qualifying mass failures on loess gully sidewalls using laboratory experimentation abstract the morphology of the failure scar has been a long debated issue concerning the loess plateau of china and the lack of normative data has hampered vital research in this area in this study a series of laboratory experiments were conducted to observe failure geometries and volumes under rainfall simulations the following six failure scar types occurred the sequence of the types described here may be same to that of the following text namely tf cd cu ia ps and co the number of failure masses in the experiment for scar types tf cd cu ia ps and co amounted to 45 26 23 3 2 and 1 of the total and the corresponding volumes were 58 16 20 2 3 and 1 of the total respectively this implies that tf cd and cu were the three major types of failure scars during the process of gravity erosion on a steep loess slope and the scar tf was the most significant the sensitivity coefficient the degree of variation in the target value caused by a change in a crucial factor when other conditions remain unchanged of the slope gradient and rainfall intensity for the total volume of the tf scar were 4 5 and 3 7 respectively in other words a relatively dangerous failure scar tf might appear if the slope became steeper or if the rainfall became more intensive in addition the sensitivity coefficients of the rainfall duration for the total volume of the cu scar was significant being 12 4 this shows that a long duration storm could easily induce a large volume failure with a cu scar the experimental results obtained here provide a morphogenic insight into the gravity erosion control on a loess gully sidewall

a model of slope formation related to landslide activity in the eastern prealps austria abstract the rhenodanubian flysch zone of the eastern alps of austria is considered to be susceptible to landslides in the study area an undulating low mountain landscape of the eastern european prealps the flysch bedrock is superimposed by quaternary periglacial cover beds and loess both the petrography of the bedrock and the soil mechanical properties of quaternary sediments control the slope dynamics a database compiled for the study area comprises about 200 datasets on landslide and rock fall hazards it covers a time span between 1771 and 2007 and shows clusters between 1940 and 1943 1965 and 1966 1979 and 1982 as well as in 2006 the study analyses slope stability in the light of slope formation phases with respect to weathering erosion and geology furthermore geomorphological and soil geographical methods are combined with soil mechanical calculations the application of the concept of periglacial cover beds facilitates the distinction between holocene and pleistocene landforms and slide masses in the research area as a result the study shows that the properties of quaternary sediments and the occurrence of the densely bedded basal cover beds are responsible for landslide susceptibility the variable permeability in loess layers in contrast to that in the underlying basal cover beds consisting mainly of marls and clayey material is one of the fundamental controlling factors of mass movements in a temporal context it is evident that the stability of slopes in the study area is influenced by several phases of slope formation the synopsis of field survey morphometrical geotechnical as well as laboratory analyses and slope stability calculation gives evidence of five morphodynamic phases that partly reoccur in an alternating pattern after having passed all phases the stability of the slopes studied is increased because modified soil mechanical properties of the slide masses become important as a consequence the critical slope angle is raised by 3 5

on the spatial relationship between landslides and causative factors on lantau island hong kong abstract this paper presents a statistical approach to study the spatial relationship between landslides and their causative factors at the regional level the approach is based on digital databases and incorporates such methods as statistics spatial pattern analysis and interactive mapping firstly the authors propose an object oriented conceptual model for describing a landslide event and a combined database of landslides and environmental factors is constructed by integrating the various databases within such a conceptual framework the statistical histogram spatial overlay and dynamic mapping methods are linked together to interactively evaluate the spatial pattern of the relationship between landslides and their causative factors a case study of an extreme event in 1993 on lantau island indicates that rainfall intensity and the migration of the center of the rainstorm greatly influence the occurrence of landslides on lantau island a regional difference in the relationship between landslides and topography is identified most of the landslides in the middle and western parts of the island occurred on slopes with slope angles of 25 35 while in the eastern part the corresponding range is 30 35 overlaying landslide data with land cover reveals that a large number of landslides occurred in the bareland and shrub covered area and in the transition zones between different vegetation types the proposed approach can be used not only to analyze the general characteristics of such a relationship but also to depict its spatial distribution and variation thereby providing a sound basis for regional landslide prediction

acid drainage at the inactive santa lucia mine western cuba natural attenuation of arsenic barium and lead and geochemical behavior of rare earth elements abstract a detailed geochemical study was conducted at the inactive zn pb mine of santa lucia in western cuba the studied mine wastes are characterized by high total concentrations of potentially toxic elements pte with average values of 17 4 fe 5 47 ba 2 27 pb 0 83 zn 1724 mg kg as and 811 mg kg cu oxidation of sulfide minerals in mine waste dumps and in the open pit produces acid mine effluents ph 2 5 2 6 enriched in dissolved so 4 2 up to 6754 mg l fe up to 4620 mg l and zn up to 2090 mg l low ph values 2 5 2 8 and high dissolved concentrations of the same pte were found in surface waters up to 1500 m downstream from the mine nevertheless concentrations of as ba and pb in acid mine effluents and impacted surface waters are relatively low 0 01 0 3 mg l as 0 002 0 03 mg l ba and 0 3 4 3 mg l pb analysis by x ray diffraction and electron microscopy revealed the occurrence of lead bearing barite and beudantite and the more common solid phases reported elsewhere in similar environments including fe oxyhydroxides jarosite anglesite and plumbojarosite because the reported solubilities for barite and beudantite are very low under acidic conditions these minerals may serve as the most important control in the mobility of as ba and pb in contrast fe oxyhydroxides are relatively soluble under acidic conditions and therefore they may have a less significant role in pte on site immobilization mine wastes and stream sediments show a light ree lree and middle ree mree enrichment relative to heavy ree hree in contrast acid mine effluents and surface waters are enriched in hree relative to lree these results suggest that the lree released during the oxidation of sulfides are captured by secondary weathering minerals while the mree are removed from the altered rocks the low concentrations of lree in acid stream water suggest that these elements can be retained in the sediments more strongly than hree and mree one possible explanation for the sharp decrease in dissolved lree might be their retention by low solubility secondary minerals such as anglesite barite and jarosite

