Multi-methodological investigation of a retrogressive thaw slump in the Richardson Mountains, Northwest Territories, Canada

2020 ◽  
Author(s):  
Julius Kunz ◽  
Christof Kneisel ◽  
Tobias Ullmann ◽  
Roland Baumhauer
Keyword(s):  
Electrical Resistivity ◽  
Active Layer ◽  
Geophysical Methods ◽  
Three Dimensional ◽  
Active Layer Thickness ◽  
Permafrost Degradation ◽  
Low Resistivity ◽  
Permafrost Table ◽  
Retrogressive Thaw Slump ◽  
Richardson Mountains

<p>The Mackenzie-Delta Region is known for strong morphological activity in context of global warming and permafrost degradation, which reveals in a large number of retrogressive thaw slumps. These are frequently found along the shorelines of inland lakes and the coast; however, this geomorphological phenomenon also occurs at inland ​​streams and creeks of the Peel Plateau and the Richardson Mountains, located in the southwest of the delta. Here several active retrogressive thaw slumps are found of which some have reached an extent of several hectares, e.g. the mega slump at the Dempster Creek.</p><p>In this study we investigated a recent retrogressive thaw slump at the edge of the Richardson Mountains close to the Dempster Highway to determine the subsurface properties using non-invasive geophysical methods. We performed three-dimensional Ground Penetrating Radar (GPR) surveys, as well as quasi-three-dimensional Electrical Resistivity Tomography (ERT) surveys in order to investigate the subsurface characteristics adjacent to the retreating headwall of the slump. These measurements provide information on the topography of the permafrost table, ice content and/or water pathways on top, within or under the permafrost layer. Additionally, we performed manual measurements of the active layer thickness for validation of the geophysical models. The approach was complemented by the analysis of high-resolution photogrammetric digital elevation models (DEM) that were generated using in situ drone acquisitions.</p><p>The measured active layer depths show a strong influence of the relief and especially of small creeks on the permafrost table topography. Likely, this influence also is the primary trigger for the initial slump activity. In addition, the ERT measurements show strong variations of the electrical resistivity values in the upper few meters, which are indicative for heterogeneities, also within the ice-rich permafrost body. Especially noticeable is a layer of low resistivity values in an area adjacent to the slump headwall. This layer is found at depths between 4m to 7m, which approximately corresponds to the base of the headwall. Here, the low resistivity values could be indicative for an unfrozen or water-rich layer below the ice-rich permafrost. Consequently, this layer may have contributed to the initial formation of the slump and is important for the spatial extension of the slump.</p><p>These results present new insights into the subsurface of an area adjacent to an active retrogressive thaw slump and may contribute to a better understanding of slump development.</p>

scholarly journals Crustal architecture of a metallogenic belt and ophiolite belt: implications for mineral genesis and emplacement from 3-D electrical resistivity models (Bayankhongor area, Mongolia)

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Matthew J. Comeau ◽  
Michael Becken ◽  
Alexey V. Kuvshinov ◽  
Sodnomsambuu Demberel
Keyword(s):  
Electrical Resistivity ◽  
Crustal Structure ◽  
Three Dimensional ◽  
Suture Zone ◽  
Fault System ◽  
Magnetotelluric Data ◽  
Low Resistivity ◽  
Ophiolite Belt ◽  
Geological Processes ◽  
Metallogenic Belt

