Landslide Deposits Research Articles

Permafrost molards as an analogue for ejecta-ice interactions at Hale Crater, Mars

When the Hale impact crater penetrated the martian cryosphere 1Ga, landforms indicating post-impact volatile mobilisation were generated. We have found landforms in the ejecta blanket of Hale Crater similar to ‘permafrost molards’ found in periglacial environments on Earth, and probably related to the past or present presence of volatiles at/near the surface. Permafrost molards are conical mounds of debris associated with landslide deposits, resulting from the degradation of blocks of ice-rich material mobilised by a landslide in periglacial terrains. Here we analyse the spatial and topographic distribution of conical mounds around the Hale crater at regional and local scales, and compare them to those of molards on the deposits of the Mount Meager debris avalanche in Canada. Hale Crater's conical mounds are located at the distal boundary of the thickest ejecta blanket, which is the closest to the main crater. We observe a similar spatial arrangement of molards along the distal parts of the terminal lobe of the Mount Meager debris avalanche. We then compare the morphology and morphometrics of the conical mounds on Hale Crater to those of terrestrial molards on the Paatuut and Niiortuut rock avalanches in western Greenland. We find that morphology and setting of conical mounds within Hale Crater ejecta are consistent with the formation pathway of molards on Earth. We infer that they originated from blocks of ice-cemented regolith that were produced by the Hale-crater-forming impact, transported by the ejecta flows, and finally degraded to cones of debris (molards) on loss of the interstitial ice. The similarities in distribution between the ejecta flows of Hale and Mount Meager debris avalanche on Earth suggest that the mounds resulted from the rheological separation of the ejecta flows, with a relatively fluid-poor phase that allowed the volatile-rich blocks to survive transport. This supports the prevailing hypothesis that the Hale impact event penetrated the martian cryosphere, providing important constraints on the rheology of martian ejecta deposits.

Inverse Estimation of Soil Hydraulic Parameters in a Landslide Deposit Based on a DE-MC Approach

Extreme rainfall is a common triggering factor of landslide disasters, for infiltration and pore water pressure propagation can reduce suction stress and shear strength at the slip surface. The subsurface hydrological model is an essential component in the early-warning system of rainfall-triggered landslides, whereas soil moisture and pore water pressure simulated by the Darcy–Richards equation could be significantly affected by uncertainties in soil hydraulic parameters. This study conducted an inverse analysis of in situ measured soil moisture in an earthquake-induced landslide deposit, and the soil hydraulic parameters were optimized with the Differential Evolution Markov chain Monte Carlo method (DE-MC). The DE-MC approach was initially validated with a synthetic numerical experiment to demonstrate its effectiveness in finding the true soil hydraulic parameters. Besides, the soil water characteristic curve (SWCC) and hydraulic conductivity function (HCF) described with optimized soil hydraulic parameter sets had similar shapes despite the fact that soil hydraulic parameters may be different. Such equifinality phenomenon in inversely estimated soil hydraulic parameters, however, did not affect the performance of simulated soil moisture dynamics in the synthetic numerical experiment. The application of DE-MC to a real case study of a landslide deposit also indicated satisfying model performance in terms of accurate match between the in situ measured soil moisture content and ensemble of simulations. In conclusion, based on the satisfying performance of simulated soil moisture and the posterior probability density function (PDF) of parameter sets, the DE-MC approach can significantly reduce uncertainties in specified prior soil hydraulic parameters. This study suggested the integration of the DE-MC approach with the Darcy–Richards equation for an accurate quantification of unsaturated soil hydrology, which can be an essential modeling strategy to support the early-warning of rainfall-triggered landslides.

Recent Technological and Methodological Advances for the Investigation of Submarine Landslides

Submarine landslides have attracted widespread attention, with the continuous development of ocean engineering. Due to the recent developments of in-situ investigation and modelling techniques of submarine landslides, significant improvements were achieved in the evolution studies on submarine landslides. The general characteristics of typical submarine landslides in the world are analyzed. Based on this, three stages of submarine landslide disaster evolution are proposed, namely, the submarine slope instability evolution stage, the large deformation landslide movement stage, and the stage of submarine landslide deposition. Given these three stages, the evolution process of submarine landslide disaster is revealed from the perspectives of in-situ investigation techniques, physical simulation, and numerical simulation methods, respectively. For long-term investigation of submarine landslides, an in-situ monitoring system with long-term service and multi-parameter collaborative observation deserves to be developed. The mechanism of submarine landslide evolution and the early warning factors need to be further studied by physical modelling experiments. The whole process of the numerical simulation of submarine landslides, from seabed instability to large deformation sliding to the impact on marine structures, and economizing the computational costs of models by advanced techniques such as parallel processing and GPU-accelerators, are the key development directions in numerical simulation. The current research deficiencies and future development directions in the subject of submarine landslides are proposed to provide a useful reference for the prediction and early warning of submarine landslide disasters.

