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1.
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.  相似文献   

2.
Surface specimens obtained from highly-weathered upland plateau outcrops at three localities in high Arctic Canada have been studied using the scanning electron microscope. Observations are given on factors influencing bedrock surface microfracturing processes. Evidence for the concentration of both salts and organic material in surface cracks which could enhance microfracturing is presented. The importance of lithological parameters including: mineralogy, texture, and structures present in influencing the actual processes of disintegration is reiterated. Under cold, dry high Arctic conditions the combined and apparently inseparable affects of frost action, salt crystallization, and organic activity may have contributed to microfracturing largely responsible for widely scattered examples of highly weathered bedrock terrain.  相似文献   

3.
An indication of the extent of weathering on different aspects of rock outcrops on Livingston Island, Antarctica, was obtained by means of a Schmidt hammer, a cone indenter and measurement of weathering rind thickness. Results show that weathering, particularly chemical weathering, is enhanced on the lee side of outcrops where snow accumulates as a result of prolonged wetting by the melting snow. Rock moisture and temperature data indicate that the south-facing, snow-accumulation side of obstacles have high rock moisture levels and maintain relatively high temperatures. Whilst chemical weathering is greater on the leeward side of outcrops, mechanical processes are greater on the windward side. The presence of late-lying snow thus appears to exert a strong influence on weathering.  相似文献   

4.
In this article we craft process‐specific algorithms that capture climate control of hillslope evolution in order to elucidate the legacy of past climate on present critical zone architecture and topography. Models of hillslope evolution traditionally comprise rock detachment into the mobile layer, mobile regolith transport, and a channel incision or aggradation boundary condition. We extend this system into the deep critical zone by considering a weathering damage zone below the mobile regolith in which rock strength is diminished; the degree of damage conditions the rate of mobile regolith production. We first discuss generic damage profiles in which appropriate length and damage scales govern profile shapes, and examine their dependence upon exhumation rate. We then introduce climate control through the example of rock damage by frost‐generated crack growth. We augment existing frost cracking models by incorporating damage rate limitations for long transport distances for water to the freezing front. Finally we link the frost cracking damage model, a mobile regolith production rule in which rock entrainment is conditioned by the damage state of the rock, and a frost creep transport model, to examine the evolution of an interfluve under oscillating climate. Aspect‐related differences in mean annual surface temperatures result in differences in bedrock damage rate and mobile regolith transport efficiency, which in turn lead to asymmetries in critical zone architecture and hillslope form (divide migration). In a quasi‐steady state hillslope, the lowering rate is uniform, and the damage profile is better developed on north‐facing slopes where the frost damage process is most intense. Because the residence times of mobile regolith and weathered bedrock in such landscapes are on the order of 10 to 100 ka, climate cycles over similar timescales result in modulation of transport and damage efficiencies. These lead to temporal variation in mobile regolith thickness, and to corresponding changes in sediment delivery to bounding streams. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

5.
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.  相似文献   

6.
We explore the contribution of fractures (joints) in controlling the rate of weathering advance for a low‐porosity rock by using methods of homogenization to create averaged weathering equations. The rate of advance of the weathering front can be expressed as the same rate observed in non‐fractured media (or in an individual block) divided by the volume fraction of non‐fractured blocks in the fractured parent material. In the model, the parent has fractures that are filled with a more porous material that contains only inert or completely weathered material. The low‐porosity rock weathers by reaction‐transport processes. As observed in field systems, the model shows that the weathering advance rate is greater for the fractured as compared to the analogous non‐fractured system because the volume fraction of blocks is < 1. The increase in advance rate is attributed both to the increase in weathered material that accompanies higher fracture density, and to the increase in exposure of surface of low‐porosity rock to reaction‐transport. For constant fracture aperture, the weathering advance rate increases when the fracture spacing decreases. Equations describing weathering advance rate are summarized in the ‘List of selected equations’. If erosion is imposed at a constant rate, the weathering systems with fracture‐bounded bedrock blocks attain a steady state. In the erosional transport‐limited regime, bedrock blocks no longer emerge at the air‐regolith boundary because they weather away. In the weathering‐limited (or kinetic) regime, blocks of various size become exhumed at the surface and the average size of these exposed blocks increases with the erosion rate. For convex hillslopes, the block size exposed at the surface increases downslope. This model can explain observations of exhumed rocks weathering in the Luquillo mountains of Puerto Rico. Published 2017. This article is a U.S. Government work and is in the public domain in the USA  相似文献   

7.
We present a statistical model of soil and rock weathering in deep profiles to expand the capacity to assess weathering to heterogeneous bedrock types, which are common at the Earth's surface. We developed the Weathering Trends (WT) model by extending the fractional mass change calculation (tau) of the geochemical mass balance model in two important ways. First, WT log transforms the elemental ratio data, to discern the log‐linear patterns that naturally develop from thermodynamic and kinetic laws of chemistry. Second, WT statistically fits log‐transformed element concentration ratio data – log(cj/ci), the only depth‐varying term in tau – as a function of depth to determine characteristic depths of transitions in weathering processes, along with confidence intervals. With no prior assumptions, WT estimates average parent material composition, average composition of the upper weathered zone and mean fractional mass change of each element over the entire weathering profile. WT displays the mean shape of weathering profiles of log‐transformed geochemical data bounded by calculated confidence intervals. We share the WT model code as an open‐source R package ( https://github.com/fisherba/WeatheringTrends ). The WT model was designed to interpret two 21 m cores from the Laurels Schist bedrock in the Christina River Basin Critical Zone Observatory in the Pennsylvania Piedmont, where our morphological and elemental data provided inconclusive estimates of bedrock depth. The WT model differentiated between rock variability and weathering to delineate the maximum extent of weathering at 12.3 m (CI 95% [9.2, 21.3]) in Ridge Well 1 and 7.2 m (CI 95% [4.3, 13.0]) in Interfluve Well 2. The water table was 5–8 m below fresh rock at Ridge Well 1, but at the same depth as fresh rock at the lower elevation interfluve. We assess statistical approaches to identify the best immobile element for use in WT and tau calculations. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

8.
Cavernous weathering (tafoni development) occurs on coastal slopes in greenschist bedrock at elevations up to 40 m above sea level. The freshly weathered surfaces of the cavern interiors are irregular in morphology, discordant to major rock structure, formed by substantially weakened rock and associated with granular weathering debris. The weathering debris contains soluble elements in proportions similar to those present in seawater, and the penetration of elements associated with sea salts into the weathering surface to estimated depths of at least 0·1–0·2 m is indicated by the presence of chlorine. Scanning electron microscopy and microprobe analyses suggest that rock breakdown occurs principally through limited chemical weathering at grain boundaries. The mechanism for the emplacement of marine salts within sheltered rock surfaces in the tafoni is postulated to be a combination of dry deposition under turbulent atmospheric conditions and wetting by coastal fog.  相似文献   

9.
The evolution of volcanic landscapes and their landslide potential are both dependent upon the weathering of layered volcanic rock sequences. We characterize critical zone structure using shallow seismic Vp and Vs profiles and vertical exposures of rock across a basaltic climosequence on Kohala peninsula, Hawai’i, and exploit the dramatic gradient in mean annual precipitation (MAP) across the peninsula as a proxy for weathering intensity. Seismic velocity increases rapidly with depth and the velocity–depth gradient is uniform across three sites with 500–600 mm/yr MAP, where the transition to unaltered bedrock occurs at a depth of 4 to 10 m. In contrast, velocity increases with depth less rapidly at wetter sites, but this gradient remains constant across increasing MAP from 1000 to 3000 mm/yr and the transition to unaltered bedrock is near the maximum depth of investigation (15–25 m). In detail, the profiles of seismic velocity and of weathering at wet sites are nowhere monotonic functions of depth. The uniform average velocity gradient and the greater depths of low velocities may be explained by the averaging of velocities over intercalated highly weathered sites with less weathered layers at sites where MAP > 1000 mm/yr. Hence, the main effect of climate is not the progressive deepening of a near‐surface altered layer, but rather the rapid weathering of high permeability zones within rock subjected to precipitation greater than ~1000 mm/yr. Although weathering suggests mechanical weakening, the nearly horizontal orientation of alternating weathered and unweathered horizons with respect to topography also plays a role in the slope stability of these heterogeneous rock masses. We speculate that where steep, rapidly evolving hillslopes exist, the sub‐horizontal orientation of weak/strong horizons allows such sites to remain nearly as strong as their less weathered counterparts at drier sites, as is exemplified by the 50°–60° slopes maintained in the amphitheater canyons on the northwest flank of the island. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

10.
Rock texture has a critical influence on the way rocks weather. The most important textural factors affecting weathering are grain size and the presence of cracks and stylolites. These discontinuities operate as planes of mechanical weakness at which chemical weathering is enhanced. However, it is unclear how different rock textures impact weathering rates and the size of weathered grains. Here, we use a numerical model to simulate weathering of rocks possessing grain boundaries, cracks, and stylolites. We ran simulations with either synthetic or natural patterns of discontinuities. We found that for all patterns, weathering rates increase with discontinuity density. When the density was <~25%, the weathering rate of synthetic patterns followed the order: grid > honeycomb > Voronoi > brick wall. For higher values, all weathering rates were similar. We also found that weathering rates decreased as the tortuosity of the pattern increased. Moreover, we show that textural patterns strongly impact the size distributions of detached grains. Rocks with an initial monomodal grain size distribution produce weathered fragments that are normally distributed. In contrast, rocks with an initial log-normal size distribution produce weathered grains that are log-normally distributed. For the natural patterns, weathering produced lower modality distributions.  相似文献   

11.
极端冰雪条件下的顺层岩质边坡滑移稳定性分析   总被引：1，自引：0，他引：1  
推导了典型岩石边坡在极端冰雪条件下的滑移稳定系数的表达式;通过计算分析,揭示了岩石边坡滑移稳定系数随裂隙内水深、坡高、坡角、滑面倾角等因素变化的规律及与冻深的关系,并绘制岩石边坡滑移稳定系数与边坡几何要素之间的关系图。研究表明,当考虑极端冰雪灾害影响时,岩石边坡滑移稳定系数发生较为明显的变化：随裂隙饱水程度、坡面角、主滑面倾角的增加而降低,随主滑面抗剪强度的减小而降低;裂隙饱水程度越高、坡体高度越低、坡面角越小、主滑面倾角越大的边坡的滑移稳定系数,对裂隙冰冻胀力的反应越敏感。  相似文献   

12.
The advance of a chemical weathering front into the bedrock of a hillslope is often limited by the rate weathering products that can be carried away, maintaining chemical disequilibrium. If the weathering front is within the saturated zone, groundwater flow downslope may affect the rate of transport and weathering—however, weathering also modifies the rock permeability and the subsurface potential gradient that drives lateral groundwater flow. This feedback may help explain why there tends to be neither “runaway weathering” to great depth nor exposed bedrock covering much of the earth and may provide a mechanism for weathering front advance to keep pace with incision of adjacent streams into bedrock. This is the second of a two‐part paper exploring the coevolution of bedrock weathering and lateral flow in hillslopes using a simple low‐dimensional model based on hydraulic groundwater theory. Here, we show how a simplified kinetic model of 1‐D rock weathering can be extended to consider lateral flow in a 2‐D hillslope. Exact and approximate analytical solutions for the location and thickness of weathering within the hillslope are obtained for a number of cases. A location for the weathering front can be found such that lateral flow is able to export weathering products at the rate required to keep pace with stream incision at steady state. Three pathways of solute export are identified: “diffusing up,” where solutes diffuse up and away from the weathering front into the laterally flowing aquifer; “draining down,” where solutes are advected primarily downward into the unweathered bedrock; and “draining along,” where solutes travel laterally within the weathering zone. For each pathway, a different subsurface topography and overall relief of unweathered bedrock within the hillslope is needed to remove solutes at steady state. The relief each pathway requires depends on the rate of stream incision raised to a different power, such that at a given incision rate, one pathway requires minimal relief and, therefore, likely determines the steady‐state hillslope profile.  相似文献   

