Earthflow Research Articles

Geological and Geomorphological Characterization of the Anthropogenic Landslide of Pie de la Cuesta in the Vitor Valley, Arequipa, Peru

This study presents the geological and geomorphological characterization of the Pie de la Cuesta landslide, a large (>60 ha) slow-moving (up 4.5 m/month) landslide in Southern Peru. The landslide has been active since 1975 and underwent a significant re-activation in 2016; the mass movement has caused the loss of property and agricultural land and it is currently moving, causing further damage to property and land. We use a combination of historical aerial photographs, satellite images and field work to characterize the landslide’s geology and geomorphology. The landslide is affecting the slope of the Vitor Valley, constituted by a coarsening upward sedimentary sequence transitioning from layers of mudstone and gypsum at the base, to sandstone and conglomerate at the top with a significant ignimbrite layer interbedded within conglomerates near the top of the sequence. The landslide is triggered by an irrigation system that provides up to 10 L/s of water infiltrating the landslide mass. This water forms two groundwater levels at lithological transitions between conglomerates and mudstones, defining the main failure planes. The landslide is characterized by three main structural domains defined by extension, translation and compression deformation regimes. The extensional zone, near the top of the slope, is defined by a main horst–graben structure that transitions into the translation zone defined by toppling and disaggregating blocks that eventually become earth flows that characterize the compressional zone at the front of the landslides, defined by thrusting structures covering the agricultural land at the valley floor. The deformation rates range from 8 cm/month at the top of the slope to 4.5 m/month within the earth flows. As of May 2023, 22.7 ha of potential agricultural land has been buried.

Probabilistic landslide hazard assessments: adaptation of spatial models to large slow-moving earth flows and preliminary evaluation in Loja (Ecuador)

Probabilistic landslide hazard assessments: adaptation of spatial models to large slow-moving earth flows and preliminary evaluation in Loja (Ecuador)

A high-performance aqueous Eu/Ce redox flow battery for large-scale energy storage application

We report the performance of an all-rare earth redox flow battery with Eu2+/Eu3+ as anolyte and Ce3+/Ce4+ as catholyte for the first time, which can be used for large-scale energy storage application. The cell reaction of Eu/Ce flow battery gives a standard voltage of 1.90 V, which is about 1.5 times that of the all-vanadium flow battery (1.26 V). Large standard voltage is conducive to the improvement of battery energy density and power density. The Eu2+/Eu3+electrode reaction in a NaCl solution on platinum electrode was investigated detailedly using cyclic voltammetry, linear sweep voltammetry, tafel plot and chronoamperometry. Unlike zinc-cerium flow battery, the active species of Eu/Ce flow battery are always present in the electrolyte, and no liquid-solid phase transition occurs. Thus, Eu/Ce flow battery is free of the problems associated with dendrite growth and theoretically have a longer cycle lifetime. The negative electrolyte is very sensitive to oxygen and can directly cause battery failure if exposed to air. The average energy efficiency of Eu/Ce flow battery exposed to air is only 22.0 %. However, the average energy efficiency of Eu/Ce flow battery stripped of oxygen reaches 82.7 % at 25 mA/cm2. Preliminary experimental studies have shown that Eu/Ce flow batteries are a promising method for large-scale energy storage.

Advances in Mapping Lowermost Mantle Convective Flow With Seismic Anisotropy Observations

