Misplaced Pages

#4995

110-583: 59°03′N 11°24′E  /  59.050°N 11.400°E  / 59.050; 11.400 This Østfold location article is a stub . You can help Misplaced Pages by expanding it . This article about a location in Västra Götaland County , Sweden is a stub . You can help Misplaced Pages by expanding it . This article about a fjord in Norway is a stub . You can help Misplaced Pages by expanding it . Fjord In physical geography ,

220-614: A fjord (also spelled fiord in New Zealand English ; ( / ˈ f j ɔːr d , f iː ˈ ɔːr d / ) is a long, narrow sea inlet with steep sides or cliffs, created by a glacier . Fjords exist on the coasts of Antarctica , the Arctic , and surrounding landmasses of the northern and southern hemispheres. Norway's coastline is estimated to be 29,000 km (18,000 mi) long with its nearly 1,200 fjords, but only 2,500 km (1,600 mi) long excluding

330-532: A Germanic noun for a travel : North Germanic ferd or färd and of the verb to travel , Dutch varen , German fahren ; English to fare . As a loanword from Norwegian, it is one of the few words in the English language to start with the sequence fj . The word was for a long time normally spelled f i ord , a spelling preserved in place names such as Grise Fiord . The fiord spelling mostly remains only in New Zealand English , as in

440-588: A NW-dipping one beneath Laurentia. About 430 Ma accretion in the Southern Uplands and Ireland switched from being orthogonal (at a right angle) to a sinistrally (left-lateral) transpressive one as indicated by cleavage transecting folds counterclockwise. Turbidite deposition in the oceanic trench overlapped onto the Lakesman-Leinster terrane. Laurentia-Avalonia convergence and Iapetus Ocean subduction ceased by C. 420 Ma as indicated by

550-823: A collision with a continental fragment. The Shelveian Orogeny occurred particularly in the Shelve area in Shropshire , in eastern Wales and in the English Midlands in the Late Ordovician and was related to the Taconic orogeny . It formed the Shelve Anticline and Rytton Castle Syncline and was the most important tectonic event in the area between the Cambrian and Devonian . Folding

660-628: A common Germanic origin of the word. The landscape consists mainly of moraine heaps. The Föhrden and some "fjords" on the east side of Jutland, Denmark are also of glacial origin. But while the glaciers digging "real" fjords moved from the mountains to the sea, in Denmark and Germany they were tongues of a huge glacier covering the basin of which is now the Baltic Sea. See Förden and East Jutland Fjorde . Whereas fjord names mostly describe bays (though not always geological fjords), straits in

770-451: A fjord as a kind of sea ( Māori : tai ) that runs by a bluff ( matapari , altogether tai matapari "bluff sea"). The term "fjord" is sometimes applied to steep-sided inlets which were not created by glaciers. Most such inlets are drowned river canyons or rias . Examples include: Some Norwegian freshwater lakes that have formed in long glacially carved valleys with sill thresholds, ice front deltas or terminal moraines blocking

880-456: A glacial river flows in. Velfjorden has little inflow of freshwater. In 2000, some coral reefs were discovered along the bottoms of the Norwegian fjords. These reefs were found in fjords from the north of Norway to the south. 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. Since this discovery

990-421: A highly productive group of phytoplankton that enable such fjords to be valuable feeding grounds for other species. It is possible that as climate change reduces long-term meltwater output, nutrient dynamics within such fjords will shift to favor less productive species, destabilizing the food web ecology of fjord systems. In addition to nutrient flux, sediment carried by flowing glaciers can become suspended in

1100-527: A late Caledonian phase and as having been driven by the closure of the Iapetus Ocean . However, there is also an argument that it would more appropriate to regard it as a proto- Variscan orogeny. This is because this Devonian event postdated the collision of Avalonia with Laurentia by 15–20 million years and was coeval with the early phase of the Variscan orogeny (Eo-Variscan or Ligerian) and because it

1210-529: A long, narrow inlet. In eastern Norway, the term is also applied to long narrow freshwater lakes ( Randsfjorden and Tyrifjorden ) and sometimes even to rivers (for instance in Flå Municipality in Hallingdal , the Hallingdal river is referred to as fjorden ). In southeast Sweden, the name fjard fjärd is a subdivision of the term 'fjord' used for bays, bights and narrow inlets on

SECTION 10

#1732780652005

1320-468: A mid- Silurian weakening of deformation in the accretionary wedge. Magma production should be larger in convergent tectonic regimes during subduction and markedly reduced with the change to post-subduction collisional regimes. However, during Iapetus subduction (455–425 Ma) this was low and intrusive rocks were largely absent across all terranes in the concerned area in this period. Most Acadian magmatism occurred post-subduction (425-390 Ma) in

1430-544: A narrower sound is called sund . In the Finnish language , a word vuono is used although there is only one fjord in Finland. In old Norse genitive was fjarðar whereas dative was firði . The dative form has become common place names like Førde (for instance Førde ), Fyrde or Førre (for instance Førre ). The German use of the word Föhrde for long narrow bays on their Baltic Sea coastline, indicates

