an experimental study of rill erosion and morphology abstract rill erosion is recognized as an important process of water erosion on agricultural land the objectives of this study are to examine the effects of rainfall intensity on rill network development and to present some indicators for a quantitative description of rill morphology a soil pan 10 m long 3 m wide and 0 5 m deep and with an adjustable slope gradient from 0 to 30 was subjected to three successive rains under rainfall intensities of 50 and 100 mm h 1 the results showed that rainfall intensity significantly affected rill erosion especially in the active period of rill network development the magnitude of rill erosion was 28 5 and 33 1 kg m 2 and contributed 78 6 and 76 2 to the soil loss under rainfall intensities of 50 and 100 mm h 1 respectively the formation of rill network under the 50 mm h 1 intensity was more complex than that under the 100 mm h 1 intensity for the latter rill networks developed fast and then varied slightly the mean rill inclination angle mean rill density degree of rill dissection and mean rill tortuosity complexity cmean increased with the increase of rains under the same rainfall intensity the value was the optimal derivative morphological indicator to estimate rill erosion and morphology which was followed in descending order by mean cmean and

mode of occupation of tabun cave mt carmel israel during the mousterian period a study of the sediments and phytoliths alternative modes of occupation of tabun cave during the deposition of the mousterian levels b and c have been proposed garrod bate 1937 excavations at the wady el mughara volume 1 oxford clarendon press interpreted the archaeological record of both levels as being indicative of domestic occupational activities jelinek et al 1973 palaeorient 1 151 183 proposed that the presence of articulated limb bones of dama mesopotamica in the level b sediments below the cave chimney indicated that the cave was used as a natural game trap they also noted that the white ash layers in level c extended across the whole cave and proposed that this was due to the burning of natural vegetation in the cave this study aims at clarifying the modes of occupation during these periods level b sediments closely resemble the terra rossa soil that is common in this region burning activity is inferred from charcoal fragments seen in thin sections a minor wood ash component is present based on the preponderance of phytoliths with a variable morphology as compared to those with a consistent morphology as well as phytoliths with shapes characteristic of those formed in wood and bark of local trees thus fires were produced in the cave during this period the cave may also have been used as a game trap level c is composed of multiple layers of brown black and white sediments micromorphology mineralogy and phytolith analyses all show that these layers are mixtures of terra rossa soil and ash with the latter being abundant in the white layers the phytoliths in these layers are derived almost entirely from wood and bark and not from grasses these observations are consistent with a domestic occupational mode 1999 academic press

pedology of archaeological soils in tells of the judean foothills israel abstract tells archaeological mounds predominantly consist of poorly consolidated to unconsolidated sediments and soils that are highly anthropogenic this study examines pedogenic processes related to carbonate mobilization in tells in comparison with their peripheral soils reference soil profiles the key objective of this study is to test the hypothesis that tell deposits evolve through concurrent processes of sedimentation and pedogenesis synlithogenic pedogenesis and further explain it case studies are presented from three tells in semi arid and mediterranean climatic zones of the levant the methods applied included field survey analyses of particle size distribution ph caco3 and organic carbon content and soil micromorphology soils of the tells contain miscellaneous cultural materials that derive mainly from degraded mud bricks pottery and burnt wood chemical data show basic ph values high caco3 content and minor amounts of organic carbon field observations and lab analyses both indicate high similarity amongst the tells and their reference soil profiles buried tell soils show same characteristics as near surface soils however the reference soil profiles show incipient horizonation slightly darker colours and more developed structure micromorphology of both the tells and the reference profiles show cohesively welded peds in a vughy microstructure groundmass with an open porphyric c f related distribution and discontinuous carbonate recrystallization relative rates of soil formation in the tells can be estimated when archaeological records are established contrary to the tells the reference soil profiles show lower porosity and only minor remnants related to earth construction materials we classify the soils of the studied tells as archaeological calcareous anthraltic xerorthents the correlative wrb classification would be calcic urbic technosols archaic the anthropogenic materials are as calcareous as the natural soils but due to human action carbonates in the tells are distributed differently based on these observations ancient human actions and the dry climate have led to very little mobilization and accumulation of carbonates the information provided in this study adds to the pedological understanding of archaeological environments specifically it can be useful for the study of site formation processes of tells

