Doleritic sill complexes, which are an important component of volcanic continental margins, can be imaged using 3D seismic reflection data.

ObjectiveTo assess the effectiveness of 2 interventions in improving the physical activity and well-being of secondary school children.DesignA clustered randomised controlled trial; classes, 1 per school, were assigned to 1 of 3 intervention arms or a control group based on a 2×2 factorial design. The interventions were peer-mentoring and participative learning. Year 7 children (aged 11–12) in the peer-mentoring intervention were paired with year 9 children for 6 weekly mentoring meetings. Year 7 children in the participative learning arm took part in 6 weekly geography lessons using personalised physical activity and Global Positioning System (GPS) data. Year 7 children in the combined intervention received both interventions, with the year 9 children only participating in the mentoring sessions.Participants1494 year 7 students from 60 schools in the North of England took part in the trial. Of these, 43 students opted out of taking part in the evaluation measurements, 2 moved teaching group and 58 changed school. Valid accelerometry outcome data were collected for 892 students from 53 schools; and well-being outcome data were available for 927 students from 52 schools.Main outcome measuresThe primary outcomes were mean minutes of accelerometer-measured moderate-to-vigorous intensity physical activity per day, and well-being as evaluated by the KIDSCREEN-27 questionnaire. These data were collected 6 weeks after the intervention; a 12-month follow-up is planned.ResultsNo significant effects (main or interaction) were observed for the outcomes. However, small positive differences were found for both outcomes for the participative learning intervention.ConclusionsThese findings suggest that the 2 school-based interventions did not modify levels of physical activity or well-being within the period monitored. Change in physical activity may require more comprehensive individual behavioural intervention, and/or more system-based efforts to address wider environmental influences such as family, peers, physical environment, transport and educational policy.Trial registration numberISRCTN82956355.

Along Hokkaido's Pacific coast near the town of Kiritappu, sandy deposits in a muddy lagoon and on a nearby beach‐ridge plain provide evidence for 15 tsunamis between 200 and 6000 years ago. Additional sand beds at the lagoon probably represent the historical tsunamis of A.D. 1843 and 1894. We observed the sequences of sandy deposits in continuous slices 2 to 4 m deep. Some of the deposits consist of just a single sand bed, whereas others contain multiple units of sand, muddy sand (or sandy mud), and mud caps including plant detritus. We also found at the lagoon a 17th century tsunami deposit that thickens and thins regardless of elevation or distance inland. We bracketed the ages of most of the inferred tsunamis by radiocarbon dating of detritus, mainly seeds and leaves at the lagoon and charcoal at the beach‐ridge plain, from pretsunami and posttsunami beds. Tsunami dates computed from the bracketing ages commonly have uncertainties spanning 2 to 4 centuries. Within these uncertainties, the inferred sequence of 15 prehistoric tsunamis at the lagoon, beginning almost 6000 years ago, can be matched tsunami by tsunami with the inferred history at the beach‐ridge plain, 15 km away. The sand sheet extents suggest that most of these tsunamis were larger than any generated at Hokkaido in the last 200 years. The intervals between these inferred outsized tsunamis average nearly 400 years but range widely from about 100 to about 800 years.

Three-dimensional seismic data from the NW European Atlantic margin provide detailed data on the relationships between sills, dykes, laccoliths and pre-existing basin structure. The data show that sills are predominantly concave-upwards in shape, being complete or partial versions of radially or bilaterally symmetrical forms that possess flat inner saucers connected to a flat outer rim by a steeply inclined sheet. Sills can be sourced from the steep climbing portions of deeper sills, and can be shown to exploit pre-existing faults to feed shallower sills and laccoliths. Magma flow patterns, as revealed by opacity rendering, suggest that sills propagate upwards and outwards away from the magma feeder. As an individual sill can consist of several leaves emplaced at different stratigraphic levels, and as a sill or dyke can provide magma to other sills and laccoliths, the data suggest that neutral buoyancy concepts may not provide a complete explanation for the mechanism and level of sill emplacement. Instead, the data suggest that the presence of ductile horizons such as overpressured shales may permit sill formation below the neutrally buoyant level. Emplacement below the level of neutral buoyancy would permit sill inflation, and the associated fracturing of the country rock would permit magma to exploit these pathways in order to ascend to shallower levels and feed shallower intrusions.

Outcropping rocks across southern Britain were exhumed from up to 2.5 km depth during Cenozoic times. This has been widely attributed to Paleocene regional uplift resulting from igneous underplating related to the Iceland mantle plume. Our compilation of paleothermal and compaction data reveal spatial and temporal patterns of exhumation showing little correspondence with the postulated influence of underplating, instead being dominated by kilometer-scale variations across Cenozoic compressional structures, which in several basins are demonstrably of Neogene age. We propose that crustal compression, due to plate boundary forces transmitted into the plate interior, was the major cause of Cenozoic uplift in southern Britain, witnessing a high strength crust in western Europe.

Abstract3D seismic data from the Dogger Bank, North Sea, allow the mapping of Late Pleistocene and Holocene depositional systems in unprecedented detail. The data demonstrate that glacial processes resulted in the development of incised tunnel valley systems during the Weichselian and that these were subsequently modified by fluvial processes in a pro-glacial setting. Subsequently, the Dogger Bank formed an emergent plain during the Holocene with a complex meandering river system, associated tributary or distributary channels and lakes, dominating the region. Prior to the sea level rising sufficiently to submerge the Dogger Bank around 7500 yr ago, the meandering river system was replaced by a dendritic channel network of potential fluvial, estuarine or intertidal origin. As the Holocene depositional features bear no systematic relationship to the bathymetry this study demonstrates that previously published bathymetry-based models for the Holocene palaeogeographic development of the North Sea require modification.

Three-dimensional seismic data from the FaeroeShetland Basin provides detailed information on the relationships between sills, dykes, laccoliths and contemporaneous volcanic activity. The data shows that sills are predominantly concave upwards, being complete or partial versions of radially or bilaterally symmetrical forms that possess flat inner saucers connected to a flat outer rim by a steeply inclined sheet. Such morphologies are only partially modified by pre-existing faults. Sills can be sourced from dykes or the steep climbing portions of deeper sills. Both sills and dykes can provide magma to overlying volcanic fissures and sills can be shown to feed shallow laccoliths. Magma flow patterns, as revealed by opacity rendering, suggest that sills propagate upwards and outwards away from the magma feeder. As an individual sill can consist of several leaves emplaced at different stratigraphic levels, and as a sill or dyke can provide magma to volcanic fissures, other sills and laccoliths, the data suggests that neutral buoyancy concepts may not provide a complete explanation for the mechanism and level of sill emplacement. Instead, the data suggests that the presence of lithological contrasts, particularly ductile horizons such as overpressured shales may permit sill formation at any level below the neutrally buoyant level.

No abstract