clast shape analysis and clast transport paths in glacial environments a critical review of methods and the role of lithology the reconstruction and tracing of transport paths in glaciated and other environments have a long tradition in the earth sciences we here present a dataset of clast shape samples from a worldwide selection of glaciated mountain environments in order to assess the reliability of this approach overall and the role of lithology on the performance of clast shape measurements in particular our findings demonstrate that the widely used ra c40 co variance approach is applicable to 63 of the 19 catchments investigated while the alternative rwr c40 approach is more widely applicable to 75 of these catchments a systematic assessment of mixing of lithologies at the catchment scale demonstrates that such mixing leads to pronounced overlaps between different control envelopes that had previously been separated thereby removing the discriminatory power of the method mixing of similar lithologies between different catchments shows an even more extreme loss of discriminatory power which strongly suggests that lithology plays a primary role in determining clast shape and that catchment specific processes are superimposed systematic analysis of the dataset also shows that nearly all catchments apart from two can be grouped into two types type i relates to sites in lesser mountain ranges and is characterised by dominantly blocky forms in the subglacial realm highlighting significant reworking processes type ii sites are dominantly in high mountain environments and characterised by a high similarity between subglacial and fluvial control envelopes this indicates that although reworking may be pronounced it is not necessarily effective enough to remove the platy shape that most likely results from extraglacial and supraglacial inputs our study highlights the potential of clast shape analysis as a tool that allows generic processes to be identified between catchments thereby enabling an understanding of debris cascades in glaciated mountain environments we finish with recommendations for ensuring that future clast shape studies are robust reproducible and comparable between different sites

stone temperature and moisture variability under temperate environmental conditions implications for sandstone weathering abstract temperature and moisture conditions are key drivers of stone weathering processes in both natural and built environments given their importance in the breakdown of stone a detailed understanding of their temporal and spatial variability is central to understanding present day weathering behaviour and for predicting how climate change may influence the nature and rates of future stone decay subsurface temperature and moisture data are reported from quarry fresh peakmoor sandstone samples exposed during summer june july and late autumn early winter october december in a mid latitude temperate maritime environment these data demonstrate that the subsurface thermal response of sandstone comprises numerous short term minutes low magnitude fluctuations superimposed upon larger scale diurnal heating and cooling cycles with distinct aspect related differences the short term fluctuations create conditions in the outer 5 10 mm of stone that are much more energetic in comparison to the more subdued thermal cycling that occurs deeper within the sandstone samples data show that moisture dynamics are equally complex with a near surface region 5 10 mm in which frequent moisture cycling takes place and this combined with the thermal dynamism exhibited by the same region may have significant implications for the nature and rate of weathering activity data indicate that moisture input from rainfall particularly when it is wind driven can travel deep into the stone where it can prolong the time of wetness this most often occurs during wetter winter months when moisture input is high and evaporative loss is low but can happen at any time during the year when the hydraulic connection between near surface and deeper regions of the stone is disrupted with subsequent loss of moisture from depth slowing as it becomes reliant on vapour diffusion alone these data illustrate the complexity of temperature and moisture conditions in sandstone exposed to the moderate conditions of a temperate maritime environment they highlight differences in thermal and moisture cycling between near surface 5 10 mm and deeper regions within the stone and contribute towards a better understanding of the development of structural and mineralogical heterogeneity between the stone surface and substrate

cracks in desert pavement rocks further insights into mechanical weathering by directional insolation the formation of cracks is a fundamental first step in the physical weathering of rocks in desert environments in this study we combine new field data from the mojave u s gobi mongolia and strzelecki australia deserts that collectively support the hypothesis that meridional cracks cracks with orientations not readily attributable to rock anisotropies or shape in boulders or cobbles form due to tensile stresses caused by directional heating and cooling during the sun s daily transit the new studies indicate that rock size surface age and latitude play important roles with respect to their influence on rock fracture rock size and pavement surface age exert an influence on the development of rock cracks as the average clast size of mature desert pavements may be at or below the threshold clast size for thermal cracking of rocks latitude controlled seasonal temperature variations play a key role as demonstrated by 1 tightly clustered mean resultant orientations that differ by latitude as predicted in mcfadden et al 2005 and 2 very cold wintertime temperatures and strong diurnal gradients that may favor crack development in wintertime given the likelihood for strong clast heating during early morning hours the consistent evidence for meridional cracks in surfaces of diverse age and desert environments climate vegetation and distance of clast transport indicate that directional insolation may play the key role in initially generating and propagating rock fractures rather than a secondary role as implied in recent field and modeling studies of physical weathering in deserts

effect of moisture and temperature conditions on the decay rate of a purple mudstone in southwestern china soil formation and geomorphology are primarily influenced by the rock decay which in turn is strongly determined by moisture and temperature conditions however it remains unclear whether rock decay is dominated by thermal stresses or by hydration disintegration and there is little information on mudstone decay rate in southwestern china this study hypothesized that rock decay is dominated by hydration mechanism and focused on the physical decay characteristics of typical purple mudstones using a combination of field and laboratory based experiments the bedrock of a penglaizhen group j 3 p in yanting county sichuan province southwestern china was exposed and covered with nylon fabric in situ soil depths of 10 20 40 and 60 cm were laid on this nylon fabric in 2003 and the decay rate the quantity of clastic particles 2 mm that were decayed from the bedrock in t km 2 yr 1 under the nylon fabric was measured both in 2005 and 2009 in addition fresh mudstones sampled from the matoushan group k 2 m the tuodian group j 3 t and the lufeng group j 1 l in yuanmou county shuangbai county and lufeng county of yunnan province southwestern china respectively were subjected to alternating applications of moisture temperature and their interaction seven treatments in the laboratory and their decay ratios the mass of decayed rock of 2 mm clastic particles to sampled rock mass in percent were measured in 2010 in the field the decay rate of the bedrock showed a significant p 0 05 positive relationship with both the daily moisture and temperature variation at the interface between the soil and bedrock in the laboratory results showed that the effect of moisture variation but not temperature alternation on rock decay was apparent suggesting that purple rock decay is dominated by hydration mechanism freezing thawing in particular affects the sampled rocks because it causes more spalling and fracturing the j 3 t rock had the highest decay ratio because it had the highest clay mineral content and porosity of the three rock types hierarchical clustering analysis suggested that the variation of moisture content and h2o phase solid or liquid within rock plays a key role in rock decay processes both field and laboratory studies consistently showed that the alteration of wetting drying and freezing thawing as well as moisture content substantially influenced rock decay c 2012 elsevier b v all rights reserved

the thermal responses of rock art pigments implications for rock art weathering in southern africa the san rock art of southern africa is an international heritage subject to degradation and loss resulting from weathering the paintings occur within rock shelters where many are exposed to direct solar radiation for varying periods rather than occurring in dark caves as part of a study on the factors thought to be impacting weathering data were collected pertaining to rock and pigment temperatures as well as humidity within the rock shelters in addition xrd analyses were undertaken on pigment samples and the pigment to rock and pigment to pigment contacts were investigated by means of sem pigments were found to be composed of ferric oxide the ochre and a gypsum clay mix the white and to occur as a layer on top of rather than penetrating into the sandstone noncontact infrared sensors were used to monitor the temperatures of the actual pigments while micro thermocouples to monitor the surrounding nonpainted rock surfaces thermal data show that there are significant differences between the white and the ochre pigments both in terms of actual temperatures and short term thermal responses noticeably the white paint exhibits relatively large thermal fluctuations as compared to the ochre or the rock over the 20 s to 1 min timescale these thermal variations may induce pigment to pigment stresses within the painting the pigmented areas also exhibit different temperatures to the surrounding paint free rock suggesting that there may be both within painting and between painting and rock including the rock beneath the painting stresses that can lead to degradation humidity data were found to be inadequate for any meaningful evaluation of the moisture conditions

