Lake pushed out by 200 m³ rock avalanche (Zugspitze / Lake Eibsee, D) - New geophysical and sedimentological insights into interactive processes

2020 ◽  
Author(s):  
Sibylle Knapp ◽  
Philipp Mamot ◽  
Bernhard Lempe ◽  
Michael Krautblatter
Keyword(s):  
Electrical Resistivity Tomography ◽  
Rock Avalanche ◽  
Mass Movements ◽  
Moving Mass ◽  
Long Runout ◽  
Resistivity Tomography ◽  
Geomorphological Mapping ◽  
Structure Thickness ◽  
Mixed Sediments ◽  
The Impact

<p>Rock avalanches destroy and reshape landscapes within only few minutes and are among the most hazardous processes on earth. Water in the travel path may accelerate the rock avalanche, with longer runouts as a result. So far no study has aimed at proving the existence of a paleolake pushed out by a rock avalanche and further analysing the interaction of the moving mass with the former lake. Especially for ancient long-runout mass movements this could be the key to explain exceptional runout lengths.</p><p>In this study at the Zugspitze / Eibsee rock avalanche we prove the existence of, and the impact onto a paleolake inside the rock-avalanche trajectories. We assume that there has been a paleo-Lake Eibsee which was displaced by the ~200 mio. m³ rock avalanche. Our approach shows a complementary application of geomorphological mapping (over ~5 km²) and Electrical Resistivity Tomography (ERT) measurements (8 profiles with in total ~9.5 km length), combined with sedimentological analysis in outcrops and drillings. The geoelectrical profiles give us up to ~120 m deep insights into the structure, thickness and distribution of the rock-avalanche deposits, the interactive processes with the lake water and sediments, and the paleotopography. Sediments exposed in outcrops show water-escape structures at the front of the rock avalanche. The data further allow for ERT-calibration at 7 different sites, where it is possible to distinguish materials (rock avalanche, bedrock, lake clay, mixed sediments) and interactive processes of the rock avalanche with the lake and substrate (bulldozing, bulging, overriding of secondary lobes). Here we show how complementary geophysical, geomorphological and sedimentological applications on terrestrial deposits provide detailed insights into multiple effects of impacting of a rock avalanche onto a lake.</p>

scholarly journals Detailed detection of fast changes in the active layer using quasi-continuous electrical resistivity tomography (Deception Island, Antarctica)

2019 ◽  
Author(s):  
Mohammad Farzamian ◽  
Gonçalo Vieira ◽  
Fernando A. Monteiro Santos ◽  
Borhan Yaghoobi Tabar ◽  
Christian Hauck ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Snow Cover ◽  
Active Layer ◽  
Electrical Resistivity Tomography ◽  
Deception Island ◽  
Freezing And Thawing ◽  
Resistivity Tomography ◽  
Thaw Depth ◽  
Set Up ◽  
The Impact

Abstract. Climate induced warming of permafrost soils is a global phenomenon, with regional and site-specific variations, which are not fully understood. In this context, a 2D automated electrical resistivity tomography (A-ERT) system was installed for the first time in Antarctica at Deception Island, associated to the existing Crater Lake site of the Circumpolar Active Layer Monitoring Network (CALM-S) I) to evaluate the feasibility of installing and running autonomous ERT monitoring stations in remote and extreme environments such as Antarctica, II) to monitor subsurface freezing and thawing processes on a daily and seasonal basis and to map the spatial and temporal variability of thaw depth, and III) to study the impact of short-lived extreme meteorological events on active layer dynamics. Measurements were repeated at 4-hour intervals during a full year, enabling the detection of seasonal trends, as well as short-lived resistivity changes reflecting individual meteorological events. The latter is important to distinguish between (1) long-term climatic trends and (2) the impact of anomalous seasons on the ground thermal regime. Our full-year dataset shows large and fast temporal resistivity changes during the seasonal active layer freezing and thawing and indicates that our system set-up can successfully map spatiotemporal thaw depth variability along the experimental transect at very high temporal resolution. Largest resistivity change took place during the freezing season in April when low temperatures induce an abrupt phase change in the active layer in the absence of a snow cover. The seasonal thawing of the active layer is associated with a slower resistivity decrease during October due to the presence of a snow cover and the corresponding zero-curtain effect. Detailed investigation of the daily resistivity variations reveals several periods with rapid and sharp resistivity changes of the near-surface layers due to the brief surficial refreezing of the active layer in summer or brief thawing of the active layer during winter as a consequence of short-lived meteorological extreme events. These results emphasize the significance of the continuous A-ERT monitoring set-up which enables to detect fast changes in the active layer during short-lived extreme meteorological events. Based on this first complete year-round A-ERT monitoring data set in Deception Island, we believe that this system shows high potential for autonomous applications in remote and harsh polar environments such as Antarctica.

