Z lotu ptaka. „Relief Praszwajcarii” Franza Ludwiga Pfyffera oraz inne modele terenu jako media naukowego zawłaszczania Alp w późnym XVIII wieku

Among the processes of “conquering, developing and appropriating mountains” is occupied by the emergence of mountain topography. In the eighteenth century raised relief, as a terrain model, played one of the most important roles in this process. This was a period when more reliable topographic data began to be collected on the basis of measurements carried out across the Alps. Possibilities of their cartographic representation were limited at the time. A graphic method for presenting orthogonal projection by means of contour curves was not invented until the nineteenth century. Before that three-dimensional terrain models were the only way to correctly represent various levels of landscape. Terrain models were accepted at the time as the best method for presenting mountain landscapes. The first attempt to carry out a comprehensive measurement of the Alps over a vast area of a continuous mountain range and represent it on a low relief was made in 1786 and concerned an area in central Switzerland around Lake Lucerne. At that time Franz Ludwig Pfyffer von Wyher, an officer in French service, became famous for advanced surveying techniques and terrain models, both civilian and military. His famous relief depicts around one-tenth of today’s Switzerland, with two-thirds of the area encompassing the Alps and foot of the Alps. From that moment on other authors began to create their models of Alpine landscape. These reliefs were appreciated by contemporary naturalists, especially those studying the Alps, because they enabled them to view the complex topography of the range, which had been impossible before. They drew attention to a number of natural and geological phenomena, and made it possible to come up with new findings relating to the following questions: At what altitude should the snow line be placed? Where is the boundary of vegetation? Where do coniferous forests begin? Where is the line of glaciers? What is the structure of the mountains? Obviously, they were not sufficient to provide all answers to the above questions, but thanks to a “bird’s eye” perspective they made it possible to place special studies of the various disciplines within a broader context, both with regard to the relevant subject matter and between disciplines.

Flugbilder. Franz Ludwig Pfyffers „Relief der Urschweiz“ und andere Geländemodelle als Medien der wissenschaftlichen Aneignung der Alpen im späten 18. Jahrhundert

Among the processes of “conquering, developing and appropriating mountains” is occupied by the emergence of mountain topography. In the eighteenth century raised relief, as a terrain model, played one of the most important roles in this process. This was a period when more reliable topographic data began to be collected on the basis of measurements carried out across the Alps. Possibilities of their cartographic representation were limited at the time. A graphic method for presenting orthogonal projection by means of contour curves was not invented until the nineteenth century. Before that three-dimensional terrain models were the only way to correctly represent various levels of landscape. Terrain models were accepted at the time as the best method for presenting mountain landscapes. The first attempt to carry out a comprehensive measurement of the Alps over a vast area of a continuous mountain range and represent it on a low relief was made in 1786 and concerned an area in central Switzerland around Lake Lucerne. At that time Franz Ludwig Pfyffer von Wyher, an officer in French service, became famous for advanced surveying techniques and terrain models, both civilian and military. His famous relief depicts around one-tenth of today’s Switzerland, with two-thirds of the area encompassing the Alps and foot of the Alps. From that moment on other authors began to create their models of Alpine landscape. These reliefs were appreciated by contemporary naturalists, especially those studying the Alps, because they enabled them to view the complex topography of the range, which had been impossible before. They drew attention to a number of natural and geological phenomena, and made it possible to come up with new findings relating to the following questions: At what altitude should the snow line be placed? Where is the boundary of vegetation? Where do coniferous forests begin? Where is the line of glaciers? What is the structure of the mountains? Obviously, they were not sufficient to provide all answers to the above questions, but thanks to a “bird’s eye” perspective they made it possible to place special studies of the various disciplines within a broader context, both with regard to the relevant subject matter and between disciplines.

