This paper is a condensed version of parts of a Dr. ing. thesis to be presented during 1983 (1). The first part of the paper deals with the regional distribution of iceberg scouring on the Norwegian continental shelf, and some general aspects related to it. The second part deals with iceberg scouring as a 1ocal phenomenon and its relation to the sea floor topography, sediment distribution, and geological and geotechnical properties of the sediments.
Iceberg scouring on the European side of the Atlantic Ocean was first reported in 1973 (2, 3). The investigations reported were carried out north and west of the British Isles (3) and in the vicinity of the Norwegian Trough (2). Belderson and Wilson (2) suggested that the iceberg plough marks also should be found in parts of the Norwegian slope and shelf areas shallower than 500 m. Later these features have been described from several areas of the Norwegian shelf (4,5,6,7,8).
In areas with scars made by grounding icebergs, they highly influence the sea floor conditions both With regard to the topography of the sea floor, and the geological and geotechnical properties of the sea floor sediments. These are all decisive factors, both with respect to technical solutions and economy, when structures or pipelines are to be installed on the shelf. The shapes and sizes of the scars vary considerably. They have been recorded more than 20 m deep, more than 250 m wide and several kilometres long. They are all fossil.
The map in Fig. 1 gives an overview over the distribution of iceberg scouring on the Norwegian shelf from about 58 N to about 72 N. The map is mainly based on side-scan sonar, boomer, and sparker records obtained during the Continental Shelf Institute's regional map- ping program. This program has a general profile grid (Fig. 2) where the main profiling directions broadly are perpendicular to the coast, and the crossing profiles run parallel to the coast. The distances between the main lines are about 10 km, and the crossing lines are about 25 km apart. Besides the information from this program, data from site surveys and other special investigations are also comprised.
As it can be seen from Fig. 1, large areas of the continental shelf are infested by iceberg scouring. As Belderson and Wilson (2) showed, there are iceberg scars on both sides of the Norwegian Trough (Figs. 1 and 3), but it is especially on the eastern slope of the trough and northward that we find the most intense scouring. Between the 61, parallel and the 71, parallel about 55% of the shelf shallower than 500 m are iceberg scoured. The iceberg scouring is mainly recorded in water depths between 100 m and 500 m. From the distribution map in Fig. 1, we can observe that, in general, the continental slope and the protruding banks on the shelf were most exposed to grounding icebergs.