weathering of granite in antarctica ii thermal stress at the grain scale granular disintegration has long been recognized and referred to in weathering texts from all environments including the antarctic despite this universal identification and referral few to no data exist regarding thermal conditions at this scale and causative mechanisms remain little more than conjecture here as part of a larger weathering study thermal data of individual grains using infrared thermometry and ultra fine thermocouples composing a coarse granite as well as the thermal gradients in the outer 10 cm using thermistors were collected from a north facing exposure measurements were also made regarding the surface roughness of the rock based on recorded temperatures the nature of the rock surface and the properties of the minerals an argument is made for complex stress fields that lead to granular disintegration mineral to mineral temperature differences found to occur were in part due to the changing exposure to solar radiation through the day and through seasons because the thermal conductivity and the coefficient of thermal expansion of quartz are not equal in all directions coupled with the vagaries of heating this leads to inter granular stresses although fracture toughness increases with a decrease in temperature it is suggested that the tensile forces resulting from falling temperatures are able to exceed this and produce granular disassociation the lack of equality with respect to crystal axis of both thermal conductivity and expansion in quartz further exacerbates the propensity to failure grain size and porosity also influence the thermal stresses and may help explain why some grains are held in place despite disassociation near the surface while the data presented here appear to beg more questions than providing answers they do provide a basis for better more detailed studies of this important weathering scale copyright 2007 john wiley sons ltd

the physical properties of quartz micaschist and their application to freeze thaw weathering studies in the maritime antarctic as part of a study on freeze thaw weathering in the maritime antarctic an investigation was made of the physical properties of the local rock tests were made of point load compressive strength schmidt hammer in situ rock strength moisture content indentor resistance and the size range of weathering products the resulting data were used to consider the form of freeze thaw weathering operative in the field and its relationship to laboratory simulations a distinct difference between massive rock and intact rock is observed in the field it is suggested that future studies should generate a greater database pertaining to rock properties as it is an invaluable aid in the study of mechanical weathering

holocene microweathering rates and processes on ice eroded bedrock roldal area hardangervidda southern norway post glacial weathering of ice eroded metamorphic bedrock was investigated in the roldal area 60 n of the hardangervidda plateau in southern norway quartz veins were used as reference surfaces to determine a mean post glacial surface lowering rate of 0 55 mm ka 1 chemical characteristics of late season runoff were determined for one catchment snoskar and a chemical erosion rate of 4 9 t km 2 a 1 was obtained a mean in situ fracture enlargement due to microweathering of 0 12 mm ka 1 was also determined these rates are low although comparable with similar environments in cold regions and suggest that microweathering has had relatively little impact on holocene landscape evolution weathering rind thickness was found to be less on fracture walls than on exposed bedrock surfaces suggesting fractures have not played a significant role in microweathering observations of weathering morphology reveal a range of forms including shallow spalling tafoni and pseudokarren indicating locally intense weathering activity analysis of interrelationships between multiple weathering indices points to the importance of bedrock microweathering as a precursor to macro breakdown and landform evolution the research reasserts the importance of chemical activity in cold environments and the importance of moisture supply for effective microweathering the geological society publishing house 2009

a spheroidal weathering model coupling porewater chemistry to soil thicknesses during steady state denudation abstract spheroidal weathering a common mechanism that initiates the transformation of bedrock to saprolite creates concentric fractures demarcating relatively unaltered corestones and progressively more altered rindlets in the spheroidally weathering rio blanco quartz diorite puerto rico diffusion of oxygen into corestones initiates oxidation of ferrous minerals and precipitation of ferric oxides a positive v of reaction results in the build up of elastic strain energy in the rock formation of each fracture is postulated to occur when the strain energy in a layer equals the fracture surface energy the rate of spheroidal weathering is thus a function of the concentration of reactants the reaction rate the rate of transport and the mechanical properties of the rock substitution of reasonable values for the parameters involved in the model produces results consistent with the observed thickness of rindlets in the rio icacos bedrock 2 3 cm and a time interval between fractures 200 300 a based on an assumption of steady state denudation at the measured rate of 0 01 cm a averaged over times longer than this interval the rate of advance of the bedrock saprolite interface during spheroidal weathering the weathering advance rate is constant with time assuming that the oxygen concentration at the bedrock saprolite interface varies with the thickness of soil saprolite yields predictive equations for how weathering advance rate and steady state saprolite soil thickness depend upon atmospheric oxygen levels and upon denudation rate the denudation and weathering advance rates at steady state are therefore related through a condition on the concentration of porewater oxygen at the base of the saprolite in our model for spheroidal weathering of the rio blanco quartz diorite fractures occur every 250 yr ferric oxide is fully depleted over a four rindlet set in 1000 yr and saprolitization is completed in 5000 yr in the zone containing 20 rindlets spheroidal weathering thus allows weathering to keep up with the high rate of denudation by enhancing access of bedrock to reactants by fracturing coupling of denudation and weathering advance rates can also occur for the case that weathering occurs without spheroidal fractures but for the same kinetics and transport parameters the maximum rate of saprolitization achieved would be far smaller than the rate of denudation for the rio blanco system the spheroidal weathering model provides a quantitative picture of how physical and chemical processes can be coupled explicitly during bedrock alteration to soil to explain weathering advance rates that are constant in time

tectonic evolution of juventae chasma mars and the deformational and depositional structural attributes of the four major light toned rock exposures therein abstract juventae chasma a canyon peripheral to the valles marineris trough system is the product of a unique merger of a martian chaotic terrain depression and an extensional tectonic chasm the chaotic terrain portion is set along a nne ssw axis while a linear trough the chasm component is present along a wnw ese axis within the chasm are four discrete bodies of layered light toned rocks of sedimentary origin features a d the chaotic terrain component formed during the early hesperian as a result of expulsion of liquid water along pre existing planes of weaknesses resulting from a wnw ene compression the chasm component formed in response to ne sw extension during the middle to late amazonian the light toned features a d are layered at

microvariability in the early stages of cobble weathering by microenvironment on a glacier foreland storbreen jotunheimen norway the initial stages of cobble weathering measured as increasing percentage porosity were calculated for sets of cobbles taken from the foreland of storbreen a cirque glacier in the jotunheimen norway cobbles were taken from in front of the 1998 glacier snout from the 1928 1870 1810 and 1750 moraine crests and from the 10 000 year old land surface beyond the neoglacial foreland limit three microenvironments were examined within each site 1 lichen free surfaces from exposed cobbles 2 lichen covered surfaces from exposed cobbles and 3 buried cobbles taken from a soil depth of 40 cm percentage porosity within plagioclase minerals was calculated using backscatter electron images of prepared thin sections porosity was calculated from five depth profiles into each cobble depth profiles were subdivided into a sequence of 50 m 50 m rectangles running to at least a nominal depth of 500 m within each cobble three cobbles from each dated land surface were sampled except for the 1750 surface which had five cobbles statistical analysis was by analysis of variance of rank order transformed data findings indicate that cobbles close to the glacier snout are largely unweathered also weathering is generally weak in the 1928 1870 and 1810 positions but statistically significantly higher in the 1750 and 10 000 year old positions weathering of buried cobbles always exceeded weathering of exposed cobbles and may possibly reach a value beyond which it cannot progress while retaining surface cohesion the degree of weathering on lichen free and lichen covered cobble surfaces is not initially distinguishable but diverges sharply after 250 years when lichen covered surfaces experience significantly higher totals overall the weathering trend in cobbles matches that found in soils at the same sites copyright 2007 john wiley sons ltd

