Doctoral defence in Environmental studies - Daniel Ben-Yehoshua
Aðalbygging
The Aula
Doctoral candidate: Daniel Ben-Yehoshua
Title of thesis: The effect of glacier retreat on paraglacial slope stability. On the dynamics of slope instabilities around Svínafellsjökull, Southeast Iceland.
Opponents:
Dr. Michel Jaboyedoff, Professor at the Faculty of Geosciences and Environment, University of Lausanne, Switzerland.
Dr. Daniel Shugar, Associate Professor at the Department of Geosciences, University of Calgary, Canada.
Advisors: Dr. Sigurður Erlingsson, Professor at the Faculty of Civil and Environmental Engineering, University of Iceland
Dr. Þorsteinn Sæmundsson, Adjunct at the Faculty of Faculty of Life and Environmental Sciences, University of Iceland
Other members of the doctoral committee:
Dr. Reginald L. Hermanns, Professor at the Department of Geology and Mineral Resources Engineering, Norwegian University of Science and Technology and Senior Researcher at the Geological Survey of Norway
Dr. Eyjólfur Magnússon, Research Scientist at the Institute of Earth Sciences, University of Iceland
Dr. Tómas Jóhannesson, Coordinator of Glaciological Research at the Icelandic Meteorological Office
Dr. Pascal Lacroix, Researcher at the Institute of Earth Sciences, University of Grenoble, France.
Chair of Ceremony: Dr. Hrund Ólöf Andradóttir, Professor and Head of the Faculty of Civil and Environmental Engineering, University of Iceland
Abstract
Since the end of the Little Ice Age, around 1890, glacial thinning has exposed recently eroded mountain slopes around Iceland’s outlet glaciers. During a period of rapid thinning between 1995 and 2011 several slope instabilities appeared around the Svínafellsjökull outlet glacier in Southeast Iceland. The first part of this study focuses on a debris avalanche which occurred in February 2013. The source area, a sediment complex made of moraine and talus material, was gradually exposed by glacial retreat prior to its failure. On February 25th and 26th, 2013 a record-breaking rainstorm caused flooding across southeast Iceland and about 24 hours after the main precipitation event the debris avalanche occurred. The debris covered about 1.7 km2 of the Svínafellsjökull glacier surface, insulating it from surface ablation since 2013. Right above these debris deposits lies the largest slope instability in the valley and one of the largest known in Iceland. It is located on a slope named Svarthamrar and is defined by a ca 2-km-long fracture system that cuts across the northernmost part of the mountain. The surface fractures started to develop in the mid-2000s, and the slope deformed until 2018. Since then, the slope hasn’t shown significant signs of movement. The apparent correlation between glacier thinning and slope movement in the mid-2000s and the halt of slope deformation following slowdown of glacier-surface lowering after 2013, strongly suggests that the glacier load on the subglacial slope affects the slope deformation. Modelling results confirm that glacial unloading has a significant destabilizing effect on the slope. This destabilization may be counteracted by drawdown of the water table in the paraglacial slope. Rapid glacier thinning might have led to a period of transiently higher hydraulic gradients in the paraglacial slopes, causing reduced slope stability until readjustment of the groundwater table in the late 2010s.
About the doctoral candidate
Daniel finished his bachelor’s degree in Earth Sciences at the University of Freiburg in Germany in 2014. In autumn of the same year he started the Master in Geology program at the University of Iceland and as a guest master student at the University Center in Svalbard. From 2017 he worked as a drone technician and surveyor at the local startup Svarmi until starting his PhD project in 2020. Since June 2024, he has been working at Efla Consulting Engineers here in Reykjavík in natural hazard mitigation and surveying.
Doctoral defence in Environmental studies - Daniel Ben-Yehoshua