Marine landscape
Marine landscape mapping is concerned with identifying the main features in the seabed topography. The classification method used at NGU is based on habitat type (Naturtyper i Norge-NIN). Bathymetric data is our starting-point to determine which areas should be classified as plains, continental slopes, valleys, strand flats, etc. NGU employs a GIS-based mapping technique that uses low-resolution depth data and parameters that can be directly extracted thereby enabling us to identify the boundaries of a seabed feature in a reliable, reproducible and objective manner.
Norway is known for its fjords which were carved by glaciers that relentlessly moved across mainland Norway. The glacial erosion that took place at the mouth of the fjord was weaker, so that the fjord is shallower there than farther in. This geological feature serves to semi-isolate the water masses, resulting in a fjord ecosystem unique to that found in the open sea. Often found outside the mouth of the fjord is flat lowland and shallow waters. This landscape is called a strand flat, and is particularly well developed in the marine area surrounding Trøndelag and along the coastline where the strand flat can be up to 40 km wide.
The landscape on the continental shelf is dominated by marine valleys and separated by plains that are often called banks. Some of the marine valleys are continuations of the fjords, while the others start off the coast. The valleys are usually up to a few hundred meters deep, but can reach 700 metres, like the Norwegian Trench in the Skagerrak.
The continental slope, which lies between the continental shelf and deep ocean, is relatively uniform. The slope is transected by submarine canyons in several places, some which are up to 1000 metres deep. The area of the continental slope outside Lofoten and Vesterålen is characterised by such canyons. Submarine slide scars with high escarpments are also commonly found on the slope. The biggest slide, "Storegga" which occurred 8200 years ago outside Møre, broke apart several thousand square kilometres of seabed.
Different biological communities may be found within the different submarine landscape types. Mud collects in the deepest recesses of the sea valleys, resulting in a soft bottom where organisms such as the sea-pen thrive. Currents and/or waves remove fine-grain material from the shallowest banks, leaving only sand, gravelpebbles and cobbles. These banks are populated by the characteristic hard-bottom fauna, like calciferous algae, sponges and sessile animals. Coral reefs may often occur along ridges protruding from the bottom of marine valleys, but they may also thrive in other sites with hard bottom and good conditions (e.g. currents that supply adequate nourishment).
