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1.
Structural settings and lithological characteristics are traditionally assumed to influence the development of erosional landforms, such as gully networks and rock couloirs, in steep mountain rock basins. The structural control of erosion of two small alpine catchments of distinctive rock types is evaluated by comparing the correspondences between the orientations of their gullies and rock couloirs with (1) the sliding orientations of potential slope failures mechanisms, and (2) the orientation of the maximum joint frequency, this latter being considered as the direction exploited primarily by erosion and mass wasting processes. These characteristic orientations can be interpreted as structural weaknesses contributing to the initiation and propagation of erosion. The morphostructural analysis was performed using digital elevation models and field observations. The catchment comprised of magmatic intrusive rocks shows a clear structural control, mostly expressed through potential wedges failure. Such joint configurations have a particular geometry that encourages the development of gullies in hard rock, e.g. through enhanced gravitational and hydrological erosional processes. In the catchment underlain by sedimentary rocks, penetrative joints that act as structural weaknesses seem to be exploited by gullies and rock couloirs. However, the lithological setting and bedding configuration prominently control the development of erosional landforms, and influence not only the local pattern of geomorphic features, but the general morphology of the catchment. The orientations of the maximum joint frequency are clearly associated with the gully network, suggesting that its development is governed by anisotropy in rock strength. These two catchments are typical of bedrock‐dominated basins prone to intense processes of debris supply. This study suggests a quantitative approach for describing the relationship between bedrock jointing and geomorphic features geometry. Incorporation of bedrock structure can be relevant when studying processes governing the transfer of clastic material, for the assessment of sediment yields and in landforms evolution models. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

2.
There is a need to assess the long-term stability of engineered landforms associated with the rehabilitation of Ranger Uranium Mine, Northern Territory, Australia, as it is a requirement that mill tailings must be contained for periods in excess of 1000 years. The geomorphic model, SIBERIA, is calibrated on hydrologic and erosion data collected by a combination of monitoring and rainfall simulation experiments on the waste rock dumps of Ranger. Preliminary analysis of Ranger's preferred above-grade option suggests that erosion of the order of 7 to 8 m will occur on the structure in a period of 1000 years. This depth of erosion may be sufficient to compromise the integrity of containment. It is shown that SIBERIA has significant advantages over steady-state erosion models. Suggestions are made for the design that will enhance the stability of the structure and extend the structural life of the containment. © 1998 John Wiley & Sons, Ltd.  相似文献   

3.
Use of a field technique recently devised by Selby for the measurement of rock mass strength has resulted in the understanding of the relationship between rock mass strength and slope form. It is suggested that the accuracy of rock mass strength assessments may be enhanced by further subdividing the rating scales for intact rock strength and the spacing of partings. The relationship between rock mass strength and gradient is reformulated using southern African data, and statistically based confidence limits for identifying strength equilibrium slopes are proposed.  相似文献   

4.
In identifying controls on rock slope form a distinction is made between: (1) rock slopes with joints which dip steeply out of a cliff and hence are subject to mass failure of the rock mass above a critical joint; and (2) rock slopes with inclinations which are either in equilibrium with the mass strength of their rocks, or have profiles which will develop towards strength equilibrium as cross joints open. In the first class of slope, stability results not just from the basic frictional resistance of the rock but also from the frictional roughness along the critical joint and from the normal stress acting across that joint. Stability may be reduced by weathering and loss of strength of the joint wall rock. As a result of normal stress variations with depth, induced by overburdens, high cliffs which are not undercut have a concave profile. The second group of slopes includes those with inclinations controlled at the scale of individual joint blocks, buttressed slopes and those on unjointed rock masses. Buttressed and unjointed rock masses develop towards a condition of mass strength equilibrium as cross joints open. Strength equilibrium slopes may be recognized by application of a rock mass strength classification proposed for geomorphic purposes. Eleven propositions are formulated which identify controls on rock slope development and some consequences of these controls.  相似文献   

