A coastline defined by fjords is one of the most rugged and beautiful in the world. A fjord or fiord is a narrow steep sided valley formed by a glacier. The word is of Scandinavian origin and was originally used in naming these features on the Scandinavian coastline. The word is now used globally where similar valleys are seen in places such as North Western America, Canada, New Zealand and Chile. It has also been used mistakenly to name some drowned river valleys such as the Lim Fjord in Istria which was in fact dug by the river Pazinica not a glacier. Fjords can be very long and deep, the Sognafjord in Norway is 126 miles long and 4291 feet deep.
The fjords have a very distinctive U shaped profile as opposed to valleys formed by rivers which have a more V shaped profile. Repeated freeze thawing at the base and sides of the glacier caused by seasonal temperature variations and the pressure of the ice causes the bedrock to fracture yielding sharp, angular pieces of rock. These rock fragments are incorporated into the ice at the sides and base of the glacier and there they can grind the bedrock deepening the valley and shaping its' sides. Fjords are most often seen on the western coasts of land masses as the prevailing winds lead to a greater snowfall on these coasts leading to more prominent glaciers.
The individual glaciers which carved these fjords were formed in mountainous highlands. Lowland areas subjected to an ice age are covered by ice sheets which tend to flatten existing topographic features rather than carve new ones. Many of the fjords in the Finnish area of Northern Norway, while containing very deep water lack the high walls, above sea level, of those seen further South as the area was totally covered by an ice sheet during part of the ice age.
At the end of the last ice age the ice retreated now only being found, year round, on higher mountains and in the Polar Regions. When a glacier retreats the rocks carried by it are dumped as a terminal moraine, this can sometimes be found forming a sill at the entrance to the fjord with deeper water further inland. The presence of such a sill can cause extremely rapid sea water currents and rapids within the fjord.
As the ice cap on a land mass melts the land starts to rise in a process called isostatic post-glacial rebound. In Norway this process has lead to the terminal moraine sill of some fjords rising above sea level thus forming a freshwater fjord. Deep freshwater lakes, formed by glacial processes, are found around the world, for example the inland lochs of Scotland, Lake Como on the Italy/Switzerland border and the Owikeno Lake in British Columbia were all formed by glacial processes.
Fjords in Norway have been found to be the home of deep cold water coral reefs. This is a recent discovery made in 2000 and is still requiring scientific study. It has been suggested that these reefs provide a valuable food source for the rich fishing grounds found around the Norwegian coast. Similar cold water coral reefs have been found in the fjords of New Zealand and can be seen in the underwater observatory at Milford Sound.
Over the centuries deep water fjords have provided safe anchorage for sea going vessels. The Vikings frequently used them as safe moorings for their long boats. More recently Nazi Germany utilised the Norwegian Fjords to anchor the vessels used to threaten the allied North Atlantic convoys. The Tirpitz, the largest battleship in the German Navy, spent most of the second world war in such fjords particularly Kafjord.