formation of alunite jarosite and hydrous iron oxides in a hypersaline system lake tyrrell victoria australia abstract alunite kal 3 so 4 2 oh 6 and jarosite kfe 3 so 4 2 oh 6 are common weathering products of aluminosilicates and pyrite long range transport of the constituents forming these minerals and the subsequent deposition of alunite and jarosite in an evaporite setting have not been previously documented such conditions for the occurrence of alunite and jarosite were investigated in a hypersaline system where acid groundwater enriched in k al fe iii and so 4 enter a saltplaya lake sediment cores were studied by thin section xrd and sem eds groundwater and pore water chemistries were also analyzed the results show that alunite and jarosite occur together or as individual layers and cements within the top 20 cm of the sediments where the groundwater is most concentrated due to evaporation hydrous fe oxides also occur as cements or vein fillings with the alunite and jarosite but are distributed throughout the 70 cm sediment column studied the results are consistent with a model in which alunite and jarosite precipitate as a result of the evaporation of water thermodynamic modeling indicates that the pore water in the playa sediments maybe in equilibrium with alunite jarosite and hydrous fe oxides

a unified landslide classification system for loess slopes a critical review abstract over the last few decades many landslide classification systems have been developed inconsistencies across these systems have inevitably led to ambiguity confusion and contradictions specifically there has been no consensus on what types of slope movements and failures constitute landslides as a result landslide classification systems based on the same criteria do not always include the same types of slope failures on the other hand general landslide classification systems do not take into account the unique characteristics of slope failures in loess which covers about 6 7 of the earth s land surface most literature on loess is in chinese and the nomenclature both within the chinese literature and between the chinese and english literature is often not readily comparable therefore there is a need for a consistent and comprehensive system for classification of loess slope failures to be developed to better manage these particular geohazards as the presence and interactions of humans with the environment in loess areas continue to increase in this paper a critical review of landslide classification systems was conducted to identify their limitations as well as their relevant criteria for classifying loess slope failures understanding the mechanisms underlying the failure of loess slopes is critical for creating a realistic and comprehensive classification system for slope failures the classification systems of loess slope failures unified in this paper are based on detailed analyses of the possible mechanisms underlying each class of failure the primary classification criteria are types of movement and materials with other descriptive criteria used to explain differences among different classes for each class one or two typical case histories are presented a comprehensive collection of the literature reviewed in this study will facilitate future research on loess geohazards

underlying mechanisms of the geohazards of macro loess discontinuities on the chinese loess plateau abstract loess discontinuities are geological interfaces that are formed and continuously developed within loess during loessification typically loess discontinuities include joints cracks fissures and layer contact planes in this study 13 798 discontinuities on the loess plateau in china were examined to demonstrate the control mechanisms underlying loess geohazards by comprehensively analyzing the collected data the following could be concluded 1 the scale of loess geohazards is proportional to the scale of the associated loess discontinuities notably a new terminology called cutting degree was defined to measure the scale of loess discontinuities 2 loess discontinuities provide sufficient conditions for both loess geohazards and preferential seepage channels 3 the control mechanism for loess geohazards can be represented by a process discontinuity cave gully and sliding abbr for dcgs furthermore these conclusions provide fundamental information for the understanding of loess geohazards controlled by the combined characters of loess discontinuities and for forecasting of loess landslides on the loess plateau

high mountain region of the northern romanian carpathians responded sensitively to holocene climate and land use changes a multi proxy analysis a high altitude lake sediment sequence buh iescu mare 1918 m a s l in the subalpine zone of the rodna mountains was analysed through a multi proxy approach to determine the sensitivity of high mountain habitats to climate fire and land use changes the early holocene regional forests were dominated by pinus sylvestris and mugo and replaced by picea abies from 9800 cal yr bp after an extended hiatus in the profile c 9800 4200 cal yr bp probably because of the physical removal of sediments through avalanche or high flow events p abies abies alba and fagus sylvatica forests developed after 4200 cal yr bp the timberline and treeline reacted sensitively to past changes in climate and human impact the site was probably situated above the treeline throughout most of the investigated period however a treeline ecotone or krummholz zone may have sporadically reached the lake s elevation in the early holocene a decline in timberline and treeline elevation was noted during the last 1200 years and more evidently over the past 200 years with replacement by subalpine shrubs alnus viridis and alpine herbaceous communities because these vegetation changes were associated with an increased prevalence of pollen based anthropogenic indicators charcoal particles and abiotic indicators human induced fires and clearance and resultant erosion inputs to the lake are implied effects of current warming on the altitude range of trees are not yet visible probably because land use has more strongly contributed to changes in land cover than the climate fluctuations of the last millennium in the rodna mountains