Styles of slope instability on a Quaternary sub-arctic continental margin: The northwest flank of the Storegga Slide

Submarine landslides are widely recognised around the Northeast Atlantic margin, some of which forming vast slide complexes. On the mid-Norwegian margin, the Storegga Slide complex has been active since the early Pleistocene, first as a regional event (Slide W) at 1.7 Ma, and later culminating in the Storegga Slide sensu stricto at 8.2 ka. By interpreting high-quality seismic data, this work investigates slope instability styles, and their geneses, on the northwest flank of the Storegga Slide complex. Seismic and borehole data prove: i) the presence of two new landslides formed prior to Slide W, ii) that mass-transport complexes occurred during the evacuation of sediment oozes, iii) the existence of a series of cracks on the seafloor, denoting modern slope instability. Fluid accumulation in glacial-marine deposits was a primary factor promoting early instability; fluid pipes increase in number below the oldest landslide deposits, with most pipes terminating at their glide planes. Furthermore, mathematical models show that vertically stacked intervals with weak layers, and older landslide deposits, are able to promote further instability. This work thus suggests episodic fluid flow as the primary factor promoting long-term instability near the Storegga Slide complex. As a corollary, we reveal the stability of the continental slope to still be precarious, at present, on the northwest flank of the Storegga Slide.

Accelerated Movements of Xiaomojiu Landslide Observed with SBAS-InSAR and Three-Dimensional Measurements, Upper Jinsha River, Eastern Tibet

Many ancient landslides in the upper reaches of the Jinsha River seriously threaten the safety of residents on both sides of the river. The river erosion and groundwater infiltration have greatly reduced the stability of the ancient landslides along the Jinsha River and revived many large landslides. Studying their deformation characteristics and mechanisms and predicting possible failure processes are significant to the safety of residents and hydropower projects. We used SBAS-InSAR and three-dimensional decomposition techniques in our study. Our results showed that the trailing edge and middle part of the landslide have rapidly deformed. The maximum vertical annual displacement rate was 12 cm/a period from July 2017 to July 2019. Correlation analysis showed that creep deformation is closely related to the river damming of the Baige landslide events and that the rising river level was an important factor in the resurrection and accelerated destruction of the Xiaomojiu landslide. As a result, we predicted the possible failure process of the Xiaomojiu landslide, which might have lasted 80 s and eventually formed a landslide deposit with a height of about 150 m, a length of approximately 1500 m, and an average width of 450 m. Our results provide data references for displacement monitoring and instability risk simulation of large landslides along the Jinsha River.

Poljes in the Sivas gypsum karst, Turkey

Karst poljes, despite their large dimensions and significant applied interest, have received limited attention in the geomorphological literature, and references to gypsum poljes are incidental. This work analyses the morpho-structural setting, characteristics, origin and controlling factors of thirteen poljes mapped in the gypsum karst of Sivas, Turkey. The poljes occur along a 38 km long belt associated with the allogenic Kızılırmak and Acısu rivers, which constitute the regional base level of the karst system. The path of these drainages is controlled by the trailing morpho-structural trough of the antiformal ridge associated with the front of the active Sivas Thrust. The floor of most of the poljes is connected with the floodplain of the main rivers, but largely lies at lower elevation, functioning as semi-closed basins that can be flooded by water table rise and the incorporation of floodwaters from the adjacent fluvial systems. The depressions, with their floors situated within the epiphreatic zone, are classified as base-level poljes. Three types of base-level poljes are differentiated based on cartographic relationships and attending to their evolutionary path: poljes associated with relict valleys; poljes developed in abandoned valley sections, poljes related to the coalescence of bedrock collapse sinkholes. The poljes expand by lateral solution planation, involving the retreat of the marginal slopes and their replacement by a solution plain (polje floor) controlled by the water table. The retreat of the slopes is mainly achieved by solutional undercutting during floods, mass movements, and the rapid removal of the gypsiferous landslide deposits. These processes are expected to operate in gypsum bedrock at much higher rates than in carbonate rocks. Dissolution acting at the foot of the scarped gypsum slopes during floods locally produce floodwater footcaves with the typical water injection features (e.g., spongework, solution pockets, tapering dead-end passages). These caves locally produce bedrock collapse sinkholes that can be incorporated into the polje depressions generating characteristic embayments. The main factors that seem to favor the development of poljes in Sivas include: (1) a morpho-structural trough with relatively low uplift rate that confined the path of the main drainages; (2) abundant aggressive water supplied by allogenic rivers; (3) a fluviokarst landscape including fluvial landforms that can transform into poljes; and (4) presence of clusters of bedrock collapse sinkholes that experience rapid expansion.

