quantifying periglacial erosion in the nepal high himalaya abstract quantifying erosion rates in high mountain environments is challenging because the erosional processes are often stochastic and catastrophic distinguishing between periglacial and glacial rates is especially challenging in this study we focus on determining erosion rates from a glaciated alpine landscape where the bedrock sidewalls are eroding predominantly by blockfall we utilize a topographically well constrained debris covered glacier on the north slope of the annapurna range central nepal himalaya to quantify an average headwall retreat rate by measuring supraglacial debris depths from 0 1 to 2 4 m and average short term down valley transport rates of 17 m yr we calculate a yearly sediment flux of 5820 1990 m3 yr the supraglacial debris originates from the steep rocky headwall of the valley and we use the calculated flux with an estimated headwall contributing area to determine a slope perpendicular headwall retreat rate of 1 3 0 5 mm yr which corresponds to a vertical lowering rate of 0 42 0 16 mm yr and a horizontal retreat rate of 1 2 0 5 mm yr this rate is significantly greater than the steady state erosion rates that we determine for the valley ridge crests and sidewalls 0 08 0 03 mm yr and 0 20 0 05 mm yr respectively using concentrations of the in situ produced cosmogenic radionuclide 10be additionally 10be exposure ages of the lateral moraine crests and supraglacial debris suggest a glacial advance about 470 yr ago and a long term supraglacial transport rate of about 10 m yr using this long term transport rate reduces our inferred headwall retreat and suggests that the up glacial bedrock slopes are eroding at roughly the same rate while our results do not quantify the rate of glacial erosion the absence of a glacial gorge suggests that there may be a rough balance between glacial downcutting and the erosion of the valley sidewalls rates quantified here are almost an order of magnitude lower than fluvial incision rates of the upper marsyandi river that drains the study area suggesting that even glaciated catchments are not keeping pace with the rapidly down cutting rivers of the himalaya

a multi method monitoring of timing magnitude and origin of rockfall activity in the japanese alps abstract a multi method monitoring was conducted to detect the timing and trigger of rockfall activity on an alpine rockslide cliff composed of cretaceous sandstone and shale in the southern japanese alps aresawa rockslide 2900 m above sea level the monitoring programme includes manual measurements of flaking from painted rock surface and collection of fallen debris daily time lapse imaging of the rockwall automated recordings of rock temperature rock moisture and influencing meteorological factors air temperature and precipitation a stereographic pair of sequential photographs is used to visually identify the location of new erosion and semi quantitative evaluation of detached materials at daily resolution six years 2010 2016 of debris trapping show major rockfall activity in winter between november and may and occasional activity associated with heavy rains in summer and yield an average rate of rockwall retreat on the order of 1 mm a 1 the rockwall shows heterogeneous debris production mainly reflecting joint spacing time lapse imaging displays at least 10 15 rockfall events per year within the shot area 500 m2 the integration of multiple data suggests at least five types of triggering processes towards rockfalls which recur annually 1 in summer and early autumn heavy rainfalls raise the moisture content of the shallow bedrock often triggering significant rockfalls probably due to raised water pressure in rock joints or lubrication of joints 2 in late autumn and late spring light or intermediate rainfalls are sometimes followed by high moisture shallow freezing rapid thawing and eventually by different scales of rockfalls 3 in winter and early spring the same process as in the second case but rainfall is replaced by snowfall triggers submeter scale rockfalls 4 deep seasonal freezing to about 5 m enables release of meter scale rockfalls during seasonal thawing periods from late spring to early summer 5 short term large thermal fluctuations that produce cyclic thermal stress may also contribute to submeter scale rockfalls mainly in winter locally enhanced by freeze thaw action

a review on freeze thaw action and weathering of rocks freeze thaw weathering is an important surface process and the complex underlying processes can be understood as an interplay between rock properties and its dynamic environment multiple researchers coming from different scientific disciplines have contributed to the present day knowledge on the matter and misconceptions still prevail in a changing climate the multidisciplinary insights into freeze thaw action are crucial for a better understanding of rock weathering in natural and anthropogenic environments in this review a series of laboratory and in situ field tests are presented to illustrate the present day methods to assess freeze thaw weathering over the last century these methods led to insights and the development of theories on damage mechanisms presently it is accepted that crystallization pressure is responsible for the majority of stresses in the material s pores damage is induced when these stresses overcome the local tensile strength since most of the methods used to derive and validate stress build up theories are indirect observations of parameters related to the phase transition it is hard to reach a consensus on the exact explanation for stress development direct observations which require actual real time observation of the pore space during a freeze thaw cycle are therefore favoured to reach agreement eventually the goal is to achieve a better insight on which processes potentially occur how these vary with different environmental temporal and spatial conditions and under which circumstances damage is inflicted

modeling the tor dotted crests bedrock edges and parabolic profiles of high alpine surfaces of the wind river range wyoming abstract broad low curvature surfaces common to many alpine landscapes and particularly well expressed in the laramide ranges of the western usa appear to be roughly in steady state with respect to the current surface processes uniform thin order 1 m regolith covers the crystalline bedrock with the exception of occasional tors at ridgecrests the surfaces are commonly edged by bedrock lips at the tops of cliffs that bound the intervening glacial troughs regolith production is low order 10 m year on bare bedrock and reaches a maximum under tens of centimeters of regolith all of these characteristics may be accounted for with a numerical model that is faithful to the periglacial surface processes presently operating on these surfaces hillslope transport is modeled assuming the dominant process is frost creep transport efficiency depends linearly upon local slope and appropriately vanishes in the absence of regolith frost frequency scales the rate of motion while the ratio of frost penetration depth to regolith thickness dictates the degree to which the process is curtailed by available regolith initial conditions include initial mean slope and bedrock roughness and a uniform regolith cover boundary conditions are imposed by dictating that the edges of the calculation space be lowered at a rate appropriate for glacial incision broad convex surfaces emerge over time scales of order 1 million years all surfaces rapidly decouple from the bounding glacial troughs as the high negative curvature at the edges disallows accumulation of regolith these bedrock edges lower at a few microns per year while the troughs lower at many times this rate as the bedrock edges therefore serve as the effective boundary condition for the remaining surface the surfaces operate independently of both lowering and widening of the glacial troughs for a reasonable set of transport and weathering rates the final steady state landscape is sensitive to the initial condition in particular the steeper the initial landscape the more likely tors are to develop as the high curvature disallows accumulation of regolith these tors in turn limit the lowering rate of the crest and the landscape retains significant local relief low relief initial conditions more likely lead to parabolic surfaces that lack tors that tors are more likely on the crests reflects the high initial curvature at the crest tors on the side slopes are eliminated the present high surfaces in the laramide ranges of the western usa imply operation of periglacial surface processes over millions of years the occasional tors imply a steeper rather than flatter initial landscape the strong decoupling of surfaces from glacial troughs justifies their use as local geomorphic markers that allow calculation of relief production since glacial incision was initiated on the other hand their present low curvature does not require a landscape history in which these surfaces were once joined as an initially widespread erosion surface