AbstractCrustal architecture strongly influences the development and emplacement of mineral zones. In this study, we image the crustal structure beneath a metallogenic belt and its surroundings in the Bayankhongor area of central Mongolia. In this region, an ophiolite belt marks the location of an ancient suture zone, which is presently associated with a reactivated fault system. Nearby, metamorphic and volcanic belts host important mineralization zones and constitute a significant metallogenic belt that includes sources of copper and gold. However, the crustal structure of these features, and their relationships, are poorly studied. We analyze magnetotelluric data acquired across this region and generate three-dimensional electrical resistivity models of the crustal structure, which is found to be locally highly heterogeneous. Because the upper crust (< 25 km) is found to be generally highly resistive (> 1000 Ωm), low-resistivity (< 50 Ωm) features are conspicuous. Anomalous low-resistivity zones are congruent with the suture zone, and ophiolite belt, which is revealed to be a major crustal-scale feature. Furthermore, broadening low-resistivity zones located down-dip from the suture zone suggest that the narrow deformation zone observed at the surface transforms to a wide area in the deeper crust. Other low-resistivity anomalies are spatially associated with the surface expressions of known mineralization zones; thus, their links to deeper crustal structures are imaged. Considering the available evidence, we determine that, in both cases, the low resistivity can be explained by hydrothermal alteration along fossil fluid pathways. This illustrates the pivotal role that crustal fluids play in diverse geological processes, and highlights their inherent link in a unified system, which has implications for models of mineral genesis and emplacement. The results demonstrate that the crustal architecture—including the major crustal boundary—acts as a first‐order control on the location of the metallogenic belt.

Optimization of Cavity Length to Obtain Low Threshold Solid-state Dye Laser

2011 ◽  
Vol 1365 ◽  
Author(s):  
Lan-Ting Shi ◽  
Feng Jin ◽  
Mei-Ling Zheng ◽  
Xian-Zi Dong ◽  
Wei-Qiang Chen ◽  
...  
Keyword(s):  
Solid State ◽  
Layer Thickness ◽  
Active Layer ◽  
Cavity Length ◽  
Three Dimensional ◽  
Colloidal Crystals ◽  
Single Mode ◽  
Active Layer Thickness ◽  
Low Threshold ◽  
Polymeric Solid

ABSTRACTWe have demonstrated and studied polymeric solid-state dye lasers (SSDLs) fabricated by three-dimensional (3D) polystyrene colloidal crystals and tert-butyl roadamine B (t-Bu RhB) doped Poly (methyl methacrylate) (PMMA) films with different film thickness. The sandwich-typed resonator cavities with different active layer thickness display single-mode lasing oscillations in the reflection bandgap of the colloidal crystals. The lasing thresholds could be optimized by changing the thickness of t-Bu RhB doped PMMA films, which is as low as 7.43 W/cm2. Adjusting active layer thickness would provide an opportunity to accelerate the development of fabricating polymeric SSDLs with low threshold.

scholarly journals Resolution capacity of geophysical monitoring regarding permafrost degradation induced by hydrological processes

2017 ◽  
Vol 11 (6) ◽  
pp. 2957-2974 ◽  
Author(s):  
Benjamin Mewes ◽  
Christin Hilbich ◽  
Reynald Delaloye ◽  
Christian Hauck
Keyword(s):  
Electrical Resistivity ◽  
Seismic Tomography ◽  
Field Data ◽  
Electrical Resistivity Tomography ◽  
Geophysical Methods ◽  
Phase Model ◽  
Permafrost Degradation ◽  
Resistivity Tomography ◽  
Refraction Seismic ◽  
Ice Content

Abstract. Geophysical methods are often used to characterize and monitor the subsurface composition of permafrost. The resolution capacity of standard methods, i.e. electrical resistivity tomography and refraction seismic tomography, depends not only on static parameters such as measurement geometry, but also on the temporal variability in the contrast of the geophysical target variables (electrical resistivity and P-wave velocity). Our study analyses the resolution capacity of electrical resistivity tomography and refraction seismic tomography for typical processes in the context of permafrost degradation using synthetic and field data sets of mountain permafrost terrain. In addition, we tested the resolution capacity of a petrophysically based quantitative combination of both methods, the so-called 4-phase model, and through this analysed the expected changes in water and ice content upon permafrost thaw. The results from the synthetic data experiments suggest a higher sensitivity regarding an increase in water content compared to a decrease in ice content. A potentially larger uncertainty originates from the individual geophysical methods than from the combined evaluation with the 4-phase model. In the latter, a loss of ground ice can be detected quite reliably, whereas artefacts occur in the case of increased horizontal or vertical water flow. Analysis of field data from a well-investigated rock glacier in the Swiss Alps successfully visualized the seasonal ice loss in summer and the complex spatially variable ice, water and air content changes in an interannual comparison.