Morphodynamics of Bedrock‐Alluvial Rivers Subsequent to Landslide Dam Outburst Floods

AbstractTectonically active mountain regions such as Southwestern China are frequently hit by catastrophic floods caused by the breach of landslide dams. However, how these extreme events influence the morphodynamics of bedrock‐alluvial rivers is not well understood. More specifically, during a landslide dam outburst flood, bedrock can be eroded by intensive transport of sediment (i.e., tools effect), but can also be buried under thick alluvial cover (i.e., cover effect). Here, we implement the MRSAA‐c (Corrected Macro‐Roughness‐based Saltation‐Abrasion‐Alluviation) model to simulate the morphodynamics of bedrock‐alluvial rivers subject to landslide dam outburst flood(s). For a single dam breach event, the evolution of a bedrock‐alluvial river shows different characteristics at different time scales. At flood time scale (within one day), bedrock is eroded by about 10 mm. The landslide deposit then mainly provides a cover effect in the decadal‐century scale, which leads to a net uplift of the bedrock underneath, and thus the formation of a bedrock “bump.” The bedrock profile returns to its initial equilibrium state at a millennial time scale, after the bedrock bump migrates upstream beyond the inlet. When subject to repeated dam breach events, the bedrock‐alluvial river can reach a dynamic equilibrium after sufficient time (tens of thousands of years). The equilibrium is characterized by sharply increased bedrock slope around the dam site, and gently decreased slope downstream. The impact of dam breach events is constrained within a scale of hundreds of kilometers, indicating the existence of a sedimentograph boundary layer.

Preservation and transportation of large landslide deposits under decadal and millennial timescales in the Taiwan orogenic belt

Landsliding is one of the primary surface processes shaping the landscapes of active mountain belts. The mobilization (or stabilization) of landslide deposits plays a crucial role in fluvial dynamics, carbon output, and topographic development of active orogens. Despite numerous previous efforts, the controls on erosion or storage of large landslide deposits remain yet to fully understand. Toward this end, we investigated eight large landslides at three locations in Taiwan. Our observations of the Jiufengershan and Tsaoling landslides, the two largest co-seismic landslides of the 1999 Chi-Chi earthquake, indicate that as high as 90 % of the original landslide volume is still preserved in Jiufengershan after two decades, whereas only less than half remains in Tsaoling. The striking difference illustrates the importance of fluvial connectivity in the preservation or removal of landslide deposits. In the longer timescale, our topographic reconstructions of six fan terrace systems along the Laonung River revealed that, even with direct connectivity with one of the largest rivers in Taiwan, approximately 10 % to 30 % of the landslide deposits are still preserved in-situ after millennia of erosion. Their preservation ratio is mainly controlled by their age, their original size, and the river/hillslope processes nearby. Wider riverbeds around these terraces imply the occurrence of large landslides and subsequent deposition on riverbeds as an important mechanism of river lateral erosion. Our results suggest that a substantial portion of large landslide deposits may persist in the hinterland over thousands of years, and such long-term preservation of landslide deposits would be important in the landscape evolution and the mass balance of active orogenic belts.