diurnal freeze thaw depth in rockwalls field measurements and theoretical considerations rock temperatures were monitored for a year at two alpine rockwalls in the akaishi range japan where permafrost is absent diurnal frost and thaw penetration depths were evaluated from subsurface isotherms drawn on the basis of the temperature records at 0 10 and 40 cm depths the surface of the rockwalls experienced more than 100 diurnal freeze thaw cycles most of which accompanied a frost or thaw penetration shallower than 50 cm and several long duration cycles with deeper frost or thaw penetration theoretical frost and thaw depths were also calculated by incorporating the surface freezing indices into the modified berggren equation the results from which were then compared with the actual values the modified berggren equation provided values that showed a strong correlation with observed depths despite somewhat underestimating the actual values using the modified berggren equation the seasonal frost depth in the observed winter was estimated to be about 4 5 m the frost and thaw depths are considered to give the maximum estimation of the depth to which frost induced cracking can propagate in the bedrock

climate and geomorphology in the uppermost geomorphic belts of the central mountain range taiwan abstract the central mountain range of taiwan is in its lower parts exposed to strong denudation by mass movements caused by extreme rainfalls and active tectonics even though the uppermost regions of the mountains are also influenced by earthquakes and typhoon rains present geomorphic activity is low investigations based on field work and air photo study in nanhuta shan 3742 m and yushan 3952 m and the analysis of climate data indicate the presence of a periglacial belt with a lower limit at 3600 3700 m the upper limit of the periglacial belt in taiwan is not met ground temperature measurements in nanhuta shan show that freeze thaw activity at 3560 m during the winter is restricted to the top few centimetres of the ground and the maximum frost depth is 25 cm the only indicator landforms within the periglacial belt are smooth slopes the high relief energy and a lack of fine material account for the absence of other periglacial landforms relict solifluction terraces debris cones and slope failures found between 3400 and 3600 m in nanhuta shan are strong evidence for a period of increased slope activity during the holocene which in two cases were dated by osl to approx 3 ka at least one solifluction unit developed during a cooler phase between 3 ka and today

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

continual erosion of bare rocks after the wenchuan earthquake and control strategies abstract the newly bared rocks created by the wenchuan earthquake are undergoing continual intensive erosion in the form of detachment and movement of individual grains grain erosion is defined as the phenomenon of breaking down bare rocks under the action of insolation and temperature change detachment of grains from the rockwalls by wind flow down of grains on the slope under the action of gravity and accumulation of grains at the toe of the mountain forming a deposit fan the wenchuan earthquake which occurred in sichuan on may 12 2008 caused thousands of avalanches and landslides and left scars on slopes and a huge area of bare rocks grain erosion causes flying stones injured humans and resulted in numerous slope debris flows the process of grain erosion and strategies to limit the erosion were studied by field investigations and field experiments according to these field investigations and field studies the most serious grain erosion occurs in spring and early summer when it is very dry rocks are broken down to grains under the action of insolation and temperature change then wind blows the grains from the bare rock down slope experimental results showed that the amount of grains blown down by wind per area of rock surface per unit time is proportional to the fourth power of the wind speed however the size of the grains blown down by wind increases linearly with the wind speed an experiment proved that grain erosion can be controlled with two moss species moss spores were mixed with clay suspension and splashed on bare rocks the moss species germinated on the rock surface in one month and greened the bare rocks in two months the moss layer protected the rocks from insolation and mitigated the effects of temperature change thus effectively mitigated grain erosion

the freeze thaw weathering regime at a section of the niagara escarpment on the bruce peninsula southern ontario canada the bedrock freeze thaw and moisture regimes at an actively eroding site on the niagara escarpment bruce peninsula southern ontario were monitored between december 1983 and april 1984 and the results compared with amounts of debris collected in an adjacent rock trap frost wedging in pre existing rock fissures is the primary mechanism responsible for the observed rockfall events hydration effects are negligible debris production was more closely related to the duration of the freezing leg of the freeze thaw cycle than to intensity or to cycle frequency release also coincided with periods of high pore saturation 60 per cent and the seepage of water from cracks and fissures fewer freeze thaw cycles were recorded in the air than at 1 and 3 5 cm in the bedrock the number of cycles that could be declared geomorphologically effective according to established temperature criteria was normally less than half the total number of freeze thaw cycles recorded in both air and bedrock under the current temperature regime at the field site few effective cycles are capable of penetrating more than 5 cm into the free face

potential weathering by freeze thaw action in alpine rocks in the european alps during a nine year monitoring period abstract a quantification of rock weathering by freeze thaw processes in alpine rocks requires at least rock temperature data in high temporal resolution in high quality and over a sufficient period of time in this study up to nine years of rock temperature data 2006 2015 from eleven rock monitoring sites in two of the highest mountain ranges of austria were analyzed data were recorded at a half hourly or hourly logging interval and at rock depths of 3 10 and 30 40 cm these data have been used to quantify mean conditions ranges and relationships of the potential near surface weathering by freeze thaw action considering volumetric expansion of ice and ice segregation for the former freeze thaw cycles and effective freeze thaw cycles for frost shattering have been considered for the latter the intensity and duration of freezing events as well as time within the frost cracking window have been analyzed results show that the eleven sites are in rather extreme topoclimatic positions and hence represent some of the highest and coolest parts of austria and therefore the eastern alps only four sites are presumably affected by permafrost most sites are influenced by a long lasting seasonal snow cover freeze thaw cycles and effective freeze thaw cycles for frost shattering are mainly affecting the near surface and are unimportant at few tens of centimeters below the rock surface the lowest temperatures during freezing events and the shortest freezing events have been quantified at all eleven monitoring sites very close to the surface the time within the frost cracking window decreases in most cases from the rock surface inwards apart from very cold years sites with very low temperatures close to the surface as shown by this study and predicted climate change scenarios assumed warmer rock temperature conditions in the future at alpine rock walls in austria will lead to less severe freezing events and to shorter time periods within the frost cracking window statistical correlation analyses showed furthermore that the longer the duration of the seasonal snow cover the fewer are freeze thaw cycles the fewer are effective freeze thaw cycles the longer is the mean and the maximum duration of freezing events and the lower is the mean annual ground temperature the interaction of the winter snow cover history and the winter thermal regime has a complex effect on the duration of the frost cracking window but also on the number of freeze thaw cycles as shown by a conceptual model predicted future warmer and snow depleted winters in the european alps will therefore have a complex impact on the potential weathering of alpine rocks by frost action which makes potential weathering predictions difficult neglecting rock moisture and rock properties in determining rock weathering limits the usefulness of solely rock temperature data however rock temperature data allow getting an estimate about potential weathering by freeze thaw action which is often substantially more than previously known