effect of seepage on shallow landslides in consideration of changes in topography case study including an experimental sandy slope with artificial rainfall abstract many studies on shallow landslides have focused on seepage mechanisms however most of these studies assumed that the hillslope was parallel to the seepage direction and force they did not consider how the seepage was changed by the topography during failure to investigate the seepage mechanism particularly the influence of the topographic change during failure flume experiments using a 30 sandy slope were performed with artificial rainfall the factor of safety fs equation which considers the seepage direction and force and the numerical simulation were also applied to analyze the effect of topographic change on the seepage mechanism the experiments were divided into two stages rainfall induced experiment rie and seepage induced experiment sie with rainfall in the rie with a rainfall intensity of 80 mm h seepage erosion occurred followed by undercutting which resulted from seepage erosion to upward direction of sandy slope the analysis of fs in rie are showing an instability when seepage direction is be a slope parallel with theoretical value i hydraulic gradient in the numerical model when topographic changes of the surface of the sandy flume were applied seepage flow concentrated from failure surface of the toe of flume to middle part of flume which is affected by saturation in sie multiple failures caused by the seepage in the vertically upward direction occurred with a high seepage force and the failure mass then moved in the downward direction with the seepage flow fs for sie showed a high instability than those of rie when seepage direction with high force already changed from vertically downward seepage flow to increasing slope parallel seepage flow applying changed topography more deep from sandy flume surface in numerical model is showing concentrated seepage flow at the bottom of failures this is one of mechanism developing failure mass to downward direction to the toe of flume because soil moisture sensors installed near failures 25 cm depth show high value than porosity value indicating soil mobilization therefore the seepage direction and force play important roles in landslide mechanism and these factors should be considered in landslide studies

ash deposits in hayonim and kebara caves israel macroscopic microscopic and mineralogical observations and their archaeological implications abstract a study of the hearths and ash layers preserved in hayonim and kebara caves israel showed that they are composed of one or several different minerals these include the polymorph of caco3 calcite a variety of phosphate minerals and a suite of siliceous minerals the major component of the latter are siliceous aggregates that are present in wood detailed studies of the mineral associations in these fossil ash layers as well as in fresh wood ash using optical and scanning electron microscopy in the back scattered electron mode together with elemental analyses showed that ash in these caves undergoes a series of diagenetic changes the best preserved ash layers resemble fresh ash and are composed mainly of calcite with minor amounts of siliceous minerals the calcite reacts with phosphate rich solutions to form carbonated apatite and with time the latter dissolves and a variety of other phosphate containing minerals form with each diagenetic change some of the more soluble minerals are lost and ultimately only the ash derived siliceous minerals remain in both caves there are local accumulations of such siliceous minerals that are metres thick in fact ash derived minerals in general are major components of the sediments in both kebara and hayonim caves their diagenesis involves a hugh reduction in volume which in turn may have important effects on the geological structures and stratigraphy of the sediments the changing mineralogy of the sediments due to diagenesis complicates the use of present day estimates of radiation content of the sediments for correcting age estimates by thermoluminescence and electron spin resonance finally the presence of the relatively stable ash derived siliceous minerals in a sedimentary layer in other caves could be a useful means of identifying the presence of ash in other archaeological sites where macroscopic hearth features are absent

water and sediment yield from a small catchment in the hilly granitic region south china abstract shenchong experimental basin is located in subtropical deqing county in the hilly region of south china it has a catchment area of 0 73 km2 and is underlain by granitic rocks with a weathering mantle of about 30 m water and sediment yield were monitored at the basin outlet and at a location about 230 m upstream such that the section between the two stations coincides with the concentration of large gullies these gullies produce most of the sediment yield of the basin and the pattern of sediment discharge mirrors that of rainfall however gullies contribute comparatively little runoff to the basin outflow other surface types including bare slopes bare rills and the valley floor together yield considerable runoff because of their large areal coverage

a long term field study for the investigation of rainfall induced landslides a two year monitoring experiment has been conducted on a slope in shallow weathered soils overlying sandstone bedrock in toessegg switzerland water balance and suctions were measured together with the meteorological inputs in preparation for predicting environmental effects on slope stability electrical resistivity tomography proved particularly helpful in establishing the spatial distribution of soil layering with clayey sand overlying silty sand and bedrock this paper describes monitoring of the field measurements and shows that the double layer causes a bi seasonal response with the smallest factor of safety after the wetter winter months

buried in ashes site formation processes at lapa do santo rockshelter east central brazil few archaeological sites in the americas contain high concentrations of human burials dating back to the early holocene the tropical karstic region of lagoa santa in central brazil state of minas gerais is one of the richest bioanthropological records available to study the behaviors and funerary practices of early holocene south americans with more than 200 skeletons found so far one of the key locations to examine the history of human settlement in lagoa santa is the site of lapa do santo a rockshelter known to contain the oldest rock art and the earliest evidence of funerary complexity in the continent in this geoarchaeological investigation we focus on the early holocene settlement at lapa do santo 7 9 12 7 cal kybp applying high resolution geoarchaeological techniques such as micromorphology organic petrology and ftir on both archaeological modern reference and experimental samples this is the first time that a micro contextual approach integrated with experimental geoarchaeology has been applied to study the formation of rockshelter deposits in a tropical setting our results show that the stratigraphic sequence formed under the dual influence of anthropogenic sedimentation through continuous combustion activities and geogenic sedimentation in the form of oxisol aggregates which fell from above the limestone cliff into the rockshelter intact hearths and remobilized combustion debris possibly hearth rake out are close to the graves suggesting repeated burning activities as part of the ritual behavior of early holocene south americans large amounts of ash are intermixed with heated and unheated oxisol aggregates heated termite mound fragments were also found mixed within the sediments post depositional alteration of the site includes limited bioturbation and localized low energy surface water and sub surface concentrations of moisture leading to precipitation of dense secondary carbonates the age inversions can be attributed to the human action of reworking the ashy sediments and not to post abandonment processes despite this the overall preservation of the sediments is good and most human burials can be considered to be in primary context

