Modelling in-situ cosmogenic nuclide inventories for common landslide geometries
This Master's project was allocated to the student Lisbeth Vedå in the Master's intake of Autumn 2022 at the Master's program in Earth Sciences, UiB
Surface-exposure dating using in-situ cosmogenic nuclides is a popular tool for age determination and reconstruction of past ice-extent. Cosmogenic nuclides are increasingly used to estimate the timing of rock avalanche events and large rock-slope failures, mainly by dating surfaces of the large boulders on a deposit. While this usually works well for relatively old failure events in formerly glaciated areas, it can be associated with large and unknown uncertainties in non-glacial environments and for relatively young failure events. This is due to the distribution of boulders with prefailure concentrations of cosmogenic nuclides, i.e., inheritance. The effect of inheritance is not constant; it is shown to be greatest for very recent shallow failures on high-elevation surfaces with low event frequencies (Hilger et al. 2019).
Inheritance can, in theory, be detected by measurement of paired (e.g., Be-10 and C-14) or multiple cosmogenic nuclides, single-nuclide measurement of paired boulder-slope bedrock samples, and/or by independent dating. Either approach is resource demanding and, in most cases, not applicable. This makes estimates of inheritance near to impossible, causing inheritance to usually only be mentioned or briefly discussed, or to be neglected altogether. Therefore, attempts to quantify potential inherited cosmogenic nuclide concentrations are rarely done. To better assess the impact of pre-failure/prior-exposure concentrations of cosmogenic nuclides on age estimates, it would be advantageous to have a numerical tool that can 1) simulate the distribution of pre- and post-production rates for different theoretical landslide geometries, and 2) subsequently estimate the probability and intensity of inherited nuclide inventories in the deposits.
One of the aims of this project is to write a computer code that allows researchers to calculate the probability and intensity of inherited cosmogenic nuclide concentrations based on different theoretical failure models. This will be done by first creating a simple landslide geometry for which a production rate distribution is produced. The next step is to generate production rate distributions for different landslide geometries and volumes. This can then be used to compute the probability and intensity of inherited cosmogenic nuclide concentrations on the surface of landslide deposits as a function of different failure scenarios.
Another aim is to test the performance of theoretical approach by comparison with data from previously investigated sites. Many rock avalanche events in Norway and other alpine areas (e.g., European Alps, Patagonia) have been dated and their geological settings allow for the reconstruction of the events (e.g., Hermanns et al. 2017; Hilger et al. 2019). Ideally, the MSc candidate will participate in a field sampling campaign during the early summer of 2023, with subsequently getting the opportunity to become familiar with sample preparation techniques and analytical analyses.
Proposed course plan during the master's degree (60 ECTS):
GEOV112 Den faste jordas fysikk 10 sp
GEOV205 Geografiske informasjonssystem 10 sp
GEOV265 Global og anvendt geofysikk 10 sp
GEOV302 Datanalyse i geovitskap 10 sp
AG-346 Snow and avalanche dynamics (UNIS, mar.-apr. 2023) 10 sp
GEO-3135 Rock-slope failures: Geology, hazard and monitoring (UiT, aug.-sep. 2023) 10 sp
Field, lab and analysis
Field/lab work is not a requirement for this project, but preferred for a broader learning outcome of the project.