freeze thaw cycles on rock surfaces below the timberline in a montane zone field measurements in kobugahara northern ashio mountains central japan abstract rock surface temperatures were measured on a tor and a large block located below the timberline in the kobugahara highlands an upland plateau composed of granodiorite in central japan 36 n e139 1300 m a s l many blocks in the region originate from core stones distributed on the plateau and there are several block streams in the valley bottoms the tor is situated at the upper end of one of these block streams the large block appears to have detached from another tor the mean air temperature of the coldest month is 4 c rock surface temperatures were recorded continually every 30 min from december 1 2002 through december 13 2004 by thermistor probes connected to miniature data loggers the diurnal and the annual freeze thaw cycles and effective freeze thaw cycles were recorded at each site the freezing index of rock surface temperature showed a marked variability from year to year in addition differences in local conditions at observation sites within a given area greatly affected the rock surface temperature these are important considerations in relation to local weathering below the timberline

variability of rock erodibility in bedrock floored stream channels based on abrasion mill experiments we quantify variations in rock erodibility kr within channel cross sections using laboratory abrasion mill experiments on bedrock surfaces extracted from streams with sandstone bedrock in utah and basaltic bedrock in the hawaiian islands samples were taken from the thalweg and channel margins the latter at a height that is inundated annually for each sample a sequence of abrasion mill experiments was completed to quantify variations in erosion rate with erosion depth erosion rate data from these experiments shows two things first the erosion rate from channel margin samples is greater than for thalweg samples with the greatest difference observed for the rock surface that was exposed in the stream channel second erosion rate decreases with depth beneath the original rock surface by an order of magnitude in most cases the erosion rate becomes steady at depths of 1 3 mm for channel margin samples and 0 1 0 4 mm for thalweg samples because only rock properties and microtopography vary throughout the sequence of mill experiments these results suggest that kr of the bedrock surface exposed in stream channels is higher at the margins than near the channel center and that kr decreases over depths of 1 mm the simplest explanation for these patterns is that kr is enhanced at the bedrock surface and along the channel margins due to the effects of weathering on rock strength and surface roughness we hypothesize that a balance exists between weathering enhanced erodibility and episodic incision to allow channel margins to lower at rates similar to the thalweg

small valley glaciers and the effectiveness of the glacial buzzsaw in the northern basin and range usa the glacial buzzsaw hypothesis suggests that efficient erosion limits topographic elevations in extensively glaciated orogens studies to date have largely focussed on regions where large glaciers tens of kilometres long have been active in light of recent studies emphasising the importance of lateral glacial erosion in lowering peaks and ridgelines we examine the effectiveness of small glaciers in limiting topography under both relatively slow and rapid rock uplift conditions four ranges in the northern basin and range idaho montana and wyoming usa were chosen for this analysis estimates of maximum pleistocene slip rates along normal faults bounding the beaverhead bitterroot mountains similar to 0 14 mm y 1 lemhi range similar to 0 3 mm y 1 and lost river range similar to 0 3 mm y 1 are an order of magnitude lower than those on the teton fault similar to 2 mm y 1 we compare the distribution of glacial erosion estimated from cirque floor elevations and last glacial maximum lgm equilibrium line altitude ela reconstructions and fault slip rate with three metrics of topography in each range the along strike maximum elevation swath profile hypsometry and slope elevation profiles in the slowly uplifting beaverhead bitterroot mountains and lemhi and lost river ranges trends in maximum elevation parallel elas independent of variations in fault slip rate maximum elevations are offset similar to 500 m from lgm elas in the lost river range lemhi range and northern beaverhead bitterroot mountains and by similar to 350 m in the southern beaverhead bitterroot mountains where glacial extents were less the offset between maximum topography and mean quaternary elas inferred from cirque floor elevations is similar to 350 m in the lost river and lemhi ranges and 200 250 m in the beaverhead bitterroot mountains additionally slope elevation profiles are flattened and hypsometry profiles show a peak in surface areas close to the ela in the lemhi range and beaverhead bitterroot mountains suggesting that small glaciers efficiently limit topography the situation in the lost river range is less clear as a glacial signature is not apparent in either slope elevation profiles or the hypsometry in the rapidly uplifting teton range the distribution of elas appears superficially to correspond to maximum topography hypsometry and slope elevations profiles with regression lines on maximum elevations offset by similar to 700 and similar to 350 m from the lgm and mean quaternary ela respectively however grand teton and mt moran represent high elevation teflon peaks that appear impervious to glacial erosion formed in the hard crystalline bedrock at the core of the range glacier size and drainage density rock uplift rate and bedrock lithology are all important considerations when assessing the ability of glaciers to limit mountain range topography in the northern basin and range it is only under exceptional circumstances in the teton range that small glaciers appear to be incapable of imposing a fully efficient glacial buzzsaw emphasising that high peaks represent an important caveat to the glacial buzzsaw hypothesis c 2008 elsevier b v all rights reserved