5.
Fractures are discontinuities in rock that can be exploited by erosion. Fractures regulate cohesion, profoundly affecting the rate, style, and location of Earth surface processes. By modulating the spatial distribution of erodibility, fractures can focus erosion and set the shape of features from scales of fluvial bedforms to entire landscapes. Although early investigation focused on fractures as features that influence the orientation and location of landforms, recent work has started to discern the mechanisms by which fractures influence the erodibility of bedrock. As numerical modeling and field measurement techniques improve, it is rapidly becoming feasible to determine how fractures influence geomorphic processes, as opposed to when or where. However, progress is hampered by a lack of research coordination across scales and process domains. We review studies from hillslope, glacial, fluvial, and coastal domains from the scale of reaches and outcrops to entire landscapes. We then synthesize this work to highlight similarities across domains and scales and suggest knowledge gaps, opportunities, and methodological challenges that need to be solved. By integrating knowledge across domains and scales, we present a more holistic conceptualization of fracture influences on geomorphic processes. This conceptualization enables a more unified framework for future investigation into fracture influences on Earth surface dynamics. © 2018 John Wiley & Sons, Ltd.  相似文献   

6.
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7.
Variation in the erodibility of rock units has long been recognized as an important determinant of landscape evolution but has been little studied in landscape evolution models. We use a modified version of the Channel‐Hillslope Integrated Landscape Development (CHILD) model, which explicitly allows for variations in rock strength, to reveal and explore the remarkably rich, complex behavior induced by rock erodibility variations in even very simple geologic settings with invariant climate and tectonics. We study the importance of relative contrasts in erodibility between just two units, the order of these units (whether hard rocks overlie soft or soft rocks overlie hard) and the orientation of the contact between the two units. We emphasize the spatial and temporal evolution of erosion rates, which have important implications for basin analysis, detrital mineral records, and the interpretation of cosmogenic isotope concentrations in detrital samples. Results of the landscape evolution modeling indicate that the stratigraphic order of units in terms of erodibility, the gross orientation of the contact (i.e. dipping away or toward the outlet of the landscape) and the contact dip angle all have measurable effects on landscape evolution, including significant spatial and temporal variations in erosion rates. Steady‐state denudation conditions are unlikely to develop in landscapes with significant contrasts in rock strength in horizontal to moderately tilted rock layers, at least at the scale of the entire landscape. Additionally, our results demonstrate that there is no general relation between rock erodibility and erosion rates in natural settings. Although rock erodibility directly controls the erosion rate constant in our models, it is not uncommon for higher erosion rates to occur in the harder, less erodible rock. Indeed erosion rates may be either greater or less than the rock uplift rate (invariant in time and space in our models) in both hard and soft rocks, depending on the local geology, topography, and the pattern of landscape evolution. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

8.
Millennial catchment–mean erosion rates derived from terrestrial cosmogenic nuclides are generally based on the assumption that the lithologies of the parent rock each contain the same proportion of quartz. This is not always true for large catchments, in particular at the edge of mountainous plateaus where quartz‐rich basement rocks may adjoin sedimentary or volcano‐sedimentary rocks with low quartz content. The western Central Andes is an example of this type of situation. Different quartz contents may be taken into account by weighting the TCN production rates in the catchment. We recall the underlying theory and show that weighting the TCN production rate may also lead to bias in the case of a spatial correlation between erosion rate and lithology. We illustrate the difference between weighted and unweighted erosion rates for seven catchments (16 samples) in southern Peru and northern Chile and show variations up to a factor of 2 between both approaches. In this dataset, calculated erosion rates considering only granitoid outcrops are better correlated with catchment mean slopes than those obtained without taking into account the geological heterogeneity of the drained watershed. This dataset analysis demonstrates that weighting erosion rates by relative proportions of quartz is necessary to evaluate the uncertainties for calculated catchment–mean erosion rates and may reveal the correlation with geomorphic parameters. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

9.
Erosion rates are key to quantifying the timescales over which different topographic and geomorphic domains develop in mountain landscapes. Geomorphic and terrestrial cosmogenic nuclide (TCN) methods were used to determine erosion rates of the arid, tectonically quiescent Ladakh Range, northern India. Five different geomorphic domains are identified and erosion rates are determined for three of the domains using TCN 10Be concentrations. Along the range divide between 5600 and 5700 m above sea level (asl), bedrock tors in the periglacial domain are eroding at 5.0 ± 0.5 to 13.1 ± 1.2 meters per million years (m/m.y.)., principally by frost shattering. At lower elevation in the unglaciated domain, erosion rates for tributary catchments vary between 0.8 ± 0.1 and 2.0 ± 0.3 m/m.y. Bedrock along interfluvial ridge crests between 3900 and 5100 m asl that separate these tributary catchments yield erosion rates <0.7 ± 0.1 m/m.y. and the dominant form of bedrock erosion is chemical weathering and grusification. Erosion rates are fastest where glaciers conditioned hillslopes above 5100 m asl by over‐steepening slopes and glacial debris is being evacuated by the fluvial network. For range divide tors, the long‐term duration of the erosion rate is considered to be 40–120 ky. By evaluating measured 10Be concentrations in tors along a model 10Be production curve, an average of ~24 cm is lost instantaneously every ~40 ky. Small (<4 km2) unglaciated tributary catchments and their interfluve bedrock have received very little precipitation since ~300 ka and the long‐term duration of their erosion rates is 300–750 ky and >850 ky, respectively. These results highlight the persistence of very slow erosion in different geomorphic domains across the southwestern slope of the Ladakh Range, which on the scale of the orogen records spatial changes in the locus of deformation and the development of an orogenic rain shadow north of the Greater Himalaya. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

10.
The Southern Alps are the topographic expression of late Cenozoic (<8 Ma ago) uplift of the crust of the leading edge of the Pacific plate in South Island, New Zealand. New fission track data on the basement exposed in the Southern Alps quantify the age, amount, and rate of rock uplift, and in combination with geomorphic parameters permit the construction of a new model of the geomorphic evolution of the Southern Alps. The model emphasizes the development over time and space of rock uplift, mean surface elevation, exhumation of crustal section, and relief. The earliest indications of mean surface uplift are between 4 and 5 Ma ago at the Alpine Fault. Mean surface uplift, which lagged the start of rock uplift, propagated southeastward from the Alpine Fault at a rate of 30 km/Ma. By about 4 Ma ago, exhumation had exposed greywacke basement adjacent to and east of the entire 300 km long central section of the Alpine Fault. At 3 Ma ago, greenschist was exposed in the southern parts of the Southern Alps near Lake Wanaka, and since then has become exhumed along a narrow strip east of the Alpine Fault. The model infers that amphibolite grade schist has been exhumed adjacent to the Alpine Fault only in the last 0·3 Ma. The age of the start of rock uplift and the amount and rate of rock uplift, all of which vary spatially, are considered to be the dominant influences on the development of the landscape in the Southern Alps. The Southern Alps have been studied in terms of domains of different rock uplift rate. At present the rate of rock uplift varies from up to 8–10 mm/a adjacent to the Alpine Fault to 0·8–1·0 mm/a along the southeastern margin of the Southern Alps. This spectrum can be divided into two domains, one northwest of the Main Divide where the present rock uplift rates are very high (up to 8–10 mm/a) and exceed the long-term value of 0·8–1·0 mm/a, and another to the southeast of the Main Divide where the long-term rate is 0·8–1·0 mm/a. A domain of no uplift lies immediately to the east of the Southern Alps, and is separated from them by a 1·0–1·5 km step in the basement topography. We argue that this spatial sequence of uplift rate domains represents a temporal one. The existing models of the geomorphic development of the Southern Alps—the dynamic cuesta model of J. Adams and the numerical model of P. Koons—are compared with the new data and evolutionary model. Particular constraints unrealized by these two earlier models include the following: the earlier timing of the start of rock uplift of the Southern Alps (8 Ma ago); the spatial variation in the timing of the start of rock uplift (8 Ma ago to 3 Ma ago); the lower long-term rock uplift rate (0·8–1·0 mm/a) of the Southern Alps for most of the late Cenozoic; the lag between the start of rock uplift and the start of mean surface uplift; and the patterns of the amounts of late Cenozoic rock uplift and erosion across the Southern Alps.  相似文献   

11.
The time-dependent failure of rock subjected to repeated loading can be explained in terms of the residual strength locus: catastrophic failure occurs when the accumulation of deformation is such that the residual strength locus is intercepted. In a preliminary experimental study of the fatigue characteristics of rock masses, highly idealized models of jointed rock were subjected to a series of cyclic uniaxial compression tests. The results of these experiments show that intact and failed models of jointed rock are extremely susceptible to cyclic fatigue failure, and that in these cases the residual strength locus interpretation of time-dependent failure is correct.  相似文献   

12.
Influence of rock mass strength on the erosion rate of alpine cliffs   总被引：1，自引：0，他引：1  
Collapse of cliff faces by rockfall is a primary mode of bedrock erosion in alpine environments and exerts a first‐order control on the morphologic development of these landscapes. In this work we investigate the influence of rock mass strength on the retreat rate of alpine cliffs. To quantify rockwall competence we employed the Slope Mass Rating (SMR) geomechanical strength index, a metric that combines numerous factors contributing to the strength of a rock mass. The magnitude of cliff retreat was calculated by estimating the volume of talus at the toe of each rockwall and projecting that material back on to the cliff face, while accounting for the loss of production area as talus buries the base of the wall. Selecting sites within basins swept clean by advancing Last Glacial Maximum (LGM) glaciers allowed us to estimate the time period over which talus accumulation occurred (i.e. the production time). Dividing the magnitude of normal cliff retreat by the production time, we calculated recession rates for each site. Our study area included a portion of the Sierra Nevada between Yosemite National Park and Lake Tahoe. Rockwall recession rates determined for 40 alpine cliffs in this region range from 0·02 to 1·22 mm/year, with an average value of 0·28 mm/year. We found good correlation between rockwall recession rate and SMR which is best characterized by an exponential decrease in erosion rate with increasing rock mass strength. Analysis of the individual components of the SMR reveals that joint orientation (with respect to the cliff face) is the most important parameter affecting the rockwall erosion rate. The complete SMR score, however, best synthesizes the lithologic variables that contribute to the strength and erodibility of these rock slopes. Our data reveal no strong independent correlations between rockwall retreat rate and topographic attributes such as elevation, aspect, or slope angle. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

13.
Beaver dam analogs (BDAs) are a stream restoration technique that is rapidly gaining popularity in the western United States. These low-cost, stream-spanning structures, designed after natural beaver dams, are being installed to confer the ecologic, hydrologic, and geomorphic benefits of beaver dams in streams that are often too degraded to provide suitable beaver habitat. BDAs are intended to slow streamflow, reduce the erosive power of the stream, and promote aggradation, making them attractive restoration tools in incised channels. Despite increasing adoption of BDAs, few studies to date have monitored the impacts of BDAs on channel form. Here, we examine the geomorphic changes that occurred within the first year of restoration efforts in Wyoming using high-resolution visible light orthomosaics and elevation data collected with unoccupied aerial vehicles (UAVs). By leveraging the advantages of rapidly acquired images from UAV surveys with recent advancements in structure-from-motion photogrammetry, we constructed centimeter-scale digital elevation models (DEMs) of the restoration reach and an upstream control reach. Through DEM differencing, we identified areas of enhanced erosion and deposition near the BDAs, suggesting BDA installation initiated a unique geomorphic response in the channel. Both reaches were characterized by net erosion during the first year of restoration efforts. While erosion around the BDAs may seem counter to the long-term goal of BDA-induced aggradation, short-term net erosion is consistent with high precipitation during the study and with theoretical channel evolution models of beaver-related stream restoration that predict initial channel widening and erosion before net deposition. To better understand the impacts of BDAs on channel morphology and restoration efforts in the western United States, it is imperative that we consistently assess the effects of beaver-inspired restoration projects across a range of hydrologic and geomorphic settings and that we continue this monitoring in the future.  相似文献   

