuation in overpressure during hydrofracing. A model is proposed linking the evolution of this hydrofracture system to the retreat of the overlying Findhorn glacier. The results of this study also indicate that the development and repeated reactivation of subglacial hydrofracture systems can have a dramatic effect on the permeability of the bed, influencing the potential for overpressure build-up within the subglacial hydrogeological system, and facilitating the migration of meltwater beneath glaciers and ice sheets.Emrys Phillips (erp@bgs.ac.uk; British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA, UK); Jez Everest (British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA, UK); Helen Reeves (British Geological Survey, Sir Kingsley Dunham Centre, Nicker Hill, Keyworth, Nottingham NG12 5GG, UK) Hydrofracture systems, also referred to as water-escape features or clastic dykes, represent a visible expression of the passage of pressurised meltwater through subglacial to ice marginal environments (Dionne & Shilts 1974;Christiansen et al. 1982;von Brunn & Talbot 1986;Burbridge et al. 1988;Dreimanis 1992;Larsen & Mangerud 1992;McCabe & Dardis 1994;Dreimanis & Rappol 1997; van der Meer et 2 al. 1999; Rijsdijk et al. 1999;Le Heron & Etienne 2005;Boulton 2006;Goździk & van Loon 2007;van der Meer et al. 2008;Phillips & Merritt 2008). Previous work has demonstrated that hydrofractures record marked fluctuations in hydrostatic pressure within the glacial hydrogeological system, leading to brittle fracturing of the preexisting sediment and/or bedrock, and the penecontemporaneo...
Landslides are one of the most widespread geohazards in Europe, producing significant social and economic impacts. Rapid population growth in urban areas throughout many countries in Europe and extreme climatic scenarios can considerably increase landslide risk in the near future. Variability exists between European countries in both the statutory treatment of landslide risk and the use of official assessment guidelines. This suggests that a European Landslides Directive that provides a common legal framework for dealing with landslides is necessary. With this long-term goal in mind, this work analyzes the landslide databases from the Geological Surveys of Europe focusing on their interoperability and completeness. The same landslide classification could be used for the 849,543 landslide records from the Geological Surveys, from which 36% are slides, 10% are falls, 20% are flows, 11% are complex slides, and 24% either remain unclassified or correspond to another typology. Most of them are mapped with the same symbol at a scale of 1:25,000 or greater, providing the necessary information to elaborate European-scale susceptibility maps for each landslide type. A landslide density map was produced for the available records from the Geological Surveys (LANDEN map) showing, for the first time, 210,544km 2 landslide-prone areas and 23,681 administrative areas where the Geological Surveys from Europe have recorded landslides. The comparison of this map with the European landslide susceptibility map (ELSUS 1000 v1) is successful for most of the territory (69.7%) showing certain variability between countries. This comparison also permitted the identification of 0.98Mkm 2 (28.9%) of landslide-susceptible areas without records from the Geological Surveys, which have been used to evaluate the landslide database completeness. The estimated completeness of the landslide databases (LDBs) from the Geological Surveys is 17%, varying between 1 and 55%. This variability is due to the different landslide strategies adopted by each country. In some of them, landslide mapping is systematic; others only record damaging landslides, whereas in others, landslide maps are only available for certain regions or local areas. Moreover, in most of the countries, LDBs from the Geological Surveys co-exist with others owned by a variety of public institutions producing LDBs at variable scales and formats. Hence, a greater coordination effort should be made by all the institutions working in landslide mapping to increase data integration and harmonization.
The performance of an open or closed loop ground source heat pump system depends on local geological conditions. It is important these are determined as accurately as possible when designing a system in order to maximise efficiency and minimise installation costs.Factors that need to be considered are surface temperature, sub-surface temperatures down to 100 -200 m, thermal conductivities and diffusivities of the soil and rock layers, groundwater levels and flows and aquifer properties. In addition rock strength is a critical factor in determining the excavation or drilling method required at a site and the associated costs. The key to determining all of these factors is an accurate conceptual site scale model of the ground conditions (soils, geology, thermogeology, engineering geology and hydrogeology).The British Geological Survey has used the modern digital geological mapping of the UK as a base onto which appropriate attributes can be assigned. As a result it is possible to generate regional maps of surface and sub-surface temperatures, rock strength and depth to water. This information can be used by designers, planners and installers of ground source heat pump systems. The use of appropriate geological factors will assist in creating a system that meets the heating or cooling load of the building without unnecessary over engineering.2
11Estimating the permeability of superficial deposits is fundamental to many aspects of catchment 12 science, but can be problematic where insufficient in situ measurements are available from pumping 13 tests in piezometers. Consequently, common practice is to estimate permeability from the material 14 description or, where available, particle size distribution using a formula such as Hazen. In this 15 study, we examine the relationships between particle size, relative density and hydraulic 16 conductivity in superficial deposits in Morayshire, Northern Scotland: a heterogeneous environment 17 typical of many catchments subject to previous glaciations. The superficial deposits comprise 18 glaciofluvial sands and gravels, glacial tills and moraines, raised marine sediments, and blown sands. 19Thirty-eight sites were investigated: hydraulic conductivity measurements were made using 20 repeated Guelph Permeameter measurements, cone resistance was measured in situ with a Panda 21 dynamic cone penetrometer; material descriptions were made in accordance with BS5930:1999; and 22 disturbed samples were taken for particle size analysis. Overall hydraulic conductivity ( independent predictors of log K and together gave a relationship with an R 2 of 0.80. Material 28 description using the largest fraction (e.g. sand or gravel) had little predictive power. Therefore, in 29 heterogeneous catchments, the permeability of superficial deposits is most strongly related to the 30 finest fraction (d10) and relative density of the material.In situ Guelph permeameter 31 measurements at outcrops with good geological characterisation provide an easy and reliable 32 method of determining the permeability of particular units of superficial deposits. 33
The Ripley Landslide is a small (0.04 km2), slow‐moving landslide in the Thompson River Valley, British Columbia, that is threatening the serviceability of two national railway lines. Slope failures in this area are having negative impacts on railway infrastructure, terrestrial and aquatic ecosystems, public safety, communities, local heritage and the economy. This is driving the need for monitoring at the site, and in recent years there has been a shift from traditional geotechnical surveys and visual inspections for monitoring infrastructure assets toward less invasive, lower cost, and less time‐intensive methods, including geophysics. We describe the application of a novel electrical resistivity tomography system for monitoring the landslide. The system provides near‐real time geoelectrical imaging, with results delivered remotely via a modem, avoiding the need for costly repeat field visits, and enabling near‐real time interpretation of the four‐dimensional electrical resistivity tomography data. Here, we present the results of the electrical resistivity tomography monitoring alongside field sensor‐derived relationships between suction, resistivity, moisture content and continuous monitoring single‐frequency Global Navigation Satellite System stations. Four‐dimensional electrical resistivity tomography data allows us to monitor spatial and temporal changes in resistivity, and by extension, in moisture content and soil suction. The models reveal complex hydrogeological pathways, as well as considerable seasonal variation in the response of the subsurface to changing weather conditions, which cannot be predicted through interrogation of weather and sensor data alone, providing new insight into the subsurface processes active at the site of the Ripley Landslide.
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