emergent characteristics of rockfall inventories captured at a regional scale high resolution rockfall inventories captured at a regional scale are scarce this is partly owing to difficulties in measuring the range of possible rockfall volumes with sufficient accuracy and completeness and at a scale exceeding the influence of localised controls this paucity of data restricts our ability to abstract patterns of erosion identify longterm changes in behaviour and assess how rockfalls respond to changes in rock mass structural and environmental conditions we have addressed this by developing a workflow that is tailored to monitoring rockfalls and the resulting cliff retreat continuously in space in 3d and over large spatial scales 10 4 m we tested our approach by analysing rockfall activity along 20 5 km of coastal cliffs in north yorkshire uk in what we understand to be the first multi temporal detection of rockfalls at a regional scale we show that rockfall magnitude frequency relationships which often underpin predictive models of erosion are highly sensitive to the spatial extent of monitoring variations in rockfall shape with volume also imply a systemic shift in the underlying mechanisms of detachment with scale leading us to question the validity of applying a single probabilistic model to the full range of rockfalls observed here finally our data emphasise the importance of cliff retreat as an episodic process going forwards there will a pressing need to understand and model the erosional response of such coastlines to rising global sea levels as well as projected changes to winds tides wave climates precipitation and storm events the methodologies and data presented here are fundamental to achieving this marking a step change in our ability to understand the competing effects of different processes in determining the magnitude and frequency of rockfall activity and ultimately meaning that we are better placed to investigate relationships between process and form erosion at critical regional scales

electrical resistivity tomography monitoring of permafrost in solid rock walls 1 this article describes the first attempt to conduct electrical resistivity tomography ert in solid permafrost affected rock faces electrode design instrument settings and processing routines capable of measuring under relevant conditions were developed four transects with nw ne east e and south s aspects were installed in solid rock faces between matter valley and turtmann valley switzerland at 3070 3150 m above sea level dc resistivity in the transects was measured repeatedly during the summer and compared by applying a time lapse inversion routine resistivity values were calibrated using observed rock surface conditions of thawed damp rocks 1 8 k m deeply frozen rocks 18 80 k m and the transition from damp thawed to frozen rocks 8 18 k m mean surface layer resistivities of transects respond to air temperatures below 0 c with a rapid increase by a factor of 1 4 to 2 9 from values of 12 15 k m to values of 22 31 k m rock layers at depths of 2 6 m display a general trend of resistivity decrease in summer corresponding to a persistent thawing process their response to anomalously cool august temperatures occurs with a time lag of 2 to 4 weeks only transects e ne and nw display persistent high resistivity permafrost bodies 50 k m mostly at depths of 6 10 m the maximum thaw depth of a continuous thawing front above permafrost is 6 m however the ert results emphasize the role of heat transfer by deep reaching cleft water systems thus permafrost occurs in lenses rather than layers ert provides rapid detection of ice and water distribution in permafrost affected bedrock

physical deterioration of sedimentary rocks subjected to experimental freeze thaw weathering ten types of sedimentary rock were subjected to repeated cycles of freezing and thawing in addition to monitoring sample weight loss throughout testing a detailed graphic record was made of deterioration mode and its relationship to pre existing rock flaws results suggest that the presence or absence of rock flaws alone does not control deterioration mode but rather that it is the coupled relationship between these flaws and rock strength and textural properties which exerts greatest influence while some pre existing flaws such as syndepositional deformation structures do not appear to influence breakdown others such as incipient fractures cavities and minor lithological boundaries frequently coincide with concentrations of deterioration a characteristic mode of deterioration which is independent of pre existing flaws tends to develop in sandstones indicating the influence in this case of rock texture particularly strong rocks such as crystalline limestone and metasediment tend to fracture preferentially along distinct linear weaknesses such as mineral veins stylolites and incipient fractures particularly weak rocks such as low density chalk break down in a random fashion without regard to pre existing flaws in addition to providing some insight into the role of pre existing flaws in rock deterioration this work also has practical implications for i the study of landform development due to weathering and ii the selection of representative rock samples in durability testing for building stone copyright 2000 john wiley sons ltd

continuous and large sediment supply in a steep landslide scar southern japanese alps abstract continuous sediment supply in the aka kuzure landslide scar in the tectonically active alpine southern japanese alps was investigated using airborne light detection and ranging data in 2000 2003 2007 and 2012 in addition we focused on the spatial variability of denudation patterns based on topographical analyses using dems denudation volume for the past 12 years reached about 106 m3 and mean annual denudation rate ranged from 0 25 to 0 31 m yr topographical analyses revealed that sediment supply in the scar consists of a combination of two denudation types sporadic deep and wide thin these denudation types have different roles in the topographical development of the landslide scar sporadic deep type supplies less volume than wide thin type but still contributes to channel development as it mainly occurs on lower order streams and tends to change the convex slope into a concave slope in contrast although denudation depth of the wide thin type is thin the area affected by this type extends to the whole landslide scar consequently the wide thin type accounts for most of the total volume lost for which detachment by frost shattering is suggested as an important role

direct observation of frost wedging in alpine bedrock width and temperature of rock joints were automatically monitored in the japanese alps three years of monitoring on a sandstone rock face shows two seasonal peaks of joint widening in autumn and spring the autumn events are associated with short term freeze thaw cycles and the magnitude of widening reflects the freezing intensity and water availability the short term freezing can produce wedging to a depth of at least 20 cm the spring events follow a rise in the rock surface temperature to 0 c beneath the seasonal snowcover and likely originate from refreezing of meltwater entering the joint some of these events contribute to permanent enlargement of the joint two other joints on nearby rock faces experience only sporadic widening accompanying freeze thaw cycles and insignificant permanent enlargement observations indicate that no single thermal criterion can explain frost weathering the temperature range at which wedging occurs varies with the bedrock conditions water availability and duration of freezing copyright 2001 john wiley sons ltd

modeling the effects of weathering on bedrock floored channel geometry 1 field and modeling studies suggest that bedrock channels equilibrate to base level change through geometry and slope adjustment to imposed discharge sediment supply and substrate erodibility conditions in this study we model the influence of bedrock weathering on channel geometry and slope as mean peak discharge qm and uplift rate u vary we find that channels in which weathering is allowed to increase erodibility are wider deeper and less steep than nonweathering channels with the same initial conditions while fixed erodibility channels maintain similar width depth ratios regardless of qm or u the width depth ratio of weathering channels is sensitive to uplift rate at low uplift rates weathering outpaces erosion and channels obtain similar width depth ratios but are wider and less steep than fixed erodibility channels with equal initial conditions at high uplift rates erosion outpaces weathering and erodibility remains near the unweathered value with channel shape and slope nearly identical to a fixed erodibility channel with equal initial conditions weathering channels differ most from fixed erodibility channels at intermediate uplift rates with greater width depth ratios and lower slopes than fixed erodibility channels with the same initial conditions our results support the hypothesis that cross channel variations in erodibility created by weathering may be an important control on channel geometry and provide guidance for further testing of this hypothesis in natural systems