chronological framework for the lateglacial pollen and macrofossil sequence in the pirin mountains bulgaria lake besbog and lake kremensko 5 the sediments of numerous cirque lakes in the pirin mountains have yielded several generalized pollen diagrams but low stratigraphic and temporal resolution has hampered detailed reconstruction of the vegetational history especially for the lateglacial new pollen and macrofossil analyses of high stratigraphic resolution combined with well controlled timedepth curves for lake besbog and lake kremensko 5 now permit the firm identification of the lateglacial interstadial interval bollingallerod dated at 13 8 12 6 ka cal bp at besbog and 14 1 12 8 ka cal bp at kremensko 5 and correlated with the greenland interstadial gi 1 14 5 12 6 ka cal bp macrofossil analyses indicate that during the bolling allerod period betula and juniperus occurred around the lakes at 2124 2250 m a s l following the younger dryas a betula woodland covered the mountains between 1900 and 2250 m in the early holocene because of higher summer insolation at this time the temperate deciduous forest reached up to 1900 m or 800 m above their present limit producing a regional pollen rain that dominated pollen deposition in the cirque lakes after about 7000 cal yr bp conifer forests replaced the birch woodland at middle and high elevations

failure mechanisms in loess and the effects of moisture content changes on remoulded strength abstract investigations into the failure mechanisms of loess slopes in the loess region of north central china have shown that a majority of mass movements are associated with shallow slab slides predominantly moving under tension the effects of soil moisture content are of paramount importance when dry vertical slopes in loess may exceed 15 m in height but under conditions close to saturation the structural strength of loess rapidly decreases causing failure of the slopes mass failure of loess occurs as collapse due to hydroconsolidation and disintegration of the loess fabric as a result of liquefaction or fluidization and can be associated with progressive failure processes local destruction of the openwork fabric of the loess can lead to small plastic movements within the loess deposits this is as close as loess can come to creep

holocene vegetation history in the upper forest belt of the eastern romanian carpathians abstract pollen analysis supported by nine ams 14 c dates from the poiana tiol peat sequence 1540 m in the rodnei mountains eastern romanian carpathians romania is used to reconstruct the holocene vegetation history in this mountain region the results are then compared with other sequences from romania and eastern europe in order to better understand the past dynamics of the main forest constituents the vegetation record at poiana tiol starts at ca 11 000 cal yr bp with the occurrence of rather closed woodlands composed of betula pinus picea abies alnus a viridis and ulmus picea abies was the dominant tree species for almost the entire period however during the last 3000 years p abies forests were largely replaced by pinus in the area temperate tree taxa fraxinus quercus acer tilia and corylus avellana were also common but likely at lower elevation c avellana expanded around 10 300 cal yr bp and reached maximum values after 9000 cal yr bp pollen of carpinus betulus and fagus sylvatica was already recorded around 7000 cal yr bp however the spread of c betulus occurred at ca 6000 cal yr bp with maximum values between 4800 cal yr bp and 3000 cal yr bp while f sylvatica spread from ca 3200 cal yr bp and attained maximum values between 2000 and 200 cal yr bp the first indications of human activities appeared around 3200 cal yr bp and intensified within the last 200 years comparison with other sequences from romania and surrounding countries reveals both similarity and great differences related to the location of glacial refugia climate change and human impact

the climate of europe 6000 years ago palaeoclimates across europe for 6000 y bp were estimated from pollen data using the modern pollen analogue technique constrained with lake level data the constraint consists of restricting the set of modern pollen samples considered as analogues of the fossil samples to those locations where the implied change in annual precipitation minus evapotranspiration p e is consistent with the regional change in moisture balance as indicated by lakes an artificial neural network was used for the spatial interpolation of lake level changes to the pollen sites and for mapping palaeoclimate anomalies the climate variables reconstructed were mean temperature of the coldest month tc growing degree days above 5 c gdd moisture availability expressed as the ratio of actual to equilibrium evapotranspiration and p e the constraint improved the spatial coherency of the reconstructed palaeoclimate anomalies especially for p e the reconstructions indicate clear spatial and seasonal patterns of holocene climate change which can provide a quantitative benchmark for the evaluation of palaeoclimate model simulations winter temperatures tc were 1 3 k greater than present in the far n and ne of europe but 2 4 k less than present in the mediterranean region summer warmth gdd was greater than present in nw europe by 400 800 k day at the highest elevations and in the alps but 400 k day less than present at lower elevations in s europe p e was 50 250 mm less than present in nw europe and the alps but was 10 15 greater than present in s europe and p e was 50 200 mm greater than present in s and e europe