Workflow for robust Scholte and Love waves phase-velocity estimation from small aperture Ocean Bottom Seismometer arrays in Lake Lucerne: deployment, location, orientation, and clock error correction

The phase-velocity dispersion curve (DC) is an important characteristic of the propagation of surface waves in sedimentary environments. Although the procedure for DC estimation in onshore environments using ambient vibration recordings is well established, the DC estimation in offshore environments using arrays of Ocean Bottom Seismometers (OBS) presents three main challenges. These are the localization, the orientation of the OBS horizontal components, and the clock error. Here, we concentrate on the workflow for a robust estimation of the phase-velocity dispersion curves from small aperture OBS array measurements in Lake Lucerne (Switzerland). OBS array campaigns were performed between 2018 and 2020 using arrays with a maximum aperture of 679 m at a maximum water depth of 81 m. The challenges related to the OBS location on the lake floor were addressed by combining the multibeam bathymetry map and the backscatter image for the investigated site with the differential GPS coordinates of the OBS at recovery. The OBS measurements were complemented by airgun surveys. Airgun data were first used to estimate the misorientation of the horizontal components of the OBS and second to estimate the clock error. Finally, we use two array processing methods, namely the three-component high-resolution frequency-wavenumber and the interferometric multichannel analysis of surface waves, to estimate the dispersion characteristics of the propagating surface waves for one of the array sites. We clearly observe the phase-velocity dispersion curve branches for Scholte and Love waves in the frequency range between 1.2 and 3.2 Hz for both array processing techniques.

Stability assessment of submerged lateral and deltaic slopes in Lake Lucerne

<p>Numerous studies indicate that tsunamis do not only occur in oceans but also in lakes. Lake Tsunamis are mainly caused by sublacustrine and subaerial mass movements that can be triggered by seismic or aseismic processes (Schnellmann et al. 2002, Strasser et al. 2007, Kremer at al. 2012, Hilbe and Anselmetti 2015). Such tsunamis can have devastating effects on the surrounding population and infrastructure.</p><p>To assess the tsunami hazard triggered by sublacustrine mass movements, the stability of the lake slopes needs to be examined. As a part of the SNSF funded SINERGIA project “Lake Tsunamis: Causes, Controls and Hazard”, we perform the slope stability analysis based on the comprehensive geotechnical in situ and laboratory dataset for the selected sites of Lake Lucerne, Central Switzerland.</p><p>During 2018-2019 dense geotechnical investigations were carried out along slope-perpendicular profiles at 10 sites where the slopes have failed in the past or are susceptible to failure and included more than 130 in-situ free-fall cone penetration tests with pore pressure measurement (CPTu) and laboratory analysis of 30 short sediment cores. Already existing reflection seismic dataset complements these data and provides the thickness of different sediment layers.</p><p>1D undrained, infinite slope stability analysis following Morgenstern and Price (1965) is used to define the Factor of Safety and critical conditions for deltaic and lateral slopes, where different triggers can be responsible for the failure. Based on the conducted analysis, static and dynamic stability together with critical failure conditions for different slopes in Lake Lucerne can be compared.</p><p> </p><p>References:</p><p>Hilbe, M. and Anselmetti, F.S. (2015) Mass Movement-Induced Tsunami Hazard on Perialpine Lake Lucerne (Switzerland): Scenarios and Numerical Experiments. Pure and Applied Geophysics 172, 545-568.</p><p>Kremer, K., Simpson, G., Girardclos, S. (2012) Giant Lake Geneva tsunami in AD 563. Nature Geoscience 5, 756-757.</p><p>Morgenstern, N.R. and Price, V.E. (1965) Analysis of stability of general slip surfaces. Geotechnique 15(1): 79–93.</p><p>Schnellmann, M., Anselmetti, F.S., Giardini, D., McKenzie, J.A., Ward, S.N. (2002) Prehistoric earthquake history revealed by lacustrine slump deposits. Geology 30, 1131–1134.</p><p>Strasser, M., Stegmann, S., Bussmann, F., Anselmetti, F.S., Rick, B., Kopf, A. (2007) Quantifying subaqueous slope stability during seismic shaking: Lake Lucerne as model for ocean margins. Marine Geology 240, 77-97.</p>

Lake Tsunamis: Causes, Consequences and Hazard investigated in a multidisciplinary project

