From rags to riches? Migration and intergenerational change in London's housing market, 1971–91

Summary In 1971 under half of London's young people, then living with their parents, lived in households that owned their homes, while well over half lived in rented housing. By 1991, now no longer living with their parents, less than a quarter of these young people were tenants. This paper identifies the components of that intergenerational tenure mobility, distinguishing between home ownership in more, and less, 'desirable' wards, and quantifies the role of migration in mediating the overall changes in Londoner's housing market status between 1971 and 1991. It analyses the moderating factors contributing to housing status mobility, such as labour market mobility and household type, and assesses the differential impact of these processes on men and women. ONS Longitudinal Study data for the period 1971–91 are analysed. Findings are that the aggregate changes concealed a range of housing careers. In particular, in-migrants fared less well in the London housing market than in its labour market.     

The impact of changing subcanopy radiation on snowmelt in a disturbed coniferous forest

Understanding the role of forests on snowmelt processes enables better estimates of snow storages at a catchment scale and contributes to a higher accuracy of spring flood forecasting. A coniferous forest modifies the snowpack energy balance by reducing the total amount of solar shortwave radiation (SWR) and enhancing the role of longwave radiation (LWR) emitted by trees. This study focuses on changes in SWR and LWR at three sites with different canopy structure (Bohemian Forest, Czechia), including one site affected by the bark beetle (Ips typographus). Measurements of incoming and outgoing SWR and LWR were performed at all sites equipped with CNR4 Net Radiometers for three cold seasons. In addition to SWR and LWR, sensible and latent heat, and ground heat and energy supplied by liquid precipitation were calculated. The results showed that net SWR at the healthy forest site represented only 7% of the amount at the open site due to the shading effect of trees. In contrast, net LWR represented a positive component of the snowpack energy balance at the healthy forest site and thus contributed the most to snowmelt. However, the modelled snowmelt rates were significantly lower in the forest than in the open area since the higher LWR in the forest did not compensated for the lower SWR. The progressive decay of disturbed forest caused the decrease in mean net LWR from −3.1 W/m² to −12.9 W/m² and the increase in mean net SWR from 31.6 W/m² to 96.2 W/m² during the study period. These changes caused an increase in modelled snowmelt rates by 50% in the disturbed forest, compared to the healthy forest site, during the study period. Our findings have important implications for runoff from areas affected by land cover changes due to either human activity or climate change.     

On the application of the coupled finite-infinite element method to geodetic boundary-value problem

Our aim is to introduce the Coupled Finite-Infinite Element Method (CFIEM) as a new alternative approach to the Earth’s gravity field modelling. We show that if the computational domain is large enough in radial direction, one can obtain the qualitatively and quantitatively comparable solution to the solution by the Finite Element Method (FEM). We study the influence of the size of the computational domain on the final CFIEM solution as well as the successive refinement of the discretization and its convergence to the exact solution. As an input data we use the synthetic boundary conditions computed from a Synthetic Earth Gravity Model (SEGM) and we test the CFIEM solution by the data generated directly from SEGM and the solution by the FEM.     

Spatial variation of erosion in a small,glaciated basin in the Teton Range,Wyoming, based on detrital apatite (U‐Th)/He thermochronology

Evolution of mountain landscapes is controlled by dynamic interactions between erosional processes that vary in efficiency over altitudinal domains. Evaluation of spatial and temporal variations of individual erosion processes can augment our understanding of factors controlling relief and geomorphic development of alpine settings. This study tests the application of detrital apatite (U‐Th)/He thermochronology (AHe) to evaluate variable erosion in small, geologically complex catchments. Detrital grains from glacial and fluvial sediment in a single basin were dated and compared with a bedrock derived age‐elevation relationship to estimate spatial variation in erosion over different climate conditions in the Teton Range, Wyoming. Controls and pitfalls related to apatite quality and yield were fully evaluated to assess this technique. Probability density functions comparing detrital age distributions identify variations in erosional patterns between glacial and fluvial systems and provide insight into how glacial, fluvial, and hillslope processes interact. Similar age distributions representing erosion patterns during glacial and interglacial times suggest the basin may be approaching steady‐state. This also implies that glaciers are limited and no longer act as buzzsaws or produce relief. However, subtle differences in erosional efficiency do exist. The high frequency of apatite cooling ages from high altitudes represents either rapid denudation of peaks and ridges by mass wasting or an artifact of sample quality. A gap in detrital ages near the mean age, or mid‐altitude, indicates the fluvial system is presently transport limited by overwhelming talus deposits. This study confirms that sediment sources can be traced in small basins with detrital AHe dating. It also demonstrates that careful consideration of mineral yield and quality is required, and uniform erosion assumptions needed to extract basin thermal history from detrital ages are not always valid.     

A facies geological test of stable isotope interpretation of the Upper Permian depositional environment in West Spitsbergen

Lithofacies analysis of two transgressive sequences within the Kapp Starostin Formation (Upper Permian, West Spitsbergen), indicates considerable differences in seawater chemistry between their depositional environments. The onshore part of the sequence represented in the Vøringen and Svenskeegga Members is largely calcareous, with allochthonous and corroded siliceous materials. In contrast, in the equivalent sequence within the Hovtinden Member, silica is ubiquitous whereas carbonate materials include mainly corroded bioclasts. These differences are consistent with predictions of the oceanographic model of ‘overfed’ and ‘hungry’ oceans proposed previously on the basis of carbon and oxygen stable isotope analysis.     