scholarly journals A Comparison of Frequency Domain Electro-Magnetometry, Electrical Resistivity Tomography and Borehole Temperatures to Assess the Presence of Ice in a Rock Glacier

2020 ◽  
Vol 8 ◽  
Author(s):  
Jacopo Boaga ◽  
Marcia Phillips ◽  
Jeannette Noetzli ◽  
Anna Haberkorn ◽  
Robert Kenner ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Frequency Domain ◽  
Layer Thickness ◽  
Active Layer ◽  
Electrical Resistivity Tomography ◽  
Temperature Data ◽  
Active Layer Thickness ◽  
Rock Glacier ◽  
Resistivity Tomography ◽  
Borehole Temperature

Alpine permafrost is currently warming, leading to changes such as active layer deepening and talik formation. Frequency domain electro-magnetometry (FDEM) measurements were tested as a simple and efficient method to investigate ground characteristics along two transects on the ice-rich Schafberg rock glacier in the Eastern Swiss Alps. The results were compared with electrical resistivity tomography (ERT) and ground temperature data acquired simultaneously in boreholes. FDEM provides information on the electrical properties of the ground, allowing to investigate ground-ice distribution. Our device allowed measurements to a depth of around 7 m. In ice-rich permafrost, FDEM can provide an approximation of the active layer thickness, and ice-free zones within the permafrost such as intra-permafrost taliks can be identified. This rapidly applicable geophysical method can be used to monitor ground ice distribution easily and efficiently, making it an ideal complement to borehole temperature data, which only provide point information and are costly to install and maintain. At the Schafberg site the three methods FDEM, electrical resistivity tomography and borehole temperature measurements provided similar results, with regard to active layer thickness and the presence of unfrozen zones within the ice-rich permafrost.

scholarly journals Thermal characterization of the active layer at the Limnopolar Lake CALM-S site on Byers Peninsula (Livingston Island), Antarctica

Solid Earth ◽  
2014 ◽  
Vol 5 (2) ◽  
pp. 721-739 ◽  
Author(s):  
M. A. de Pablo ◽  
M. Ramos ◽  
A. Molina
Keyword(s):  
Thermal Behavior ◽  
Active Layer ◽  
Thermal Characterization ◽  
Active Layer Thickness ◽  
Freezing And Thawing ◽  
Thermal Amplitude ◽  
Permafrost Table ◽  
Different Depths

Abstract. The Limnopolar Lake site (A25), of the Circumpolar Active Layer Monitoring-South network (CALM-S), is located on Byers Peninsula, where the active layer thickness is monitored systematically (by mechanical probing during the thawing season and by temperature devices continuously since 2009). Air, surface, snow and ground temperature devices have been installed to monitor ground thermal behavior, which is presented and characterized here. We use the air and ground mean daily temperature values to define the following parameters: maximum, minimum and mean temperatures, the zero annual thermal amplitude, and the depth and position of the top of the permafrost table. The freezing and thawing seasons (defining their starting dates as well as their length) and the existence of zero curtain periods have also been established. We also derive apparent thermal diffusivity and plot thermograms to study the thermal behavior of the ground at different depths and seasons. After this complete thermal characterization of the active layer, we propose the potential existence of a permafrost table at approximately 130 cm in depth as well as a former transitional layer above it, and discuss the role of water in connection with the thermal behavior of the ground during the study period.

scholarly journals Internal structure of two alpine rockglaciers investigated by quasi-3D electrical resistivity imaging (ERI)

2016 ◽  
Author(s):  
Adrian Emmert ◽  
Christof Kneisel
Keyword(s):  
Electrical Resistivity ◽  
Internal Structure ◽  
Geophysical Methods ◽  
Swiss Alps ◽  
Electrical Resistivity Imaging ◽  
Active Layer Thickness ◽  
Ground Ice ◽  
Resistivity Imaging ◽  
Wide Range ◽  
Ice Content