1540-500: A protected passage almost the entire 1,601 km (995 mi) route from Stavanger to North Cape , Norway. The Blindleia is a skerry-protected waterway that starts near Kristiansand in southern Norway and continues past Lillesand . The Swedish coast along Bohuslän is likewise skerry guarded. The Inside Passage provides a similar route from Seattle , Washington , and Vancouver , British Columbia , to Skagway , Alaska . Yet another such skerry-protected passage extends from

1650-420: A regional tectonic setting with alternating transpression and transtension phases. High rates of magma generation coincided with a c. 418–404 Ma Early Devonian sinistral transtension phase. This decreased during the 404–394 Ma Acadian transpression. In addition, the Southern Uplands accretionary wedge lacks evidence of the presence of a volcanic arc as usually found near subduction zones. This has led to

1760-752: A series of tectonically related events. In the Neoproterozoic most of the Earth's landmasses were united in the Rodinia supercontinent . The majority of its bulk consisted of the landmass of Gondwana . Near the end of the Neoproterozoic, during the breakup of this supercontinent, Laurentia and Baltica rifted from the western ( Amazonian craton ) and northern (African) margins of Gondwana respectively. Laurentia first drifted westward away from Gondwana and then migrated northward. This led to

1870-523: A sill or shoal (bedrock) at their mouth caused by the previous glacier's reduced erosion rate and terminal moraine . In many cases this sill causes extreme currents and large saltwater rapids (see skookumchuck ). Saltstraumen in Norway is often described as the world's strongest tidal current . These characteristics distinguish fjords from rias (such as the Bay of Kotor ), which are drowned valleys flooded by

1980-585: A stretching lineation perpendicular to the fold hinges. The Southern Belt and the rest of the Central belt underwent sinistral transpression . This reflects a Late Ordovician – Silurian change from an orthogonal to an oblique tectonic plate collision. In the Central Belt the cleavage transects folds in a clockwise sense and is accompanied by a sub-horizontal stretching lineation. In the Southern belt

2090-675: 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 . The differences in usage between the English and the Scandinavian languages have contributed to confusion in the use of the term fjord. Bodies of water that are clearly fjords in Scandinavian languages are not considered fjords in English; similarly bodies of water that would clearly not be fjords in

2200-535: A transition from orthogonal compression to transpression during the later stages of Acadian deformation. This makes the island more similar to the Southern Uplands terrane of Scotland than the Lake District inlier in this respect. In Ireland the Acadian Orogeny affected the four main terranes of the island: Grampian, Midland Valley, Longford-Down and Leinster. Tectonic deformation was mild as

2310-641: A westward direction. The combined convergence of this microcontinent and the two continents created continental collisions between them, the mentioned orogenic events and the closure of the Iapetus and Tornquist oceans. Continental collisions started in the Mid Silurian and mountain building and ended in the Early Devonian (420–405 Ma). The Grampian orogeny involved collisions between two landmasses of Laurentia and an oceanic island arc in

SECTION 20

#1732780652005

2420-653: Is 160 m (520 ft) deep with a threshold of only 1.5 m (4 ft 11 in), while the 1,300 m (4,300 ft) deep Sognefjorden has a threshold around 100 to 200 m (330 to 660 ft) deep. Hardangerfjord is made up of several basins separated by thresholds: The deepest basin Samlafjorden between Jonaneset ( Jondal ) and Ålvik with a distinct threshold at Vikingneset in Kvam Municipality . Hanging valleys are common along glaciated fjords and U-shaped valleys . A hanging valley

2530-582: Is 2,000 m (6,562 ft) below the surrounding regional topography. Fjord lakes are common on the inland lea of the Coast Mountains and Cascade Range ; notable ones include Lake Chelan , Seton Lake , Chilko Lake , and Atlin Lake . Kootenay Lake , Slocan Lake and others in the basin of the Columbia River are also fjord-like in nature, and created by glaciation in the same way. Along

2640-483: Is a tributary valley that is higher than the main valley and was created by tributary glacier flows into a glacier of larger volume. The shallower valley appears to be 'hanging' above the main valley or a fjord. Often, waterfalls form at or near the outlet of the upper valley. Small waterfalls within these fjords are also used as freshwater resources. Hanging valleys also occur underwater in fjord systems. The branches of Sognefjord are for instance much shallower than

2750-598: Is a large basement massif. It is part of a magmatic belt which, starting from the Lake District , to the north of this massif, bears record of the subduction of part of the Tornquist Sea beneath Avalonia and its closure. The closure of the Rheic Ocean , which took place soon after, occurred through subduction along the southern margin of this massif. The Trans-European Suture Zone or Tornquist Zone

2860-412: Is also often described as a fjord, but is actually a freshwater lake cut off from the sea, so is not a fjord in the English sense of the term. Locally they refer to it as a "landlocked fjord". Such lakes are sometimes called "fjord lakes". Okanagan Lake was the first North American lake to be so described, in 1962. The bedrock there has been eroded up to 650 m (2,133 ft) below sea level, which

2970-436: Is an exposed N–S trending thrust zone which marks the western limit of intense Caledonian deformation. The dominant structures are interpreted as having resulted from sinistral transpression , which involved strain partitioning of regional deformation between sinistral strike-slip movements in the east and NW-directed oblique thrusting and folding further to the west. This orogenic event also affected Scotland and

