摘要:

AbstractA distinction is made betweenslumpingandspalling. Slumping involves a compound slide with rotation and translation: the latter along one of the bedding plane shear surfaces in the Barton Beds. Spalling is an isolated failure of the exposed cliff face due to weathering. Where slumping is the dominant mode of cliff top recession, the latter is an incremental process with the increments being equal to the breadth of the slumps. A statistical study has been made of the breadth, length and plan area of 42 slumps observed over a 2 km stretch of the Christchurch Bay coastal cliffs and significant trends deduced.

ISSN:0197-9337    

DOI:10.1002/esp.3290080503

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractRelict Flandrian estuarine deposits in the Ythan valley are confined to an area in the lower valley around the present estuary. They rest upon a discontinuous layer of peat over an irregular surface of sand and gravel, and consist for the most part of a grey silty clay, or carse deposit, which forms terraces or small areas of carseland. At the seaward end of the estuary the grey silty clay contains a layer of grey, micaceous, silty fine sand, which tapers into the basal peat, whilst in places the surface of the grey silty clay is covered by peat and/or blown sand. The vegetational context and age of these deposits have been determined at Waterside, near the mouth of the present estuary. Here, the grey silty clay accumulated as the result of a marine transgression which began in the early Flandrian, and culminated between about 6189·95 and some time prior to 4000·80 radiocarbon years B.P. The carseland surface produced by this phase of accumulation is the highest Flandrian estuarine surface in the valley, at about 4·5 m O.D., and is correlated with the Main Postglacial Shoreline elsewhere in eastern Scotland. Withdrawal of the sea from this level may have been interrupted by the formation of a lower carseland surface before present levels were reached, though this is far from certain. The grey, micaceous, silty fine sand layer is dated at approximately 6850·140 radiocarbon years B.P., and is correlated with similar layers that may have been deposited following a storm surge. The paper concludes with some considerations on the age and distribution of the Main Postglacial Shoreline in eastern Scotl

ISSN:0197-9337    

DOI:10.1002/esp.3290080504

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractStudies of block fields at Massanutten Mountain, Virginia, document and provide information on the magnitude and frequency of mass movement on these coarse‐grained slopes. Block fields, which traditionally have been considered relicts of Pleistocene climate, occur on and downslope from resistant Massanutten Sandstone in Passage Creek basin. Slopes are strewn with boulders and vegetative cover on the open block fields is absent to sparse. Several block fields were investigated for evidence of recent movement using the degree of lichen growth, differences in block weathering, and rock‐fall damaged trees. Temporal and spatial aspects of geomorphic processes can be inferred through dendrogeochronology. Corrasion scars and stem ages infer a minimum age for a geomorphic or hydrologic event. High flows on Passage Creek coincided with tree‐ring determined dates of block‐field movement. Although, Pleistocene periglacial climate may have facilitated original formation of block fields, some block fields now continue to spread downslope during intense runoff events. Present block‐field mass wasting may be the principal erosional process in these areas of resis

ISSN:0197-9337    

DOI:10.1002/esp.3290080505

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractThe occurrence of rapid movement of suspended sediment in subsurface stormflow on a large field plot in California is described. Concentrations of over 1000mgl−1were recorded in storms of only low to moderate intensity. The observed sediment was composed of uniformly fine‐sized particles 4 to 8 μm in diameter. The mode of transport seems different from processes previously reported. Differences in sediment concentrations in different events, levels of137Cs on the sediment, and several other types of evidence indicate that the sediment was detached and entrained at the ground surface by raindrop impact and that the water and sediment flow occurred mainly through macropores in the soil. As conditions similar to those at the study site are not uncommon, it seems probable that the phenomenon may occur in many reg

ISSN:0197-9337    

DOI:10.1002/esp.3290080506

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractThe relationships between two‐dimensional image analysis of soil thin‐sections and tracer breakthrough curves has been studied for a silty clay loam brown earth soil under saturated conditions. Initial tracer breakthrough is well in advance of one pore volume. Discrepancies between Quantimet image analysis and breakthrough curve characterization were related by inference to the role of infrequently occurring macropores not necessarily sampled on the two‐dimensional images. A fundamental difficulty found in the use of image analysis is the uncertain nature of the relationship between the two‐dimensional image and the three‐dimensional pore system. Caution is needed in using Quantimet image analysis to describe gross properties of the three‐dimensional

ISSN:0197-9337    

DOI:10.1002/esp.3290080507

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractResults taken from 270 publications on rates are summarized, and collated with those from 149 publications reviewed previously (Young, 1969, 1974). The data are classified by major climatic zone, normal or steep relief, and consolidated or unconsolidated rocks. Representative rates and their ranges are given for soil creep, solifluction, surface wash, solution (chemical denudation), rock weathering, slope retreat, cliff (free face) retreat, marine cliff retreat, and denudation, the last being compared with representative rates of uplift. Solifluction is of the order of 10 times faster than soil creep, but both cause only very slow ground loss. Solution is an important cause of ground loss for siliceous rocks, on which it may be half as rapid as on limestones. Total denudation, brought about mainly by surface wash, reaches a maximum in the semi‐arid and probably also the tropical savanna zones. Acceleration of natural erosion rates by human activities ranges from 2–3 times with moderately intense land use to about 10 times with intensive land use (and considerably higher still where there is recognized accelerated soil erosion). Where there is active uplift, typical rates are of the order of 10 times faster than denudation, although in some high, steep mountain ranges these may approach equal

ISSN:0197-9337    

DOI:10.1002/esp.3290080508

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractAlternative indices of cross‐section asymmetry are compared. Observed values of two preferred indices for 567 natural sections across eleven confined upland channels are predictably low along such low sinuosity reaches. Variation in asymmetry of sections located around confined, unconfined but stable, and freely‐migrating bends is evaluated. Consideration of the influence of bed topography emphasizes local plan curvature of bed forms as an important control on degree of asymmetry. Variation in indices for bed forms in similar planform locations indicates the levels of asymmetry at different stages of the transformation of channel geometry over t

ISSN:0197-9337    

DOI:10.1002/esp.3290080509

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

ISSN:0197-9337    

DOI:10.1002/esp.3290080510

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

ISSN:0197-9337    

DOI:10.1002/esp.3290080511

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

ISSN:0197-9337    

DOI:10.1002/esp.3290080513

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY