摘要:

AbstractTafoni and honeycomb weathering are abundant in sandstones at Capitol Reef National Park. Cavities are particularly common in talus blocks resting on alkali‐rich soil, in vertical walls of desert washes, and in sandstones containing calcareous cement. Chemical analyses, X‐ray diffraction data, and field observations suggest that salt weathering is the most important cause of disintegration, but dissolution of calcite cement also occurs in calcareous sandstones. Cavernous weathering at Capitol Reef produces cavities similar in appearance to features found in arkose outcrops along the coast of northwest Washington, even though the environmental conditions at these two locations are very differ

ISSN:0197-9337    

DOI:10.1002/esp.3290080603

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractTwo types of wind ripples are distinguished in an active drift sand area near Hulshorst in The Veluwe (Central Netherlands). The common type has amplitudes of about 0·5 cm and wavelengths of some 11 cm, the atypical ripple has amplitudes of about 1 cm and wavelengths of some 16 cm. In both cases, the sand grains in the crests are coarser than those in the troughs. However, the coarseness of the grains in the crests of the higher ripples is much more pronounced than that of the lower. It is tentatively suggested that wind ripples are initiated by a regular downwind alternation in the impact energy of the descending grains in saltation, possibly due to fixed gravity waves in the sheared flows of air with grains which have strong density gradients with height

ISSN:0197-9337    

DOI:10.1002/esp.3290080604

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractRecently it has been proposed that stress generated by the adsorption of water to clay surfaces in argillaceous rocks may be an important agent of mechanical weathering in polar and alpine environments, implying that long‐held views on the status of frost action in these areas may be in need of revision.This study documents the response, under controlled experimental conditions, of aggregates of fresh and partlyweathered schist and fresh pre‐cut schist blocks to 500 accelerated (12 hour) freeze‐thaw and hydration‐dehydration cycles. Aggregate samples subjected to freezing cycles produced the largest amounts of material in the less than 2 mm size range (an average of 8 per cent and 16 per cent for the fresh and partly‐weathered aggregates respectively), whereas humidity cycles above and below freezing yielded lesser amounts (3 per cent and 4 per cent respectively). The fresh schist blocks were found to be highly resistant to both mechanisms; only those experiencing freeze‐thaw oscillations produced measurable amounts of detritus.Although hydration effects were not as effective as frost action in causing particle size reduction in aggregates, the two mechanisms may well reinforce one another in periglacial environments, enhancing the ability of these areas to serve as source region

ISSN:0197-9337    

DOI:10.1002/esp.3290080605

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractThe one dimensional heat conduction equation is applied to a non‐uniform soil in which harmonic boundary conditions are specified. The analytic solutions are derived for practical use and satisfy a law that the thermal diffusivity is proportional to the square of the speed of the temperature wave. Depending on the nature of this speed the solutions may be categorized as circular, parabolic, hyperbolic, or exponential. A practical example is given in which the damping depth and thermal capacity of the soil both vary with depth. It shows that there may be considerable differences between uniform and nonuniform soils as far as temperature is concerned. A case of a slowly varying soil layer is also examined and is compared with the constant soil solutio

ISSN:0197-9337    

DOI:10.1002/esp.3290080606

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractUranium‐series ages have been obtained for 87 speleothems collected from nine major cave systems in the Craven district of northern England. Large systems such as Ease Gill Caverns, the West Kingsdale caves, and Gaping Gill‐Ingleborough Cave, which contain relict high‐level tunnels, are found to be older than 350,000 years (the limit of the230Th/234U dating method). There is little evidence to indicate a significant enlargement of these passages since this time. Estimates of the age of Victoria Cave from234U/238U isotopic ratios suggest that the cave has been fully relict for more than 500,000 years. Ages ofin situspeleothems immediately adjacent to local base level cave streams show that mean maximum downcutting rates in limestone channels are about 2 to 5 cm 1000 yr. These rates are significantly lower than those obtained from direct measurements on limestone bedrock in stream channels but are comparable to areal denudation rates based on solute budgets. Using the present elevation of caves with respect to adjacent valley floor levels, mean maximum valley entrenchment rates are found to range between 5 cm/ky and<20cm/ky, which corresponds to 6 m to<24 m of lowering per glacial/interglacial cycle. These rates suggest that upper beds of the limestone were incised to form the Yorkshire Dales between 1 and 2 million years ago.The results indicate that the erosional effects of individual glaciations are not as severe as previously proposed in the liter

ISSN:0197-9337    

DOI:10.1002/esp.3290080607

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractRates of splash detachment from a sandy soil of the Cottenham Series, subjected to a five‐minute design storm of 50 mm/h with a kinetic energy of 127 J/m2and a median volume drop size of 3·2 mm supplied from a rotating‐disc rainfall simulator, are determined without a plant cover and with the cover of a single Brussels sprouts plant. Measurements are made at regular intervals throughout the growing season. Plant canopies of 10 to 25 per cent result in reductions of 10 to 25 per cent in rainfall volume and 10 to 81 per cent in rainfall energy. The volume and energy of the rain beneath the plant are significantly (P<0·05) correlated with its number of leaves (r= −0·84 and −0·92 respectively forn= 49). No reduction was observed in the rate of splash detachment which averages 1·2 kg/m2for the design storm with and without the plant. The detachment rate was found rather surprisingly to be inversely related to the energy of the rainfall under the plant and positively related to the number of leaves. As the number of leaves increases, so does the detachment rate per unit of rai

ISSN:0197-9337    

DOI:10.1002/esp.3290080608

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractDebris‐flow deposits, dated by lichenometry, indicate that the majority of hillslope debris flows in Scotland have occurred within the last 500 years. Progressive weathering and climatic change can be discounted as the prime cause of the increase in the incidence of debris flows. The timing of the increase suggests that it is related to landuse changes in the Scottish Highlands during the 19th and early 20th centuries. Both burning and overgrazing can be cited as potential causal factor

ISSN:0197-9337    

DOI:10.1002/esp.3290080609

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractA chronology of landsliding is presented, including suggestions as to a date for initiation. Periods of activity known from historical sources are correlated with known periods of climatic deterioration. The current morphology of the landslide slopes is closely related to the geological succession and structure. These permit the landslides and their development to be differentiated on the basis of whole slope and toe morphology, and much of the whole‐slope activity can be related to conditions at the toe. Examples of geomorphological maps, slope categories maps, and cross sections are presented along with an example of the ‘evolutionary’ maps which may be derived from Ordnance Survey plans and aerial photographs. These generally indicate that weakening of materials by weathering, seepage erosion at the toe, and marine erosion result in frequent mass movement events of a low magnitude. These events ultimately influence the stability of larger slipped blocks behind, which fail less frequently. It is suggested that whole‐slope failures in this region have a maximum frequency of once in 120 to 150 years, and that problems of interpretation of historical accounts may mean that it is very much less frequent th

ISSN:0197-9337    

DOI:10.1002/esp.3290080610

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

ISSN:0197-9337    

DOI:10.1002/esp.3290080611

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

ISSN:0197-9337    

DOI:10.1002/esp.3290080612

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY