| Summary: | The 1996 Finneidfjord landslide, which took four human lives in northern Norway, initiated along a weak layer in the fjord-marine sediments before developing retrogressively across the shoreline. The integration of results from sediment cores, free-fall cone penetrometer tests and high-resolution 3D seismic data indicates that the slide-prone layer is a regional bed likely sourced from clay-slide activity in the catchment of the fjord. The sediments in this regional layer are softer and more sensitive than the typical bioturbated, fjord-marine deposits, which explains their role in slope instability. In addition, biogenic gas in the stratified event bed may further affect its geotechnical properties. Similar, fine-grained, stratified beds with comparable origin and properties occur in other Norwegian fjords. They are presum- ably also present along coastlines of other previously glaciated margins, where they could contribute to mass movements.
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