frost cracking control on catchment denudation rates insights from in situ produced 10be concentrations in stream sediments ecrins pelvoux massif french western alps the potential tectonic and climatic controls on erosion rates in the european alps and other mountain belts remain strongly debated we have quantified denudation rates at catchment scales using in situ produced cosmogenic nuclides 10be in stream sediments sampled at the outlets of twelve variously sized 27 1072 km2 catchments of the ecrins pelvoux massif french western alps with average elevations ranging from 1700 to 2800 m spatially averaged denudation rates corrected for potential shielding by little ice age glaciers vary from 0 27 0 05 to 1 07 0 20 mm yr on millennial timescales our results exhibit a correlation 2 0 56 between denudation rate and mean catchment elevation in the absence of significant correlation with any other morphometric parameters relief slope catchment size hypsometry etc although such variations in erosion rates have been previously linked to variations in tectonic uplift rate the relatively small size and tectonic homogeneity of our study area exclude a strongly variable tectonic control we interpret the increase in erosion rate with elevation as the effect of frost controlled processes which are strongly temperature dependent we use a one dimensional heat flow model driven by high resolution instrumental temperature records from the study area to correlate the variability in denudation rates with the integral of the absolute temperature gradient within the frost cracking window 3 to 8 c a proxy of the frost cracking intensity for each catchment the results imply that the efficiency of frost cracking constitutes a major control on catchment wide denudation rates in the study area explaining more than half the measured variability in these rates our study shows that present day denudation of the ecrins pelvoux massif is controlled by a climatically driven factor and suggests that frost cracking processes impose an important control on the post glacial topographic evolution of mid latitude mountain belts

significance of rockfall magnitude and carbonate dissolution for rock slope erosion and geomorphic work on alpine limestone cliffs reintal german alps abstract the proportional contribution of low mid and high magnitude rock slope failure orchestrates rock slope erosion and rockfall hazard in alpine and arctic environments in this study we compare sediment yield geomorphic work and rock wall retreat of carbonate dissolution and five different magnitudes of rock slope failure in the steep alpine reintal trough valley we combine a four year rockfall collector measurement of 140 mg of fragmental rockfall a 20th century scientific record of mid magnitude rockfall as well as carbon dating and a historical record of 15th to 19th century rock avalanche activity the total rockfall sediment yield of 8 6 3 4 10 3 m 3 year 1 is dominated by high magnitude rock avalanches 10 6 m 3 62 and low magnitude debris falls 3 18 while mid magnitude boulder block and cliff falls are less important the magnitude signal contradicts studies on siliceous rocks where mid magnitude rockfall dominates rock slope erosion the geomorphic work released in the 17 3 km 2 large catchment by rockfalls 123 47 w km 2 i e 0 38 0 15 mm year 1 and solute transport 34 18 w km 2 i e 0 05 0 03 mm year 1 exceeds previously published alpine values by one to multiple orders of magnitude we hypothesise that the magnitude signal of enhanced small and high magnitude rockfall is characteristic for carbonate cliffs the elevated porosity related susceptibility to fragmentation and persistent carbonate dissolution along potential sliding planes are likely to favour both low and high magnitude rock slope failures here we show how the magnitude signal of rock slope failure influences rock wall retreat geomorphic work rockfall deposition and sediment connectivity

a theoretical model of the fracture of rock during freezing we present a mathematical model for the breakdown of porous rock by the growth of ice within cracks the model is founded upon well established principles of fracture mechanics and recent advances in soil physics ijong with the assumption that progressive crack growth results from water migrating to ice bodies in cracks much as water migrates to ice lenses in freezing soil our model predicts crack growth rates compatible with empirical data calculations for a granite and a marble indicate that sustained freezing is most effective in producing crack growth when temperatures range from 4 c to 15 c at higher temperatures thermodynamic limitations prevent ice pressure from building up sufficiently to produce significant crack growth at lower temperatures the migration of water necessary for sustaining crack growth is strongly inhibited in hydraulically open systems in which pore water pressure remains near atmospheric pressure during the freezing process crackgrowth rates during continuous cooling will generally be greatest at low rates of cooling less than 0 1 0 5 c h at higher rates of cooling the influx of water to growing cracks is significantly inhibited the model delineates clearly the role of material parameters elastic moduli fracture mechanical properties grain size and shape and crack size environmental conditions temperature temperature gradient water pressure and time in frost damage to rocks our calculations along with recent experimental work on water migration in freezing rocks fukuda 1983 lead us to question the widely accepted importance of two phenomena freezing of water in sealed cracks and freeze thaw cycling in the fracture of rock exposed to natural freezing conditions

10be ages reveal 12 ka of gravitational movement in a major sackung of the western alps france abstract the rognier sackung which extends ne sw for more than 9 km is a major gravitational morpho structure located in the western alps we used the 10 be cosmic ray exposure dating method on 23 samples to unravel its history and better understand its genetic mechanism we found that the average slip rate on sackung faults varies from 0 3 to 3 2 mm yr 1 conjugate sackung faults are contemporaneous in agreement with a model in which the whole mountain ridge is involved in the gravitational deformation 600 m thick multiple samples on single faults suggest that the development of this sackung started before 12 ka and that it is still active we cannot exclude the possibility that the dissolution of the underlying triassic evaporites participated in the sagging of mt rognier however the age of this sackung and the presence of the lauziere sackung on the other side of the arcs valley support glacial erosion and debuttressing following the retreat of the valley glacier as the main causes of these large gravitational structures the long and permanent activity of the rognier sackung contrasts with that of the neighbouring arcs sackung which we previously dated using the same method and showed that it is a result of flexural toppling along with the proximity of the rognier sackung to the belledonne border active fault its long history suggests that earthquake shaking contributed to maintain its activity additionally two ages confirm that in the western alps rock glaciers formed mainly during the younger dryas this study allowed the determination of the best sampling strategy for future cre dating of these types of gravitational structures

