Keynote Lecture: The Jettan Rockslide—An Engineering Geological Overview

A recognised cluster of gravitational slope deformations in northern Norway is the result of a protracted geological history. A combination of nappe metamorphosis, strain localisation, basin extension, glacial loading and unloading and exposure to weathering has resulting in a significantly weakened rock mass. We present the engineering geology of one such site, the Jettan rockslide, compiled from existing studies and multiple field campaigns. We show that these geological processes manifest in the Jettan rockslide as mylonitic foliation, pervasive jointing and faulting, and ductile shear zones degraded by weathering. These structural factors accommodate the deformation at Jettan and contribute to the overall failure path. Channelised fluid flow through vertical joints and subhorizonal shear zones interplay with permafrost processes to reduce the strength of the presented failure path. These factors work together to form a failure hazard, which threatens to trigger a displacement wave, a scenario validated by the Holocene record and past performance.