Unterstützung 2020


Sandra Grazioli / Departement of Earthsciences / ETH Zürich, Switzerland

Reconstructing fluctuations of the Rossboden Glacier (Valais, Switzerland)

The Rossboden Glacier is situated southwest of Simplon Dorf, Valais and shows prominent moraine sets of different glacial stages. The aim of this master thesis is to investigate, reconstruct and date the retreat history of the glacier until the present. The glacier has left distinct moraine ridges situated between 1500 and 2300 m.a.s.l., with the present main glacier front being around 2700 m.a.s.l. The focus of this thesis is on the younger upper moraine system and related dead-ice structures, as well as on the older moraine ridges that extend down to the village of Simplon Dorf. The interest lies on the reconstruction of the retreat history until the Little Ice Age, as well on the recent retreat in the upper part since the beginning of the 20th century as aerial photos can be compared for this time span. The deposits of the large rock-ice-avalanche from 1901 are also mapped out and could be recognized in the field. During the field work of 3 weeks in total in August and September 2020 the moraine systems were investigated and mapped in detail and 21 boulders were sampled across the study area. Sampling locations were chosen on the main ridges in the old and younger moraine systems on left and right laterals. These samples are now being prepared in the Laboratory of Ion Beam Physics at ETH for 10Be exposure dating to determine the absolute ages of the moraines. The ages are crucial to reconstruct the sequence of events in the Rossboden area and can then be compared with other sites for Alpine-wide paleoclimate analysis to gain better understanding of glacier fluctuations in the Alps.

The approach of combining detailed geomorphological mapping using DEMs, aerial photos and field observations with absolute dating based on cosmogenic 10Be, can provide crucial insights into the history of the Rossboden Glacier. Studying the evolution of the recently deglaciated area at the stagnant ice tongue below the bedrock step will generate fundamental data for understanding process-landform associations during ice decay both in the present and in the past.

With the financial support of CH-QUAT the field work could be conducted as planned and I was able to visit the study site three times this summer and fall for detailed geomorphological mapping and sampling. I am very grateful for CH-QUAT supporting my project. Thank you.

Contact:
Sandra Grazioli
grsandra@student.ethz.ch

S. Grazioli
S. GrazioliBild: O.Steinemann

Ladina Hügli/Departement of Earth Sciences / ETH Zürich, Switzerland

A reconstruction of the Debris-Flow Fan Evolution in Maienfeld and Hazard-Assessment for Maienfeld and Fläsch

The village Maienfeld of the Bündner Herrschaft is built on a prominent and active debris-flow fan. The aim of this master thesis is to reconstruct the evolution of this debris-flow fan, by identifying the different lobes and constraining their absolute ages. A reconstruction of the temporal and spatial evolution of the debris-flow fans allows an assessment of their activity and therewith, the potential geohazard-risk they hold for the villages located on the debris-flow fan.

To rebuild the debris-flow fan development the terrain is analysed both in the field with detailed mapping of the surface morphology and preservation of debris-flow deposits and remotely with LiDAR and aerial images. In addition to these geomorphologic elements, the field mapping of the fan was complemented with the sampling of 21 boulders, the recording of outcrops and examination of the geology in the catchment area. The 21 boulders were sampled for age determination by applying cosmogenic nuclide dating. By choosing regularly distributed boulders across the fan, the ages of the different lobes can be identified. A sampling of boulders in an original depositional context was ensured by choosing boulders that were well embedded in the sediment of a levee, that had a minimal size of 1.5m and that showed no tendency to a strong brittle weathering. To minimize the shielding effect, only boulders with an inclination of the upper surface below 20° were included. The boulders are further examined in terms of lithology, shape and size and degree of weathering. This data will be combined with a remote analysis of the bedrock in the catchment areas for evidence of past or future failure. The findings of these investigations may provide understanding into the mechanisms that control the spatial and temporal evolution of debris-flow fans, which is necessary to assess the future development of fans and their potential risk for human settlements.

With this I would like to thank sincerely for the financial support of CH-QUAT, which allowed the realization of the field work for my master thesis in the summer/autumn 2020. Thank you very much, CH-QUAT!