scholarly journals Detailed detection of active layer freeze–thaw dynamics using quasi-continuous electrical resistivity tomography (Deception Island, Antarctica)

2020 ◽  
Vol 14 (3) ◽  
pp. 1105-1120
Author(s):  
Mohammad Farzamian ◽  
Gonçalo Vieira ◽  
Fernando A. Monteiro Santos ◽  
Borhan Yaghoobi Tabar ◽  
Christian Hauck ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Snow Cover ◽  
Active Layer ◽  
Electrical Resistivity Tomography ◽  
Deception Island ◽  
Freezing And Thawing ◽  
Resistivity Tomography ◽  
Thaw Depth ◽  
The Impact ◽  
First Time

Abstract. Climate-induced warming of permafrost soils is a global phenomenon, with regional and site-specific variations which are not fully understood. In this context, a 2-D automated electrical resistivity tomography (A-ERT) system was installed for the first time in Antarctica at Deception Island, associated to the existing Crater Lake site of the Circumpolar Active Layer Monitoring – South Program (CALM-S) – site. This setup aims to (i) monitor subsurface freezing and thawing processes on a daily and seasonal basis and map the spatial and temporal variability in thaw depth and to (ii) study the impact of short-lived extreme meteorological events on active layer dynamics. In addition, the feasibility of installing and running autonomous ERT monitoring stations in remote and extreme environments such as Antarctica was evaluated for the first time. Measurements were repeated at 4 h intervals during a full year, enabling the detection of seasonal trends and short-lived resistivity changes reflecting individual meteorological events. The latter is important for distinguishing between (1) long-term climatic trends and (2) the impact of anomalous seasons on the ground thermal regime. Our full-year dataset shows large and fast temporal resistivity changes during the seasonal active layer freezing and thawing and indicates that our system setup can resolve spatiotemporal thaw depth variability along the experimental transect at very high temporal resolution. The largest resistivity changes took place during the freezing season in April, when low temperatures induce an abrupt phase change in the active layer in the absence of snow cover. The seasonal thawing of the active layer is associated with a slower resistivity decrease during October due to the presence of snow cover and the corresponding zero-curtain effect. Detailed investigation of the daily resistivity variations reveals several periods with rapid and sharp resistivity changes of the near-surface layers due to the brief surficial refreezing of the active layer in summer or brief thawing of the active layer during winter as a consequence of short-lived meteorological extreme events. These results emphasize the significance of the continuous A-ERT monitoring setup which enables detecting fast changes in the active layer during short-lived extreme meteorological events. Based on this first complete year-round A-ERT monitoring dataset on Deception Island, we believe that this system shows high potential for autonomous applications in remote and harsh polar environments such as Antarctica. The monitoring system can be used with larger electrode spacing to investigate greater depths, providing adequate monitoring at sites and depths where boreholes are very costly and the ecosystem is very sensitive to invasive techniques. Further applications may be the estimation of ice and water contents through petrophysical models or the calibration and validation of heat transfer models between the active layer and permafrost.

scholarly journals Case study of electrical resistivity tomography measurements used in landslides investigation, Southern Poland

2018 ◽  
Vol 7 (1) ◽  
pp. 110-126 ◽  
Author(s):  
Magdalena Mita ◽  
Michał Glazer ◽  
Radosław Kaczmarzyk ◽  
Michał Dąbrowski ◽  
Karolina Mita
Keyword(s):  
Electrical Resistivity ◽  
Electrical Resistivity Tomography ◽  
A Priori ◽  
Slope Instability ◽  
Mass Movements ◽  
Structural Differentiation ◽  
Data Set ◽  
Resistivity Tomography ◽  
Wide Range

