Topic for a PhD project in the Cluster of Excellence “The Future Ocean”, Kiel, Germany.
Is the loss of sediment structure responsible for large submarine landslides at open
continental slopes?
Submarine landslides, or the gravity driven down-slope movement of material, represent the
largest mass flows on Earth. Historically, these landslides have caused devastating tsunamis, broke seafloor communication cables and seriously damaged offshore hydrocarbon exploration infrastructure. The scale of submarine landslides can exceed terrestrial events by two orders of magnitude. For instance, the Storegga Slide offshore Norway affected an area larger than Scotland and moved sufficient sediment to bury this area to a depth of 80 m. Remarkably, these events typically occur on nearly flat slopes of ~2° or even less, which makes them difficult to explain. For particular continental slopes with comparatively high sedimentation rates failure could be explained by high excess pore pressures due to rapid deposition and/or lateral fluid transfer. However, large submarine landslides also occur in areas where sediment accumulation is slow. Preliminary modelling shows that a zone of high compressibility is one way to cause slope instability in such settings. Stress-induced rapid loss of structure, which allows the sediment to maintain high porosity initially and is caused by inter-particle forces and the geometrical arrangement or fabric of the particles, may provide such high compressibility. This project aims to test this hypothesis by examining the mechanical behaviour of deep sea sediments and developing numerical models incorporating resultant sediment behaviour. We wish to understand how and why structure develops in marine sediments, and whether rapid loss of this structure can promote slope failures in locations worldwide. This will directly feed into the broader research direction “Dangerous Ocean” which is part of the excellence cluster “Future Ocean” ensuring that the results of the thesis are disseminated and become visible.
The main part of the project will use geomechanical modelling to explore the role of destructuring on the stability of continental slopes. The candidate will set up finite element models of continental slopes including layers of structured sediment using the commercial software package ABAQUS. The constraints and input parameters will be assembled from existing geotechnical and sedimentological data sets. Down-core Scanning Electron Microscopy imaging and petrographic microscope analysis (perfomed pre- and post-testing) will be used to investigate the onset of destructuring, and to characterise loss of structure with increasing burial depth in IODP cores. In addition, the candidate will analyse oedometer as well as direct and cyclic shear test data from a variety of sources to determine the degree of structure of various deep sea sediments. In this respect the project benefits from a close collaboration with Fugro GeoConsulting Limited, who perform engineering geological, geohazard and geotechnical appraisals for offshore oil and gas developments.
Hazard assessments for submarine landslides are difficult to quantify, mainly because the reason(s) for submarine slope failure are contentious. The project has the potential to significantly advance the current understanding of these reasons. Hence, this research may help to identify hazardous areas of potential future landslides, to protect the increasing population in coastal areas and increase safety of the new ventures in offshore human activities as a response to the growing demand on resources. The development of robust testing methodologies that can be used to inform credible, forward looking geohazard analyses will provide valuable tools for the offshore industry as a whole.
Training opportunities:
The project will be will be based at the GEOMAR Helmholtz Centre for Ocean Research Kiel, one of the leading marine research institutions in Europe and the world. The successful candidate will enroll in the Integrated School of Ocean Sciences of the Cluster of Excellence Future Ocean, where they will have access to a full range of research and generic training opportunities that are aimed to support the development as an independent researcher. The integrated geotechnical, sedimentological and numerical approach of this project leads to training over a wide range of methods and techniques, including soil mechanical principles required to understand and interpret geotechnical test results, geological datasets from the present-day ocean floor, and numerical modelling. This broad approach gives the doctoral candidate a solid base for a further career in either academia or industry. The candidate will have the opportunity for a short-term placement at Fugro GeoConsulting Limited in Wallingford to work on industry data to provide broader industry context for the study. The candidate will gain important international experience through frequent visits to the UK partners.
Essential skills: Numerate with a good degree in Earth Sciences or Geotechnical Engineering.
Desired skills: Experience in geotechnical testing and data analysis, numerical modelling, knowledge of FORTRAN.
Background reading:
Urlaub, M., Talling, P., & Zervos, A. (2014). A numerical investigation of sediment destructuring as a potential globally widespread trigger for large submarine landslides on low gradients. In Submarine Mass Movements and Their Consequences (pp. 177-188). Springer International Publishing.
Masson, D. G., Wynn, R. B., & Talling, P. J. (2010). Large landslides on passive continental margins: processes, hypotheses and outstanding questions. In Submarine mass movements and their consequences (pp. 153-165). Springer Netherlands.
Supervisors and partners:
Prof Christian Berndt and Dr Morelia Urlaub (GEOMAR Helmholtz Centre for Ocean Research Kiel, Geodynamics), Dr Peter Talling (National Oceanography Centre Southampton, Marine Geosciences)
Dr Antonis Zervos and Prof Chris Clayton (Engineering and the Environment, University of Southampton), Mike Clare (FUGRO, Engineering Geology and Geohazards).
Funding notes:
The candidate has to apply for a PhD position to the Cluster of Excellence “The Future Ocean”, Kiel, Germany. The application includes a scientific proposal of the here outlined research project, which should be written in consultation with the supervisors. More information regarding the proposal format, full application requirements and typical salaries can be found here: http://www.futureocean.org/en/cluster/postdoc_network/project-call/index3.php.
If you are interested, please contact Dr Morelia Urlaub (murlaub@geomar.de) no later than 06/02/2014. The final application deadline is 28/02/2014.