A Three-Dimensional Visualization and Optimization Method of Landslide Disaster Scenes Guided by Knowledge

The rapid acquisition of deposit volume information and dynamic modeling, as well as the visualization of disaster scenes, have great significance for the sharing of landslide information and the management of emergency rescue. However, existing methods have shortcomings, such as a long and costly deposit volume acquisition cycle, lack of knowledge and guidance, complex operations for scene modeling expression, and low scene rendering efficiency. Therefore, this paper focuses on the study of a three-dimensional visualization and optimization method for landslide disaster scenes guided by knowledge, and discusses key technologies such as the rapid acquisition of landslide deposit volume information based on three-dimensional reconstruction, the knowledge-guided dynamic modeling visualization of disaster scenes, and scene optimization considering visual significance. The prototype systems are developed and used in a case experiment and analysis. The experimental results show that the proposed method can quickly obtain the deposit volume, and the results are equivalent to ContextCapture, Metashape, and Pix4Dmapper software. The method realizes the dynamic visualization of the whole disaster process, provides rich information, achieves high readability, and improves the efficiency of scene rendering, with a stable average rendering frame rate of more than 80 frames/second.

Shear behavior of sliding zone soil of loess landslides via ring shear tests in the South Jingyang Plateau

Since the 1970s, a large number of loess collapses and landslides have occurred in the Loess Plateau of China due to water diversion and irrigation projects. A large amount of ancient landslide deposits are accumulated at the foot of the tableland, which is likely to slide again in the case of a rapid increase in short-term rainfall or long-term irrigation. The weak characteristics of the sliding zone soil often become the key factor affecting the revival of old landslides. To explore the effects of water content and shear rate on shear behavior of the sliding zone soil, a series of ring shear tests were conducted on reconstituted loess in the South Jingyang Plateau. Experimental results suggest that under the condition of normal consolidation, the soil sample with the optimum moisture content has the highest shear strength. The increase in the shear rate effectively reduces the strength of the soil. Because of the high shear rate, the pore water that cannot be dissipated and fine particles accumulated at the shear plane form a weak base (slurry making theory), which cannot be easily stopped once the landslides start, leading to high-speed and long-distance landslides. In addition, the changes in the soil particles and pores were observed using a scanning electron microscope (SEM), and the observations were consistent with macroscopic results. From these studies, we come to the conclusion that the motion mechanism of reactivated landslide was associated with the interaction of water content and shear rate, which reduces the shear strength of the displaced materials to a great extent.

Development of a morphometric connectivity model to mitigate sediment derived from storm-driven shallow landslides

In silvopastoral environments, landslide erosion results in loss of productive soils and pasture. Sediment delivered to streams from landslides contributes to the degradation of freshwater and marine receiving environments by smothering benthic habitats and increasing turbidity, light attenuation, and sediment-bound contaminants. Biological mitigation is an important strategy in pastoral environments to combat landslide erosion and improve the health of downstream aquatic ecosystems. Using lasso logistic regression, we investigate determinants of sediment connectivity for a landslide-triggering storm event in 1977 in the Wairarapa, New Zealand. Furthermore, we develop the first morphometric connectivity model to predict the likelihood of sediment delivery to streams following landslide initiation. We explore a range of connectivity scenarios by defining a set of sinks and simulating varying rates of sediment generation during flood events of increasing magnitude. The likelihood of sediment delivery is greatly enhanced where landslide deposits coalesce. Besides scar size variables, overland flow distance and vertical distance to sink were the most important morphometric predictors of connectivity. When scar size variables were removed from the connectivity model, median AUROC was reduced from 0.88 to 0.75.By coupling landslide susceptibility and connectivity predictions in a modular form, we quantify the cost effectiveness of targeted versus non-targeted approaches to shallow landslide mitigation. Sediment delivery ratios range from 0.21 to 0.29, equating to an event sediment yield of 3548 t km−2 to 9033 t km−2. Targeted mitigation of landslide-derived sediment is approximately an order of magnitude more cost-effective than a non-targeted approach. Compared with a pasture-only baseline, a 34% reduction in sediment delivery can be achieved by increasing slope stability through spaced tree planting on 6.5% of the pastoral land. The maximum reduction achievable through comprehensive coverage of widely spaced planting is 56%. The landslide connectivity model provides an objective method to support management decisions relating to mitigation of landslide erosion and sediment delivery to streams.