AbstractMass movements are an ever present threat to building construction, water management, vegetation formation and biodiversity. This paper presents an approach to landslides research based on non-invasive geoelectrical method - Electrical Resistivity Tomography (ERT). Mapping and displacement monitoring of unstable slopes is crucial for the hazards prevention and assessment. The ERT technique is an effective tool to obtain structural differentiation of geological medium through interpretation of 2D electrical resistivity models. The main advantage of the method is a wide range of applicability what makes its useful during field works on a landslide. It is commonly used for measurements of slope instability, determination of shear surface, landslide susceptibility, depth of bedrock, slip plane geometry. The aim of the work is to identify the geological structures underneath three selected landslides in south Poland: in Racibórz, Milówka and Porąbka. Attempts have been focused on determination of the usefulness of the proposed ERT methodology for evaluation of possible further development of mass movements. On two investigation sites two different arrays have been used: Wenner-Schlumberger and dipole-dipole which allowed to prepare combined data set and resistivity models based on them. Forward modelling of synthetic models based on a priori information allowed to understand anomalies present on resistivity models. Applied approach ensured quality increase of final interpretation of resistivity models.

scholarly journals Monitoring drying and wetting of a cement bentonite mixture with Electrical Resistivity Tomography

2020 ◽  
Vol 195 ◽  
pp. 03015 ◽  
Author(s):  
Guido Musso ◽  
Antonio Zibisco ◽  
Renato Maria Cosentini ◽  
Paolo Trischitta ◽  
Gabriele Della Vecchia
Keyword(s):  
Electrical Conductivity ◽  
Electrical Resistivity ◽  
Relative Humidity ◽  
Electrical Resistivity Tomography ◽  
Hydraulic Performance ◽  
Resistivity Tomography ◽  
Bentonite Slurry ◽  
Slurry Walls ◽  
The Impact ◽  
Water Contents

Cement bentonite slurry cutoff walls are used to encapsulate pollutants within contaminated areas, so avoiding their spreading in the environment. In both temperate and arid climates, at shallow depths, slurry walls are exposed to interaction with the atmosphere and thus to relative humidity values which might induce desaturation and significant shrinkage. This note presents the main results of a study aimed at investigating the impact of drying processes on the integrity and the hydraulic performance of cement bentonite slurry walls. Cement bentonite samples were cured under water for different times (1 months, 2 months and 4 months) and then dried naturally by exposing them to the laboratory environment (T = 21 °C, relative humidity approximately 38%). Once dried, the bottom of the samples was placed in contact with a thin layer of water to induce wetting. The distribution of the electrical conductivity within these samples was evaluated through Electrical Resistivity Tomography measurements, and electrical conductivity maps were converted then into maps of water contents on basis of a phenomenological relationship. The reconstructed water contents compared very well to the measured ones. Drying induced a limited cracking of the samples, which might affect to some extent the hydraulic performance of the barriers.

SIMULATION OF ELECTRICAL MONITORING OF DAMS WITH LEAKAGE WITH A TRANSVERSE PLACEMENT OF THE MEASURING INSTALLATION

2020 ◽  
Vol 8 (4) ◽  
pp. 69-82
Author(s):  
D.S. Rakisheva ◽  
◽  
B.G. Mukanova ◽  
I.N. Modin ◽  
◽  
...  
Keyword(s):  
Numerical Modeling ◽  
Water Level ◽  
Electrical Resistivity Tomography ◽  
Resistivity Tomography ◽  
Measuring Installation ◽  
Basic Functions ◽  
Tomography Method ◽  
Dam Monitoring ◽  
The Mathematical Model ◽  
Measurement Line

Numerical modeling of the problem of dam monitoring by the Electrical Resistivity Tomography method is carried out. The mathematical model is based on integral equations with a partial Fourier transform with respect to one spatial variable. It is assumed that the measurement line is located across the dam longitude. To approximate the shape of the dam surface, the Radial Basic Functions method is applied. The influence of locations of the water-dam, dam-basement, basement-leakage boundaries with respect to the sounding installation, which is partially placed under the headwater, is studied. Numerical modeling is carried out for the following varied parameters: 1) water level at the headwater; 2) the height of the leak; 3) the depth of the leak; 4) position of the supply electrode; 5) water level and leaks positions are changing simultaneously. Modeling results are presented in the form of apparent resistivity curves, as it is customary in geophysical practice.

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