the influence of shallow landslides on sediment supply a flume based investigation using sandy soil abstract the impact of rainfall induced shallow landslides on hillslope sediment discharge is not well understood this paper reports experimental measurements of sediment discharge after water induced shallow landslides are triggered on sandy soil in a flume under simulated rainfall the principal aim of the research was to investigate how varying soil depth affects the location and occurrence of shallow slope failures as well as how it affects sediment yields downslope four experiments were conducted using the same sandy soil and a 30 and 10 compound slope configuration under average rainfall intensity of 50 mm h 1 for up to 390 min soil depths were set to 200 300 400 and 500 mm engineering and geotechnical properties of the soil were examined sediment discharge and runoff were collected from the flume outlet at 15 minute intervals changes in the soil slope profiles after landslides and soil physical properties resulted from soil armouring under continuous rainfall were also recorded results showed that sediment yields at the flume outlet before landslides occurred were very low and limited to the finer soil particles as would be expected for a sandy soil however subsequent variations in sediment discharge were strongly related to failure events and their proximity to the outlet sediment yield was also affected by the original soil depth the greater the depth the higher the sediment yields post failure reductions in sediment discharge were observed and attributed to post failure slope stabilization under continuing rainfall and extensive soil armouring near the flume outlet the results provide a clear linkage between landslides and sediment discharge due to hydrological processes occurring in the hillslope this knowledge is being used to develop a model to predict sediment discharges from hillslopes following shallow landslide events

human induced calcretisation in anthropogenic soils and sediments field observations and micromorphology in a mediterranean climatic zone israel abstract for over a century the study of pedogenic calcrete and its formation focuses on natural processes disregarding the possible role of humans in its formation here we present field and micromorphological evidence from archaeological and modern sites in the eastern mediterranean region israel that indicate that some specific calcretes are human induced we demonstrate that anthropogenic affected calcrete differs from natural non human induced calcrete we show that the occurrence of the human induced calcrete is spatially limited and is associated with both macro and micro scale remnants and occasionally high content of organic material we propose an operative definition for anthropogenic calcretisation as the interference of humans with a component s that influence the formation of calcrete we assume that if present day calcretised environments will retain their calcretisation prone conditions for the next 5 10 millennia a distinct calcretic morphology could become a significant terrestrial formation this discovery can be particularly useful for evaluating past human impact on the environment adding a new archaeological set of research tools that should further be developed

hydrological responses and stability analysis of shallow slopes with cohesionless soil subjected to continuous rainfall understanding the hydrological and physical responses of shallow slopes subject to rainfall events is vital for the efficiency of a warning system setup in this research a series of experiments were undertaken to evaluate the hydrological responses of shallow slopes of varying steepness and when subjected to varying intensities periods and inter storm periods of rainfall an analysis of infinite slopes was also undertaken to develop a fundamental understanding of rainfall induced shallow slope failure characteristics the hydrological and physical responses were characterized in the infiltration and saturation phases during the infiltration phase the maximum magnitude of water content was found behind the wetting front termed as the water content behind the wetting front wb for a certain soil type the magnitude of wb was found to be dependent on the magnitude of rainfall intensity regardless of the slope gradient and initial water content based on the relative depth of the failure plane th

erosional effects on runout of fast landslides debris flows and avalanches a numerical investigation the mechanism of mass changes in debris transportation process is an important topic in the study of fast landslides debris flows and avalanches basal erosion is recognised as a dynamic interaction between the original moving material and the entrained basal topsoil shearing along their non slip contact surface in this paper we propose a new concept of yield rate and establish the erosional relationship to bridge these two systems a pertinent mathematical model and numerical implementation are formulated parametric numerical experiments are conducted to compare the erosional effects the simulated results are consistent with available experimental and field observations the influence of the involvement of the erosive material on runout behaviour and the global mobility of the moving material are elucidated the proposed method is then employed to analyse a recent debris flow event in northern italy the excellent match to the field data gives it a plausible potential application to the analysis of this type of gravity driven flow with significant erosion defined in a dimensionless form the proposed yield rate can be estimated conveniently in general geotechnical practices

aspects of the chemical and microscopic characteristics of plant ashes found in archaeological soils abstract ash from plants occurs in archaeological soils all over the world it is particularly significant in cave deposits but is also found on open air sites where dissolution has been discouraged by aridity deep burial or calcareous surrounding sediments this paper describes the main microscopic characteristics of ash as well as providing details and illustrations of their origin from plant mineral and organomineral compounds chemical summaries are presented which reflect the major trends in phytomineralogy and highlight some additional groupings running through plant physiology emphasis is placed on the importance of understanding the complete range of transformations acting on ash as a result of heating and cooling followed by weathering and dissolution finally some future directions for ash research are suggested both from within the central topic of plant ashes and extending to other types of ash