AbstractConvective flow in the deep mantle controls Earth's dynamic evolution, influences plate tectonics, and has shaped Earth's current surface features. Present and past convection‐induced deformation manifests itself in seismic anisotropy, which is particularly strong in the mantle's uppermost and lowermost portions. While the general patterns of seismic anisotropy have been mapped for the upper mantle, anisotropy in the lowermost mantle (called D′′) is at an earlier stage of exploration. Here we review recent progress in methods to measure and interpret D′′ anisotropy. Our understanding of the limitations of existing methods and the development of new measurement strategies have been aided enormously by the availability of high‐performance computing resources. We give an overview of how measurements of seismic anisotropy can help constrain the mineralogy and fabric of the deep mantle. Specifically, new and creative strategies that combine multiple types of observations provide much tighter constraints on the geometry of anisotropy than have previously been possible. We also discuss how deep mantle seismic anisotropy provides insights into lowermost mantle dynamics. We summarize what we have learned so far from measurements of D′′ anisotropy, how inferences of lowermost mantle flow from measurements of seismic anisotropy relate to geodynamic models of mantle flow, and what challenges we face going forward. Finally, we discuss some of the important unsolved problems related to the dynamics of the lowermost mantle that can be elucidated in the future by combining observations of seismic anisotropy with geodynamic predictions of lowermost mantle flow.

Structural control of igneous intrusions on fluid migration in sedimentary basins: the case study of large bitumen seeps at Cerro Alquitrán and Cerro La Paloma, northern Neuquén Basin, Argentina

Abstract Cooling subvolcanic igneous intrusions are known to have a tremendous impact on fluid flow in the shallow Earth's crust. However, the long-term post-cooling legacy of subvolcanic intrusions on fluid flow has received much less attention. Here we describe geological examples in the Andean foothills, Argentina, showing that igneous intrusions have long-term effects on fluid flow after their emplacement and cooling. The case study consists of ∼11 Myr-old eroded andesitic intrusions of Cerro Alquitrán and Cerro La Paloma, northern Neuquén Basin, Argentina, at the rims of which large volumes of bitumen are naturally seeping out at the Earth's surface. The intrusions exhibit laccolithic shapes with steep-sided contacts with the host rock. Near the intrusive contacts, the andesite is intensely broken along concentric breccia bands and fracture bands, interpreted as resulting from syn-emplacement brittle magma deformation, which represent high-permeability pathways for the migrating bitumen. Organic geochemical analyses of the bitumen show that the seeping oils were generated from incipiently mature Vaca Muerta sections located in a regional kitchen to the west, implying a lateral migration of ∼10–20 km. The Cerro Alquitrán and Cerro La Paloma intrusions are demonstrative examples highlighting how extinct subvolcanic intrusions have long-term consequences for subsurface fluid circulations in sedimentary basins.

Geotechnical and slope stability analysis in the landslide-prone area: A case study in Sawla – Laska road sector, Southern Ethiopia

Examining the factors underlying landslides and assessing the stability of slopes is crucial for reducing the negative impact of landslides on the environment and the lifespan of infrastructure. This study assessed certain slope portions along the Sawla to Laska Road to determine the factors contributing to landslides and identify the mechanisms and conditions that lead to slope failure. Slope stability analysis was conducted using the limit equilibrium method, and a range of laboratory tests were conducted following ASTM standards. The analysis has shown that the three slope portions, specifically sections 1, 2, and 3, had distinct shear strength characteristics, as shown by variations in their cohesion and internal friction angle values. The average values for cohesion were 19.24, 10.41, and 12.9, respectively, while the internal friction angle values ranged from 11.32 to 17.8 for slope section three, 18.96 to 21.12 for slope section two, and 30.08 to 37.26 for slope section one. The limit equilibrium method was utilized to compute the safety factor of slopes. Five methods were employed to evaluate the safety factor: the ordinary method, Bishop method, Janbu method, Spencer method, and Morgenstern-Price method while considering three groundwater conditions (GWT at great depth, GWT at half of the slope, and GWT on the surface). Only slope section one exhibited a slightly stable safety factor that exceeded one under dry conditions. The slope-mass rating analysis showed that rock slopes one and two were deemed stable under class II, rock slopes three and four were partially stable under class III, and rock slope five was unstable under class IV. A slope mass range of 78 to 79 indicates excellent to very good rock mass quality and high stability potential for RSs1. In contrast, RSs5 shows a wide SMR range from 7 to 57, indicating a spectrum of very poor to fair to good quality rock mass and an associated range of stability from extremely low to moderate. RSs2 and RSs3 fall within the SMR range of 71.1–72 and 49.9–55.9, respectively, indicating good to fair rock mass quality with varying degrees of stability potential. Last, RSs4, with an SMR range of 39.6–45.1, shows poor rock mass quality and substantial stability concerns. RSs1 has a UCS of 28.68 MPa, indicating a "Medium strong" classification, and it belongs to the lithology type of "Trachyte." RSs2 showcases a higher UCS value of 32.25 MPa, similarly classified as "Medium strong," and is also identified as "Trachyte." RSs3, with a UCS of 28.83 MPa, falls under the "Medium strong" classification and is categorized as "Basalt." In contrast, RSs4 demonstrates a lower UCS of 18.41 MPa, leading to a "Weak" classification associated with the lithology type "Basalt." Lastly, RSs5 presents a UCS of 25.77 MPa, classified as "Medium strong," and shares the lithology type of "Basalt." The study identified that the landslide types in the study area were rockfall, earth flow, and soil/rock slides. The factors contributing to landslides in the study area were slope steepness, weathering, groundwater, and rainfall.