selective mineralization of microbes in fe rich precipitates jarosite hydrous ferric oxides from acid hot springs in the waiotapu geothermal area north island new zealand abstract a group of small springs that are informally called orange spring located near hakereteke stream in the northern part of the waiotapu geothermal area feed hot 80 c acidic ph 2 1 2 4 as rich sulfate waters into a discharge channel that is up to 25 cm deep submerged reddish brown precipitates on the channel floor are formed largely of noncrystalline as rich hydrous ferric oxide hfo mainly goethite poorly crystalline lepidocrocite and crystalline jarosite well preserved coccoid and rod shaped microbes are found in the as rich hfo but not in the lepidocrocite or jarosite the jarosite was probably precipitated when the water had a low ph 4 and lower so4 content the fluctuations in the ph and so4 content which led to precipitation of the different mineral phases may reflect mixing of the spring water with stream water that flowed through the channel when hakereteke stream was in flood stage the goethite probably formed when coccoid and rod shaped bacteria acidithiobacillus ferrooxidans mediated rapid oxidization of the fe2 to fe3 that was then immediately coprecipitated with the as such rapid precipitation promoted mineralization of the microbes the lack of mineralized microbes and the lower as in the lepidocrocite and jarosite may reflect precipitation rates that were slower than the decay rates of the microbes or ecological factors that limited their growth

characterization of jarosite natrojarosite in two northern scandinavian soils abstract jarosite type minerals mfe 3 so 4 2 oh 6 m k jarosite m na natrojarosite were studied in two sulfic cryaquepts developed in sulfidic sediments deposited in the baltic between 7000 and 4000 bp the jarosites were characterized by x ray diffraction xrd and a selective dissolution technique selective dissolution showed that the k na molar ratio in the jarosites was 0 32 1 27 and the xrd patterns indicated that the jarosite and natrojarosite components formed solid solutions saturated pastes of soil samples were equilibrated for different periods 6 hours to 8 days in order to estimate solubility product constants k so for the jarosite and natrojarosite estimated values of k so for jarosite 10 94 1 10 94 2 corresponded well with literature values for pure or nearly pure synthetic jarosite for natrojarosite only one determination or k so was found in the literature the discrepancy between this value and the k so values obtained in the present study 10 93 1 10 93 9 is about four orders of magnitude which is too large to be explained as an effect of solid solution formation thus we suggest that the literature value is not valid for the pedogenic natrojarosite in these soils i e it is less soluble than the value indicates we hypothesize that natrojarosite forms mainly where the supply of k limits jarosite formation e g under conditions where marine or brackish water has a minor influence the weathering of silicate minerals might be the main source of k and na in such a case by contrast in coastal areas concentrations of k na and so 4 are high and jarosite formation probably is limited by fe oxidation in such environments mainly jarosite is formed owing to its more rapid formation kinetics

heavy rainfall triggered loess mudstone landslide and subsequent debris flow in tianshui china abstract continuous and heavy precipitation triggered a large loess landslide at the southern dagou village of mapaoquan town tianshui city gansu province of china on july 21 2013 the landslide debris rapidly turned into a debris flow that was deposited in the ravine mouth with the volume of 1 9 105 m3 detailed field mapping three dimensional laser scanning aerial photograph interpretation and laboratory tests were carried out to study the formation and moving characteristics of the landslide and subsequent debris flow the results showed that 1 the peak flow velocity and peak discharge of the debris flow were estimated to be approximately 7 2 m s and 730 m3 s respectively the velocity had a tendency to first increase and then decrease from the head to entrance in the dagou gully 2 the analysis of rainfall conditions showed that the effective antecedent rainfall within 7 days and hourly rainfall intensity which triggered the slide debris flows was 239 mm and 20 mm h respectively compared with the critical rainfall in this area the effective antecedent rainfall was found to be more significant in triggering this event 3 the mean and effective particle sizes were approximately 0 73 1 3 mm and 0 036 0 087 mm respectively and had the same distribution along the gully as the velocity which confirmed the process of the variation in the flow velocity 4 the scale amplification was very obvious in the formation and moving process of the slide debris flows

reduction of jarosite by shewanella oneidensis mr 1 and secondary mineralization abstract jarosite is a common mineral in a variety of environments formed by the oxidation of iron sulfide normally accompanying with the generation of acid mine drainage amd in mining areas or acid rock drainages ard in many localities decomposition of jarosite by dissimilatory iron reducing bacteria dirb influences the mobility of many heavy metals generally accommodated in natural jarosite this study examined the anaerobic reduction of synthesized jarosite by shewanella oneidensis strain mr 1 a typical facultative bacteria the release of ferrous and ferric ion as well as sulfate and potassium in the inoculated experimental group lasting 80 days is much higher than that in abiotic control groups the detection of bicarbonate and acetate in experimental solution further confirms the mechanism of microbial reduction of jarosite in which lactate acts as the electron donor the produced ferrous iron stimulates the subsequent secondary mineralization leading to precipitation and transformation of various iron containing minerals green rust and goethite are the intermediate minerals of the microbial reduction process under anoxic conditions and the end products include magnetite and siderite in aerobic environments goethite magnetite and siderite were also detected but the contents were relatively lower while in abiotic experiments only goethite has been detected as a product thus the microbial reduction and subsequent mineral transformation can remarkably influence the geochemical cycling of iron and sulfur in supergene environments as well as the mobility of heavy metals commonly accommodated in jarosite