Abstract. Interactions between different formative processes are reflected in the internal structure of rockglaciers. Its detection can therefore help to enhance our understanding of landform development. For an assessment of subsurface conditions, we present an analysis of the spatial variability of active layer thickness, ground ice content and frost table topography at two different rockglacier sites in the Eastern Swiss Alps by means of quasi-3D electrical resistivity imaging (ERI). This approach enables an extensive mapping of subsurface structures and hence the performance of a spatial overlay between site-specific surface und subsurface characteristics. At Nair rockglacier, we discovered a gradual descent of the frost table in a downslope direction and a homogenous decrease of ice content which follows the observed surface topography. This is attributed to ice formation by refreezing meltwater from an embedded snowbank or from a subsurface ice patch which reshapes the permafrost layer. The heterogeneous ground ice distribution at Uertsch rockglacier indicates that multiple processes on different time domains were involved in rockglacier development. Resistivity values which represent frozen conditions vary within a wide range and indicate a successive formation which includes several rockglacier advances, past glacial overrides and creep processes on the rockglacier surface. In combination with the observed rockglacier topography, quasi-3D ERI enables us to delimit areas of extensive and compressive flow in close proximity. Excellent data quality was provided by a good coupling of electrodes to the ground in the pebbly material of the investigated rockglaciers. Results show the value of the quasi-3D ERI approach but advice the application of complementary geophysical methods for interpreting the results.

scholarly journals GEOELECTRIC PROSPECTION OF COPPER OCCURRENCE IN FOLDING LAYERS IN THE SUL-RIOGRANDENSE SHIELD (BRAZIL)

2018 ◽  
Vol 36 (3) ◽  
pp. 1
Author(s):  
Shaiely Fernandes Santos ◽  
Cesar Augusto Moreira ◽  
Fernanda Teles Gomes Rosa ◽  
Karolliny Borssatto ◽  
Marly Aparecida Silva
Keyword(s):  
Electrical Resistivity ◽  
Geophysical Methods ◽  
High Resistivity ◽  
Electrical Tomography ◽  
Mineral Research ◽  
2D Inversion ◽  
Copper Sulfides ◽  
Low Resistivity ◽  
Quartz Veins ◽  
Probable Presence

ABSTRACTSulfide prospecting with the geophysical methods, such as electrical resistivity and induced polarization, are promising due to the contrast of electrical resistivity and chargeability, where deposits with disseminated sulfides or filoneans are characterized by low resistivity and high polarizability. This work carried out a study of geophysical prospecting by means of tomographic acquisition in mineral copper occurrence, in the region of Caçapava do Sul. Three acquisition lines were performed by means of electrical tomography technique using a Dipole-dipole arrangement, with a length of 400 m and a spacing of 5 m between the electrodes, arranged in perpendicular layout to the structure of the area, represented by a large synclinal where research galleries with carbonates and copper sulfides were recognized in the ridge. The 2D inversion models and 3D multilevel maps indicate central and lateral regions with high resistivity and chargeability with indication of probable presence of copper sulfide, possibly housed in quartz veins. Peripheral zones with moderate resistivity and chargeability infer possible areas with presence of argilization, zones with high chargeability and low resistivity are likely to be zones of sulfation and possible silicification zones with high resistivity and low chargeability, observed in the vicinity of the probable mineralized zones.Keywords: Chargeability, Mineral Research, Resistivity, Sulfide, 3D Multilevel modeling.RESUMO A prospecção de sulfetos por meio de métodos geofísicos de eletrorresistividade e polarização induzida são altamente efetivos devido ao contraste de resistividade elétrica e cargabilidade, uma vez que os depósitos com sulfetos disseminados ou filoneanos são cvaracterizados por baixa resistividade e alta polarizabilidade. Esse trabalho realizou aquisição de tomografia elétricas em ocorrência mineral de cobre, na região de Caçapava do Sul (RS). Foram realizadas 3 linhas de tomografia elétrica em arranjo dipolo-dipolo, com 400 m de comprimento e 5 m de espaçamento entre eletrodos, dispostas de forma perpendicular à crista de um anticlinal, onde no passado foram reconhenhecidos carbonatos e sulfetos de cobre, em galerias de exploração mineral. Os modelos de inversão 2D e mapas de multiníveis 3D indicam regiões centrais e laterais com alta resistividade e alta cargabilidade com provável zona de sulfetos alojados em veios de quartzo. Zonas periféricas com moderada resistividade e cargabilidade sugerem a presença de argilização; zonas com alta cargabilidade e baixa resistividade são prováveis zonas de sulfetação e altos valores de resistividade e baixos de cargabilidade indicam zonas de silicificação.Palavras-chave: Cargabilidade, Pesquisa Mineral, Resistividade Elétrica, Sulfeto, Modelamento Multinível 3D.