Classification of cryogenic-landslide landforms for mapping and prediction

A classification of cryogenic-landslide landforms is developed for mapping their distribution and dynamics. It is based on the previously suggested classification subdividing cryogenic landsliding into two main types: cryogenic translational landslides (or active-layer detachment slides), and cryogenic earth flows (or retrogressive thaw slumps). The increased proportion of retrogressive thaw slumps compared to active layer detachments in the North of West Siberia in the last decade creates the need for an expanded classification of cryogenic earth flows. One of the important issues is separating the process of landsliding and resulting landforms, which in English are covered by one term ‘retrogressive thaw slump’. In dealing with the landforms, we distinguish (1) open and (2) closed ones. Open cryogenic-landslide landforms are those formed by the retreating of the coast bluff due to the thaw of ice or ice-rich deposits with an additional impact from wave or stream action. Closed cryogenic-landslide landforms are those initiated on a slope landward, and thawed material is delivered to the coast or stream through an erosional channel. Morphologically we distinguish thermocirques and thermoterraces depending on the shape of the retreating headwall, crescent or linear, respectively. An important issue is the type of ground ice subjected to thaw: tabular, ice-wedge or constitutional ground ice are distinguished. Landforms can be active, stabilized or ancient. One can find both single landforms and their combination. The classification is based on a significant amount of field studies and interpretation of remote sensing data. Mapping of the cryogenic-landslide landforms is suggested using the proposed classification and indication features. The classification is based on the experience obtained mainly in the north of West Siberia. Applying it to other regions may require additional studies.

Under the volcano: Encountering La(r)val anxieties in Metal

This article explores how recent intercultural contemporary concert dance collaborations in Asia and Australasia address questions of authorship and the subjectivity that concert dance performances produce. The work examined here is Metal (2020), created by Melbourne-based company Lucy Guerin Inc and Ensemble Tikoro, a heavy-metal choir based in West Java led by composer Robi Rusdiana. This work is critically analysed in terms of the production of subjectivity in dance and the influence of culture, politics and hegemonic regimes of representation in contemporary performance. Metal, which features five dancers and eight choir-members, was created in both Melbourne and Bandung. The work incorporates the aesthetics of heavy metal music culture; but it is a shadowy and decelerated piece. It has a quiet, disappearing-at-the-edges quality and a dramatic structure that develops through a series of enigmatic interactions between two groups. In these meetings, body practices and cultural practices are negotiated in a process of gradual unlearning, problematizing the conventions by which performers are turned into subjects. It is the depiction of solidities returning to a state of flux. The work was partly inspired by the place of its creation: the slopes of the active Tangkuban Perahu Volcano. Motifs of shifting earth and molten flows are referenced in both the composition of movement and sound, and in the work’s dramaturgical structure. As the work progresses, the fragments merge, culminating in a long series of tableaux performed in a wash of red light. In this volcanic scene, the performers are finally suspended in a state of potential subjectivity or becoming-individual. In this way, Metal points to the possibility of a choreographic practice that is a reversal and return to plurality, a subjectivity that is not multicultural but properly transcultural.