Unravelling a 2300 year long sedimentary record of megathrust and intraslab earthquakes in proglacial Skilak Lake, south‐central Alaska

AbstractSeismic hazards in subduction settings typically arise from megathrust, intraslab and crustal earthquake sources. Despite the frequent occurrence of intraslab earthquakes in subduction zones and their potential threat to communities, their long‐term recurrence behaviour is barely studied. Sedimentary sequences in lakes may register ground shaking from different seismic sources. This study investigates two long sediment cores (13 m and 16 m) from Skilak Lake, a proglacial lake in south‐central Alaska, to evaluate whether different seismic sources leave a distinct imprint. The sedimentary record shows a continuously varved sediment sequence, occasionally interrupted by turbidites, slump deposits and tephra beds. Turbidites and slump deposits were objectively identified using a statistical outlier analysis on varve thickness. The earthquake origin of these deposits was ascertained by resemblance with deposits induced by instrumentally recorded earthquakes (for example, 1964 ce Mw 9.2 megathrust and 1954 ce Mw 6.4 intraslab earthquakes) and correlation with multiple coeval landslide deposits on sub‐bottom profiles. The Skilak Lake record chronicles 19 earthquakes with moderate to very high confidence level in the past 1350 years. The sedimentary evidence of instrumentally‐recorded intraslab and megathrust earthquakes within the past 70 years demonstrates that not only megathrust earthquakes, but also past intraslab events are recorded. Although reported seismic intensities at Skilak Lake are comparable for the 1964 ce megathrust and the 1954 ce intraslab earthquakes, the long duration and low frequency content of seismic ground motion during megathrust earthquakes facilitate the triggering of multiple, voluminous landslides and the generation of megaturbidites. In contrast, the shorter duration and higher frequency source spectrum of intraslab earthquakes may only induce surficial slope remobilization and the generation of thinner turbidites. This study demonstrates that the sedimentary record of Skilak Lake has the potential to decipher multiple seismic sources, which opens possibilities for a comprehensive seismic hazard analysis for south‐central Alaska.

Internal igneous growth, doming and rapid erosion of a mature ocean island: the Miocene evolution of Maio (Cabo Verde)

Maio Island (Cabo Verde Archipelago) is composed of uplifted Early Mesozoic MORB-type pillow lavas and deep-sea sediments, unconformably overlain and intruded by Miocene igneous rocks. Combined structural analyses and 40Ar–39Ar dating were used to constrain the Miocene evolution of Maio. Structures and ages of uplifted Mesozoic sequences and crosscutting Miocene dykes showed that numerous intrusive events were associated with the intense growth of an igneous core complex in the middle to upper crust, causing semi-circular doming and partial disruption of the Mesozoic strata. Two nosean nephelinite dykes cut the Valanginian Batalha Formation and yielded phlogopite 40Ar–39Ar ages of 10.405 ± 0.033 Ma and 10.570 ± 0.053 Ma (2σ errors). A nosean nephelinite dyke that cuts the overlying Valanginian to Early Aptian Morro Formation yielded an age of 9.273 ± 0.020 Ma. Combined with existing K–Ar and 40Ar–39Ar ages, this confirmed a main period of island growth between ~ 16 and 8.7 Ma. We re-interpreted extensive polymict conglomerates, which occur below the Late Miocene Monte Penoso Formation, as landslide deposits. A nephelinite lava clast yielded a phlogopite 40Ar–39Ar age of 8.666 ± 0.0274 Ma, which represents a maximum age for these landslides and thus confined a period of large-scale flank collapses and erosion to between 8.7 and 6.7 Ma. Flank collapses and further mass wasting during this period may have rejuvenated the igneous activity, i.e., resulting in the formation of the Tortonian/Messinian Monte Penoso and Malhada Pedra Formations, due to decompression-induced melting at upper mantle depths. Such interaction between flank collapses and rejuvenated volcanism may be a key to better understand ocean island evolution worldwide.

Widespread Fluid Seepage Related to Buried Submarine Landslide Deposits in the Northwestern South China Sea

AbstractFluid seepage sometimes impacts occurrences of submarine landslides, but the role of landslide deposits in fluid seepage is often neglected. Bathymetric data show that more than 1,000 seabed mounds are scattered over an elongated area at the shelf edge of the northwestern South China Sea. Vertical seismic pipes in the subsurface are spatially correlated with both surface mounds and buried landslide deposits. Detailed analyses within the three‐dimensional (3D) seismic survey show that at least 221 of 231 (∼96%) of the mounds have spatial correlation with the top edges of multiple stages of buried landslide scarps that are stepping seawards from deep to shallow, indicating a causal relationship between buried landslide deposits and fluid seepage. Fluids emitted via differential compaction and hydrofracturing in geological setting characterized by frequent tectonism, flowed upwards along shear surfaces and scarps of landslide deposits and pipes, and eventually provided hard substrates for mound building.