Database of giant landslides on volcanic islands—first results from the Atlantic Ocean

Giant landslides on volcanic islands represent the largest formations which can be created in a single geological moment. Such landslides are distributed across the globe and have attracted a significant amount of research interest. Yet, no coherent attempts have been made to rationalise this information into a single online resource. This report summarises information about the structure of the recently created database of giant landslides on volcanic islands and presents some observations regarding the uncertainties inherent in the inventories. The database is being prepared over a 3-year period: the first year of the project has focused on rationalising information about giant landslides around the Atlantic Ocean while the second and third years will focus on rationalising information about such landslides from the Pacific Ocean and Indian Ocean, respectively. Using this database, it should be possible to interrogate the spatial and temporal patterns of land sliding and landslide reactivation as well as to better assess the hazard and potential risks posed by giant landslides on volcanic islands. It will be particularly interesting to see if any evidence can be found for global triggers, such as eustatic or climatic changes, instead of the more commonly expounded local triggers. Ultimately, it is hoped that the database will benefit both the geoscientific community and those agencies responsible for civil defence. This work is part of the activities of the International Consortium on Landslides, namely its International Programme on Landslides (Project n. 212). The database is available from the giant landslides project webpage: https://www.irsm.cas.cz/ext/giantlandslides.     

Sedimentology and geochemistry of an exceptionally preserved last interglacial sapropel S5 in the Levantine Basin (Mediterranean Sea)

A combined study of lithological, geochemical and physical sediment properties is reported from a completely laminated S5 sapropel, recovered in three gravity cores (M40-4 SL67, M51-3 SL103, M51-3 SL104) from the Pliny Trench region of the eastern Mediterranean. The thickness of the studied sapropel S5 varies between 85 and 91 cm and tops most S5-sapropels in the Mediterranean. Based on optical features like color and thickness of laminae, the sapropels were subdivided into thirteen distinct lithostratigraphic zones. These zones, as well as the finer layering pattern within them, could be followed exactly among the three cores, indicating that the processes responsible for this variation acted at least on a regional scale. The sapropel sediment is characterized by exceptionally high porosity, which is strongly correlated with Si/Ca. This relationship implies that the sapropel is in essence an organic-matter rich diatomite and its exceptional thickness can be explained by preservation of diatoms forming a loosely packed sediment fabric. Compared to other S5 sapropels, the preservation of diatoms has apparently led to a twofold increase in the thickness of the sapropel layer. Relative abundances of 10 elements were determined at ultra-high resolution (0.2 mm) by XRF-scanner over the complete length of each sapropel including several cm of enclosing marl. An analysis of the chemical data indicates that the lowermost 13 cm of the sapropel is chemically more similar to the underlying marl and that the sediment chemistry shows different signals at different scales. The strongest pattern is the contrast between the sapropel and the surrounding marl, which is accentuated in elements indicative for redox conditions as well as terrigenous sediment input and productivity. Within the sapropel, a mm- to cm-scale layering is observed. The abundances of many elements are systematically linked to the pattern of these layers, indicating a common origin, related to productivity and/or terrigenous sediment and/or redox conditions. This pattern indicates a link to a regional climatic process, making the S5 sapropel horizon in M40-4 SL67, M51-3 SL103 and M51-3 SL104 a potential high-resolution archive of climatic variability during the last interglacial in the Mediterranean Sea and its adjacent landmasses.     

Impact of reservoirs and channelization on lowland river macroinvertebrates: A case study from Central Europe

In order to assess and compare the ecological impacts of channelization and shallow lowland reservoirs, macroinvertebrate communities of a lowland metapotamal river below reservoirs with epilimnial release were studied. The study was carried out in the Dyje River (Czech Republic) at five sites located from 1.5 to 22.5 km downstream of the reservoir outfall. The five sites differed in the degree of channel modification from natural muddy banks to riprap regulation. Seven samples were collected during the years 1998 and 1999 at each site using a semiquantitative method. The data were processed using multivariate analyses and methods for assessing the ecological and functional structure of communities. Altogether, 261 species of benthic macroinvertebrates were recorded including several rare and threatened taxa. Based on the results of principal component analysis (PCA), most of the variability within the species data (the first PCA axis) was explained by the degree of channel modification, from natural muddy banks with aquatic vegetation to a man-made riprap. The second axis was strongly correlated with current velocity. The sites differed in species richness, total abundances, proportion of individual functional feeding groups, pattern of the distribution of the current preference groups, and values of several biotic indexes, all of which also corresponded to the degree of channel modification. Thus, the morphological man-made modifications of the river channel were found to be the main factor affecting lowland river macroinvertebrates and their biodiversity. Our results suggest that the biggest threat to benthic macroinvertebrate diversity of lowland rivers comes from channelization. The impact of reservoirs can be completely overwhelmed by the impact of channelization, especially when muddy banks with aquatic vegetation present a substantial part of habitat diversity and significantly contribute to the total species pool.