The Contribution of Digital Image Correlation for the Knowledge, Control and Emergency Monitoring of Earth Flows

Earth flows are complex geological processes that, when interacting with linear infrastructures, have the potential to cause significant damage. Consequently, conducting comprehensive investigations and continuous monitoring are becoming paramount in designing effective mitigation measures and ensuring sustainable risk management practices. The use of digital image correlation (DIC) algorithms for the displacement monitoring of earth flows is a relatively new and growing field with a limited number of dedicated works in the literature. Within this framework, the present paper contributes by evaluating DIC techniques at several earth flow sites. These assessments were founded upon data obtained from both low-cost and multi-platform sensors, used to assess the displacement field, pinpointing the most active sectors, and gauging their rates of movement during different kinematic phases. In this regard, the highest localized movement velocities reached in the Pietrafitta (0.01 m/day) and Grillo (0.63 m/day) earth flows experience different ongoing kinematic processes. The versatility of these techniques is notable, manifesting in the ease of installation, cost-effectiveness, and adaptability to various platforms. The proven reliability in terms of maximum accuracy (1 pixel) and sensitivity (0.05 m) lays the foundation for the extensive use of the presented techniques. The amalgamation of these attributes positions DIC techniques as competitive, adaptable, and readily deployable tools in earth flow studies.

Irrigación de largo plazo como desencadenante de flujos de tierra en Chenque Malal, Norpatagonia argentina

Because of their social, ecological, and economic impacts, landslides are an issue of global concern. Episodes occurring worldwide have been associated with natural and human causes, although the latter have been poorly explored. Despite recent scientific insight into intensive irrigation as a cause, research remains scarce. This paper focuses on determining the anthropogenic influence on the triggering of earth flows by long-term intensive irrigation, based on temporal and geospatial information. This analysis covers a sector of Northern Patagonia in Argentina, an area of transhumant pastoralism. Our results show that excessive water input creates favorable conditions for the triggering and evolution of earth flows in the region, even under water deficit conditions. As a result, on 22 September 2020, a collapse was recorded which mobilized ~19,000 m³ of earth debris along 360 m and produced economic losses estimated at 168,000 USD. Other landslides are expected to occur in the area if irrigation amounts remain at the same level.

Landslide Susceptibility Analysis on the Vicinity of Bogotá-Villavicencio Road (Eastern Cordillera of the Colombian Andes)

Landslide occurrence in Colombia is very frequent due to its geographical location in the Andean mountain range, with a very pronounced orography, a significant geological complexity and an outstanding climatic variability. More specifically, the study area around the Bogotá-Villavicencio road in the central sector of the Eastern Cordillera is one of the regions with the highest concentration of phenomena, which makes its study a priority. An inventory and detailed analysis of 2506 landslides has been carried out, in which five basic typologies have been differentiated: avalanches, debris flows, slides, earth flows and creeping areas. Debris avalanches and debris flows occur mainly in metamorphic materials (phyllites, schists and quartz-sandstones), areas with sparse vegetation, steep slopes and lower sections of hillslopes; meanwhile, slides, earth flows and creep occur in Cretaceous lutites, crop/grass lands, medium and low slopes and lower-middle sections of the hillslopes. Based on this analysis, landslide susceptibility models have been made for the different typologies and with different methods (matrix, discriminant analysis, random forest and neural networks) and input factors. The results are generally quite good, with average AUC-ROC values above 0.7–0.8, and the machine learning methods are the most appropriate, especially random forest, with a selected number of factors (between 6 and 8). The degree of fit (DF) usually shows relative errors lower than 5% and success higher than 90%. Finally, an integrated landslide susceptibility map (LSM) has been made for shallower and deeper types of movements. All the LSM show a clear zonation as a consequence of the geological control of the susceptibility.