A geotechnical index for landslide dam stability assessment

Effective disaster countermeasures of landslide dams hinge on the stability prediction in the emergency and mid-long-term stages. Variable morphological characteristics and multiple geomorphic indices as well as complicated geotechnical parameters pose significant challenges to a quick stability assessment. A particle size distribution (PSD) database was established based on 83 landslide deposits, including damming and non-damming landslides from around the world. Characteristic parameter K for quantitatively measuring landslide dam material properties were suggested on the basis of statistical analysis of deposit PSDs. Here we proposed a geotechnical index MMI (morphometry & material index) including dam volume, height and width, as well as characteristic parameter K, grain size d 90 and lake volume that helps to estimate landslide dam stability. Besides, landslide dams in our inventory were divided into four levels based on their material composition, longevity and spillway form. With this we achieved the stability classification criterion according to the relation between these historical cases stability levels and MMI values. This study underlines the need to include geotechnical aspects such as grain size distribution for assessing dam stability, because the impact of material conditions on landslide dam evolution cannot be ignored.

Multiscale Study on Deterioration Characteristics of Soil-Rock Mixtures Under the Immersion-Air dry Circulation

Soil-rock mixtures (S-RMs) composed of rock slope colluvium and landslide deposits are common in superficial hazards of bank slopes. The physical and mechanical properties of S-RMs are closely related to environmental conditions, especially reservoir water level fluctuation. Therefore, immersion-air dry (I-AD) circulations tests were carried out to simulate the phenomenon in this study. The macroscopic, mesoscopic, and microcosmic studies of S-RMs are carried out after experiencing cycles (N) of 0, 1, 5, and 10, respectively. Conventional triaxial tests, particle analysis tests, and scanning electron microscopy were performed to study the physical and mechanical properties of S-RMs. According to test results, the maximum deviator stress of S-RMs samples with confining pressures of 100, 200, 300, and 400 kPa after ten cycles is reduced by 41.13, 37.11, 32.17, and 30.20%. With the increase in N there is a significant trend towards reducing the strength of S-RMs, and the strength deterioration after the first I-AD circulation reached 15.73%. After I-AD circulations, the content of fine particles in S-RMs decreases, the grain-size characteristic and non-uniformity coefficient increase significantly, and the gradation of S-RMs shows discontinuity. Moreover, the repeated changes of water pressure have an irreversible impact on the microstructure of S-RMs, which will cause an increase in pore size and a higher pore disorder. In addition, it is found from the established strength parameter evolution equation that when N approaches infinity, S-RMs decomposes the weathering into cohesionless silt with an angle of repose of 0.90322φ0. The study results in this paper clarify the deterioration characteristics of wading S-RMs, and might be used in the bank slopes stability analysis.

Catchment-scale impacts of shallow landslides on stream water chemistry

Catchment water quality plays an important role in ecosystem and water resource management in mountainous areas. Shallow landslides triggered by earthquakes or heavy rainfall can cause a sudden and long-term deterioration in stream water quality by releasing contaminants into streams. Although many studies have been undertaken on the relationship between a single landslide and the water chemistry of a nearby river, little is known about the impact of densely distributed shallow landslides on stream water chemistry at the catchment scale. To this end, this study determined the major ion concentrations and isotopic compositions of stream water along with the shallow landslide area/catchment area ratio (LCR) in 37 headwater subcatchments in the southern part of Hokkaido, Japan, where an earthquake caused more than 6000 shallow landslides on September 6, 2018. In subcatchments with a high LCR, stream water exhibited significantly higher Ca2+ and HCO3− concentrations, while there was no correlation between the LCR and concentrations of Na+ and Cl−. The δ18O and δD values of stream water plotted between the local meteoric water lines of summer and winter precipitation, indicating that they originated from meteoric water. Shallow landslides formed sliding surfaces, landslide deposits, and landslide-dammed lakes, which enhanced the interaction between the surface soil and stream water, leading to Ca–HCO3 type water. The results showed that shallow-landslide-driven changes in stream water quality could be linearly approximated by the fraction of the landslide area at the catchment scale, which is a more versatile approach than the local framework of a single landslide and a nearby stream. In future research, these findings could be combined with a slope stability model and the background climatic, geological, topographical, and water quality conditions of a watershed to evaluate water pollution triggered by shallow landslides at the catchment scale.