study of the 1920 haiyuan earthquake induced landslides in loess china many large scale landslides induced by earthquakes have been reported in loess soils they often cause catastrophes because they travel long distances at high velocity to clarify the mechanism of these landslides field survey was performed on the landslides triggered by the haiyuan earthquake china 1920 and a series of ring shear tests was conducted on the loess soils collected from a landslide the field surveys revealed that most of the loess landslides triggered by the haiyuan earthquake occurred on concave slopes gentler than 15 with long runout distance showing very small equivalent friction angle cyclic ring shear tests on saturated specimens in the undrained condition showed that when cyclic shear stress was applied to a loose loess specimen pore pressure was built up gradually before the failure and after that large pore pressure was quickly generated due to the failure of loess soil structure meanwhile to investigate the mechanism that produces the high mobility of loess landslides ring shear tests were conducted on loess specimens with large shear displacement of up to several meters under the undrained condition and it was found that the initial normal stress has no effects and overconsolidation ratio has little if any effects on the apparent friction angle in the steady state for loess soils results of tests on soils at different saturation degrees revealed that the reduction in shear strength results more likely from the generation of pore water pressure not of pore air pressure

field testing of irrigation effects on the stability of a cliff edge in loess north west china as it is not uncommon that irrigation has triggered landslides in the chinese loess plateau a full scale field testing in a typical cracked plateau in heifangtai gansu province of china to simulate such phenomenon was conducted in the study piezometers were installed to measure the groundwater and crackmeters as well as inclinometers were used to measure the slope movement water was pumped from the nearby source daily to simulate the irrigation process there was a sharp increase of pore pressure in the undisturbed loess below the crack when the inclinometer registered considerable movement due to the inflow of water via the crack such increase in pore pressure also dissipated rapidly eventually the irrigation water daylighted at the major cracks from the face of the plateau leading to local failures the results show that cracks have significant effects on the flow of the irrigation water into the ground the rapid rise in the local pore water pressure had reduced the stability of the slope

chinese loess record of monsoon climate during the last glacial interglacial cycle the thick loess paleosol succession of central china contains a detailed record of changes in east asian monsoon climate since the late miocene epoch the alternating loess paleosol stratigraphy closely resembles the marine oxygen isotope record implying that episodic dust deposition and pedogenesis are in phase with global ice volume fluctuations and controlled by variations in solar radiation reaching the land surface deposits equivalent to marine isotope stages mis 5 through 1 have been dated by 14c 10be luminescence and magnetic susceptibility and grain size models malan loess mis 4 2 decreases in thickness southeastward from 30 m in the western loess plateau to 5 m east of xi an downwind asian dust is found in japan the north pacific ocean and the greenland ice sheet where it has a chemical signature that points to a primary source in western china during glacial times the mean dust flux in the central loess plateau reached 0 35 mm year whereas in interglacial times it fell to 0 1 mm year times of high dust influx and reduced soil development coincided with strengthened winter monsoon conditions which are inferred from variations in loess grain size times of decreased dust accumulation and strong pedogenesis marked by high values of magnetic susceptibility represent times of strengthened summer monsoon conditions high frequency fluctuations in dust influx during deposition of the malan loess include peaks that likely correlate with north atlantic heinrich events the younger dryas oscillation is recorded in chinese eolian and organic deposits by a shift from cool humid late glacial conditions to cold and dry conditions followed by a return to milder humid climate at the beginning of the holocene warm moist climate associated with a strong summer monsoon characterized the first half of the holocene epoch when a widespread paleosol complex developed on the loess plateau increased dust deposition during the middle to late holocene marked a shift to cooler drier conditions

lateglacial to holocene vegetation development in the central rila mountains bulgaria the vegetation history of the central rila mountains for the last 14 000 years was reconstructed by means of pollen analysis and radiocarbon chronology of a core retrieved from lake manastirsko 2

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

characteristics of late quaternary activity along the southern border fault zone of weihe graben basin abstract the weihe graben basin located in the centre of shaanxi china is a tectonic depression on the southern border of ordos massif a subtectonic unit in the sino korean paraplatform in the light of new information exhibited from geological mapping on the scale of 1 50 000 the active history and the feature of the southern border fault zone of weihe graben basin have been researched the fault zone may be subdivided into two segments the piedmont fault of huashan mt in the east sector and the northern border fault of qinling mts in the west sector the research shows that new activity of the piedmont fault of huashan mt is obvious since the late quaternary a great number of relics of earthquake deformation such as the newest fault scarps bedrock fractures loess crevices landslides and mountain creep are distributed along this fault and its two flanks this fault is most likely the causative fault zone of the huaxian great earthquake in 1556 m 8 the analysis of two palaeoseismic profiles shows the earthquake recurrence interval is 2000 2500 years for the huashan mt piedmont fault whereas 2000 4000 years for the northern border fault of qinling mts