Landslides triggered by an extraordinary rainfall event in Central Italy on September 15, 2022

Timely and systematic collection of landslide information after a triggering event is pivotal for the definition of landslide trends in response to climate change. On September 15, 2022, a large part of central Italy, particularly Marche and Umbria regions, was struck by an anomalous rainfall event that showed characteristics of a persistent convective system. An extraordinary cumulated rainfall of 419 mm was recorded by a rain gauge in the area in only 9 h. The rainfall triggered 1687 landslides in the area affected by the peak rainfall intensity and caused widespread flash floods and floods in the central and lower parts of the catchments. In this work, we describe the characteristics of the landslides identified during a field survey started immediately after the event. Most of the mass movements are shallow, and many are rapid (i.e., debris flows, earth flows) and widely affecting the road network. Landslide area spans from a few tens of square meters to 105 m2, with a median value of 87 m2. Field evidence revealed diffuse residual risk conditions, being a large proportion of landslides located in the immediate vicinity of infrastructures. Besides reporting the spatial distribution of landslides triggered by an extreme rainfall event, the data collected on landslides can be used to make comparisons with the distribution of landslides in the past, validation of landslide susceptibility models, and definition of the general interaction between landslides and structures/infrastructures.

DEVELOPMENT OF EXOGENOUS GEOLOGICAL PROCESSES AND PHENOMENA ON THE UDOKAN – NAMINGA HIGHWAY (THE NORTHERN TRANSBAIKALIA)

The paper considers exogenous geological processes and phenomena on the Udokan–Naminga highway in 2017, which are compared with the previous results obtained by the expedition of the Lomonosov Moscow State University in 1986. The engineering geological conditions and manifestation specifics of these processes and phenomena are analyzed. The geocryological conditions and the relevant combinations of engineering geological processes and phenomena were typified according to various geological features. As proceeds from the comparison of the results for different years, the type and number of exogenous geological processes and phenomena have not changed much. The concentrated transport of fine earth and temporary water runnel flows on roads appear to be the most active and frequently occurring processes. The most deformed sections of the road were those that run along the cut slopes with stone streams (kurums). The results of the study show that special attention should be paid to stone streams because of their wide distribution along the road and their cooling effect on the average annual temperatures of the surrounding soils and rocks.

The long‐term legacy of subvolcanic intrusions on fluid migration in sedimentary basins: The Cerro Alquitrán case study, northern Neuquén Basin, Argentina

AbstractCooling subvolcanic igneous intrusions are known to have a substantial impact on fluid flow in the shallow Earth's crust, for example activation of geothermal systems, circulation of mineralized fluids in ore deposits, fast maturation of organic matter in sedimentary rocks and the potential release of large volumes of greenhouse gases, which have triggered mass extinctions during the Earth's history. However, the long‐term post‐cooling legacy of subvolcanic intrusions on fluid flow received much less attention. Here we describe a demonstrative geological example in the Andean foothills, Argentina, showing that igneous intrusions have long‐term effects on fluid flow after their emplacement and cooling. The case study is a ca. 11‐million‐year‐old, eroded subvolcanic conduit, at the rims of which large volumes of bitumen are naturally seeping out on the Earth's surface. This contribution highlights that intense syn‐emplacement fracturing of the magma has created high‐permeability pathways that affect the regional fluid circulations, even millions of years after cooling. Our observations reveal how extinct subvolcanic intrusions have long‐term consequences on subsurface fluid circulations, which need to be accounted for in the exploration of geothermal energy, drinkable groundwater, hydrocarbons and CO2 sequestration in volcanic basins and regions hosting ancient shallow magma intrusions.