micromorphological indicators for degradation processes in archaeological bone from temperate european wetland sites abstract micromorphological investigations of archaeological bones make it possible to study decay processes and the associated depositional environment in one go a selection of micromorphological thin sections from soil samples from three wetland sites in switzerland the netherlands and norway that contained bone fragments were studied the goal was to investigate the type and the timing of decay processes to better understand the taphonomy of bones in such sites using optical microscopy and scanning electron microscopy with energy dispersive x ray spectroscopy sem edx a range of biological decay processes and chemical mineralogical transformations were observed in two of the sites zug riedmatt in switzerland and hazendonk in the netherlands a relatively short exposure to adverse conditions must have occurred some of the bones from zug riedmatt show localized collagen decay related to exposure to fresh ashes others show cyanobacterial tunnelling related to submersion in shallow clear water in hazendonk bone fragments and fish scales apparently have first been exposed to bacterial decay related to putrefaction subsequently alternations between wet and dry conditions resulted in the dissolution of some of the bone mineral and the formation of ca fe iii phosphates probably mitridatite fungal decay caused extensive tunnelling of bone and fish scales as well as the secondary phosphates these processes apparently ended when the bone rich layer became permanently waterlogged and anoxic in stavanger bone mineral is transformed into mitridatite and possibly other ca fe iii phosphates indications that the redox conditions are variable at present suggest that these processes are still active

sea land oxygen isotopic relationships from planktonic foraminifera and speleothems in the eastern mediterranean region and their implication for paleorainfall during interglacial intervals the oxygen and carbon stable isotope compositions of cave speleothems provide a powerful method for understanding continental climate change here we examine the question of the regionality of this isotopic record and its linkage with the marine isotopic record in the eastern mediterranean em region the study presents a new accurately dated 250 kyr 18o and 13c record determined from speleothems of the peqiin cave northern israel its comparison with the continuous 185 kyr isotopic record of the soreq cave speleothems from central israel reveals striking similarities thus a strong regional climatic signal brought about by variations in temperature and rainfall amount is reflected in both cave records low 18o minima in the peqiin profile for the last 250 to 185 kyr period interglacial marine isotopic stage 7 match the timing of sapropels 9 to 7 and are indicative of high rainfall in the em region at these times the combined soreq and peqiin 18o record for the last 250 kyr excellently matches the published globigerinoides ruber g ruber marine 18o record for the em sea with the isotopic compositional difference g ruber speleothems remaining relatively constant at 5 6 0 7 thus establishing for the first time a robust exploitable link between the land and the marine isotopic records the correspondence of low 18o speleothem values and high cave water stands with low g ruber 18o values during interglacial sapropel events indicates that these periods were characterized by enhanced rainfall in the em land and sea regions by use of sea surface temperatures derived from alkenone data as a proxy for land temperatures at the soreq cave we calculate the paleorainfall 18o values and its amounts maximum rainfall and lowest temperature conditions occurred at the beginning of the sapropel events and were followed by decrease in rainfall and increase in temperatures leading to arid conditions the record for the last 7000 yr shows a trend toward increasing aridity and agrees well with climatic and archeological data from north africa and the middle east

the influence of slope angle on sediment water and seed losses on badland landscapes abstract by means of simulated rainfall the influence of the slope angle on the soil water and seed erosion has been studied on badland surfaces slope angle has a clear positive effect controlling soil erodibility and erosion rates but it does not have any influence on the volume of runoff after 40 minutes of rain at an intensity of 55 mm h 1 in contrast slope angle has a clear influence on runoff initiation with cracks and crusts as the main factors controlling the time to ponding and time to runoff both ponding and runoff initiation start earlier on pediments than on slopes where more cracks exist steady state infiltration rates and seed losses have an inverse relationships with slope angle pediments have 40 times lower erosion rates and 6 times higher seed losses than slopes the different behaviour of seed losses between pediment and slope is due to the strategy of the seeds against erosion processes

how hydrological factors initiate instability in a model sandy slope knowledge of the mechanisms of rain induced shallow landslides can improve the prediction of their occurrence and mitigate subsequent sediment disasters here we examine an artificial slope s subsurface hydrology and propose a new slope stability analysis that includes seepage force and the down slope transfer of excess shear forces we measured pore water pressure and volumetric water content immediately prior to a shallow landslide on an artificial sandy slope of 32 the direction of the subsurface flow shifted from downward to parallel to the slope in the deepest part of the landslide mass and this shift coincided with the start of soil displacement a slope stability analysis that was restricted to individual segments of the landslide mass could not explain the initiation of the landslide however inclusion of the transfer of excess shear forces from up slope to down slope segments improved drastically the predictability the improved stability analysis revealed that an unstable zone expanded down slope with an increase in soil water content showing that the down slope soil initially supported the unstable up slope soil destabilization of this down slope soil was the eventual trigger of total slope collapse initially the effect of apparent soil cohesion was the most important factor promoting slope stability but seepage force became the most important factor promoting slope instability closer to the landslide occurrence these findings indicate that seepage forces controlled by changes in direction and magnitude of saturated and unsaturated subsurface flows may be the main cause of shallow landslides in sandy slopes copyright 2013 john wiley sons ltd