scholarly journals Permafrost table depth in soils of Eastern Antarctica oases, King George and Ardley Islands (South Shetland Islands)

2020 ◽  
Vol 10 (1) ◽  
pp. 7-22 ◽  
Author(s):  
Ivan Alekseev ◽  
Evgeny Abakumov
Keyword(s):  
Electrical Resistivity ◽  
Anthropogenic Disturbance ◽  
South Shetland Islands ◽  
Organic Layer ◽  
Active Layer Thickness ◽  
Resistivity Sounding ◽  
Shetland Islands ◽  
Larsemann Hills ◽  
Permafrost Table ◽  
Antarctic Research

This study was aimed to investigate the electrical resistivity in soils and permafrost of various ice-free areas of Antarctica and Sub-Antarctica (from coastal Eastern Antarctica oases to Maritime Antarctica). Measurements of electrical resistivity of soil and permafrost strata were performed with a portable device LandMapper. It was found that the permafrost table depth ranged 82 to106 cm in Bunger Hills, 95 to 122 cm in Larsemann Hills, 27 to 106 in Thala Hills, and 89 to 100 cm on King George Island and Ardley Island. Presence (and thickness) of organic layer and influence of snow patches melting were found the main reasons for differentiation of permafrost table depth in the studied ice-free areas. Anthropogenic disturbance at waste disposal sites resulted in more pronounced soil profile heterogeneity and formation of scattered electrical resistivity profiles. Permafrost layer was found less homogenous in the upper part of permafrost strata compared to the lower part. An application of vertical electrical resistivity sounding (VERS) may be very useful for evaluation of active layer thickness in Antarctic environments, especially when they are facing severe anthropogenic influence due to maintaining of numerous Antarctic research stations and logistical operations

scholarly journals Thermal characterization of the active layer at the Limnopolar Lake CALM-S site on Byers Peninsula (Livingston Island), Antarctica

2014 ◽  
Vol 6 (1) ◽  
pp. 679-729 ◽  
Author(s):  
M. A. de Pablo ◽  
M. Ramos ◽  
A. Molina
Keyword(s):  
Thermal Behavior ◽  
Active Layer ◽  
Thermal Characterization ◽  
Transitional Zone ◽  
Active Layer Thickness ◽  
Freezing And Thawing ◽  
Thermal Amplitude ◽  
Permafrost Table ◽  
Different Depths

Abstract. The Limnopolar Lake CALM-S site (A25) is the unique location on Byers peninsula where the active layer thickness is systematically monitorized (by mechanical probing during the thaw season and by temperature devices continuously since 2009). An air, surface, snow and ground temperature monitoring devices have been installed to monitor ground thermal behavior. We analyzed these data to present there the active layer thermal characterization. We use the air and ground mean daily temperature data to define the following parameters: maximum, minimum and mean temperatures at the air and at different depths, the zero annual thermal amplitude depths and position of the top of the permafrost table. The freezing and thawing seasons (defining their starting dates as well as their length), and the existence of zero curtain periods has been also established. We also derive apparent thermal diffusivity and plot thermograms to study the thermal behavior of the ground at different depths. After this complete thermal characterization of the active layer, we propose the potential existence of a~permafrost table at about 130 cm in depth as well as the transitional zone above it, and discuss the role of water in connection with the thermal behavior of the ground during the study period.

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