aspect related microclimatic influences on slope forms and processes northeastern arizona 1 climate is a major control on geomorphology yet the effects of aspect related differences in microclimate have been little studied we examined several 60 100 m deep canyons in semiarid northeastern arizona where rock type and structure are essentially constant but where field data and a high resolution digital elevation model reveal consistent morphologic and microclimatic differences between asymmetric north and south facing sideslopes cliffs account for 29 of the vertical relief of south facing slopes but only 2 5 of north facing slopes excluding cliffs south facing slopes are 1 3 steeper than north facing slopes and have significantly less weathered bedrock we monitored air surface and subsurface temperatures and soil moisture at 0 5 h intervals at four locations over 1 year south facing slopes were 1 4 5 6 c warmer and soil moisture tension at 10 cm depth averages at least 78 kpa lower drier than on north facing slopes the dominant rock type in the study area morrison formation sandstone weathers primarily by clay hydration these sandstones form disaggregated mantles where weathering exceeds erosion but also maintain steep slopes and cliffs where little weathered south facing slopes were too dry during most of the instrumented year for significant clay expansion whereas the north facing bedrock slope was moist all year cliff growth thus occurs preferentially on warmer and drier slopes where weathering is reduced small north facing cliffs typically 3 m could have formed during the holocene but cliffs up to 70 m high on southerly aspects require more time to form and likely persisted or expanded under cooler and wetter late pleistocene climates

field experiments on physical weathering and wind erosion in an antarctic cold desert field experiments were carried out over a five year period with the aim of understanding contemporary weathering and erosional environments in the sor rondane mountains an antarctic cold desert region these include observations of 1 scaling from rockwalls 2 disintegration of tuff blocks with or without saline solutions and 3 abrasion of artificial walls by wind monitoring was also made of rock surface temperature and wind speed despite frequent temperature oscillations across 0 c rock scaling due to frost action was generally very slow because of low moisture content in the rockwalls exposure to the cold dry climate led to the rapid disintegration of porous tuff blocks including soluble salts like halite and thenardite this indicates that rates of weathering are increased greatly with the accumulation of such salts in the bedrock although gypsum did not cause any visible damage over four years its widespread occurrence in heavily damaged rocks demonstrates that increasing gypsum contents may also intensify rock breakdown the snow laden katabatic wind resulted in rapid wearing of the windward face of an asbestos board with the peak erosion at 30 40 cm above the ground nonetheless the landforms expected from the unidirectional wind characteristics are by no means common features because of lack of abrasive materials such as snow and sand particles these experiments suggest that frost weathering and wind erosion are only locally effective where plenty of moisture or an abrasive material is available whilst salt weathering and removal of the waste by wind play a major role in constructing erosional landforms over the mountains

erosion rates of the bhutanese himalaya determined using in situ produced 10be abstract western bhutan provides an ideal setting to understand the interplay between uplift erosion and fluvial sediment transport in an active mountain environment using in situ produced 10 be 49 samples and 26 al 5 samples in fluvial sediment from nested catchments throughout the puna tsang chhu drainage basin we examine erosion rates in different geomorphic environments including two high relief regions a glacierized zone in the north and a high rainfall zone in the south as well as remnants of an uplifted lower relief paleosurface between them the erosion rates roughly mirror this north south zonation lower rates avg 388 32 m my 1 n 16 prevail in the low relief zone roughly coinciding with lower relief terrain where mean annual precipitation is 1500 mm yr 1 the highest rates avg 956 160 m my 1 n 13 are in the south 27 10 27 35 n where rainfall is 4000 mm yr 1 high rates avg 700 62 m my 1 n 15 also occur in the northern glacierized region 27 70 28 10 n all 49 purified mineral separates used in this study contain measurable amounts of native 9 be up to 900 g violating the assumption of negligible 9 be that is commonly made in the isotope dilution method used to quantify 10 be to correct for this native 9 be we use high precision replicate measurements of 9 be in each sample to calculate 10 be concentrations from measured isotopic ratios neglecting native 9 be would have led to erosion rate overestimates from 400 the pervasive nature of 9 be in these samples underscores the importance of quantifying the native 9 be concentration in mineral separates used for cosmogenic 10 be analysis

stochastic processes of soil production and transport erosion rates topographic variation and cosmogenic nuclides in the oregon coast range landscapes in areas of active uplift and erosion can only remain soil mantled if the local production of soil equals or exceeds the local erosion rate the soil production rate varies with soil depth hence local variation in soil depth may provide clues about spatial variation in erosion rates if uplift and the consequent erosion rates are sufficiently uniform in space and time then there will be tendency toward equilibrium landforms shaped by the erosional processes soil mantle thickness would adjust such that soil production matched the erosion previous work in the oregon coast range suggested that there may be a tendency locally toward equilibrium between hillslope erosion and sediment yield here results from a new methodology based on cosmogenic radionuclide accumulation in bedrock minerals at the base of the soil column are reported we quantify how soil production varies with soil thickness in the southern oregon coast range and explore further the issue of landscape equilibrium apparent soil production is determined to be an inverse exponential function of soil depth with a maximum inferred production rate of 268 m ma 1 occurring under zero soil depth this rate depends however on the degree of weathering of the underlying bedrock the stochastic and large scale nature of soil production by biogenic processes leads to large temporal and spatial variations in soil depth the spatial variation of soil depth neither supports nor rejects equilibrium morphology our observed catchment averaged erosion rate of 117 m ma 1 is however similar to that estimated for the region by others and to soil production rates under thin and intermediate soils typical for the steep ridges we suggest that portions of the oregon coast range may be eroding at roughly the same rate but that local competition between drainage networks and episodic erosional events leads to landforms that are out of equilibrium locally and have a spatially varying soil mantle copyright 2001 john wiley sons ltd

do periglacial landscapes evolve under periglacial conditions polar and alpine periglacial areas are traditionally regarded as necessarily submitted to very efficient frost driven processes that control the holocene and ongoing geomorphic activity during the last decade the validity of this academic view has been increasingly questioned among the international scientific community the search for the real past and present processes responsible for landform evolution in cold nonglaciated areas is based mainly on more and more refined monitoring protocols relying upon sophisticated equipment to assess the representativeness and significance of monitoring data collected in restricted sites it appears necessary however to widen the perspective by adopting a twofold multiscale approach as proposed in the present paper 1 in space by integrating various scales from the general slope system to the bioclimatic nanoenvironment and 2 in time by taking into account the landscape history from tertiary inherited features to recent process changes induced by the contemporary warming reintegrating the historical approach should help both to place the ongoing processes within a succession and or combination of interoperating processes and to avoid misinterpretations of features considered wrongly as emblematic of frost action overall both the historical and monitoring approaches tend to reduce the geomorphic efficiency of frost derived processes instead the role of noncold related processes such as chemical thermal biogenic and rainfall induced ones is being emphasized of special interest would be an interdisciplinary discussion between geomorphologists and various disciplines of biological sciences including biochemistry and ecology studying processes of primary successions