the interaction between armouring and particle weathering for eroding landscapes the interaction between particle weathering and surface armouring and its effect on erosion has been investigated the effect of soil armouring is to decrease sediment transport with time by preferentially stripping away fine particles on the other hand the effect of weathering which breaks down the particles in the armour is generally believed to increase erosion by extending an existing armouring model armour and using a variety of published weathering mechanisms this interaction has been explored the model predicts that while this is generally true in some cases erosion can be decreased by weathering when the particles generated by weathering were approximately of equal diameter erosion increased while armouring decreased when weathering produced very fine particles by spalling erosion increased and armouring also increased when weathering produced a range of particles from fine to coarse the armour layer broke down and erosion decreased relative to the no weathering case this latter decrease in erosion was due to the high entrainment of coarser transportable materials from the bed decreasing the sediment transport capacity of the flow in these studies clear regimes could be identified where erosion was limited by either the energy of the flow alone i e transport limited or the rate of weathering weathering limited however for some mechanisms there was an interaction between the two which we called weathering transport limited copyright 2006 john wiley sons ltd

rock slope instability and erosion toward improved process understanding rock slopes in a range of environments are among the landscape elements most sensitive to climate change the latter affecting rock mass properties altering slope boundary conditions and changing geosystem configurations major climate dependent influences promoting destabilization include stress redistribution with changing glacial ice extents degradation of mountain permafrost altered slope hydrology and weathering environments loading and unloading due to deposition and erosion and changes in the spectrum of magnitude and frequency of driving forces in steep bedrock terrain erosional processes control slope morphology by modulating rates of i weathering in response to climate and pre disposition ii rock slope retreat in response to magnitude and frequency of detachment and iii channel incision or valley infilling in response to variable sediment supply modelling landscape evolution and anticipating natural hazards in these environments thus requires deeper insights into the processes driving rock slope instability and erosion this special issue emphasizes new understanding of rock slope processes through a collection of manuscripts at the forefront of research in the field copyright 2014 john wiley sons ltd

management of topsoil for geo environmental reclamation of coal mining areas topsoil is an essential component for land reclamation in mining areas it is seriously damaged if it is not mined out separately without being contaminated eroded and protected systematic handling and storage practices can protect topsoil while in storage and after it has been redistributed onto the regraded area impact of coal mining on topsoil quality in indian context has been described systematic removal of topsoil its storage practice geometry of topsoil heap are discussed in this study removed topsoil should be reclaimed technically and its shelf life period should be ascertained to assess the shelf life period an investigation was conducted in a large opencast coal project soil dumps of different age classes in the area were identified and analyzed critically to evaluate the deterioration of soil quality with respect to time and compared with those of unmined areas changes in soil quality showed a continuous decrease every year and ultimately became biologically sterile biological reclamation is essential if the soil is to be stored beyond the shelf life period preservation of stockpiled topsoil its redistribution on the regraded areas nutrients and amendments to be added are discussed briefly in this study

the geological constraints of the development of sandstone landforms in central europe a case study of the świetokrzyskie holy cross mountains poland abstract eighty sites of crag groups and individual crags occurring in the wietokrzyskie holy cross mts upland situated in central poland were described in detail in order to examine the lithological structural mechanic properties and the tectonic features of sandstones and quartzites representing six crag forming lithostratigraphic units cambrian quartzites devonian quartzitic sandstones triassic and jurassic sandstones specific features of these rocks are their occurrence within the sequences consisting of different rock series high energy depositional environments and siliceous composition the cragforming rocks differ in the amount of cement from strongly cemented quartzites to very porous sandstones with poor cement which determines the diverse mechanical properties from very strong to friable rocks the crucial feature enabling formation of crags built of porous and friable sandstones is very dense grain packing due to chemical and mechanical compaction regarding the principal role of the gravitational disintegration of rock massifs under the periglacial conditions in the late pleistocene other factors constraining the crag formation and shaping are the tectonic situation of rocks the orientation of strata and joints as well as adequate joint spacing and bed thickness petrographic structural and tectonic features are interrelated

geomorphology and the law of unintended consequences locke 1691 lessons from coastal weathering and erosion at prawle uk and kaikoura nz the sites of two field experiments based on micro erosion metering one in uk the other in new zealand were independently revisited respectively 33 and 17 years after installation at both sites natural weathering and erosion processes had been inadvertently interrupted by the experimental works leading to the development of new microscale landforms these are interpreted in the context of modifications of the controls on weathering processes leading to enhanced understanding of the processes themselves this has lessons for the geomorphologist in maintaining a long term watching brief over former experimental sites lest some unintended and potentially beneficial outcome has ensued this theme is embraced by the law of unintended consequences

lightning as a geomorphic agent on mountain summits evidence from southern africa abstract the presence of angular bedrock derived debris on mountain summits worldwide has usually been associated with present or past periglacial frost shattering thermal fracturing and other climatically mediated weathering processes climatic inferences are commonly made based on such geomorphological evidence even if frost shattering and other processes are unlikely under present climatic conditions this paper questions this assumed genetic link between present past climate and production of angular bedrock derived debris by describing the geomorphological impacts of lightning strikes on exposed mountain summits using examples from the high drakensberg of eastern lesotho southern africa the impacts of lightning strikes are described which include the generation of angular fractured bedrock derived debris these impacts are identified in the field based on clear and unambiguous criteria that can be used to distinguish between lightning induced weathering processes and those processes associated with more typical alpine weathering this paper argues that lightning strikes are an important geomorphic agent of in particular low latitude mountain summits and that to make uncritical climatic inferences based on the presence of frost shattered debris on mountain summits is wholly erroneous

the influence of aspect on the biological weathering of granites observations from the kunlun mountains china abstract bedrock and boulder weathering in the higher elevation permafrost areas of the qinghai tibetan plateau have usually been ascribed to frost action for short periods during two summers an attempt was made to better elucidate weathering processes in this region a combination of visual observation coupled with rudimentary data regarding removable weathered material from the four cardinal aspects of granite boulders at elevations of 4600 5000 m in the kunlun mountains qinghai tibetan plateau showed that there was a distinct aspect influence south west north east on weathering it was also observed that there were aspect constrained variations in chasmoendolithic communities and for lichen distribution to further aid understanding temperature data for the four aspects were collected for several weeks during the summers of 2 years with data recording at 1 min intervals using ultraresponsive 0 05 s high precision 0 1 c ultrasmall 0 15 mm diameter thermocouples humidity data were also collected at the rock face based on these data an attempt is made to evaluate the nature of granite weathering in this region to better understand what the impact of the lichens endolithic communities was and how this varies use is made of xrd and sem analyses on samples from each aspect in addition iron rich patinas were found on a number of the boulders and these too were analyzed in an attempt to see their relationship if any to the biological action

bedrock fracture by ice segregation in cold regions the volumetric expansion of freezing pore water is widely assumed to be a major cause of rock fracture in cold humid regions data from experiments simulating natural freezing regimes indicate that bedrock fracture results instead from ice segregation fracture depth and timing are also numerically simulated by coupling heat and mass transfer with a fracture model the depth and geometry of fractures match those in arctic permafrost and ice age weathering profiles this agreement supports a conceptual model in which ice segregation in near surface permafrost leads progressively to rock fracture and heave whereas permafrost degradation leads episodically to melt of segregated ice and rock settlement