benggang erosion the influencing factors abstract in the tropical and southern subtropic granite areas of south china a special kind of small scale erosional landform is widely distributed called benggang by the local people many natural factors are responsible for the development of benggang such as lithology precipitation relief vegetation etc which are discussed in detail in this paper study shows that the development of benggangs is the outcome of a joint operation of natural factors and human activities lithology especially the characteristics of the granite weathering mantle provides material in which benggangs can develop while intense rainstorms in a tropical monsoon climate act as a powerful force to cause benggang erosion the slope characteristics such as steepness and exposure control the spatial difference of the distribution of benggangs the development of benggangs results from the reverse succession of vegetation induced by human activities in this region and the density of benggangs is closely related to forest cover and unit timber growing stock

investigation of relationships between measured field indicators and erosion processes on badland surfaces at petrer spain abstract indicators were obtained to measure and predict rill erosion and mass wasting in biancana and calanchi like badland areas rainfall simulation experiments were used to find a relationship between soil moisture change and sediment concentration behaviour this relationship appeared to be able to show in its role as indicator differences between materials affected by various degrees of rill erosion or mass wasting indicators explaining this relationship are surface characteristics runoff and infiltration characteristics and chemical and mineralogical soil properties from the experimental study it was concluded that the high infiltration capacity in materials affected by mass wasting resulted in an unstable soil and a high degree of erodibility the materials which were more affected by rill erosion or had a continuous crust at the surface were saturated earlier during the experiment than the other materials this saturation caused an increase in runoff the mechanism is explained as the system crossing a threshold after which flow hydraulics at the surface are more important for erosion processes than dynamic soil properties and infiltration characteristics

soil erosion by surface water flow on a stony semiarid hillslope soil erosion on hillslopes occurs by processes of soil splash from raindrop impacts and sediment entrainment by surface water flows this study investigates the process of soil erosion by surface water flow on a stony soil in a semiarid environment a field experimental method was developed whereby erosion by concentrated flow could be measured in predefined flow areas without disturbing the soil surface the method allowed for measurements in this study of flow erosion at a much wider range of slopes 2 6 to 30 1 per cent and unit discharge rates 0 0007 to 0 007 m2 s 1 than have been previously feasible flow velocities were correlated to discharge and hydraulic radius but not to slope the lack of correlation between velocity and slope might have been due to the greater rock cover on the steeper slopes which caused the surface to be hydraulically rougher and thus counteract the expected effect of slope on flow velocity the detachment data illustrated limitations in applying a linear hydraulic shear stress model over the entire range of the data collected flow detachment rates were better correlated to a power function of either shear stress r2 0 51 or stream power r2 0 59 published in 1999 by john wiley sons ltd

soil freeze thaw induced changes to a simulated rill potential impacts on soil erosion abstract flows in natural rills on hillslopes transport significantly more sediment down slope than overland flows which makes rills geomorphically significant landscape features the erosivity e g sediment transport capacity of the flows in rills is partially a function of the cross sectional geometry of the rill which determines flow velocity and depth conversely rill geometry is determined by flow erosivity and by soil processes that affect the erodibility and stability of soil along the rill thus complex feedbacks exist in the mechanics of rill erosion the objective of this study was to measure the effects of one of the soil processes that affect rill geometry soil freeze thaw ft cycling an unvegetated rectangular rill was subjected to two ft cycles each lasting several days in a controlled laboratory setting the ft cycling increased the water content and reduced the cohesion in the surface soil along the rill sufficiently to induce soil slumps and mud flows along the sidewalls of the rill these mass failures changed the rectangular rill to a triangular one which reduced the hydraulic radius of the rill by 32 using manning s equation it was estimated that this new geometry could reduce the velocity of the flow in this altered rill by about 25 the persistence of the new rill shape and thus that of the slower flow would depend on the complex interactions between flow velocity and the resistance of the slumped sediment to those flows that persistence was not investigated in this experiment these results can be used in parameterizing models of rill evolution that incorporate widening of rills by mass failures along the rill sidewalls

distinguishing between calcites formed by different mechanisms using infrared spectrometry archaeological applications infrared spectrometry is a well established method for the identification of minerals due to its simplicity and the short time required to obtain a result it can be practiced on site during excavation using portable infrared spectrometers however the identification of a mineral may not be sufficient for example a lime plaster floor and a crushed chalk surface have a similar appearance and are composed of the same mineral calcite here we exploit differences in the infrared spectra of geogenic biogenic and pyrogenic calcites for the identification of each calcite type the infrared calcite spectrum has three characteristic peaks in the region of 400 4000 cm 1 designated 2 3 and 4 when a calcite sample is ground as part of the measurement preparation procedure some grinding dependent changes will be revealed in the infrared spectrum with additional grinding the 3 peak narrows and the heights of the 2 and 4 peaks decrease when both are normalized to the 3 height by plotting the normalized heights of the 2versus the 4 of several grindings of the same sample a characteristic trend line is formed for each calcite type the trend lines of geogenic calcites have the shallowest slopes and highest 4 values when compared to pyrogenic calcites which can be further divided to ash and plaster mortar samples this method can assist in distinguishing between the various calcites and provide insights into homogeneity and preservation state of the calcitic materials in question

