949 resultados para OUTER-SPHERE


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One particularly complex phenomenon is the episodic, tidally driven variation of navigable depth level as a result of fluid mud settlement. This paper presents results from dynamic cone penetration testing with pore pressure measurement (CPTU) as a nonacoustical, direct device to support surveying and management of these areas. The new technique is modular and uses a disk configuration for fluid mud detection. Both disk resistance and pore pressure measurements accurately identify suspended matter concentrations of 90 g/L or more, and the transition from fluid mud to consolidating mud once concentrations exceed 150 g/L. Hence, the procedure attests the potential for rapid, reliable assessment of a fluid mud layer and concurrent characterization of the underlying consolidated sediment by monitoring the pore pressure and strength changes during penetration.

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Knowing the extent of the West Antarctic Ice Sheet (WAIS) at the Last Glacial Maximum (LGM) is crucial for initiating and calibrating numerical ice sheet models that can predict future ice-sheet change and contributions to sea level. However, empirical data are lacking for key areas of outer continental shelves, where the LGM-WAIS must have terminated. We present detailed marine geophysical and geological data documenting an up to ~12 m-thick sequence of glaciomarine sediments within a relict glacial trough in the outer parts of the Amundsen Sea Embayment. Continuous deposition must have persisted here since at least >40 ka BP, pre-dating the established LGM by >13,000 years. Observations constrain the LGM grounding line to a distinct grounding-zone wedge ~100 km inland from the continental shelf edge. Thus, a substantial shelf area (~6000 km**2) remained ice free through the last glacial cycle.