13.
Erosion processes in bedrock‐floored rivers shape channel cross‐sectional geometry and the broader landscape. However, the influence of weathering on channel slope and geometry is not well understood. Weathering can produce variation in rock erodibility within channel cross‐sections. Recent numerical modeling results suggest that weathering may preferentially weaken rock on channel banks relative to the thalweg, strongly influencing channel form. Here, we present the first quantitative field study of differential weathering across channel cross‐sections. We hypothesize that average cross‐section erosion rate controls the magnitude of this contrast in weathering between the banks and the thalweg. Erosion rate, in turn, is moderated by the extent to which weathering processes increase bedrock erodibility. We test these hypotheses on tributaries to the Potomac River, Virginia, with inferred erosion rates from ~0.1 m/kyr to >0.8 m/kyr, with higher rates in knickpoints spawned by the migratory Great Falls knickzone. We selected nine channel cross‐sections on three tributaries spanning the full range of erosion rates, and at multiple flow heights we measured (1) rock compressive strength using a Schmidt hammer, (2) rock surface roughness using a contour gage combined with automated photograph analysis, and (3) crack density (crack length/area) at three cross‐sections on one channel. All cross‐sections showed significant (p < 0.01 for strength, p < 0.05 for roughness) increases in weathering by at least one metric with height above the thalweg. These results, assuming that the weathered state of rock is a proxy for erodibility, indicate that rock erodibility varies inversely with bedrock inundation frequency. Differences in weathering between the thalweg and the channel margins tend to decrease as inferred erosion rates increase, leading to variations in channel form related to the interplay of weathering and erosion rate. This observation is consistent with numerical modeling that predicts a strong influence of weathering‐related erodibility on channel morphology. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

14.
Rock fragments in the regolith are a persistent property that reflects the combined influences of geologic controls, erosion, deposition, bioturbation, and weathering. The distribution of rock fragments in regoliths of the Ouachita Mountains, Arkansas, shows that sandstone fragments are common in all layers, even if sandstone is absent in parent material. Shale and sandstone fragments are produced at the bedrock weathering front, but the shale weathers rapidly and intact fragments are rare in the solum. Sandstone is weathered from ridgetop outcrops and transported downslope. Some of these fragments are moved downward, by faunalturbation and by transport into pits associated with rotting tree stumps. Upward movement by treethrow is common, resulting in a net concentration of rocks near the surface. However, the highest fragment concentrations are in the lower regolith, indicating active production at the weathering front. The regolith is a dynamic feature, reflecting the influences of vertical and horizontal processes, of active weathering at the bedrock interface, and of surficial sediment movements. The role of trees in redistributing rock fragments suggests that significant regolith mixing occurs over time scales associated with forest vegetation communities, and that forest soils have likely been extensively mixed within Holocene and historic time. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

15.
Reduced major axis analysis is used to describe monthly temperature averages for daily maxima, minima, means and ranges at a sequence of bedrock microenvironments in the alpine zone of the Colorado Front Range. Seven thermistors buried at 1 cm in bedrock provide comparative data on easterly, southerly and westerly aspects, and also upon the impact of snow accumulation (?0.5m to ≥4.0m deep) against an east-facing rock wall. Intersite temperatures commonly differ by less than 5°C and, rarely, by more than 10°C. The freezing intensity of freeze-thaw cycles occurring within the confines of a seasonal snow patch rarely dropped to ?5°C, while at snowfree, vertical faces freezing dropped to ?5°C quite commonly. Comparison with laboratory established criteria for effective freeze-thaw weathering (abundant moisture and freezing to at least ?5°C) suggests that moisture rich microsites lack adequate freezing intensity, while adequately frozen sites lack moisture. Available data suggest that the overlap between freeze-thaw and hydration weathering requires careful re-evaluation.  相似文献   