Local estimation of quasi-geostrophic flows in Earth’s core

SUMMARYThe inference of fluid motion below the core–mantle boundary from geomagnetic observations presents a highly non-unique inverse problem. We propose a new method that provides a unique local estimate of the velocity field, assuming quasi-geostrophic flow in the core interior (which implies equatorial mirror symmetry) and negligible magnetic diffusion. These assumptions remove the theoretical underdetermination, enabling us to invert for the flow at each point of a spherical grid representing the core surface. The unreliable reconstruction of small-scale flows, which arises because only large-scale observations are available, is mitigated by smoothing the locally estimated velocity field using a Gaussian process regression. Application of this method to synthetic data provided by a state-of-the-art geodynamo simulation suggests that using this approach, the large-scale flow pattern of the core surface flow can be well reconstructed, while the flow amplitude tends to be underestimated. We compare these results with a core flow inversion using a Bayesian framework that incorporates statistics from numerical geodynamo models as prior information. We find that whether the latter method provides a more accurate recovery of the reference flow than the local estimation depends heavily on how realistic/relevant the chosen prior information is. Application to real geomagnetic data shows that both methods are able to reproduce the main features found in previous core flow studies.

Remote Sensing Monitoring of the Pietrafitta Earth Flows in Southern Italy: An Integrated Approach Based on Multi-Sensor Data

Earth flows are complex gravitational events characterised by a heterogeneous displacement pattern in terms of scale, style, and orientation. As a result, their monitoring, for both knowledge and emergency purposes, represents a relevant challenge in the field of engineering geology. This paper aims to assess the capabilities, peculiarities, and limitations of different remote sensing monitoring techniques through their application to the Pietrafitta earth flow (Southern Italy). The research compared and combined data collected during the main landslide reactivations by different ground-based remote sensors such as Robotic Total Station (R-TS), Terrestrial Synthetic Aperture Radar Interferometry (T-InSAR), and Terrestrial Laser Scanner (TLS), with data being derived by satellite-based Digital Image Correlation (DIC) analysis. The comparison between R-TS and T-InSAR measurements showed that, despite their different spatial and temporal resolutions, the observed deformation trends remain approximately coherent. On the other hand, DIC analysis was able to detect a kinematic process, such as the expansion of the landslide channel, which was not detected by the other techniques used. The results suggest that, when faced with complex events, the use of a single monitoring technique may not be enough to fully observe and understand the processes taking place. Therefore, the limitations of each different technique alone can be solved by a multi-sensor monitoring approach.

Study on Geothermal Genesis Mechanism and Model in the Western Margin of Ordos Basin

Among so many fault basins around Ordos presenting good geothermal background, Yinchuan Plain is the key development and protection area of the Ecological and Economic Belt along the Yellow River in Ningxia and Yinchuan Metropolitan Area. The study of geothermal resources in this region is of great significance to the sustainable economic development of Yinchuan Plain. Most scholars suggested that Yinchuan Plain geothermal resources are low-to-medium temperature geothermal resources and have high value in terms of development and utilization due to their large reserves, good water quality conditions, and wide distribution. However, there is much controversy over the geothermal mechanism of this region. As an effective means to study geothermal mechanism, geophysical methods can be used to study regional basement uplift and structural distribution characteristics. Based on the discussion of regional geothermal geology background, this paper studies the distribution rules of Moho and Curie depths in the region by applying different geophysical data. The results show that the western margin of Yinchuan Plain is obviously uplifted. As inferred from the epicentral distribution of Yinchuan Plain section, there is a significant difference of the seismic bottom interface on the east and west sides of the Yellow River fault in Yinchuan Plain. The three-dimensional gravity inversion confirms basement uplift in this region. By referring to results obtained by the inversion of gravity and magnetic data and deep seismic exploration, the paper presents a comprehensive analysis of the regional geothermal geology conditions and proposes a geothermal conceptual model of Yinchuan Plain. The heat source comes from the earth heat flow and migrates to the thermal reservoir through the fault or fissure convection. The deep-large active faults provide a channel for deep heat flow to the shallow part, and the thermal fluid accumulates in the uplift area to form the high geothermal anomaly area. There should be two large-scale geological activities in the geotropics around Ordos. One is the basement uplift of the basins around Ordos platform, which provide the heat source. The other is the uplift of Ordos, which places the surrounding basin in an extensional environment and provides a channel for the heat source upwelling.

