The coasts of the Norwegian Sea were shaped during the last Ice Age. Large glaciers several kilometres high pushed into the land, forming fjords, removing the crust into the sea, and thereby extending the continental slopes. This is particularly clear off the Norwegian coast along Helgeland and north to the Lofoten Islands. The Norwegian continental shelf is between 40 and 200 kilometres wide, and has a different shape from the shelves in the North Sea and Barents Sea. It contains numerous trenches and irregular peaks, which usually have an amplitude of less than 100 metres, but can reach up to 400 metres. They are covered with a mixture of gravel, sand, and mud, and the trenches are used by fish as spawning grounds. Deeper into the sea, there are two deep basins separated by a low ridge (its deepest point at 3,000 m) between the Vøring Plateau and Jan Mayen island. The southern basin is larger and deeper, with large areas between 3,500 and 4,000 metres deep. The northern basin is shallower at 3,200-3,300 metres, but contains many individual sites going down to 3,500 metres. Submarine thresholds and continental slopes mark the borders of these basins with the adjacent seas. To the south lies the European continental shelf and the North Sea, to the east is the Eurasian continental shelf with the Barents Sea. To the west, the Scotland-Greenland Ridge separates the Norwegian Sea from the North Atlantic. This ridge is on average only 500 metres deep, only in a few places reaching the depth of 850 metres. To the north lie the Jan Mayen Ridge and Mohns Ridge, which lie at a depth of 2,000 metres, with some trenches reaching depths of about 2,600 meters.. Which basin is more shallow, the southern basin or the northern basin?