Contact:
Ladina Hügli
lhuegli@student.ethz.ch

L. Hügli
L. HügliBild: L. Hügli & M. Caduff

Isabelle Pfister / Departement of Earthsciences / ETH Zürich, Switzerland

Geomorphological mapping and denudation of the Sèche de Gimel, VD

The Sèche de Gimel is a vast karst outcrop in the Jurassic strata of the Swiss Jura Mountains, which was covered by a glacier in the late Pleistocene glaciation. The vast occurrence of karst features in the region and the surprisingly low glacial erosion rate on the carbonate substratum compared to crystalline bedrock leads to the question to which extend landscape evolution is affected by karst dissolution. Thus, the Sèche de Gimel offers a suitable location to examine the influence and importance of karst and glacial erosion relative to each other.

The financial contribution of CH-QUAT allowed me to work five days in the field during my Bachelor’s Thesis. During this time, a detailed mapping of the geomorphological features (karst and glacial) was performed. Further, denudation experiments on a bare lying karren field (with and without contact to soil formation) were carried out. This provided information about the limestone denudation rate in this area. Later, a geomorphological map was produced with ArcGIS Pro.

Contact:
Isabelle Pfister
Isabelle Pfister pfisteri@student.ethz.ch

I. Pfister
I. PfisterBild: A. Schnyder & I. Pfister

Patricia Hug / Departement of Earth Sciences / ETH Zürich, Switzerland

Holocene rock avalanches and evolution of the polygenic Frébouze cone, Val Ferret Mont Blanc Massif

The Mont Blanc Massif presents a striking, glacially scoured high-relief topography; when combined with steep slopes and fractured rock walls, high rates of gravitational movements, such as rock avalanches, are inevitable. The focus of my MSc thesis is on deciphering the evolution of the Frébouze polygenic cone in the Italian part of the Val Ferret. The cone is built-up of rock avalanche and debris flow material, glacial sediments, but also debris delivered by ice, snow avalanches and rockfalls. To identify the evolution, several landscape reconstruction tools are combined.

I’m very grateful for the cost contribution of CH-QUAT which supported me with the costs of the ten days lasting fieldwork in August. During this time, detailed geomorphological mapping and sedimental description were performed. Furthermore, drone images were taken in order to get a high resolution orthophoto and DEM for additional mapping. Finally, samples were taken on different geomorphological features (debris flows, moraines, rock avalanche) and are dated with cosmogenic radionuclides in autumn 2020 to get a deeper insight in the temporal evolution of the cone. Later, the rock avalanche will be modelled using Dan3D runout modelling to compare possible release areas to the distribution of the rock avalanche deposits.

Contact:
Patricia Hug
Patricia Hug hugp@student.ethz.ch

P. Hug
P. HugBild: P.Deline & N. Akçar

Adeline Cojean / Biogeochemistry, Center for Hydrogeology and Geothermics (CHYN)/ University of Neuchatel, Switzerland

My project consists of investigating the different pockmark systems (e.g. crater-like depressions formed by upward transport of fluid through the unconsolidated sediment column) located in Lake Thun, Switzerland. In contrast to the marine realm, pockmark systems in lakes are much less investigated. By using a multidisciplinary approach (sedimentology, geology, biogeochemistry, and microbiology), we aimed to better understand the mechanism of formation of these pockmarks and quantify their potential influence on the lake hydrological and biogeochemical budget.

The financial support from CH-QUAT allowed me to participate in a 2-day conference (“Pockmarks et Ecosystèmes Benthiques”, Paris) specialized on pockmarks. During this conference, I have presented my research in front of many researchers from different fields, as well as participated in workshops during which we brought together our knowledge to identify the proxies that can be used to investigate pockmarks in marine and lacustrine environments. Thanks to the CH-QUAT and this conference, I have received relevant inputs that will be useful to develop my project further.

Contact:
Adeline Cojean
Adeline.cojean(at)unine.ch

A. Cojean
A. CojeanBild: J. Venetz & A. Cojean