A comparison of the NW European glaciated margin with other glaciated margins

The present paper provides an overview of glacial related seabed features and sedimentary sequences found along the formerly glaciated NW European margin and compare it with those found on contemporary glaciated margins from both the Southern and Northern Hemispheres. A brief review of the seabed physiography and strata architecture of the margins under consideration is followed by comparison of the most relevant similarities and differences. Comparison of the present-day bathymetric setting of both former and contemporary glaciated margins reveals no clear link to the effect of neither ice sheet or sediment load. Three different types of glacially eroded shelf transverse troughs have been identified, while marginal troughs seem connected to similar geological settings everywhere. Beyond the shelf edge interaction between downslope and alongslope processes has occurred resulting, amongst others, in the formation of large sedimentary mounds on the rise. More frequent large-scale mass wasting occurs on the former glaciated NW European margin than the Greenland and Antarctic margins in the latest Neogene to recent times. A two-stage evolution of the shelf prograding wedges is observed on all margins under consideration, which may reflect a general development of an ice cover from an initial phase of non- to restricted glaciation, evolving to a mature stage of expansive glaciation.     

Two oceanographic releases

A high-reliability, dual-mode release has been used on untethered, mid-water vehicles successfully since 1970. This device is operated by electrical signal or by hydrostatic pressure. A second release which is self-contained and includes a relocation pinger has been designed for precisely timed release at minimum cost. The release function in this device occurs after the preset time by electrical corrosion of a wire link. This release has been used to recover sedimen trap arrays.     

Fishery control and regulation compliance: a case for co-management in Swedish commercial fisheries

The results from a survey of Swedish commercial fishers on regulation compliance and attitudes to control and restrictions are reported. According to the responding fishers, 90% of all Swedish catches are reported, in spite of limited control efforts. From an economic perspective we would expect substantially lower levels of compliance. The results also show that the majority of Swedish fishers are in favour of co-management on a regional basis. However, on this and other management issues opinions divert significantly between large vessel operators and small vessel operators, which reveals conflicting interests for such and similar changes in Swedish management of fisheries.     

The Nature of Decision Making in the Practice of Dwelling: A Practice Theoretical Approach to Understanding Maintenance and Retrofitting of Homes in the Context of Climate Change

In order to make existing private housing more energy efficient, various policies aim at influencing decisions made by homeowners regarding renovation and retrofitting in Scandinavia. Presenting two case studies from Denmark and Norway, we take one step back and observe the whole process of keeping a home habitable. Inspired by theories of Tim Ingold and Elizabeth Shove, we suggest calling this process “the practice of dwelling.” Rather than focusing on decisions and acts pertaining to retrofitting alone, we observe how maintenance and retrofitting are parts of an ongoing practice of dwelling. The cases demonstrate how decisions can be understood as embedded in the practice of dwelling, and how a readiness for decisions regarding retrofitting is created, or not, in this practice. We suggest shifting focus from the outcome of decisions, to attention toward the process that leads to readiness for making the decision in the first place.     

Seismic wave velocities in the lower mantle

Summary The vertical velocity variations of longitudinal and transverse waves in the earth's interior in the depth range of 413 to 2800 km are put into mathematical form. Expressions of the velocities in terms of power functions of the radius are found to conform closely to the given velocities, as well as to be very simple in applications. Examples of the use of such formulas are given, including calculations of travel times and of radial velocity gradients.     

Die kartographische Methode von R. Eötvös in ihrer heutigen Form

Summary The Torsion Balance is to be used only in case if more information than presented by the Gravimeter is required. Being so, it is advisable then to make most of the fineness obtainable by the Torsion Balance. Therefore, a survey must be done carefully and reliably. One of its accessories is a proper calculus of the cartographic effects, specially for the curvature data which in their crude state — over a hilly topography — are of not much use. The cartographic method of Eötvös is right, for it works with a prism resting over a circle parcel which best fits the contourlines. The method itself is good, but Eötvös's approximate formulae — simple as they are — are accurate only within 2/10s of topographic elevation or depression. Generally speaking this limit is sufficient for the curvature data as beyond it they are rarely reliable. In order to speed up their evaluations from the map the author drew up a scale. On the other hand, for the gradient-effects a table was computed; it contains the effects of prisms of different heights at different distances. This table is handy in use; the basis used for it is the exact formula of gradient-effect. Same has to be done for curvature data beyond the two-tenth elevation. Suitably constructed tables for both effects may also be used for masses of three dimensions.

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Szilárd Oslaczky, Mitarbeiter des Instituts für Geodäsie und Markscheidekunde der Technischen Universität inSopron, Obergeophysiker beim MAORT.     

Effect of soil parameters on the threshold wind velocity and maximum eroded mass in a dry environment

The present study aims to investigate the relationships between several soil parameters (texture, organic matter and CaCO₃ content) and the threshold wind velocity and erodibility of different soil types. Our aim was to determine the role of these soil parameters play in soil loss due to wind erosion and also to statistically evaluate these correlations. The erodibility studies were carried out in wind tunnel experiments, and the resulting data were analysed with multiple regression analysis and the Kruskal-Wallis test. We found that both the threshold wind speed and the erodibility of soils were mostly determined by silt fraction (0.05–0.02 mm), while sand fractions had a lesser effect on it. Our experiences with organic matter and CaCO₃ similar, i.e. in spite of their correlation with the erosion, their contribution was not significant in the multivariate regression model. Consequently, based on mechanical composition of soils, one can predict threshold wind velocity and erodibility of soils.     

