Investigations of slides at the upper continental slope off vesterålen, North Norway

Abstract

Multibeam bathymetry, high-resolution seismic profiles and sediment cores were collected from the upper continental slope outside Andøya, the northernmost island in Vesterålen, northern Norway (69°N). Eight small slides are identified at water depths between 500 and 800 m. These are linked to a larger slide related to the development of the Andøya Canyon by high resolution seismic. Slope angles adjacent to the headwalls of the small slides are 3-4° while slide deposits have accumulated where slope angles are 2-3°. The slides occurred in parallel-stratified glacial marine sediments, and three seismic horizons are interpreted. One of these horizons coincides with failure planes in four of the slides. A 12 m long core terminates above this level, but penetrates another horizon representing a slip plane in two of the slides. The core comprises silty clay with varying content of ice rafted debris. The upper slope shallower than 450 m appears stable although it may be up to 8° steep. Tension cracks up to 2 m deep on the lower slopes may suggest that deformation is active near the canyon systems. © Springer Science+Business Media B.V. 2012.