Formation of a large submarine crack during the final stage of retrogressive mass wasting on the continental slope offshore northern Norway

Abstract

High-resolution swath-bathymetry data integrated with sub-bottom profiles and single-channel seismics reveal an 18 km long, up to 1000 m wide and 10-15 m deep crack located approx. 4 km upslope from a slide scar on the continental slope off northern Norway. This crack is formed by subsidence of the sea-floor sediments to a depth of 120 m due to downslope movement of a ~80 km2 large sediment slab that represents the final stage of retrogressive mass wasting in this area. From its morphological freshness, the crack this is inferred to have formed sometime during the last 13 cal. ka BP. These findings add to our understanding of the origin of sea floor cracks on passive continental margins where explanations as slip of normal faults or gas expulsion from the dissociation of gas hydrates previously have been suggested for the formation of cracks in similar settings.