16.
Source rock lithology and immediate modifying processes, such as chemical weathering and mechanical erosion, are primary controls on fluvial sediment supply. Sand composition and Chemical Index of Alteration (CIA) of parent rocks, soil and fluvial sand of the Savuto River watershed, Calabria (Italy), were used to evaluate the modifications of source rocks through different sections of the basin, characterized by different geomorphic processes, in a sub‐humid Mediterranean climate. The headwaters, with gentle topography, produce a coarse‐grained sediment load derived from deeply weathered gneiss, having sand of quartzofeldspathic composition, compositionally very different from in situ degraded bedrock. Maximum estimated CIA values suggest that source rock has been affected significantly by weathering, and it testifies to a climatic threshold on the destruction of the bedrock. The mid‐course has steeper slopes and a deeply incised valley; bedrock consists of mica‐schist and phyllite with a very thin regolith, which provides large cobble to very coarse sand sediments to the main channel. Slope instability, with an areal incidence of over 40 per cent, largely supplies detritus to the main channel. Sand‐sized detritus of soil and fluvial sand is lithic. Estimated CIA value testifies to a significant weathering of the bedrock too, even if in this part of the drainage basin steeper slopes allow erosion to exceed chemical weathering. The lower course has a braided pattern and sediment load is coarse to medium–fine grained. The river cuts across Palaeozoic crystalline rocks and Miocene siliciclastic deposits. Sand‐sized detritus, contributed from these rocks and homogenized by transport processes, has been found in the quartzolithic distal samples. Field and laboratory evidence indicates that landscape development was the result of extensive weathering during the last postglacial temperature maximum in the headwaters, and of mass‐failure and fluvial erosional processes in the mid‐ and low course. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

17.
以2018年"8·11"大安山反倾岩质崩塌为研究对象,通过对大安山地区区域性节理、崩塌及斜坡结构、危岩体变形特征等进行调查研究,运用水力劈裂理论,剖析大安山崩塌机制。研究结果表明:在区域性节理和差异性风化共同作用下,大安山地区发育大量高20~50 m高陡反倾岩质斜坡,为崩塌灾害发生提供充分条件;同时,节理裂隙网络与强硬岩层的空间组合为降雨入渗、运移、储藏提供了良好的地质条件,当遭遇降雨时,雨水沿岩体裂隙渗流并充满裂隙,在降雨停止后短期内,裂隙受高水头作用仍发生水力劈裂,致使裂隙发生扩展贯通,并最终导致危岩体失稳崩塌。  相似文献   

18.
An Erratum has been published for this article in Earth Surface Processes and Landforms 28(13) 2003, 1491. Granite domes, boulders and knobs buried within saprolite have been detected beneath lateritic weathering landsurfaces using 2D electrical resistivity tomography (ERT). This technique provides a valuable means of mapping the bedrock topography and the regolith structures underneath landsurfaces, as it is intrinsically very sensitive to the electrical properties of superimposed pedological, hydrological and geological layers, allowing the determination of their relative geometry and spatial relationships. For instance, 2D inverse electrical resistivity models including topographic data permit the de?nition of lithostratigraphic cross‐sections. It shows that resistive layers, such as the more or less hardened ferruginous horizons and/or the bedrock, are generally well differentiated from poorly resistive layers, such as saprolite, including water‐saturated lenses, as has been corroborated by past and actual borehole observations. The analysis of the 2D geometrical relations between the weathering front, i.e. the bedrock topography, and the erosion surface, i.e. the landsurface topography, documents the weathering and erosion processes governing the development of the landforms and the underlying structures, thus allowing the etching hypothesis to be tested. The in?ltration waters are diverted by bedrock protrusions, which behave as structural thresholds compartmentalizing the saprolite domain, and also the regolith water table, into distinct perched saturated subdomains. The diverted waters are thus accumulated in bedrock troughs, which behave like underground channels where the saprolite production rate may be enhanced, provided that the water drainage is ef?cient. If the landsurface topography controls the runoff dynamics, the actual bedrock topography as depicted by ERT imaging in?uences the hydrodynamics beneath the landsurface. In some way, this may control the actual weathering rate and the shaping of bedrock protrusions as granite domes and knobs within thick saprolite, before their eventual future exposure. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