bioprotection and disturbance seaweed microclimatic stability and conditions for mechanical weathering in the intertidal zone as well as their destructive roles plants animals and microorganisms contribute to geomorphology and ecology via direct and indirect bioprotection which can reduce weathering and erosion for example indirect bioprotection can operate via biotic influences on microclimate whereby physical decay processes associated with fluctuations in temperature and moisture salt crystallization thermal fatigue and wetting drying are limited in the intertidal zone the spatial and temporal distribution of macroalgae seaweeds is patchy related to physical and ecological conditions for colonization and growth and the nature and frequency of natural and anthropogenic disturbance we examined the influence of seaweed canopies fucus spp on near surface microclimate and by implication on conditions for mechanical rock decay and under canopy ecology monitoring on hard artificial coastal structures in south west england uk built from limestone and concrete showed that both the range and maxima of daily summertime temperatures were significantly lower by an average of 56 and 25 respectively in areas colonized by seaweed compared to experimentally cleared areas short term microclimatic variability minutes hours was also significantly reduced by an average of 78 for temperature and 71 for humidity under algal canopies during low tide events using seaweed as an example we develop a conceptual model of the relationship between biological cover and microclimate in the intertidal zone disturbance events that remove or drastically reduce seaweed cover mediate shifts between relatively stable and unstable states with respect to mechanical decay and ecological stress associated with heat and desiccation in urban coastal environments where disturbance may be frequent facilitating the establishment and recovery of canopy forming species on rocks and engineered structures could enhance the durability of construction materials as well as support conservation planning and policy targets for biodiversity enhancement

the historical legacy of spatial scales in freeze thaw weathering misrepresentation and resulting misdirection discussion of weathering in cold regions has historically been dominated by widespread acceptance of the significance of the freeze thaw concept among periglacial geomorphologists and an essentially universal acceptance by those geomorphologists not directly involved in researching the topic debris produced by freeze thaw is frequently deemed to be angular in form and the observation of such debris has been used to identify the former or present operation of this weathering mechanism large debris blocks and small debris grains or flakes have been recognised as the outcome of the two scales of freeze thaw weathering macrogelivation and microgelivation respectively however the fusion of climatic geomorphology and process geomorphology in the ongoing development of the freeze thaw concept has resulted in the confusion of product with process whereby microgelivation producing small products and macrogelivation producing large products are seen due to the product dichotomy as distinctly different processes despite the recent highly sophisticated laboratory experimentation on freeze thaw weathering this historical process scale dichotomy still pervades thinking and experimental evaluation here we consider the historical development of microgelivation macrogelivation and outline what are thought to be fundamental flaws with the concepts and their underpinnings built within the two notions are elements of rock properties hard and soft and scale issues regarding rock attributes solid rock and existing weaknesses in rock that serve only to confuse the process and scale issues even more the whole notion of frost weathered debris having a specific form is also highly spurious there being no shape attribute that is uniquely diagnostic of frost action and this in turn leads to the further problem of process synergy or other processes entirely being the cause of rock failure in cold regions ultimately we argue that while there may be a range of product sizes and shapes resulting from frost weathering per se the widely invoked scale concepts are fraught with problems and are best dropped as too are any process shape connotations

the influence of petrophysical properties on the salt weathering of porous building rocks the influence of pore structure water transport properties and rock strength on salt weathering is evaluated by means of a thorough rock characterisation and a statistical analysis the pore structure was described in terms of its porosity pore size distribution quantified by mean pore radius and specific surface area density and water transport was characterised by means of water permeability saturated flow and capillary imbibition unsaturated flow whilst the rock strength test was carried out using uniaxial compressive strength compressional and shear wave velocities dynamic elastic constants and waveform energy and attenuation were obtained from the digital analysis of the transmitted signal a principal component analysis and a stepwise multiple regression model was carried out in order to examine the direct relationships between salt weathering and petrophysical properties from the principal component analysis two main components were obtained and assigned a petrophysical meaning the first component is mostly linked to mechanical properties porosity and density whereas the second component is associated with the water transport and pore structure salt weathering quantified by the percentage of weight loss after salt crystallisation was included in both principal components showing its dependence on their petrophysical properties the stepwise multiple regression analysis found that rock strength has a predominant statistical weight in the prediction of salt weathering with a minor contribution of water transport and pore structure parameters

comment on lightning as a geomorphic agent on mountain summits evidence from southern africa by knight and grab 2014 insights into the possible effect of lightning strikes on rock breakdown are presented by knight and grab 2014 from a summit area in the lesotho highlands based on their findings the authors challenge the association of angular debris with frost shattering and use this as a platform for directing critique against palaeo geomorphic studies while the lightning strike data are not questioned directly here the palaeo environmental context within which the paper is set the portrayal of former findings and the assumptions regarding weathering mechanisms in lesotho are commented on frost shattering is the centre of knight and grab s weathering critique but contrary to that stated in their text none of the cited authors invoke this process in lesotho other weathering processes that are speculated upon are not specific to cold climates either and thus cannot be used in support of their argument in terms of debris and block distribution lightning will not account for the preferential location of relict blocks and debris below the summits on south facing slopes or for the extensive valley floor accumulations that are documented in lesotho knight and grab also falsely portray former studies by implying that palaeo environmental inferences in the area are drawn from block origin or morphology alone when the climatic signatures were derived from integrated assessments in a palaeo context the relative contribution of lightning to debris production under dryer and colder conditions when convective thunderstorm activity in the highlands was likely reduced is also questioned the weathering context as well as the critique that knight and grab direct at other studies on relict landforms is thus shown as inappropriate

characterization of the paleocrusts of weathered carboniferous volcanics from the junggar basin western china significance as gas reservoirs abstract volcanic reservoirs comprise reservoir spaces made up of pores and cracks with secondary solution pores and tectonic induced cracks being the most dominant various volcanic lithologies and lithofacies show differences in porosity and permeability because resistance to weathering differs among volcanic rock types this study shows that among volcaniclastic rocks volcanic breccia shows higher porosity and permeability as well as poor pore radius sorting and connectivity compared with volcanic tuff basalt and monzonitic porphyry show higher porosity and permeability compared with other volcanic lava and subvolcanic rocks the level of porosity of different facies is in the order of effusive facies explosive facies subvolcanic rock facies volcanic sedimentary facies eruptive facies reservoirs show relatively high porosity and permeability near the top surface of the weathered crust porosity and permeability generally decrease with an increase in the distance from the carboniferous top weathered crust this condition indicates that weathering controls the properties of volcanic reservoirs the distribution pattern of porosity and permeability in the weathered crust of volcanic facies differs strong weathering contributes to a decrease in porosity and permeability at the top part of the weathered crust various weathering effects on volcanic rocks control porosity and permeability vertically and the gas accumulates mainly in the range of 0 m 200 m from the top of the weathered crust gas accumulation in subvolcanic and volcaniclastic rocks is better than that in volcanic lava the log curve in geophysical exploration can help determine the vertical structure of weathered crust the strong weathering belt shows high gamma low electrical resistivity low density high neutron porosity and high interval transit time

laboratory simulation of rock weathering by salt crystallization and hydration processes in hot arid environments the results of a series of experiments are reported in this paper which were designed to differentiate between the forces of crystal growth and hydration in salt weathering using a single salt hydrate system sodium sulphate five contrasting rock types and several diurnal temperature relative humidity cycles which permitted or inhibited these processes and simulated ground surface climates in hot arid environments it was shown that hydration of sodium sulphate is an effective mechanism of rock disintegration but that it is significantly less destructive than crystal growth pressure crystallization of thenardite na2so4 is in turn more effective in rock weathering than the crystal growth of mirabilite na2so4 10h2o in general rates of disintegration were most rapid where the diurnal temperature range was extreme and relative humidity lowest

geophysical approach to the study of a periglacial blockfield in a mountain area ztracene kameny eastern sudetes czech republic abstract fluctuation of climatic events in central europe with oceanic and continental influences intensified during the pleistocene especially above the timberline enabled the analysis of this record on the ridge and slopes of the ztracene kameny massif 1245 m a s l czech republic seismic refraction tomography srt and electrical resistivity tomography ert are geophysical methods that that allow the comprehensive recognition of shallow geological structures in a strongly folded area of the high jesenik mountains geophysical surveys were performed to determine structure and thickness of the quartzite blockfield and its boundary with consolidated rock the measured resistivity values were compared with the seismic wave velocities the resistivity values of the block cover show significant differences according to its morphology slope orientation and altitude the data analysis indicates an occurrence of remnants of pleistocene permafrost the subnival traces within the blockfield demonstrate the intensity of past slope processes and the role of frost weathering even during the holocene