analysis of physical testing of rainfall induced soil slope failures rainfall is a significant factor that triggers slope failures around the world this paper reports a series of physical tests which were conducted to simulate rain induced slope failures the experiments dealt with two scenarios including 1 rainwater infiltration into the slope and 2 slope failures induced by artificial rainfall with different initial conditions slope deformation and slope failures were observed and possible mechanisms were interpreted based on the experimental results the results confirm the hypothesis that pore water pressure and water content in a loose soil slope change rapidly and that water infiltration into cracks in the slope has a great impact on landslide development the observed slope failures can be divided into three types overall sliding failure partial sliding failure and flow slide the effect of slope gradient rainfall intensity and distribution of initial suction on the slope deformation and failure process are also summarized for possible applications under the similar conditions

pollen and plant macrofossil analyses of radiocarbon dated mid holocene profiles from two subalpine lakes in the rila mountains bulgaria pollen analysis plant macrofossil determination and radiocarbon dating were performed on profiles of holocene age obtained from two subalpine lakes 2320 2340 m a s l in the central rila mountains bulgaria the palaeovegetational reconstruction dates back to the mid atlantic 6500 6700 cal bp the plant macrofossil record revealed that groups of pinus mugo and juniperus sibirica were distributed in the subalpine zone the treeline was shaped by pinus sylvestris and pinus peuce and was higher up to 2200 2300 m a s l compared with the present day a change to cooler summers and warmer winters after 6700 cal bp characterized by a rise in humidity and precipitation stimulated the formation of a coniferous vegetation belt dominated by pinus sylvestris pinus peuce and abies alba the pollen assemblages also indicated a dominance of deciduous trees quercetum mixtum corylus phase at low altitudes until c 6000 cal bp the sub boreal was characterized by a wider distribution of abies alba in the lower part of the coniferous belt and a gradual enlargement of the areas occupied by fagus sylvatica and picea abies after 3800 3500 cal bp the macrofossil finds of picea abies testify to its expansion after 2800 cal bp when average temperatures dropped and precipitation increased traces of human disturbance in the subalpine area are continuously registered in the pollen and plant macrofossil records since 3770 cal bp indicating livestock grazing burning of dwarf pine pinus mugo for new pasture land and lowering of the treeline

the formation of goethite jarosite and alunite during the weathering of sulfide bearing felsic rocks quantities of goethite and jarosite produced by weathering correlate with abundance and composition of sulfide minerals originally in rocks to characterize processes forming these minerals chemical weathering of sulfide bearing rocks was simulated using differential equations which describe mass transfer between aqueous solutions and minerals helgeson 1968 goethite begins precipitating during reaction between meteoric water f sub o 2 10 super 06 atm and sulfides after dissolution of 6 7 x 10 super 9 g pyrite or 6 0 x 10 super 9 g chalcopyrite per 1 000 g h 2 o reaction of the oxygen dissolved in 1 000 g water that is initially saturated with the atmospheric abundance of oxygen consumes 0 0085 g pyrite or 0 013 g chalcopyrite goethite is the only reaction product the calculations predict that weathering produces jarosite or alunite after goethite when 0 04 moles of oxygen have been consumed per 1 000 g h 2 o and where rates of oxygen replenishment approximately equal or exceed consumption simultaneous reactions between k feldspar an aqueous solution and pyrite or chalcopyrite produce alunite and goethite if the irreversible molar flux of fe al is less than 0 5 reactions with fluxes of fe al between 0 5 and 1 0 produce alunite goethite and jarosite those with fe al fluxes greater than 1 0 generate only jarosite after goethite following saturation of the solution with jarosite the mass ratio goethite goethite jarosite decreases smoothly from 1 0 to 0 0 accompanying continuous dissolution of pyrite and chalcopyrite the interval of reaction progress over which goethite and jarosite coexist increases relative to pyrite and k feldspar reactions when weathering involves muscovite or chalcopyrite in simulations whose sulfides have been totally oxidized this ratio varies antithetically with the volume percent sulfide and or ratio of pyrite pyrite chalcopyrite initially present a prediction consistent with geologic observations

influence of topography and volume on mobility of loess slides within different slip surfaces mobility of loess slides has been evaluated using an empirical approach based on a detailed field investigation and remote sensing image interpretation for all the loess slides the affected area increases with increasing loess slides volume from the statistical analysis it is seen that the travel distance has an increasing trend while the coefficient of friction has a decreasing trend with the increase in landslide volume landslide volume determine its travel distance and coefficient of friction that can be shown with a regression equation having simple power law form which indicates that the mobility of loess slides increases with increasing volumes by analogy the greater the energy of the sliding loess mass the stronger is the mobility of loess slide a plot of the travel distance of loess slide versus fall height shows a significant positive power law correlation indicating the increase in mobility of loess slide with fall height the negative power law correlation observed between the travel distance and slope inclination implies that the mobility decreases with the increase of slope inclination three datasets of loess slides characterized by different slip surfaces were distinguished the red clay contact landslides have the strong mobility than landslides in loess and bedrock contact