Improving the galvanic contact resistance for geoelectrical measurements in debris areas: A case study

ABSTRACTThis paper aims to test, in a quantitative way, the different approaches that can be applied to improve the contact resistance problem in a debris environment for the acquisition of electrical resistivity tomography. We collected various datasets on the same investigation line in a blocky ground surface of a landslide deposit, using different coupling systems: single electrodes placed between the boulders, adding extra electrodes in parallel and drilled single electrodes inside the blocks. We performed the measurements in natural dry conditions, then we added salt water nearby the electrodes hammered among the boulders and we filled the drilled holes with a conductive carbomer‐based gel. The results clearly demonstrate that using salt water significantly reduces the contact resistances, but also that, if salt water is not available, we can collect a good quality dataset in dry conditions by connecting more electrodes in parallel. Drilling the electrodes directly inside the boulders decreases the data quality but, if necessary, we demonstrate that the use of a commercial carbon polymer gel can provide a marked improvement in contact resistances.

Machine learning as a tool to classify extra-terrestrial landslides: A dossier from Valles Marineris, Mars

Many researchers studied Martian landslides, and most of these studies are in the Valles Marineris (VM). Those studies are mainly morphologic analysis, estimates of landslide deposit volumes, thermal properties of the landslides, spectral analyses, and mapping and classifying landslides. But, this study created a robust landslide inventory of 682 incidents by collation of data from different sources, apart from our own mapping. This mapping was done for the completeness and accuracy of the landslide inventory. This inventory consists of 141 debris flows, 291 rock avalanches, and 250 slumps. This classification was based on the available literature, and these landslides covered Hebes, Ophir, Candor, Melas, Coprates, Ius and Tithonium chasmas. Landslides were mapped with the aid of images from Mars Reconnaissance Orbiter (MRO) Context Camera (CTX), Mars Orbiter Mission (MOM) Mars Colour Camera (MCC), and high-resolution Google Mars. Digital Elevation Model (DEM) from the Mars Express (MEX) High-Resolution Stereo Camera (HRSC), Thermal Inertia (TI) from Thermal Emission Imaging System (THEMIS), and available geological map were used to define 15 critical parameters of the landslide inventory viz., length (L), width (W), relative relief (RR), area, L/W ratio, RR/L ratio, TI of landslide (mean, minimum, maximum), and slope statistics (mean, minimum, maximum), TI of the scarp, the slope of the scarp, and geology. These 15 parameters were subjected to a multicollinearity testing, which excluded the dependent variable TI (mean). Further, the rest of the variables were analyzed using multiple discriminant analysis (MDA), where the parameters RR/L, L/W, and RR showed higher canonical discriminant function coefficients of 1.245, 0.461 and 0.159, respectively, suggesting that these are the parameters that primarily discriminates the landslides. The classification of landslides was evaluated using a 10-fold cross-validation method using different machine learning algorithms. The five models that provided the best results are simple logistic, logistic regression, meta-classifier, multi-layer perceptron, and Sequential Minimal Optimization (SMO). Of these, simple logistics has the maximum classification accuracy of 81.09%. Thus, this study demonstrates the potential of using machine learning models to classify extra-terrestrial landslides, especially the long-runout landslides that are characteristics of other planets and satellites.

A Late Pleistocene landslide damming event and its implications for the evolution of river valley landforms in the upper Jinsha River, southeastern Tibetan Plateau

Numerous damming landslides have occurred at the southeastern margin of the Tibetan Plateau due to intense tectonic activities, strong river erosion, and extreme climate change. A Late Pleistocene paleo-landslide damming event has been detected in the Induba area in the upstream reaches of the Jinsha River, preserving various river-blocking phenomena, such as landslide dammed deposits and fluvial and paleo-dammed lacustrine sediments. Based on remote sensing and field investigations, we determined that the damming landslide originated from the inclined counter rock mass and experienced intense fragmentation, forming rock avalanches, which were possibly triggered by paleo-earthquakes or a combination of paleo-earthquakes and rainfall. To better understand the evolution of dam breaching and river valley landforms, optically stimulated luminescence (OSL) dating of lacustrine sediments was attempted. The results show that the landslide damming occurred ∼79.30 ka ago and formed a dammed lake upstream, which existed at least ∼20.86 ka before the dam breaching. The horizontal fluvial layers adhered to relict landslide deposits on the left bank, indicating that the process of dam breaching was conducted under the multiple circulations of lake water overtopping, fluvial deposition, and river undercutting. This study enriches our understanding of the formation of old dammed landslides and the evolution of river valley landforms in this region.