regional scale controls on the spatial activity of rockfalls turtmann valley swiss alps a multivariate modeling approach abstract in mountain geosystems rockfalls are among the most effective sediment transfer processes reflected in the regional scale distribution of talus slopes however the understanding of the key controlling factors seems to decrease with increasing spatial scale due to emergent and complex system behavior and not least to recent methodological shortcomings in rockfall modeling research in this study we aim i to develop a new approach to identify major regional scale rockfall controls and ii to quantify the relative importance of these controls using a talus slope inventory in the turtmann valley swiss alps we applied for the first time the decision tree based random forest algorithm rf in combination with a principal component logistic regression pclr to evaluate the spatial distribution of rockfall activity this study presents new insights into the discussion on whether periglacial rockfall events are controlled more by topo climatic cryospheric paraglacial or and rock mechanical properties i both models explain the spatial rockfall pattern very well given the high areas under the receiver operating characteristic roc curves of 0 83 highest accuracy was obtained by the rf correctly predicting 88 of the rockfall source areas the rf appears to have a great potential in geomorphic research involving multicollinear data ii the regional permafrost distribution coupled to the bedrock curvature and valley topography was detected to be the primary rockfall control rockfall source areas cluster within a low radiation elevation belt 2900 3300 m a s l consistent with a permafrost probability of 90 the second most important factor is the time since deglaciation reflected by the high abundance of rockfalls along recently deglaciated the study demonstrates the benefit of combined statistical approaches for predicting rockfall activity in deglaciated permafrost affected mountain valleys and highlights the complex interplay between rock mechanical paraglacial and topo climatic controls at the regional scale

the effects of weathering on the physical and mechanical properties of igneous and metamorphic saprolites abstract the present paper presents three extensive datasets of laboratory testing on weathered geomaterials which are emblematic of soil types widely found worldwide the overall dataset includes soils originating from igneous and metamorphic rocks either coarse or fine grained and having either felsic or mafic minerals in particular the data are interpreted to highlight the effects that weathering has on the physical and mechanical properties of these natural geomaterials comparing them with published data with the aim to provide a general framework of interpretation that takes into account this geological process and links soil mechanics to engineering geology generally weathering induces a reduction in the grain size both due to physical actions e g opening of grain contacts and to the chemical decomposition of minerals resulting in the formation of clay minerals as weathering proceeds and the soil becomes finer the in situ specific volume and the location of the normal compression and critical state lines move upwards in the volumetric plane on the other hand the clay minerals cause its angle of shearing resistance to reduce when analysing the behaviour of the intact soil in all cases positive effects of structure albeit small compared to some sedimentary soils were observed and these reduced as a consequence of weathering

impacts of simulated acid solution on the disintegration and cation release of purple rock mudstone in southwest china abstract rock disintegration and cation release not only impact on terrestrial geomorphology but also provide nutrients for plants further fractal theory has been widely used to characterize the distribution of fragments in rocks for measuring the degree of disintegration yet the effects of an acidic environment on the trajectory of fractal dimensions of rock disintegration and cation release are not fully clear therefore to investigate the impacts of a solution s ph on disintegration and cation release from the purple rock in southwest china a series of laboratory experiments were performed by soaking the purple rocks in solutions with phs from 2 5 to 7 0 over 24 treatment cycles the results show that the lower the ph the fewer cycles required to obtain a stable fractal dimension the fractal dimension of purple rock under different ph values approached three after 24 treatment cycles until decay ratios the mass of decayed rock of 90 acidic treatment increased cation release especially when the ph value of the solution was below 3 5 compared with a deionised water soaking solution the amounts of k na ca2 and mg2 were increased by 4 92 1 27 1 12 and 1 08 times with ph values of 2 5 3 5 4 5 and 5 6 soaking solution respectively at the disintegration stage in addition the release of ca2 and mg2 were more sensitive to acid than that of k and na and ca2 weathering occupied the dominant position in the cation weathering rates moreover due to disintegration processes that transformed each rock sample into fragments fresh surfaces were exposed from which cations were liberated creating a significant p

durability assessments of rare green andesites widely used as building stones in buca izmir turkey miocene volcanism was active in the city area of izmir turkey where volcanic deposits formed predominantly made of gray and pinkish colored andesite these rocks have been widely used in the construction of many buildings in the region in the northern part of izmir known as the buca region there is an area where andesite presents green color the occurrence of the green andesite is rather rare and historically this rock type has been used in the construction of ancient valuable architectonic structures including aqueducts historical buildings and mosques some of these structures date back to the beginning of the first century ad when the region was under the control of the roman empire interestingly the recent survey of these structures showed that after all of these years the green andesite still appears pretty much well preserved only showing slight deterioration in the form of limited crumbling although these rocks were used in this particular region in the past their material properties have not been investigated so far the purpose of this study was therefore to identify mineralogical chemical physical and mechanical properties of these rocks which eventually determine their durability the first phase of the research focused on detailed site investigation which resulted in the definition of the geological extent of the green andesite and the identification of two historical quarries from one of which representative samples was collected for laboratory investigation which was the main task of the second phase of the research the main cause for the green color of the andesite resulted the presence of celadonite which is also accompanied by cristobalite the presence of cristobalite in the pores as a secondary mineral appears to have contributed to the increased strength and durability of buca andesite laboratory evaluation of the durability was in general agreement with field observations although some test gave ambiguous results this discrepancy revealed some weakness of laboratory tests to precisely assess durability of building stones

causes of scaling on bush hammered heritage ashlars a case study plaza mayor of madrid spain masons have traditionally used granite anisotropy to cut and lay the stone scaling a common type of granite decay is observed worldwide this study explored the relationship between weathering and cut planes in heritage ashlars specifically in the stone on madrid s plaza mayor whose construction dates back to 1590 the 71 rectangular granite columns that support its porticoes are oriented towards the four cardinal points all 71 have one exposed side that faces the square one protected side facing inward and two semi protected sides perpendicular to the other two the sides of the columns are also oriented to the points of the compass this study aimed to identify the prevailing orientation of scaling if any in the granite ashlars and to determine how this process is affected by climate microclimate orientation use hewing and exfoliation microcracks all four sides of the 71 columns were mapped 284 in all to analyse scaling height distribution and orientation the findings showed that the microcracks are vertically oriented and decline in density and length with depth from the surface scaling was observed on the lower ashlars in the columns to a maximum depth of 3 mm determining the direction of exfoliation microcracks is imperative to understanding decay mechanisms in granite ashlars and sculptures and that information must be taken into consideration when applying conservation treatments

quenching of phosphorus fixation with organic wastes in a bauxite mine overburden capabilities of two phosphate rich organic wastes to quench phosphorus p fixation in a stored high phosphorus fixing tropical bauxite overburden were examined in a field experiment prior grinding and ensiling of shrimp shell waste facilitated increased solubility and hence phosphorus fixation quenching in the soil normal plant available p concentrations were exhibited by the overburden for up to 4 months after application despite the cultivation and harvesting of plants in the treated beds ten year old stored overburden treated with ensiled shrimp shell silage or chicken manure exhibited p levels of 1 0 and 1 1 respectively 4 months after treatment application this represents a small excess over normal concentrations of free p in the overburdens these p levels dropped to 0 055 and 0 060 respectively after 8 months the capacity of the soil to fix phosphorus was thus rapidly filled with an excess of p in the overburden however increased p fixation in the second 4 month period was attributed to the inherently high levels of ca2 in the ground therefore amelioration based on quarterly applications promises a long term corrective for p fixing in stored bauxite overburdens