combined roles of saturated permeability and rainfall characteristics on surficial failure of homogeneous soil slope abstract both rainfall characteristics rainfall intensity and duration and saturated permeability of soil may influence the type and mechanism of surficial slope failures in general the failures can be initiated by two mechanisms i e loss of matric suction through propagation of wetting front and rise of water table up to date there are still no clear indicators to identify the dominant parameters that control the type of failure for these shallow landslides this paper investigates the hydraulic responses of soils to the variations of rainfall characteristics and soil permeability through numerical analyses the results showed that the hydraulic responses to rainfall for a homogeneous infinite slope underlain by an impermeable layer can be divided into two stages 1 the propagation of wetting front and 2 the rise of water table based on these hydraulic responses the type and mechanism of failures were deduced from the analytical analyses both the rainfall characteristics and saturated permeability were found to be predominant in controlling the hydraulic responses of soil and hence the occurrence time depth of failure plane and type of surficial slope failures

moisture content pore water pressure and wetting front in granite residual soil during collapsing erosion with varying slope angle abstract collapsing erosion is very severe in subtropical regions that are covered extensively by granite residual soil however detailed information about hydraulic responses during collapsing erosion especially for different slope angles remains unclear therefore to control collapsing erosion it is important to attain a more comprehensive understanding of the complex hydraulic responses due to rainfall in this study an artificial rainfall simulator and an experimental device were used to evaluate the collapsing erosion process with particular consideration of the influence of slope angle flume experiments using three slope angles 0 10 and 20 were performed under artificial rainfall this study explored the evolutions and hydraulic responses of collapsing erosion of granite residual soil by simultaneously monitoring moisture content pore water pressure and wetting front during heavy rainfall the results showed that collapsing erosion occurred faster with steeper slope angle collapse occurred in an upslope direction when the corresponding moisture content of the soil was between 30 and 40 pore water pressure increased until the development of collapsing erosion but was released when the soil mass collapsed the descending process of the wetting front on a gentle slope and a steep slope can be divided into two stages and three stages respectively this study presents an improved characterization of collapsing erosion and provides valuable evidence for slope angle impacts on infiltration events during collapsing erosion under heavy rainfall

effects of rain intensity slope gradient and particle size distribution on the relative contributions of splash and wash loads to rain induced erosion abstract soil erosion during rainfall is a complex phenomenon resulting from detachment by raindrop impact and overland flow the objective of this study is to investigate the transportation rate of splash load sl and that of wash load wl and their relative contributions to the rain induced erosion rate affected by rain intensity slope gradient and particle size distribution a total of 60 simulation runs were carried out using a detachment tray under simulated rainfall with no inflow the experiments were done on two soil samples aggregate sizes finer than 2 and 4 75 mm from an agricultural land use at different rain intensities 57 and 80 mm h 1 and varying slope gradients 0 5 2 5 5 10 and 20 under unsteady state conditions wl showed relatively high dependency on slope gradient whereas approaching steady state conditions nearly similar values of wl occurred at different slopes sl and wl increased with increasing rain intensity and slope gradient implying the importance of rain induced erosion on bare agriculture lands especially at steeper slopes the ratio of wl sl decreased when slope gradient increased however wl increased more significantly than sl as soil aggregates became finer the result indicates that at all the slope gradients wl was much larger than sl indicating that wash load significantly contributes to the rain induced erosion in the agricultural soil furthermore with increasing slope gradient the contribution of wash load to rain induced erosion decreased while it was greater in the soil containing finer aggregates also with increasing rain intensity at lower slope gradients 10 the finding of this study revealed that the rain induced erosion was transport limited at the gentler slopes whereas at the steeper slopes it shifted to detachment limited conditions

nucleation of aragonite upon carbonation of calcium oxide and calcium hydroxide at ambient temperatures and pressures a new indicator of fire related human activities wood ash found at archaeological sites is the most direct evidence of the presence of combustion features the preservation of wood ash within archaeological deposits is often poor due to diagenetic processes and therefore its identification requires the use of spectroscopic methods ftir spectrometry is able to detect the main calcite component of wood ash unless this is mixed with other calcitic phases of geologic origin using ftir spectrometry we identified non biogenic aragonite in archaeological heat altered sediments and lime plasters the presence of aragonite in such conditions is unusual as it is unlikely to crystallize at ambient temperatures and pressures or in absence of mg the experimental conditions which favor the nucleation of this aragonite phase were investigated with ftir spectrometry xrpd and sem imaging of modern lime plaster and quicklime samples prepared in the laboratory using different calcium carbonate starting materials we show that aragonite forms at ambient temperatures and pressures upon carbonation of calcium oxide and calcium hydroxide together with calcite and its nucleation and growth are influenced by environmental parameters such as carbon dioxide partial pressure relative humidity and temperature this pyrogenic aragonite is a reliable indicator for calcareous materials exposed to temperatures above 600 c and therefore it can be used to determine the presence of heat altered sediments and ash in the absence of structured combustion features this mineral phase could have applications in radiocarbon dating as well