Controlled source electromagnetic three‐dimensional grid‐modelling based on a complex resistivity structure of the seafloor: effects of acquisition parameters and geometry of multi‐layered resistors

A comprehensive controlled source electromagnetic (CSEM) modelling study, based on complex resistivity structures in a deep marine geological setting, is conducted. The study demonstrates the effects of acquisition parameters and multi‐layered resistors on CSEM responses. Three‐dimensional (3D) finite difference time domain (FDTD) grid‐modelling is used for CSEM sensitivity analysis. Interpolation of normalized CSEM responses provides attributes representing relative sensitivity of the modelled structures. Modelling results show that fine grid, 1 × 1 km receiver spacing, provides good correlations between CSEM responses and the modelled structures, irrespective of source orientation. The resolution of CSEM attributes decreases for receiver spacing >2 × 2 km, when using only in‐line data. Broadside data in the grid geometry increase data density by 100 – approximately 200% by filling in in‐line responses and improve the resolution of CSEM attributes. Optimized source orientation (i.e., oblique to the strike of an elongated resistor) improves the structural definition of the CSEM anomalies for coarse‐grid geometries (receiver spacing ≥3 × 3 km). The study also shows that a multi‐resistor anomaly is not simply the summation but a cumulative response with mutual interference between constituent resistors. The combined response of constituent resistors is approximately 50% higher than the cumulative response of the multi‐resistor for 0.5 Hz at 4000 m offset. A gradual inverse variation of offset and frequency allows differentiation of CSEM anomalies for multi‐layered resistors. Similar frequency‐offset variations for laterally persistent high‐resistivity facies show visual continuity with varying geometric expressions. 3D grid‐modelling is an effective and adequate tool for CSEM survey design and sensitivity analysis.     

Widespread dispersal of Icelandic tephra: how does the Eyjafjöll eruption of 2010 compare to past Icelandic events?

The Eyjafjöll AD 2010 eruption is an extraordinary event in that it led to widespread and unprecedented disruption to air travel over Europe – a region generally considered to be free from the hazards associated with volcanic eruptions. Following the onset of the eruption, satellite imagery demonstrated the rapid transportation of ash by westerly winds over mainland Europe, eventually expanding to large swathes of the North Atlantic Ocean and the eastern seaboard of Canada. This small‐to‐intermediate size eruption and the dispersal pattern observed are not particularly unusual for Icelandic eruptions within a longer‐term perspective. Indeed, the Eyjafjöll eruption is a relatively modest eruption in comparison to some of the 20 most voluminous eruptions that have deposited cryptotephra in sedimentary archives in mainland Europe, such as the mid Younger Dryas Vedde Ash and the mid Holocene Hekla 4 tephra. The 2010 eruption, however, highlights the critical role that weather patterns play in the distribution of a relatively small amount of ash and also highlights the spatially complex dispersal trajectories of tephra in the atmosphere. Whether or not the preservation of the Eyjafjöll 2010 tephra in European proxy archives will correspond to the extensive distributions mapped in the atmosphere remains to be seen. The Eyjafjöll 2010 event highlights our increased vulnerability to natural hazards rather than the unparalleled explosivity of the event. Copyright © 2010 John Wiley & Sons, Ltd.     

Middle and Late Weichselian (Devensian) glaciation history of south-western Norway,North Sea and eastern UK

Data from eastern England, Scotland, the northern North Sea and western Norway have been compiled in order to outline our current knowledge of the Middle and Late Weichselian glacial history of this region. Radiometric dates and their geological context from key sites in the region are presented and discussed. Based on the available information the following conclusions can be made: (i) Prior to 39 cal ka and most likely after ca 50 cal ka Scotland and southern Norway were extensively glaciated. Most likely the central North Sea was not glaciated at this time and grounded ice did not reach the shelf edge. (ii) During the time interval between 29 and 39 ka periods with ameliorated climate (including the Ålesund, Sandnes and Tolsta Interstadials) alternated with periods of restricted glaciation in Scotland and western Norway. (iii) Between 29 and 25 ka maximum Weichselian glaciation of the region occurred, with the Fennoscandian and British ice sheets coalescing in the central North Sea. (iv) Decoupling of the ice sheets had occurred at 25 ka, with development of a marine embayment in the northern North Sea (v) Between 22 and 19 ka glacial ice expanded westwards from Scandinavia onto the North Sea Plateau in the Tampen readvance. (vi) The last major expansion of glacial ice in the offshore areas was between 17.5 and 15.5 ka. At this time ice expanded in the north-western part of the region onto the Måløy Plateau from Norway and across Caithness and Orkney and to east of Shetland from the Moray Firth. The Norwegian Channel Ice Stream (NCIS), which drained major parts of the south-western Fennoscandian Ice Sheet, was active at several occasions between 29 and 18 ka.