rockfall activity from an alpine cliff during thawing periods abstract rockfall activity during thawing periods was investigated by collecting rockfall debris fallen on the snow covered talus slope in a cirque in the japanese alps near surface rock temperature was also monitored on the cirque wall maximum rockfall activity occurs on average about 10 days after the meltout of the cirque wall the intensive activity is rarely associated with precipitation events or diurnal frost cycles on the rockface a thermal conduction model suggests that rockfalls at this site occur most frequently when the seasonal thawing front penetrates to a depth of about 1 m in the bedrock while the freeze thaw penetration controls the maximum dimensions of detachable rock mass joint spacing on the rockface affects the size distribution of rockfall debris boulder falls resulting from seasonal frost weathering are considered to be the most important process responsible for the contemporary modification of the cirque wall the rockfall volume during a thawing period is usually 1 3 m3 which is equivalent to the rate of cirque wall retreat of the order of 0 01 mm year 1 however big boulder falls that occur once per decade can increase the retreat rate significantly

the impact of local geochemical variability on quantifying hillslope soil production and chemical weathering soil mantled upland landscapes are widespread across the habitable world support extensive life and are the interface between the atmosphere hydrosphere and lithosphere but typically are not cultivated soil found across such landscapes fits the conceptual framework of a physically mobile layer derived from the underlying parent material along with some locally derived organic content the extent and persistence of these upland soils depend on the long term balance between soil production and erosion here we briefly review methods used to quantify the physical and chemical processes of soil production and erosion and revisit three granitic study areas in southeastern australia and northern california that enabled early quantification of the soil production function and topographic controls on chemical weathering we then present new major and trace element data from 2 m by 2 m pits dug at each field site to quantify local variability of zr concentrations and the chemical index of alteration cia weathering indices used to determine chemical weathering rates and extents in soils and saprolites using both new and previously published data we compare differences between local variability and regional as well as intersite variability of these important indices for each of the 2 m pits we collected 25 samples and found that the simple mean and the 2 standard deviation best describe the local variation in the data we also find that the variability in the 2 m pit data lies within variability observed in the same data from samples collected in individual soil pits across each of the field sites and that the differences between sites are consistent with previously published results these observations highlight the importance of quantifying local scale variability in studies that use similar multifaceted measurements to quantify hillslope soil production and erosion processes

application of refraction seismics in alpine permafrost studies a review abstract refraction seismics is a common geophysical application to investigate permafrost in alpine studies this study reviews the physical basis of the use of refractions seismics and introduces the history of its application in alpine environments seismic properties are influenced by rock or soil properties and fluid or ice effects in laboratory measurements these influences are determined and linked to mechanical properties or used for calibration of field studies in field conditions supplementary environmental factors influence the seismic properties of landforms in this paper laboratory studies of rocks from different lithologies and with different properties as well as case studies on rock glaciers moraines talus slopes and debris covered slopes are collected and influencing factors quantitatively analyzed the data demonstrate how lithology porosity and anisotropy influence p wave velocity environmental factors result in a high variation of p wave velocities in landforms however p wave velocities enable the differentiation of active layer and permafrost in rock glaciers and moraines in talus slopes and debris covered slopes p wave velocity contrasts between active layer and permafrost layer might be insufficient and require the application of additional methods for a final differentiation

using dynamic modelling to simulate the distribution of rockglaciers abstract rockglaciers permafrost creep features on mountain slopes are common landforms in high mountain areas the present contribution reports about the exploration of a dynamic modelling approach using cellular automata to assess their regional distribution patterns the designed prototype model allows the numerical simulation of the spatial and temporal occurrence of talus derived rockglaciers in the upper engadine eastern swiss alps during the holocene the dynamic model considers processes in the spatial and temporal domain and accounts for both external and internal processes implemented by means of six modules a to g the external processes are a rock debris accumulation b hydrology c climate d glacier extent the internal processes are e creep initiation f advance rate g creep termination comparison between field evidence and modelling results shows that the dynamic model enables the simulation of spatio temporal creep processes on a regional scale but that the model is highly dependent on the accurate modelling of the relevant input parameters these deficiencies have been recognized and analyzed and it is planned that future research activities will address these issues

the effect of wet dry weathering on the rate of bedrock river channel erosion by saltating gravel abstract previous work has shown that the bedrock erosion rate e because of collisions of saltating bedload can be expressed by e qb 1 pc where qb is the sediment transport rate pc is the extent of alluvial cover and is the abrasion coefficient however the dependence of the abrasion coefficient on the physical characteristics of the bedrock material is poorly known and in particular the effects of wet dry weathering on the saltation abrasion bedrock incision has not been specifically characterized observation suggests that the typical wet dry cycling of exposed bedrock in river beds gives rise to cracks and voids that are likely to alter the incision rate of the material when subjected to impacts of moving sediment in this study flume experiments are performed to develop an understanding of how wet dry cycling affects the rock tensile strength and the bedrock erosion rate to represent the physical effects of weathering boring cores taken from natural bedrock channel are exposed to artificial wet dry cycles the experimental results suggest the following 1 the abrasion coefficient for fresh bedrock is estimated by 1 0 10 4 t 2 d ksb 0 5 where t is the tensile strength d is the diameter of colliding gravel and ksb is the hydraulic roughness height of bedrock 2 the tensile strength of the bedrock decreases exponentially as a result of repeated wet dry cycles t t0 exp ctnwa0 t0 where t0 is the initial tensile strength wa0 is the initial normalized rate of water absorption n is the number of wet dry cycles and ct is a constant 3 the erosion rate of fresh bedrock depends on the inverse of the square of tensile strength but the erosion rate of weathered bedrock depends on the 1 5 power of tensile strength

erosion rates of alpine bedrock summit surfaces deduced from in situ 10be and 26al we have measured the concentration of in situ produced cosmogenic 10be and 26al from bare bedrock surfaces on summit flats in four western u s mountain ranges the maximum mean bare bedrock erosion rate from these alpine environments is 7 6 3 9 m my 1 individual measurements vary between 2 and 19 m my 1 these erosion rates are similar to previous cosmogenic radionuclide crn erosion rates measured in other environments except for those from extremely arid regions this indicates that bare bedrock is not weathered into transportable material more rapidly in alpine environments than in other environments even though frost weathering should be intense in these areas our crn deduced point measurements of bedrock erosion are slower than typical basin averaged denudation rates 50 m my 1 if our measured crn erosion rates are accurate indicators of the rate at which summit flats are lowered by erosion then relief in the mountain ranges examined here is probably increasing we develop a model of outcrop erosion to investigate the magnitude of errors associated with applying the steady state erosion model to episodically eroding outcrops our simulations show that interpreting measurements with the steady state erosion model can yield erosion rates which are either greater or less than the actual long term mean erosion rate while errors resulting from episodic erosion are potentially greater than both measurement and production rate errors for single samples the mean value of many steady state erosion rate measurements provides a much better estimate of the long term erosion rate