unsaturated soil mechanics in rainfall induced flow landslides abstract rainfall induced flow landslides in coarse grained soils pose significant threats to populations and structures due to their high velocities long travel distance and the absence of definite warning signs during the pre failure stage the triggering phase of these phenomena is frequently related to rainfall events which significantly reduce matric suction in the shallower soil layers in this paper the processes leading to the onset of such phenomena are illustrated and some observations on their modelling are briefly recalled the failure stage at different scales is then modelled with reference to a case study from southern italy which draws on high quality experimental data sets from extensive in situ and laboratory investigation

stable carbon and oxygen isotopic compositions of wood ash an experimental study with archaeological implications abstract wood ash composed mainly of the mineral calcite is an important component in many archaeological sites identification of wood ash in the archaeological record is often difficult due to mixing of ash with other calcitic components of geogenic origin and or due to diagenetic changes a recent empirical study using the stable isotope compositions of carbon 13 c and oxygen 18 o in wood ash enabled the identification of mixtures of wood ash with geogenic calcite and to follow diagenetic changes due to partial dissolution and re precipitation of ash in two prehistoric cave sites in israel little however is known about the processes responsible for the isotopic compositions of wood ash in relation to formation at various temperatures and the influence on isotopic composition of ash from a variety of plant species here we present an experimental study of wood ash formed by burning three c3 tree species and one c4 desert bush at different temperatures the results indicate that there are significant differences in the isotopic compositions of carbon and oxygen between wood ash that forms by combustion at a relatively low temperature 500 c and at a higher temperature 900 c in addition we show that the isotopic composition of carbon and oxygen in high temperature wood ash approaches equilibrium over a period of several months and that the carbon isotopic composition of low temperature wood ash may reflect the photosynthetic pathway of the burnt woody species lastly we show that the isotopic compositions obtained from wood ash prepared at different temperatures do not reflect a temperature dependent fractionation process but a mixing line between calcite that formed by low temperature combustion and calcite formed by high temperature combustion which later underwent re carbonation with atmospheric co 2 in addition we suggest that exchange processes may possibly occur during combustion between decomposing calcium oxalate and atmospheric o 2 co 2 and co the archaeological implications of this study are discussed in relation to identification of wood ash in the archaeological record identification of fuel sources and burning temperatures and diagenetic changes expected in karstic cave environments the method presented here can be applied at any archaeological site

quantifying and modeling post failure sediment yields from laboratory scale soil erosion and shallow landslide experiments with silty loess rainfall events on steep hillslopes can cause both soil erosion and shallow landslides these processes interact with each other and need to be studied in an integrated way to understand hillslope sediment yields the main aim of this research is to study post failure sediment yield following landslides that alter local slope gradients a laboratory flume under a rainfall simulator was used to quantify erosion and shallow landslides in fine grained silty loess soils the flume was divided into an upper and a lower section the slopes of which could be altered a total of 12 experiments were conducted on slopes ranging from 35 to 47 in the upper and 5 to 10 in the lower flume sections shallow landslides were triggered in four of the 12 experiments sediment and runoff were collected from the flume outlet every minute during landslides and every 10 min before and after landslides changes in the soil slope after landslides occurred were recorded results showed that peak sediment yields were related to landslide occurrence and proximity to the outlet post failure reduction in sediment yields was related to the evolution of the hillslope after slope failures a simple rule based soil redistribution model of runout distance was validated using the experimental results the water erosion prediction project wepp model was used to simulate runoff and soil erosion during pre and post failure rainfall events predicted runoff rates and sediment yields using wepp were in good agreement with those measured in both pre and post failure events indicating that the model can be used successfully as part of an integrated approach to modeling sediment yields in landslide prone landscapes