simulating weathering of basalt on mars and earth by thermal cycling physical weathering induced by heating and cooling may cause rock breakdown on mars and earth we report results from parallel weathering simulations on basalt blocks exposed to diurnal cycles representing mars like two simulation runs from 55 to 20 oc and 75 to 10 oc 1 100 relative humidity 4 8 mbar pressure co 2 atmosphere and hot arid earth 23 72o c 30 100 relative humidity conditions under earth conditions thermally pre stressed blocks showed measurable strength declines whilst salt pre treated blocks showed strength gains under mars like conditions pre stressed blocks recorded greater or similar strength declines and salt pre treated blocks showed more muted strength declines than under earth conditions the results imply that on earth and mars diurnal cycling of temperature alone can cause deterioration of basalt with a pre existing stress history the type of stress history is important with salt pre treatment affecting the response of thermally pre stressed blocks under both earth and mars conditions

the role of thermal stress fatigue in the breakdown of rock in cold regions abstract many geomorphological studies have ignored the role of thermal stress fatigue engineers have long maintained that thermal stress is an effective process physicists and the ceramics industry have provided a theoretical foundation to explain the nature and mode of operation of thermal breakdown recent geomorphological studies have shown the importance of thermal stress in cold regions by means of high frequency rock temperature data which can identify rates of temperature change in excess of 2 c min 1 the occurrence of weathered material in cold but dry regions can be explained by thermal stress shock differential radiation receipts on slopes of varying orientation and gradient can exert a very strong effect

wind blown particles as weathering agents an antarctic example abstract observations from taylor valley antarctica suggest that the wedging effect of sand particles packed by powerful winds into cracks in rocks may act as a weathering mechanism the strong winds and their accompanying solid material may cause stresses to the rock in three ways the direct pressure of the wind and material the hammering effect of the particles and by preventing the closure of cracks opened by other forces although crude estimations of the forces involved have been calculated actual field measurements are needed this is a process which may operate in other dry environmentson our planet ond possibly on some of the hyper dry inner planets of our solar system

thermal fatigue and thermal shock in bedrock an attempt to unravel the geomorphic processes and products widespread acceptance in science at large notwithstanding the ability of thermal stresses to produce thermal fatigue tf and or thermal shock ts in bedrock and coarse debris in the field is often doubted commonly called insolation weathering in geomorphology the results of questionable laboratory experiments have led many geomorphologists to consider terrestrial temperatures to be inadequate to generate thermally induced stresses leading to rock failure the exceptions are the action of fire or lightning we comprehensively survey the general scientific literature on tf and ts while rigorously scrutinizing that relating to geomorphology findings indicate theoretical and experimental information is adequate to establish the feasibility of tf and ts in rock stemming from rock temperatures monitored in the field while ts may exhibit fracture patterns that are uniquely diagnostic those of tf lack any such attributes it would appear unlikely that tf can prepare or weaken rock to increase the likelihood of ts the question of whether widespread polygonal versus rectilinear cracking is diagnostic of ts is presently an open one as possible explanations invoke process es and or host material s and consequently to assign palaeoenvironmental significance to such fracture patterns is premature at this time further geomorphological laboratory research into tf and ts is merited as sufficient theoretical underpinning already exists however laboratory experimentation needs to be much more rigorously defined and executed and is faced with significant hurdles if it is to be effectively linked to field observations

on the persistence of weathering abstract the term weathering has been in use for a very long time but it has come to mean different things to different people and hence as scientific short hand it no longer functions here we question the tenets underpinning the most common usage of the term and note that the climate process linkage implicit to the term is often missing and amounts to misdirection rather than climate as the primary driver behind specific weathering processes it is argued that rock properties constitute the dominant control further a case is made for reconsideration of our present bipartite mechanical chemical division of weathering processes and of the weathering processes currently deemed to be those that occur as process studies become evermore reductionist in nature so the functionality of the term comes more and more into question the linkage between process and landform the scaling up attribute is seen as a current weakness and one that will become more confusing as reductionist approaches continue as a way forward it is suggested that weathering stripped of specific preconceived notions of specific processes be envisaged as a function of energy transfer and be investigated in that light identification of new processes as well as restructuring of known processes particularly when considering weathering on other planets is a potential outcome of such an approach with a process foundation rooted in energy transfer rock decay provides a better umbrella term and liberates researchers from the inescapable conceptual baggage implicit to the term weathering

boulders and ponds on the asteroid 433 eros abstract there are 300 features on the asteroid 433 eros that morphologically resemble ponds flat floored and sharply embaying the bounding depression in which they sit because boulders on eros are apparently eroding in place and because ponds with associated boulders tend to be larger than ponds without blocks we propose that ponds form from thermally disaggregated and seismically flattened boulder material under the assumption that repeated day night cycling causes material fatigue that leads to erosion of the boulders results from a simple boulder emplacement thermal erosion model with boulders emplaced in a few discrete events i e large impacts match well the observed size distribution under this scenario the subtle color differences of ponds somewhat bluer than the rest of the surface might be due to some combination of less space weathered material and density stratification of silicate rich chondrules and more metal rich matrix from a disaggregated boulder volume estimates of ponds derived from near laser rangefinder profiles are consistent with what can be supplied by boulders ponds are also observed to be concentrated in regions of low slope and high elevation which suggests the presence of a less mobile regolith and thus a contrast in the resistance to seismic shaking between the pond material and the material that makes up the bounding depression future tests include shake table experiments and temperature cycling fatigue of ordinary chondrites to test the thermal erosion mechanism

evidence for freeze thaw events and their implications for rock weathering in northern canada ii the temperature at which water freezes in rock many undertakings have used either a single value or a narrow window of temperatures as a threshold for the freezing of water within rock these temperatures vary from 0 to 5 c with most windows being in the range 1 to 4 c based on thermal data these thresholds are commonly used to count the number of freeze thaw events as a basis for determining freeze thaw weathering data collected from northern canada indicate that the temperature at which freezing occurs can vary substantially even for the same site using exotherm and zero curtain observations from bricks at angles of 90 and 45 aligned to the four cardinal aspects the various temperatures at which water froze are shown bricks on the north and east commonly did exhibit freezing based on exotherms within the window 1 to 5 c while data for the south and west aspects showed substantial variation with freezes sometimes between 6 4 and 8 9 c the data were evaluated for evidence of zero curtain effects indicative of water freezing but no unequivocal events could be found and it is suggested that at the scale of observation used here they are unlikely it would therefore appear that the use of thermal thresholds may not be meaningful for evaluation of freeze thaw events the available data also indicate many instances when temperatures went substantially sub zero e g 20 c and yet no indication of water freezing occurred most likely because there was no water available to freeze this indicates that any form of freeze thaw event counting in the absence of some indicator of the presence of water and that it actually froze is flawed as thermal conditions alone are not adequate to indicate the occurrence or not of actual freeze thaw weathering events these data suggest that evaluations of freeze thaw occurrence based simply on thermal thresholds may be substantially in error copyright 2006 john wiley sons ltd

landslides triggered in weathered crystalline rocks of moderate latitudes a case study in mediterranean environment the maures massif france abstract the main purpose of this study is to characterize shallow and moderately deep landslide prone materials in crystalline rocks at moderate latitudes the procedure is based by a four step approach coupling the geomorphological approach the geotechnical approach and slope stability analyses based on limit equilibrium equations firstly different weathering horizons were identified with different thicknesses and characteristics depending on the original lithology these observations led to the development of a weathering model with two steps a regional paleo weathering step and a geomorphological weathering step secondly conceptual models of weathered horizon thicknesses were created according to the lithological context these models led to the identification of three major weathering types thirdly slope stability models were computed for three types of weathered lithology favourable theoretically to slope failure granit micaschists gneiss for each case the different models properly computed landslide occurrences and their locations for highly saturated weathered materials that corresponded to field observations to finalize the study a first analysis of precipitation data was carried out to define some triggering trends for slope failures in this environment therefore based on this simple approach it is possible to define some trends for shallow and moderately deep landslides in weathered crystalline environment located in moderate latitudes with mediterranean climate finally the information can be used by end users and practitioners for public works management on these slopes