pebbly versus bouldery rock glaciers morphology structure and processes abstract differences in rockwall geology cause two types of rock glaciers a bouldery rock glacier having the active layer composed of matrix free boulders derived from crystalline rocks and massive limestone and a pebbly rock glacier consisting of matrix supported debris derived from less resistant shale and platy limestone such material composition controls transport processes responsible for the shape size and internal structure of the two types of rock glaciers this paper compares the major processes controlling the morphology and structure of the two types in the swiss alps based on mapping description of geological and morphological characteristics direct observation of stratigraphy and geophysical soundings of internal structure in the swiss alps pebbly rock glaciers are distinguished from bouldery rock glaciers by the clast size of 15 20 cm in the mean b axis diameter the former are fed by small scale rockfalls debris flows and solifluction whereas the latter mainly originate from large rockfalls pebbly rock glaciers are generally smaller 100 k m in bouldery rock glaciers appears to originate from snow banks buried with deposits of large rockfalls from the large source rockwall

frost weathering and rockwall erosion in the southeastern swiss alps long term 1994 2006 observations abstract rates and processes of frost weathering in the alps were investigated by visual observations of intensively shattered rocks continuous monitoring of frost wedging and rock temperatures in bedrock and measurements of rockfall activity rapid frost weathering of hard intact rocks occurs along lakes and streams where seasonal freezing promotes ice segregation in the rock otherwise rocks require pre existing weakness or a long exposure period for intensively shattered automated monitoring shows that crack opening occurs at three scales including small opening accompanying short term frost cycles slightly larger movements during seasonal freezing and occasional large opening originating from refreezing of snow melt water during seasonal thawing the opening events require at least partial water saturation in the crack the repetition of crack opening frost wedging results in permanent opening and finally debris dislocation debris collections below fractured rockwalls show that pebble falls occur at an average rate of about 0 1 mm a 1 with significant spatial and inter annual variations occasional large boulder falls significantly raise the rockwall erosion rates controlled by such factors as the joint distribution in the bedrock repetition of annual freeze thaw cycles and extraordinary summer thaw

rock moisture measurements techniques results and implications for weathering rock moisture is an important factor for the intensity and distribution of frost weathering processes however quantitative measurements are scarce which is partly due to the lack of reliable measurement techniques this paper presents five different techniques for obtaining rock moisture data while collecting rock pieces and two dimensional geoelectric measurements allow determination of the spatial moisture distribution the temporal variability can be derived from conductivity and time domain reflectometry records computer simulations using rock properties and climatic records as input data render it possible to clarify the important aspects that are responsible for the moisture distribution it proved to be advisable to use several methods to check and validate the results the results obtained in study areas in the bavarian alps make it clear that direct rainfall is the main source of rock moisture the influence of snow is limited to the immediate vicinity of the snow fields and is not equally pronounced at different times and positions rock moisture levels are higher in summer than they are in winter since in winter less water is supplied in liquid form northerly exposed rockwalls are generally more moist than those exposed in a southerly direction which is due to the different insolation as well as to the wind direction during rainfall in every position the rock is on average wetter on the inside than it is on the surface this means that shallow frost cycles as typical for south exposed sites are not affecting weathering since they take place at a depth level that is mostly dried out numerous spatial and temporal patterns of rockfall found in the same study areas can be explained through variations in rock moisture thus the moisture content of the rock is considered to be one of the major controlling factors of the frost shattering rate copyright 2005 john wiley sons ltd

the rate of bedrock weathering by frost action field measurements and a predictive model shattering rate surface temperature moisture content and the physical and strength properties of bedrock were measured in four rockwall sites of the japanese alps five year observations revealed that the bedrock shattering rate was usually much higher in the freeze thaw period from october to next may than in the frost free period from june to september this indicates that frost action is the most important shattering process although unusual heavy rainstorms in summer are also responsible for the shattering a combination of some empirical relationships derived from recent laboratory experiments leads to a predictive model of the frost shattering rate this model shows that the annual shattering rate is dependent on the annual freeze thaw frequency on the rock surface and the degree of saturation and tensile strength of the rock masses the coefficients involved in the model were determined using the field data

rock moisture content in the field and the laboratory and its relationship to mechanical weathering studies rock moisture content is a major control of mechanical weathering particularly freeze thaw and yet almost no data exist from field situations this study presents moisture content values for rocks taken from a variety of positions and conditions in the maritime antarctic additional information regarding the amount of water the rock could take up as observed from laboratory experiments is also presented the results show that the approaches used in simulation experiments particularly that of soaking a rock for 24 hours may produce exaggerated results it was found that the saturation coefficient s value was a good indicator of frost susceptibility based on water content but that the derivation of that value may underestimate the potential of some rocks the distribution of moisture within rocks is seen as an important but unkown factor the results of these field moisture contents suggest that for simulations of freeze thaw or hydration to be meaningful then they should have rock water contents based on field observations

controls on basalt terrace formation in the eastern lesotho highlands abstract the objective of this study is to ascertain the relative importance of lithological controls and geomorphological processes in the development of drakensberg basalt terraces various hypotheses for terrace formation are considered including geological controls macroscale geomorphology and climatic geomorphological controls the variations in strength and relative age differences for scarp surface exposures on two slopes of varying aspect are determined so that a comparison can be made between various scarp outcrops and relative rates of weathering scarp outcrops were measured for their rock mass strength rock surface roughness and percentage lichen cover the ethylene glycol test was performed on prepared rock samples to determine susceptibility to tensional breakup a satellite image depicting the distribution of late lying contemporary snow was used to assist in the construction of topo climatic linkages with scarp terrace localities findings show that terraces are most common on southeast facing aspects and coincide with the major joint strike direction lithological factors are thus considered the primary control to such terrace development it is suggested that a different set of geomorphological processes operates on various slope altitudinal and slope orientational positions at any given time