19.
Rock moisture during freeze–thaw events is a key factor for frost weathering. Data on moisture levels of natural rockwalls are scarce and difficult to obtain. To close this gap, we can benefit from the extensive knowledge of moisture‐related phenomena in building materials, which is incorporated into simulation software, for example the WUFI® package of the Fraunhofer Institute of Building Physics. In this paper we applied and adapted this type of simulation to natural rockwalls to gain new insights on which moisture‐related weathering mechanisms may be important under which conditions. We collected the required input data on physical rock properties and local climate for two study areas in the eastern European Alps with different elevation [Sonnblick, 3106 m above sea level (a.s.l.) and Johnsbach, 700 m a.s.l.] and different lithologies (gneiss and dolomite, respectively). From this data, moisture profiles with depth and fluctuations in the course of a typical year were calculated. The results were cross‐checked with different thermal conditions for frost weathering reported in the literature (volumetric expansion and ice segregation theories). The analyses show that in both study areas the thresholds for frost cracking by volumetric expansion of ice (90% pore saturation, temperature < ?1 °C) are hardly ever reached (in one year only 0.07% of the time in Johnsbach and 0.4% at Sonnblick, mostly in north‐exposed walls). The preconditions for weathering by ice segregation (?3 to ?8 °C, > 60% saturation) prevail over much longer periods; the time spent within this ‘frost cracking window‘ is also higher for north‐facing sites. The influence of current climate warming will reduce effective frost events towards 2100; however the increase of liquid precipitation and rock moisture will promote weathering processes like ice segregation at least at the Sonnblick site. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

20.
The conversion of bedrock to regolith marks the inception of critical zone processes, but the factors that regulate it remain poorly understood. Although the thickness and degree of weathering of regolith are widely thought to be important regulators of the development of regolith and its water‐storage potential, the functional relationships between regolith properties and the processes that generate it remain poorly documented. This is due in part to the fact that regolith is difficult to characterize by direct observations over the broad scales needed for process‐based understanding of the critical zone. Here we use seismic refraction and resistivity imaging techniques to estimate variations in regolith thickness and porosity across a forested slope and swampy meadow in the Southern Sierra Critical Zone Observatory (SSCZO). Inferred seismic velocities and electrical resistivities image a weathering zone ranging in thickness from 10 to 35 m (average = 23 m) along one intensively studied transect. The inferred weathering zone consists of roughly equal thicknesses of saprolite (P‐velocity < 2 km s?1) and moderately weathered bedrock (P‐velocity = 2–4 km s?1). A minimum‐porosity model assuming dry pore space shows porosities as high as 50% near the surface, decreasing to near zero at the base of weathered rock. Physical properties of saprolite samples from hand augering and push cores are consistent with our rock physics model when variations in pore saturation are taken into account. Our results indicate that saprolite is a crucial reservoir of water, potentially storing an average of 3 m3 m?2 of water along a forested slope in the headwaters of the SSCZO. When coupled with published erosion rates from cosmogenic nuclides, our geophysical estimates of weathering zone thickness imply regolith residence times on the order of 105 years. Thus, soils at the surface today may integrate weathering over glacial–interglacial fluctuations in climate. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

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