weathering assessment in the achala batholith of the sierra de comechingones cordoba central argentina i granite regolith fractionation abstract weathering assessment in a weathering limited environment is a difficult task because a significant proportion of the regolith has been removed by tectonically induced denudation in such an environment the remnants of the altered mineral debris must be studied with care in order to attain a meaningful picture of the rate and intensity of ongoing weathering a monolithologic i e granite small 2 km2 and mountainous 1500 m elevation drainage basin in the sierras de comechingones 31 54 07 s 64 45 28 w 31 53 11 s 64 44 16 w cordoba central argentina was selected as a pilot area to survey the nature of weathering in a weathering limited erosional setting and a semiarid climatic regime a relatively thin layered coarse grained regolith and scattered sediment i e fine grained regolith that had accumulated in valleys and topographic depressions were analyzed the most abundantly identified clay mineral in the regolith is illite followed by kaolinite smectite smectite seems to be the only clay mineral clearly associated with weathering petrographic observations and geochemical analyses supported by statistical tests define chemical weathering as incipient petrography indicates that plagioclase and biotite are the main mineral phases affected by alteration which is more intense in the fine grained regolith coarse and fine grained regoliths are chemically similar among them and with the country rock with statistically significant losses in the fine fraction of mgo mno and p2o5 depletions of trace elements and ree which are best explained by sorting than by actual rock alteration are not statistically significant ternary diagrams reveal that the masses of al2o3 cao na2o and k2o were not significantly altered during weathering and transportation and that regolith samples correspond to a coarse residue relatively enriched in feldspars and quartz where the mud fraction with high clay mineral contents has been removed from the drainage basin by high energy processes

3 d numerical modelling of the conductive heat flow of sw england summary the effect of 3 d geology on conductive heat flow was investigated using the finite element technique on two models from sw england one a regional model centred on the comubian batholith as a whole and the other a more detailed model centred on the cammenellis pluton only two rock types granite and country rock were used to represent the geology of the region and yet good agreement between modelled and observed data was obtained provided that the granite was assumed to be highly homogeneous with surface heat production values persisting throughout its depth and the base of the batholith was assumed to be flat at a depth of 15 km the results show that the surface heat flow pattern is dominated by the 3 d shape of the batholith which controls the relative importance of the two opposing effects that operate at its margins heat refraction due to conductivity contrasts enhancing heat flow in the granite and lateral flow of heat caused by heat production contrasts diminishing it the highest heat flows occur at the boundaries of outcrops facing the axis of the batholith where there is significant heat refraction but little lateral loss a high degree of correlation between mineralized zones and areas of very high heat flow in both granite and country rock is also noticeable the temperature field at any depth displays wide ranging lateral variations over relatively short distances the highest values occurring in areas of granite which are covered by insulating country rock and which lie towards the centre of the batholith regions of highest heat flow are not necessarily the regions where the highest sub surface temperatures are likely to be found and it is shown that the hot dry rock geothermal test project at rosemanowes is not optimally sited from temperature considerations when the constraints on the physical parameters of the model are sufficiently reliable as they are in sw england the heat flow and temperature predictions from 3 d numerical models can be of enormous value in the assessment of the geothermal potential of a region

bedrock erosion by root fracture and tree throw a coupled biogeomorphic model to explore the humped soil production function and the persistence of hillslope soils 1 in 1877 g k gilbert reasoned that bedrock erosion is maximized under an intermediate soil thickness and declines as soils become thinner or thicker subsequent analyses of this humped functional relationship proposed that thin soils are unstable and that perturbations in soil thickness would lead to runaway thinning or thickening of the soil to explore this issue we developed a numerical model that simulates the physical weathering of bedrock by root fracture and tree throw the coupled biogeomorphic model combines data on conifer population dynamics rootwad volumes tree throw frequency and soil creep from the pacific northwest usa although not hardwired into the model a humped relationship emerges between bedrock erosion and soil thickness the magnitudes of the predicted bedrock erosion rates and their functional dependency on soil thickness are consistent with independent field measurements from a coniferous landscape in the region imposed perturbations of soil erosion during model runs demonstrate that where bedrock weathering is episodic and localized hillslope soils do not exhibit runaway thinning or thickening the pit and mound topography created by tree throw produces an uneven distribution of soil thicknesses across a hillslope thus although episodes of increased erosion can lead to temporary soil thinning and even the exposure of bedrock patches local areas of thick soils remain these soil patches provide habitat for trees and serve as nucleation points for renewed bedrock erosion and soil production model results also suggest that where tree throw is a dominant weathering process the initial mantling of bedrock is not only a vertical process but also a lateral process soil mounds created by tree throw flatten over time spreading soil over bedrock surfaces

tafoni development in a cryotic environment an example from northern victoria land antarctica tafoni are a type of cavernous weathering widespread around the world despite the extensive distribution of the tafoni their genesis is not clear and is still a matter of debate also because they occur in such different climatic conditions and on so many different types of substrate geomorphological characterization of more than 60 tafoni in three different antarctic sites two coastal and one inland between 74 and 76 s with sampling of weathering products and salt occurrences are described together with thermal data on different surfaces and wind speed recorded in different periods of the year in a selected tafone close to the italian antarctic station the aim of this present study is to provide further information to help understand the processes involved in the growth of tafoni in a cryotic environment and the relationship of these processes to climate with particular attention to the thermal regime and the role of wind the new data presented in this paper suggest that there is no single key factor that drives the tafoni development although thermal stress seems the most efficient process particularly if we consider the short term fluctuations the data also confirm that other thermal processes such as freezing thawing cycles and thermal shock are not really effective for the development of tafoni in this area the wind speed measured within the tafoni is half that recorded outside thus favouring snow accumulation within the tafoni and therefore promoting salt crystallization on the other hand the wind effect on the thermal regime within the tafoni seems negligible while both salt weathering and thermal stress appear active in this cryotic environment these are azonal processes and are therefore active in other climatic areas where tafoni are widespread such as the mediterranean region copyright 2007 john wiley sons ltd

grus weathering mantles problems of interpretation abstract grus is an ill defined product of deep weathering of coarse grained rocks whose relationships to other weathering changes remain unclear this paper attempts to address this issue by reviewing a number of examples of coarse saprolites from a variety of climatic and topographic settings grus is the category of weathering mantle that possesses the following characteristics sand gravel 75 100 silt clay

laboratory simulation of the salt weathering of schist 1 weathering of schist blocks in a seasonally wet tropical environment data describing sediment generation focusing on the temporal evolution of size gradation are required for the prediction of long term landform evolution this paper presents such data for the salt weathering of a quartz chlorite schist obtained from the ranger uranium mine in northern australia rock fragment samples are subjected to three different climate regimes 1 a dry season climate 2 a wet season climate both based on observations at the ranger site and 3 an oven drying sequence designed to test the sensitivity of the weathering process by exposing the rocks to more extreme temperatures two mgso4 salt solutions are applied one being typical of wet season runoff and the other a more concentrated solution salt solution is applied daily in the wet season experiments and once only at the beginning of the dry season experiments results of the experiments reveal four stages of weathering the kinetics of each stage are described and related to the formation of sediment of different sizes wet season climate conditions are shown to produce greater moisture variability and lead to faster weathering rates however salt concentrations in the wet season are typically lower and so when climate is combined with observed salt concentrations the dry and wet season experiments weather at approximately equal rates finally small variations in rock properties were shown to have a large impact on weathering rates leading to the conclusion that rock weathering experiments need to be carefully designed if results are to be used to help predict weathering behaviour at the landscape scale copyright 2006 john wiley sons ltd