<p>Tsunamis can occur in lacustrine environments, similar to marine settings. In lake settings, these tsunamis are mainly generated by mass-movement processes displacing large volumes of water, and triggered by seismic or aseismic phenomena. In Swiss lakes, several historical tsunamis are reported. Some of the most prominent examples are: the 563 AD Lake Geneva tsunami presumably caused by a rockfall-induced delta failure, the 1601 AD Lake Lucerne tsunami caused by earthquake-triggered sublacustrine mass movements, and the 1687 AD Lake Lucerne tsunami that was caused by a delta failure.</p><p> </p><p>Nowadays, the shorelines of many Swiss lakes are densely populated and host important infrastructures. The occurrence of lake tsunamis in Switzerland is known, however, we still miss a workflow to assess the hazard related to tsunamis. Within the framework of a multidisciplinary project (Lake Tsunamis: Causes, Consequences and Hazard), funded by the Swiss National Science Foundation and the Federal Office for the Environment, we aim towards better understanding lake-tsunami processes using Swiss lakes as laboratories.</p><p> </p><p>The major objectives of this project are to investigate a) the diverse causes of lake tsunamis, b) the geotechnical and sedimentological properties of unstable slope sediment, c) the potentially unstable sediment volumes on charged slopes, d) the wave generation, propagation and shore run-up, e) the onshore and shallow offshore tsunami deposits and d) their related hazard.</p><p> </p><p>Since 2018, extensive field work using ocean bottom seismometers and cone penetration tests, as well as laboratory tests on sediment sample have been performed to assess the slope stability during seismic shaking on Lake Lucerne. Tsunami waves have been reproduced at laboratory scale to benchmark the numerical simulations of generation, propagation and run-up of tsunamis in lakes. To characterize and date historical and prehistorical tsunami deposits, on and off-shore sediment cores have been retrieved at Lake Lucerne, Geneva, Zurich and Sils. A first work-flow to assess the tsunami hazard related to earthquake-triggered sublacustrine mass movements is proposed. In this contribution, we will summarise the current status of this project.</p>

Reconstruction and actual trends of landslide activities in Bruust–Haltiwald, Horw, canton of Lucerne, Switzerland

A spatiotemporal reconstruction of slope movements on the edge of Lake Lucerne near the municipality of Horw, canton of Lucerne, is presented. The reconstruction was realized by analyzing growth reactions of beech (Fagus sylvatica L.) and fir (Abies alba Mill.) trees growing on this slope. Before dendrochronological sampling, a detailed geomorphological mapping of the landslide was conducted with the aim to determine the spatial extent of the sliding area. For tree-ring analyses, 124 increment cores from 62 trees were analyzed following standard techniques of dendrogeomorphology. In addition, long micro-sections were prepared from the entire cores to extend the common eccentricity analyses by microscopic determination of the onset of reaction wood in fir and beech. Results clearly show that the area is moving at least since 1948. A significant concentration of events was observed between the years 1990 and 2000 as well as after 2006. The definition of a threshold to define events using an eccentricity index alone is problematic and needs to be adapted to specific site conditions. For this reason, we recommend always combining the application of an eccentricity index with a detailed visual (anatomical) inspection to check for the occurrence of reaction wood.

Piecing together the Lateglacial advance phases of the Reussgletscher (central Swiss Alps)

Exposure dating has substantially improved our knowledge about glacier advances during the Younger Dryas (YD) and the early Holocene. The glacier development after the Last Glacial Maximum (LGM) and the timing of morphologically evidenced, earlier Lateglacial re-advances is, however, still widely unknown. In this study we used 10Be surface exposure and radiocarbon dating to address these phases and corresponding landforms in the catchment of the former Reussgletscher (central Swiss Alps). We obtained clear indication for moraine deposition prior to the YD. The oldest samples predate the Bølling–Allerød interstadial (>14.6 ka). Morphostratigraphically even older lateral moraines, probably corresponding to terminal positions in the Lake Lucerne, could not be dated conclusively. Due to the geomorphological constraints of the sampling environment, the establishment of a local pre-YD chronology remains a challenge: moraines with adequate numbers of datable boulders were rarely preserved, and age attributions based on few samples are complicated by outliers.