14.
《国际泥沙研究》2019,34(6):537-549
Dam removal can generate geomorphic disturbances, including channel bed and bank erosion and associated abrupt/pulsed release and downstream transfer of reservoir sediment, but the type and rate of geomorphic response often are hard to predict. The situation gets even more complex in systems which have been impacted by multiple dams and a long and complex engineering history. In previous studies one-dimensional (1-D) models were used to predict aspects of post-removal channel change. However, these models do not consider two-dimensional (2-D) effects of dam removal such as bank erosion processes and lateral migration. In the current study the impacts of multiple dams and their removal on channel evolution and sediment delivery were modeled by using a 2-D landscape evolution model (CAESAR-Lisflood) focusing on the following aspects: patterns, rates, and processes of geomorphic change and associated sediment delivery on annual to decadal timescales. The current modeling study revealed that geomorphic response to dam removal (i.e., channel evolution and associated rates of sediment delivery) in multiple dam settings is variable and complex in space and time. Complexity in geomorphic system response is related to differences in dam size, the proximity of upstream dams, related buffering effects and associated rates of upstream sediment supply, and emerging feedback processes as well as to the presence of channel stabilization measures. Modeled types and rates of geomorphic adjustment, using the 2-D landscape evolution model CAESAR-Lisflood, are similar to those reported in previous studies. Moreover, the use of a 2-D method showed some advantages compared to 1-D models, generating spatially varying patterns of erosion and deposition before and after dam removal that provide morphologies that are more readily comparable to field data as well as features like the lateral re-working of past reservoir deposits which further enables the maintenance of sediment delivery downstream.  相似文献   

15.
This paper compares hydrologic records and geomorphic effects of several historic floods in the central Appalachian region of the eastern United States. The most recent of these, occurring in November 1985, was the largest ever recorded in West Virginia, with peak discharges exceeding the estimated 500-year discharge at eight of eleven stations in the South Branch Potomac River and Cheat River basins. Geomorphic effects on valley floors included some of the most severe and widespread floodplain erosion ever documented and exceeded anything seen in previous floods, even though comparable or greater rainfall and unit discharge have been observed several times in the region over the past 50 years. Comparison of discharge-drainage area plots suggests that the intensity and spatial scale of the November 1985 flood were optimal for erosion of valley floors along the three forks of the South Branch Potomac River. However, when a larger geographic area is considered, rainfall totals and discharge-drainage area relationships are insufficient predictors of geomorphic effectiveness for valley floors at drainage areas of 250 to 2500 km2. Unit stream power was calculated for the largest recorded flood discharge at 46 stations in the central Appalachians. Maximum values of unit stream power are developed in bedrock canyons, where the boundaries are resistant to erosion and the flow cross-section cannot adjust its width to accommodate extreme discharges. The largest value was 2570 W m?2; record discharge at most stations was associated with unit stream power values less than 300 W m?2, but more stations exceeded this value in the November 1985 flood than in the other floods that were analysed. Unit stream power at indirect discharge measurement sites near areas experiencing severe erosion in this and other central Appalachian floods generally exceeded 300 W m?2; reach-average values of 200-500 W m?2 were calculated for valleys where erosion damage was most widespread. Despite these general trends, unit stream power is not a reliable predictor of geomorphic change for individual sites. Improved understanding of flood impacts will require more detailed investigation of interactions between local site characteristics and patterns of flood flow over the valley floor.  相似文献   

16.
Sea stacks are common and striking coastal landforms, but few details are known about how, how quickly, and under what conditions they form. We present numerical and analytical models of sea stack formation due to preferential erosion along a pre‐existing headland to address these basic questions. On sediment‐rich rocky coasts, as sea cliffs erode and retreat, they produce beach sediment that is distributed by alongshore sediment transport and controls future sea cliff retreat rates. Depending on their width, beaches can encourage or discourage sea cliff erosion by acting either as an abrasive tool or a protective cover that dissipates wave energy seaward of the cliff. Along the flanks of rocky headlands where pocket beaches are often curved and narrow due to wave field variability, abrasion can accelerate alongshore‐directed sea cliff erosion. Eventually, abrasion‐induced preferential erosion can cut a channel through a headland, separating it from the mainland to become a sea stack. Under a symmetrical wave climate (i.e. equal influence of waves approaching the coastline from the right and from the left), numerical and analytical model results suggest that sea stack formation time and plan‐view size are proportional to preferential erosion intensity (caused by, for example, abrasion and/or local rock weakness from joints, faults, or fractures) and initial headland aspect ratio, and that sea stack formation is discouraged when the sediment input from sea cliff retreat is too high (i.e. sea cliffs retreat quickly or are sand‐rich). When initial headland aspect ratio is too small, and the headland is ‘rounded’ (much wider in the alongshore direction at its base than at its seaward apex), the headland is less conducive to sea stack formation. On top of these geomorphic and morphologic controls, a highly asymmetrical wave climate decreases sea stack size and discourages stack formation through rock–sediment interactions. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