the temperature of europe during the holocene reconstructed from pollen data we present the first area average time series reconstructions of warmest month coldest month and mean annual surface air temperatures across europe during the last 12 000 years these series are based on quantitative pollen climate reconstructions from over 500 pollen sites assimilated using an innovative four dimensional gridding procedure this approach combines three dimensional spatial gridding with a fourth dimension represented by time allowing data from irregular time series to be focussed onto a regular time step we provide six regional reconstructed temperature time series as well as summary time series for the whole of europe the results suggest major spatial and seasonal differences in holocene temperature trends within a remarkably balanced regional and annual energy budget the traditional mid holocene thermal maximum is observed only over northern europe and principally during the summer this warming was balanced by a mid holocene cooling over southern europe whilst central europe occupied an intermediary position changes in annual mean temperatures for europe as a whole suggest an almost linear increase in thermal budget up to 7800 bp followed by stable conditions for the remainder of the holocene this early holocene warming and later equilibrium has been mainly modulated by increasing winter temperatures in the west which have continued to rise at a progressively decreasing rate up to the present day

irrigation induced loess flow failure in heifangtai platform north west china because the construction of dams and hydro electric power stations of liujiaxia and yanguoxia across the yellow river in west gansu province north west china inhabitants in the reservoir areas were resettled in heifangtai loess platform irrigation thus started in 1968 perched water table was significantly raised and resulted in many loess flow failures in the past 30 years this type of landslide was often featured by long runout distance high speed and recurrence laboratory tests along icu and csd stress paths were performed it is shown that the loess has a strong strain softening behavior and instability can occur in drained condition before undrained liquefaction the failure mechanism of loess flow can be interpreted as the following process with increasing perched water table collapse in loess was first triggered in drained condition and led to undrained loading to adjacent soil in the lower saturated part of the loess platform under gravity loading applied by upper dry loess undrained flow failure mobilized eventually

influence of lixiviation by irrigation water on residual shear strength of weathered red mudstone in northwest china implication for its role in landslides reactivation abstract irrigation in loess tableland areas of northwest china has induced a large number of landslides around their edges of which loess red mudstone landslide is one of the most frequent types salt sinters commonly observed at the toes of these landslides where the weathered red mudstone wrm outcrops have raised the possibility that removal of soluble salts in the wrm by irrigation water could be crucial in the reduction of its shear strength and thus in the occurrence of these landslides in order to investigate the effects of lixiviation by irrigation water on residual shear strength of the wrm samples of the wrm close to two landslides in lanzhou city one of the largest cities in northwest china were tested after being treated under different conditions these included 1 saturation with the yellow river water the only source of irrigation 2 saturation with groundwater and 3 saturation and leaching with deionized water based on the results of these tests specific mechanisms of residual shear strength reduction of the wrm due to lixiviation by irrigation water were discussed in terms of physico chemical interactions between the wrm and water it was found that lixiviation reduced residual shear strength and residual friction angle r of the wrm by up to 65 and 62 respectively after being leached 6 times this coincided with a dramatic dissolution and leaching of soluble salts from the wrm particle size distribution showed that the more the wrm was leached the more the clay fraction and the lesser coarser fractions this suggested that reduction in residual shear strength of the wrm could be attributed to mainly disaggregation of particles coarser than clay and to a lesser degree to weakening of interparticle forces among individual clays it was further postulated that variation in clay mineralogy may influence performance of particle disaggregation

glaciation in the rila mountains bulgaria during the last glacial maximum abstract relict glacial landform complexes have been studied in the mountains of the central balkan peninsula since the end of the 19th century since their existence was proved for the first time by cvijic various authors have debated the number of glacial phases as well as their age at present the problem of age determination is being solved by the application of the new methods for numerical dating this paper is a detailed study of the maximum glaciation in the rila massif which is the highest mountain in bulgaria and in the whole balkan peninsula the application of cosmogenic nuclide dating 10be on moraine samples confirmed that the largest extent of former glaciers that left moraine deposits was around the time of the last glacial maximum most probably the maximum extent occurred in two phases the first around the beginning and the second around the end of the lgm 24 23 ka bp and 18 16 ka bp respectively separated by a retreat phase during the coldest but also driest phase of the glacial stage the gis processed calculations on the basis of field evidence of the former glacier extent and the preliminary calculations of the equilibrium line altitude ela through the accumulation ablation ratio aar method show that the ela during the lgm had quite small differences throughout the rila massif from about 2150 to 2200 m a s l in the nw to about 2250 2290 m in the se despite the considerable differences in terminal moraine depositional altitudes from 1150 to 2000 m a s l this is due to both the complicated pattern in the directions of moisture supply and to the influences of local topography

