Professor,dr. phil. et scient. Axel Schou 70 år 18.8.1972

Prior, D. D. &; Eve, R. M. 1975: Coastal landslide morphology at Røsnæs, Denmark. Geografisk Tidsskrift 74: 12–20. København, Juni, 1, 1975.

Based on the field studies the coastal landslide morphology and the moss movement types in the Røsnæs area are described and classified, followed by a general discussion of the factors which promote slope instability.     

Landslides in the Magho district of Fermanagh, Northern Ireland

Prior, D.B. and Graham, J., 1974. Landslides in the Magho district of Fermanagh Northern ireland. Eng. Geog., 8: 341–359.

Rotational slumps, shallow debris slides and active shallow rotational slides are identified on slopes developed on rocks of Carboniferous Age. The rotational slides occur on shales which weather to produce a clay-rich soil. Direct shear tests give drained values ofφ′_r = 8.2° andc′_r = 5.0kN/m². Conventional stability analyses suggest that the residual cohesion parameter is significant. Stability calculations are facilitated by the use of a dimensionless stability coefficient.     

Spatial variability of bottom types in the lower Chesapeake Bay and adjoining estuaries and inner shelf

The spatial distributions of the bed textural and morphologic properties that influence boundary-layer roughness characteristics in the lower Chesapeake Bay, the lower portions of the York, James and Elizabeth Rivers, and the adjacent inner continental shelf were systematically mapped. A high resolution, fully-corrected side-scan sonar mapping system (100 kHz) was used for remote acoustic detection of bottom roughness, supported by ‘ground-truthing’ by direct in situ observations by divers. These complementary methods proved to be especially effective in detecting a wide range of roughness-controlling bed surface properties at various scales. Fine-scale variations in sediment size and associated bottom texture are considered to be the main source of heterogeneity in Nikuradse (skin friction) roughness. A wide variety of small- and intermediate-scale morphologic elements provide meso-scale and small-scale distributed (form drag) roughness. Depending upon location, the distributed roughness may be either biogenic or hydrodynamically induced (by currents and waves), although anthropogenic roughness prevails in certain instances (e.g. port areas). In terms of particular combinations of roughness scales and types, combined sonar and diver observation data allow the beds to be systematically but qualitatively classified into 10 bottom types, each of which is associated with a particular type of subenvironment.     

Developing a saltmarsh classification tool for the European water framework directive

The Water Framework Directive (WFD) identifies marine angiosperms (seagrasses and saltmarshes) as one of the biological elements used to classify water body status. This paper concentrates on the saltmarsh classification tools currently under development in the UK and RoI by the Marine Plants Task Team (MPTT) of the UK Technical Advisory Group (UK TAG). Saltmarsh classification is presently focusing on habitat extent, zonation and species diversity in order to fulfil the requirements of the WFD normative definitions. One of the many issues is that the natural rates of erosion and/or accretion differ between locations - this spatial and temporal natural variation is difficult to quantify; the tools and reference conditions developed will need to take this into consideration. To accurately quantify the classification boundaries and natural variability has posed a number of challenges; possible solutions are identified in this paper. Novel future classifications may also include saltmarsh ecosystem functioning (e.g., as a marine fish nursery) which may be further developed in an integrated saltmarsh tool.     

A scatterer map for the Malta plateau

A method is described by which reverberation data gathered on a cardioid array can be processed to produce a 'scatterer map' of an area. Such a map shows the locations of strong seabed scatterers and gives a qualitative estimate of their strength. The method cannot give absolute values for scattering strength but its output is nonetheless useful in describing the locations of strong scatterers in an area. Low-Frequency Active Sonar (LFAS) data gathered on the Malta Plateau are presented and the physical causes of observed strong scatterers are described, along with an assessment of the degree of certainty to which these causes are known.     

Estimation of Depth and Yield of Underwater Explosions From First and Second Bubble-Oscillation Periods

In this communication, a method is described for estimating the order of magnitude of energy yield and detonation depth for underwater explosions, based on the acoustical signals radiated. The method determines the ratio of the periods of the first two oscillations made by the gas bubble formed by an explosion, with bubble-oscillation periods being extracted from the cepstra of signals recorded on hydrophones. The results of laboratory studies, taken from the literature [H. G. Snay and R. V Tipson, “Charts for the parameters of migrating explosion bubbles,” Tech. Rep., NOLTR 62–184 (1963)], are used to convert this ratio into a measure of the maximum bubble radius achieved during the first oscillation, expressed as a fraction of the detonation depth. This fraction, combined with the period of the first oscillation, allows detonation depth and explosion energy yield to be estimated on an order-of-magnitude basis. The method is applied to signals gathered in the Pacific Ocean, at ranges of thousands of kilometers from a series of chemical explosions. Reported values of detonation depths and explosion yields are shown to agree with the order-of-magnitude estimates derived using the method. The method is shown to have a bias towards underestimating explosion energy yield. It is hypothesized that this bias results from the different scales of the at-sea explosions and the laboratory measurements on which the estimation method is based. The uncertainty associated with the method's estimation of charge yield is comparable with those of seismic methods for the estimation of energy yields of underground nuclear tests.      

Drought in the Southern United States over the 20th century: variability and its impacts on terrestrial ecosystem productivity and carbon storage

Drought is one of the most devastating natural hazards faced by the Southern United States (SUS). Drought events and their adverse impacts on the economy, society and environment have been extensively reported during 1895?C2007. Our aim is thus to characterize drought conditions in the SUS and explore the impacts on terrestrial ecosystem function (i.e., net primary productivity (NPP) and net carbon exchange (NCE)). Standard precipitation index (SPI) was used to characterize drought intensity and duration, and a process-based ecosystem model was used to explore the relationship between drought and ecosystem function. Combining overall information on growing-season SPI, drought area and duration, we concluded there was no significant change in drought conditions for the SUS during 1895?C2007. However, increased drought intensity was found for many areas in the east, resulting in significant decreases in NPP for these areas, with the largest decrease up to 40% during extreme droughts. Changes in precipitation patterns increased C emissions of 0.16 Pg (1 Pg?=?10¹⁵?g) in the SUS during 1895?C2007. The west (dry region) acted as a C sink due to increased precipitation, while the east (water-rich region) acted as a C source due to increased drought intensity. Both NPP and NCE significantly increased along a gradient of declining drought intensity. Changes in precipitation resulted in C sources in forest, wetland, and cropland ecosystems, while C sinks in shrubland and grassland ecosystems. Changes in air temperature could either enhance or reduce drought impacts on NPP and NCE across different vegetation types.     

Unraveling the Schneeberg garnet puzzle: a numerical model of multiple nucleation and coalescence

A quantitative kinetic model for the growth of the different garnet porphyroblast microstructures (type 1 and type 2) of the Western Schneeberg Complex (WSC) is presented. These porphyroblasts formed by a multiple nucleation and coalescence mechanism. Our numerical simulation shows that at constant diffusion rates: (1) low interface reaction rates result in a fully amalgamated porphyroblast (type 2); (2) intermediate reaction rates result in a porphyroblast, where coalescence of grains closer to the margin prevented amalgamation of those in the centre (similar to type 1 porphyroblasts); and (3) high interface reaction rates result in a porphyroblast microstructure with an atoll form. All three microstructures are characterised by distinctive cluster size distributions. A 2-D cluster size distribution analysis of type 1 porphyroblasts of WSC shows that these did not form because of intermediate interface reaction rates, but because the diffusion rate of nutrients was too low to keep pace with the interface reaction rate.Editorial responsibility: T.L. Grove