17.
Knickpoints in bedrock streams are often interpreted as transient features generated by a change in boundary conditions. It is typically assumed that knickpoints propagate upstream with constant vertical velocities, though this relies on a stream being in erosional steady state (erosion rate equals rock uplift rate) prior to the knickpoint's formation. Recent modeling and field studies suggest that along-stream contrasts in rock erodibility perturb streams from erosional steady state. To evaluate how contrasts in rock erodibility might impact knickpoint interpretations, we test parameter space (rock erodibility, rock contact dip angle, change in rock uplift rate) in a one-dimensional (1D) bedrock stream model that has variable rock erodibility and produces a knickpoint with a sudden change in rock uplift rate. Upstream of a rock contact, the vertical velocity of a knickpoint generated by a change in rock uplift rate is strongly correlated with how the rock contact has previously perturbed erosion rates. These knickpoints increase vertical velocity upon propagating upstream of a hard over soft contact and decrease vertical velocity upon propagating upstream of a soft over hard contact. However, interactions with other transient perturbations produced by rock contacts make for nuances in knickpoint behavior. Rock contacts also influence the geometry of knickpoints, which can become particularly difficult to identify upstream of soft over hard rock contacts. Using our simulations, we demonstrate how a contact's along-stream horizontal migration rate and cross-contact change in rock strength control how much an upstream reach is perturbed from erosional steady state. When simulations include multiple contacts, the knickpoint is particularly prone to colliding with other transient perturbations and can even disappear altogether if rock contact dips are sufficiently shallow. Caution should be taken when analyzing stream profiles in areas with significant changes in rock strength, especially when rock contact dip angles are near the stream's slope.  相似文献   

18.
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   

19.
In this paper, we develop a mechanical model that relates the destabilization of thawing permafrost rock slopes to temperature‐related effects on both, rock‐ and ice‐mechanics; and laboratory testing of key assumptions is performed. Degrading permafrost is considered to be an important factor for rock–slope failures in alpine and arctic environments, but the mechanics are poorly understood. The destabilization is commonly attributed to changes in ice‐mechanical properties while bedrock friction and fracture propagation have not been considered yet. However, fracture toughness, compressive and tensile strength decrease by up to 50% and more when intact water‐saturated rock thaws. Based on literature and experiments, we develop a modified Mohr–Coulomb failure criterion for ice‐filled rock fractures that incorporates fracturing of rock bridges, friction of rough fracture surfaces, ductile creep of ice and detachment mechanisms along rock–ice interfaces. Novel laboratory setups were developed to assess the temperature dependency of the friction of ice‐free rock–rock interfaces and the shear detachment of rock–ice interfaces. In degrading permafrost, rock‐mechanical properties may control early stages of destabilization and become more important for higher normal stress, i.e. higher magnitudes of rock–slope failure. Ice‐mechanical properties outbalance the importance of rock‐mechanical components after the deformation accelerates and are more relevant for smaller magnitudes. The model explains why all magnitudes of rock–slope failures can be prepared and triggered by permafrost degradation and is capable of conditioning long para‐glacial response times. Here, we present a synoptic rock‐ and ice‐mechanical model that explains the mechanical destabilization processes operating in warming permafrost rocks. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

20.
The ~0.2 km3 Eibsee rock avalanche impacted Paleolake Eibsee and completely displaced its waters. This study analyses the lake impact and the consequences, and the catchment response to the landslide. A quasi-3D seismic reflection survey, four sediment cores from modern Lake Eibsee, reaching far down into the rock avalanche mass, nine radiocarbon ages, and geomorphic analysis allow us to distinguish the main rock avalanche event from a secondary debris avalanche and debris flow. The highly fluidized debris avalanche formed a megaturbidite and multiple swashes that are recorded in the lake sediments. The new calibrated age for the Eibsee rock avalanche of ~4080–3970 cal yr BP indicates a coincidence with rockslides in the Fernpass cluster and subaquatic landslides in Lake Piburg and Lake Plansee, and raises the possibility that a large regional earthquake triggered these events. We document a complex history of erosion and sedimentation in Lake Eibsee, and demonstrate how the catchment response and rebirth of the lake are revealed through the complementary application of geophysics, sedimentology, radiocarbon dating, and geomorphology. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd  相似文献   

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