Interplay Between Friction and Cohesion: A Spectrum of Retrogressive Slope Failure

AbstractRetrogressive failures occur in slopes consisting of sensitive materials such as snow or quick clay. They can be triggered by a small disturbance at the slope toe, but can cause propagated failure spreading miles away. Understanding the physical mechanism and predicting the retrogressive failure process are particularly important. Previous studies have discussed the failure criteria, the soil properties or the method of numerical modeling of retrogressive slope failure. However, little attention has been paid to the microscopic failure mechanism, especially relating to various possible failure patterns. In this study, multiscale modeling is incorporated to study the physical mechanism of different retrogressive failure patterns, including earth flow, flowslide and spread failure, within a unified framework. Utilizing multiscale analysis, we found that earth flow failure is related to the shear failure of granular materials. In contrast, the development of macroscopic shear bands is accompanied by tensile failure. As shear and tension failures are typical failure mechanisms of frictional and cohesive materials, it is deduced that friction and cohesion effects play key roles in different retrogressive failure patterns. Therefore, the distributions of attractive and repulsive contact forces are explored and a novel parameter η is proposed to quantify the interplay between friction and cohesion. Further analysis proves that η can capture the effect of friction and cohesion and distinguish different retrogressive failure patterns. Finally, a spectrum of retrogressive failures for a granular slope is established, in which the failure mechanism is explained by the changeable dominant effect, that is, frictional or cohesive in soil.

UAV Application for Short-Time Evolution Detection of the Vomice Landslide (South Italy)

This paper investigates the possibility to detect the short-time evolution of the slow-moving Vomice earth flow, located in the northeastern sector of the Calabria region (South Italy), by combining the information obtained from two different drone flights, carried out in February 2019 and June 2022, with field surveys. The obtained results consisted of delimiting all landslide bodies constituting the Vomice earth flow, detecting landslide types and the state of activity, as well as identifying spatial and volumetric changes. The obtained results showed that depletion and transition zones of the Vomice earth flow are active, while the accumulation zone appears prevalently dormant. Particularly, in the analyzed period, the depletion zone was characterized by local collapses of the main scarps where several slides evolving in earth flows caused more than 20 m of retrogressive fail upslope. The maximum elevation changes observed in these zones were about ±5 m. The volume of the material mobilized by mass movements was about 114.2 × 103 m3, whereas the volume of the accumulated material was approximately 92.7 × 103 m3. The transition zone was affected by several slow earthflows that re-mobilized the displaced material located in the middle portion of the landslide and reached the accumulation zone. Overall, the results of this study demonstrated the practicality and feasibility of using UAV tools for detecting the short-time evolution of a large landslide.

Geological characterization and failure analysis of a catastrophic landslide in volcaniclastic soils: the Banjarnegara–Jemblung Landslide (Indonesia)

The Banjarnegara–Jemblung Landslide was triggered on 12 December 2014 near the village of Jemblung in Central Java (Indonesia). The disaster occurred on the northern slope of Gunung Telagalele and caused more than 100 fatalities, making it the most disastrous landslide to have occurred in Indonesia in the past few decades. The event was characterized by multiple slope failures forming two landslide events A and B, with two connected scarps but two separated runout paths. According to eyewitnesses, landslide A was mobilized only a few minutes after the initial failure of B. Initially, both landslides began as earth slides that developed subsequently into very to extremely rapid earth flows. Although the failure volume was moderate, both slide flows reached very high velocities of several metres per second and travelled long distances, leading to remarkably low travel angles of 14° and 15°. Field investigations confirmed that slope failure was exacerbated by its geological predisposition based on a slope-parallel layering of volcaniclastic sediments of different origin and age, as well as intensive tropical weathering that generated clay-rich soils. Temporal relationships, as well as stability analysis, indicate that antecedent rainfall over 2 months and heavy rainfall the day before triggered the slope failure. Thematic collection: This article is part of the Leading to Innovative Engineering Geology Practices collection available at: https://www.lyellcollection.org/topic/collections/leading-to-innovative-engineering-geology-practices