soil erosion and hydrology of the western mediterranean badlands throughout rainfall simulation experiments a review abstract rainfall simulation experiments are widely used in geomorphological research in badland areas this technique contributed significantly to our understanding of badland geomorphology in the mediterranean belt due to the different types of simulated rainfall applied and the variable size of the plots a review of the state of the art is necessary this study confirmed that rainfall simulations are well suited to i analyse runoff infiltration processes and sediment detachment within badlands and ii to establish the factors determining the hydrological and erosion response at interrill scale in badland areas the hydrological response of badlands is characterized by rapid responses low to moderate infiltration rates ranging from close to 0 to 55 mm h 1 and high runoff coefficients i e 60 positive relationships are observed between antecedent soil moisture content and rainfall intensity on the one hand and runoff coefficients on the other sediment concentration and soil detachment rates are among the highest measured on the mediterranean region i e up to 84 8 g l 1 and 4722 4 g m 2 h 1 results show that rainfall intensity runoff coefficient and slope angle have a positive influence on sediment concentration and sediment detachment in the case of rock fragment cover its influence is variable according to the soil cover percentage rainfall simulations increase our understanding of the temporal and spatial variability of the soil erosion processes however rainfall simulation provides mostly qualitative rather than quantitative information because of the small plot size and the simulated rainfall characteristics due to facility for repeating experiments and recording a high quantity of data in short time however this method allows the comparison amongst different environments and soil conditions as the rainfall properties can be reproduced

enhanced magnetization of the marlboro clay as a product of soil pyrogenesis at the paleocene eocene boundary abstract the kaolinite rich marlboro clay was deposited on the inner shelf in the salisbury embayment of the u s atlantic margin at the onset of the carbon isotope excursion marking the 56 ma paleocene eocene boundary and is characterized by an anomalously high concentration of magnetic nanoparticles of enigmatic origin that give rise to notably intense bulk magnetization recent studies point to a magnetic assemblage that is dominated by single domain magnetite particles that tend to be isolated rather than arranged in chains the most distinguishing feature of magnetotactic bacteria fossils on the other hand it is very unlikely that the nanoparticles can be condensates of an impact plume given the meter scale thickness of the marlboro clay we obtained new data from a landward proximal site at wilson lake on the new jersey coastal plain and find that the abrupt increase in magnetite nanoparticles is virtually coincident stratigraphically with the recently reported impact spherule layer at the base of the marlboro clay in the same core yet the high field magnetic susceptibility a measure of total iron concentration and strontium isotope values on bulk sediment an indicator of sediment weathering provenance are not different in the marlboro clay from the immediately underlying vincentown formation we suggest that the distinctive magnetic properties of the marlboro clay originated from pyromagnetic soil enhancement by widespread wildfires on the adjoining drainage area the pyrogenetic products were soon washed from the denuded landscape and rapidly deposited as mud waves across the shelf becoming the marlboro clay a few percent of incinerated biomass ends up as calcite known as wood ash stone and can inherit its light carbon isotope composition disseminated wood ash stone entrained in the marlboro clay could contribute to the landward increase in amplitude of the carbon isotope excursion in bulk carbonate data a plausible trigger for the initial conflagration is a fireball from the impact of a sizable extraterrestrial object at moderate range

formation processes and combustion features at the lower layers of the middle palaeolithic open air site of nesher ramla israel the lower stratigraphic sequence units iii vi of the middle palaeolithic site of nesher ramla was studied using geoarchaeological methods field observations indicate that the site formed within a karst depression that was infilled by colluvium and in which intermittent human activity occurred including two layers highly rich in anthropogenic remains units iii and v infrared analysis of bones determined that black bones are carbonized and that certain white bones are calcined quantitative analysis of wood ash pseudomorphs indicates specific areas of high concentrations of ash micromorphological analysis enabled identification of two distinct features associated with ash and burnt bones one is a thinly bedded complex of blacked soil overlain by ash and charcoal and the second is a 20 cm thick massive fine grained layer of mixed ash the first feature is interpreted as an in situ hearth macroscopically similar features have not yet been analyzed the second feature is interpreted as ash in secondary position i e an ash pile midden that formed following hearth rake out activities these findings are unique considering that most middle palaeolithic open air sites in the levant are single layered and that in most evidence for hominin use of fire is scarce or absent we discuss the factors that may affect the preservation of ash in open air sites and conclude that the setting of nesher ramla in a topographic low provided relative protection from wind which prevented ash deflation and at the same time hominin activity remains were buried relatively fast which detached the ashes and combustion features from direct rainfall and from decalcifying root activity

stable carbon isotope ratios and their relevance to the determination of accurate radiocarbon dates for lime mortars abstract attempts have been made to date mortar by radiocarbon analysis potential problems are discussed and the possible use of stable carbon isotopes to detect contamination by geological carbonates is investigated

laboratory characterization of rainfall induced loess slope failure loess slopes are widely distributed throughout the northwestern region of china and are prone to slope failure in response to heavy rainfall we undertook three groups of flume experiments in the laboratory to study loess slope dynamics under artificial rainfall conditions additionally a laser scanner was used to observe loess landslide deformation characteristics and failure development a numerical analysis of unsaturated seepage in loess slopes because of rainfall infiltration was performed moisture content pore water pressure and slope deformation were monitored to quantify the relationship between rainfall infiltration and loess slope stability movement of the wetting front near the slope surface was triggered by rainfall and related to rainfall intensity and duration which is consistent with the numerical solution rainfall infiltration increased pore water pressure producing gravity driven landslides we observed that landslide development began with local failure in the toe slope that gradually retreated toward the crown forming a multi sliding displacement and eventually resulting in total slope failure