The relatively steep continental slope offshore north Norway (3–7°) is dissected by several valleys (e.g. Taylor et al. 2000; Rise et al. 2013), none of which is related to coastal rivers opening into the fjords dominating the coast (Corner 2005). Two end-member valley forms have been identified: (1) classical submarine canyons characterized by a V-shaped cross-section, which can be followed from the shelf edge to the base of the continental slope where they continue as deep-sea channels; and (2) steep-sided, flat-floored valleys, some of uniform width, others widening upslope, some of which can be followed upslope to the shelf break while others have their headwalls located further downslope; debris-flow lobes occur beyond their downslope terminations (Rise et al. 2013). The Andoya Canyon (Fig. 1) exemplifies the morphology of the classical submarine canyons on the Lofoten–Vesteralen margin (Laberg et al. 2007). The canyon is about 40 km long (from the headwall to 2100 m water depth), about 9 km wide between the canyon shoulders and the maximum incision is …