experimental frost weathering of sandstone by various combinations of salts weathering experiments are reported combining frost and a range of salts that occur naturally on rock faces in western and central europe potassium and ammonium alums enhanced frost weathering quite considerably both singly and in combination though they were less potent than halite the destructiveness of which at sub zero temperatures was again confirmed by contrast alunogen and gypsum had little or no effect on rates of frost weathering either singly or in combination combining halite and gypsum produced breakdown that was intermediate between that of the two salts individually as did the combination of gypsum and potassium alum breakdown in solutions of ammonium alum and gypsum and in a combination of potassium and ammonium alum with gypsum caused greater breakdown over 25 cycles of freeze thaw than was recorded with the salts singly the results extend the range of salts known to enhance frost weathering and show that it is difficult to predict the aggressiveness of combinations of salts by experimenting with each salt separately copyright 2001 john wiley sons ltd

stone runs in the falkland islands periglacial or tropical abstract stone runs is the falklands vernacular term for openwork boulder accumulations which include extensive blockstreams like the famous darwin stone river and associated features such as stone stripes since the early 20th century they have been interpreted as the product of a suite of periglacial processes including frost wedging gelifluction frost heave frost sorting and snowmelt runoff following a literature review the results of recent field investigations of the valley floor blockstreams of east falkland are presented access to the internal structure of these forms provides evidence for the existence of a three fold profile with clear vertical size gradation presenting striking similarities with an inverted weathering profile micromorphological analyses sem xrd thin sections and grain size analyses lead to the hypothesis of an alternative model of stone run formation it is suggested that the material forming the stone run profile lato sensu including the superficial pavement is not of periglacial origin but derives directly from the stripping and accumulation downslope of a regolith possibly tertiary in age and formed under subtropical or temperate conditions the valley floor stone runs should therefore be considered as complex polygenetic landforms that may have formed according to a six stage scenario including in situ chemical weathering regolith stripping by mass movements soil formation further regolith stripping downslope accumulation and matrix washing out all phases possibly achieved by the early quaternary periglacial reworking of the stone run material would have operated at a final stage i e during quaternary cold stages with boulder bioweathering and limonite staining operating during the temperate intervals including the present one the suggested antiquity of the falklands blockstreams is in accordance with caine s pioneer interpretation of tasmania blockfields and with recent analyses and cosmogenic datings of blockfields from scandinavia and north america

granite landform evolution factors and implications most granite landforms are due to the exploitation of weaknesses especially fractures by meteoric waters and particularly groundwaters moisture attack produces grus which commonly forms the bulk of the regolith in granitic terrains the transition from weathered to fresh rock is typically abrupt and takes the form of a narrow transition zone called the weathering front

the chemical weathering regime of karkevagge arctic alpine sweden abstract karkevagge is a valley located in swedish lapland at approximately 68 n and represents an arctic alpine landscape it is a presently periglacial glaciated trough incised into essentially horizontal metamorphic rocks some of which are presumably pyrite rich a set of coordinated studies was undertaken to investigate the nature of chemical weathering and pedogenesis in the valley and upon the abutting ridges august 1996 water quality measures reveal considerable spatial variation in solute totals with the highest total dissolved solute abundances being correlated with high sulfate abundances ridge crest soils exhibited poor horizonation but more extensive development of secondary clay minerals developed in situ than was found in valley flank and valley bottom soils valley soils exhibited multiple thin horizons many of which were buried and are taken to reflect great paraglacial and periglacial instability favorable microenvironments in the valley permit significant development of spodosols coarse debris along and across the valley bears both weathering rinds and rock coatings rock coatings in the valley include several types of iron films sulfate crusts carbonate skins and heavy metal skins karkevagge represents a mild arctic environment which does not preclude substantial chemical weathering in locations where abundant pyrite rich bedrock and water coincide this weathering follows pathways which are eminently expectable given that weathering of the pyrite rich rock permits generation of sulfuric acid which in turn weathers muscovite mica and calcite in local schists and marble respectively zones of intense chemical weathering also generate clearly visible deposits of gypsum and iron sulfate deposits such as jarosite not all arctic and or alpine environments are likely to be so active chemically but the results from karkevagge clearly show that dismissal of chemical weathering in cold regions on the basis of presumed first principles is erroneous consequently chemical weathering in such environments merits substantially more attention than it has hitherto received

methods for measuring rock surface weathering and erosion a critical review studies of rates processes and modes of rock surface and near surface deterioration and also hardening are central to rock weathering and building stone research conservation and management there is a need to measure and monitor weathering at the rock atmosphere interface to facilitate understanding of climatic environmental and lithological controls on the evolution and development of surface weathering features this paper reviews long established and recently developed field and laboratory methods used by geomorphologists to monitor and measure the impact of weathering and erosion on physical and mechanical properties of exposed rock surfaces and their immediate subsurface key advances are highlighted their application to multi scalar understanding and modelling of rock surface weathering in different contexts is discussed and potential future advances to provide new insights into rock weathering durability and materials conservation are identified in highlighting key advantages and disadvantages of a wide range of methods to the broader earth science community the paper aims to contribute to further innovative thinking across disciplines to develop new methods for measuring and monitoring rock weathering

post mining deterioration of bauxite overburdens in jamaica storage methods or subsoil dilution rapid degradation of disturbed soil from a karst bauxite mine in jamaica was recorded substantial macronutrient losses were incurred during a short 1 month or a long 12 months storage of the replaced topsoils during frequent wet dry changes the results suggested very high rates 70 in the first year of soil degradation from storage alongside moderate rates 30 within the same storage dump however higher levels of soil organic matter som were indicated just below the surface compared with the surface horizons it was unlikely that under a high leaching humid tropical rainfall regime natural degradation processes could have re emplaced such material firmly intact in the 15 30 cm zone it was therefore concluded that these som anomalies were due to mechanical dilution of surface soil with subsoil material during overburden removal and emplacement rather than from long storage increasing the soil organic content during storage could be one corrective approach however it is far less costly to exercise greater care to apply more precise overburden removal and emplacement techniques initially than it is to correct the results of topsoil contamination with subsoil although this study was limited to one mine in the context of imminent large scale mining expansion and current practices further investigations are needed to accurately ascertain the proportion of similar subsoil contamination in other bauxite mined sites

inland notches lithological characteristics and climatic implications of subaerial cavernous landforms in israel inland notches are elongated concave shape indentations that develop on the carbonate rocky cliffs of mountainous zones down to the desert fringe these rock shelters form as a result of the interaction between specific petrologic characteristics and climatic controls emphasizing the importance of environment upon rock decay inland notches are shaped due to slight differences 1 15 in the porosity of the visor and cavity bed the cavity bed is more porous so more likely to erode by exfoliation and dissolution thus the cavity bed retreats at a faster rate compared to the slower subaerial dissolution of the visor bed until a critical point is reached where the visor collapses in israel inland notches inhabit the same lithostratigraphic units as do large caves the vast majority 71 of inland notches are formed in hard dense and crystalline limestone deposited throughout the turonian age another 27 are cut into the dolomitic sequence of the upper albian and lower cenomanian the rest 2 are dispersed in the various formations of the cenomanian and eocene eras notches are most common in semi arid and in mediterranean climates but mainly in areas with annual rainfall of between 400 mm and 850 mm in more humid areas 900 mm yr notches are negligible or completely absent due to the rapid rate of chemical dissolution of carbonate rocks in the desert fringe 200 300 mm yr mechanical decay is accelerated and notches exhibit disintegration processes visor collapse and rock falls in the desert area 200 mm yr salt decay replaces the chemical decay characteristic of inland notches encouraging tafoni formation in addition notches form through fluvial activity or on account of greater petrophysical differences between consecutive beds i e elongated cavities may form in soft rocks shaded by harder visors or crusts copyright 2017 john wiley sons ltd