Fjord

In physical geography, a fjord (also spelled fiord in New Zealand English; /ˈfjɔːrd, fiːˈɔːrd/ ⓘ[1]) is a long, narrow sea inlet with steep sides or cliffs, created by a glacier.

[4][5] A true fjord is formed when a glacier cuts a U-shaped valley by ice segregation and abrasion of the surrounding bedrock.

Fjords generally have a sill or shoal (bedrock) at their mouth caused by the previous glacier's reduced erosion rate and terminal moraine.

These characteristics distinguish fjords from rias (such as the Bay of Kotor), which are drowned valleys flooded by the rising sea.

Drammensfjorden is cut almost in two by the Svelvik "ridge", a sandy moraine that was below sea level when it was covered by ice, but after the post-glacial rebound reaches 60 m (200 ft) above the fjord.

[9] In the 19th century, Jens Esmark introduced the theory that fjords are or have been created by glaciers and that large parts of Northern Europe had been covered by thick ice in prehistory.

John Walter Gregory argued that fjords are of tectonic origin and that glaciers had a negligible role in their formation.

[12] Preglacial, tertiary rivers presumably eroded the surface and created valleys that later guided the glacial flow and erosion of the bedrock.

Offshore wind, common in the fjord areas during winter, sets up a current on the surface from the inner to the outer parts.

[16] Bolstadfjorden has a threshold of only 1.5 m (4 ft 11 in) and strong inflow of freshwater from Vosso river creates a brackish surface that blocks circulation of the deep fjord.

In the deeper parts of the fjord the cold water remaining from winter is still and separated from the atmosphere by the brackish top layer.

The marine life on the reefs is believed to be one of the most important reasons why the Norwegian coastline is such a generous fishing ground.

Most are specially adapted to life under the greater pressure of the water column above it, and the total darkness of the deep sea.

By this channel, one can travel through a protected passage almost the entire 1,601 km (995 mi) route from Stavanger to North Cape, Norway.

The Inside Passage provides a similar route from Seattle, Washington, and Vancouver, British Columbia, to Skagway, Alaska.

In polar fjords, glacier and ice sheet outflow add cold, fresh meltwater along with transported sediment into the body of water.

In addition to nutrient flux, sediment carried by flowing glaciers can become suspended in the water column, increasing turbidity and reducing light penetration into greater depths of the fjord.

This effect can limit the available light for photosynthesis in deeper areas of the water mass, reducing phytoplankton abundance beneath the surface.

The word fjord is borrowed from Norwegian, where it is pronounced [ˈfjuːr], [ˈfjøːr], [ˈfjuːɽ] or [ˈfjøːɽ] in various dialects and has a more general meaning, referring in many cases to any long, narrow body of water, inlet or channel (for example, see Oslofjord).

[27][29] The Norse noun fjǫrðr was adopted in German as Förde, used for the narrow long bays of Schleswig-Holstein, and in English as firth "fjord, river mouth".

[33] The use of the word fjord in Norwegian, Danish and Swedish is more general than in English and in international scientific terminology.

In Scandinavia, fjord is used for a narrow inlet of the sea in Norway, Denmark and western Sweden, but this is not its only application.

This word has survived only as a suffix in names of some Scandinavian fjords and has in same cases also been transferred to adjacent settlements or surrounding areas for instance Hardanger, Stavanger, and Geiranger.

Examples include: Some Norwegian freshwater lakes that have formed in long glacially carved valleys with sill thresholds, ice front deltas or terminal moraines blocking the outlet follow the Norwegian naming convention; they are frequently named fjords.

The resulting landform is an isthmus between the lake and the saltwater fjord, in Norwegian called "eid" as in placename Eidfjord or Nordfjordeid.

[45][46] Such deposits are valuable sources of high-quality building materials (sand and gravel) for houses and infrastructure.

[46] Another example is the freshwater fjord Movatnet (Mo lake) that until 1743 was separated from Romarheimsfjorden by an isthmus and connected by a short river.

During a flood in November 1743, the river bed eroded and sea water could flow into the lake at high tide.

At the time of the Vikings Drammensfjord was still four or five m (13 or 16 ft) higher than today and reached the town of Hokksund, while parts of what is now the city of Drammen was under water.

Along the British Columbia Coast, a notable fjord-lake is Owikeno Lake, which is a freshwater extension of Rivers Inlet.