a process model of natural attenuation in drainage from a historic mining district a process model was used to better understand the controls on the chemical evolution of drainage in a historic mining district at the pecos mine operable unit new mexico drainage near the waste rock pile is acidic ph varies from 3 0 5 0 and carries high concentrations of zn al cu and pb as drainage flows toward the pecos river ph increases to greater than 7 and heavy metal content decreases a process model of natural attenuation in this drainage shows the main controls on ph are reaction with a local bedrock that contains limestone and concurrent mixing with tributary streams models that account for both calcite dissolution and mixing reproduce the observed decrease in aqueous metal concentrations with increasing ph contaminant concentrations attenuate primarily via two distinct pathways al cu fe and pb precipitate directly from solution whereas zn mg mn and so sub 4 concentrations decrease primarily through dilution additionally pb adsorbs to precipitating hydroxide surfaces

analysis of the causes of large scale loess landslides in baoji china landslide hazards are common in western china understanding the mechanism of landslides in loess covered regions is particularly important for landslide risk assessment a detailed landslide survey including large scale slide drilling and geophysical exploration was carried out at the edge of the loess plateau on the north side of the wei river in china we reconstructed the geomorphological evolution model of the wei river and analyzed slope structures and lithology engineering geologic conditions and active fault properties in the landslide regions were investigated the results showed that paleogeomorphology of the north slope of the river gradually lowered from south to north ancient landforms showed a gradual transition to the south sanmen lake basin from the piedmont alluvial plain during the pliocene to early pleistocene the lake basin in the southern part of the study area gradually retreated and the wei river formed in the early pleistocene the main river flow shifted northward because of neotectonic movement and periodic climate changes until the holocene and then gradually moved southward to produce the current landforms the active wei river fault at the edge of the loess plateau acted as a route of water infiltration weakening the structural planes erosion and rise of the groundwater table caused old occurrence during the late pleistocene and ancient occurrence before the late pleistocene landslides to form on the edge of the plateau along active fractures and interfaces of pliocene sand gravel and clay these were multiple deep seated rotational slides and or multiple perched translational landslides slope stability analysis indicated that the complex landslides that occurred in the loess areas in recent years were closely related to the distribution of water and pliocene clay

iron mineralogy across the oxycline of a lignite mine lake iron rich pelagic aggregates of microbial origin named iron snow are formed in the water column of some acidic lignite mine lakes we investigated the evolution of fe mineralogy across the oxycline of the lusatian lake 77 germany at two sampling sites differing by their ph and mixing profiles the central basin cb of this lake shows a dimictic water regime with a non permanent anoxic deep layer and a homogeneous acidic ph all over the water column ph 3 in contrast the northern basin nb is meromictic with a permanently anoxic bottom layer and a ph increase from ph 3 in the mixolimnion superficial part of the lake to ph 5 5 in the monimolimnion anoxic bottom layer fe minerals above and below the oxycline were identified using x ray absorption spectroscopy xas at the fe k edge and further characterized down to the atomic scale by high resolution transmission electron microscopy hrtem and scanning transmission electron microscopy stem coupled to energy dispersive x ray spectroscopy edxs we explored local fe redox state and c speciation using scanning transmission x ray microscopy stxm at the fe l2 3 edges and c k edge schwertmannite fe8o8 oh 8 2x so4 x identified as the sole fe mineral in cb was polycrystalline consisting in the aggregation of nanodomains of 2 3 nm each one exhibiting the crystal structure of schwertmannite in contrast schwertmannite was partly 40 converted to aluminous ferrihydrite when reaching the oxycline in nb this mineralogical transformation was most probably due to a combination of abiotic and microbial anaerobic processes promoting ph increase and release of fe ii e g via heterotrophic fe iii reduction that induce the catalytic hydrolysis of schwertmannite to ferrihydrite mineral products were stabilized in the monimolimnion by the adsorption of aluminum silicate and organic matter noteworthy local fe redox state heterogeneities were observed with a few areas enriched in fe ii as evidenced by stxm analyses at the fe l2 3 edges these local redox heterogeneities could arise from microbial activity e g fe iii and or sulfate reduction all these results provide an in depth mineralogical overview of iron phases forming in lake 77 as a basis for future investigations of microbial vs abiotic parameters controlling their stability and transformation

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

pore pressure generation and fluidization in a loess landslide triggered by the 1920 haiyuan earthquake china a case study abstract during the 1920 haiyuan earthquake numerous catastrophic landslides were triggered in the loess area in northwest china we investigated in detail a large example of these landslides referred to as dangjiacha landslide in this paper this landslide originated from a slope of about 20 and the displaced soil mass traveled about 3200 m damming a valley we performed a field survey and found that standing water existed in the landslide area and the loess had high porosity we infer that it was the liquefaction of the water saturated loess layer rather than the suspension of silt in the pore air in the loess that caused the great mobility of this landslide to test this inference we performed undrained triaxial compression and ring shear tests on loess samples to examine the shear behavior of loess saturated by either air or water the test results showed that the water saturated loess soil was highly susceptible to flow liquefaction failure fast shear tests on naturally air dried loess samples revealed that the generated pore air pressure was small under the undrained condition and no significant reduction in the shear resistance was observed implying that air entrapped in the loess was unlikely to be the main contributor to the high mobility of this large scale landslide