3080-430: Is at least 500 m (1,600 ft) deep and water takes an average of 16 years to flow through the lake. Such lakes created by glacial action are also called fjord lakes or moraine-dammed lakes . Some of these lakes were salt after the ice age but later cut off from the ocean during the post-glacial rebound . At the end of the ice age Eastern Norway was about 200 m (660 ft) lower (the marine limit). When

3190-456: 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 ). The Norwegian word is inherited from Old Norse fjǫrðr , a noun which refers to a 'lake-like' body of water used for passage and ferrying and

3300-620: Is closely related to the noun ferð "travelling, ferrying, journey". Both words go back to Indo-European *pértus "crossing", from the root *per- "cross". The words fare and ferry are of the same origin. The Scandinavian fjord , Proto-Scandinavian * ferþuz , is the origin for similar Germanic words: Icelandic fjörður , Faroese fjørður , Swedish fjärd (for Baltic waterbodies), Scots firth (for marine waterbodies, mainly in Scotland and northern England). The Norse noun fjǫrðr

3410-589: Is composed mainly of the Manx Group and the Dalby Group which were deformed in a sinistral transpression zone during the sinistral, oblique closure of the Iapetus Ocean. Folds are transected clockwise by their cleavage , major strike-parallel sinistral faults and ductile shear zones thought to be related to this transpression. All primary folds have the same style and are associated with

Iddefjord - Misplaced Pages Continue

3520-653: Is fairly new, little research has been done. The reefs are host to thousands of lifeforms such as plankton , coral , anemones , fish, several species of shark, and many more. Most are specially adapted to life under the greater pressure of the water column above it, and the total darkness of the deep sea. New Zealand's fjords are also host to deep-water corals , but a surface layer of dark fresh water allows these corals to grow in much shallower water than usual. An underwater observatory in Milford Sound allows tourists to view them without diving. In some places near

3630-976: Is indicated by the absence of orogenic structures or high-pressure metamorphic rocks , which are either not present or buried. This event occurred close to the end of the Ordovician , 440 Ma. It docked with the Baltica margins in southern Denmark , the south-western corner of the Baltic Sea and Poland . It came to comprise Silesia in Poland , northern Germany , the Netherlands , Belgium and part of north-eastern France (the Ardennes Mountains). The Anglo-Brabant massif or London-Brabant Massif in central and southern England and in Belgium

3740-505: Is located on the southern shore of Lake Superior in Michigan . The principal mountainous regions where fjords have formed are in the higher middle latitudes and the high latitudes reaching to 80°N (Svalbard, Greenland), where, during the glacial period, many valley glaciers descended to the then-lower sea level. The fjords develop best in mountain ranges against which the prevailing westerly marine winds are orographically lifted over

3850-597: Is the area of the suture of Baltica and Eastern Avalonia. It runs from a portion of the North Sea close to Denmark , through southern Denmark, a portion of the Baltic Sea between Denmark and Poland (by Germany's Rügen Island), and through Poland. It then follows the eastern margin of the Eastern Carpathian Mountains in western Ukraine . Finally, it runs to the Black Sea . However, in

3960-470: 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. Eventually, Movatnet became a saltwater fjord and renamed Mofjorden ( Mofjorden ). Like fjords, freshwater lakes are often deep. For instance Hornindalsvatnet

4070-409: Is the isthmus with a village between Hornindalsvatnet lake and Nordfjord . Such lakes are also denoted fjord valley lakes by geologists. One of Norway's largest is Tyrifjorden at 63 m (207 ft) above sea level and an average depth at 97 m (318 ft) most of the lake is under sea level. Norway's largest lake, Mjøsa , is also referred to as "the fjord" by locals. Another example

4180-793: Is the toe end of the Southern Uplands turbidite accretionary wedge onlapping or thrust onto the Avalonia continental margin. The broad deformation style and age of the Manx Group are very similar to the equivalent features of the Skiddaw Group in the Lake District and the Ribband Group in SE Ireland. This group is thought to be their regional equivalent. It underwent two main deformation phases which also affected

4290-410: Is usually a large inflow of river water in the inner areas. This freshwater gets mixed with saltwater creating a layer of brackish water with a slightly higher surface than the ocean which in turn sets up a current from the river mouths towards the ocean. This current is gradually more salty towards the coast and right under the surface current there is a reverse current of saltier water from the coast. In

4400-676: The Anglo-Scottish border . It consists of a series of faults with no traces of subduction , such as ophiolite remnants or oceanic trench -derived rocks. The Iapetus Suture also extends along the margin of the Baltoscandian platform of the Fennoscandian Peninsula which collided with the eastern margin of Greenland along the eastern margin of Laurentia in the Scandian orogeny. According to some authors,

4510-636: The British Columbia Coast , a notable fjord-lake is Owikeno Lake , which is a freshwater extension of Rivers Inlet . Quesnel Lake , located in central British Columbia, is claimed to be the deepest fjord formed lake on Earth. A family of freshwater fjords are the embayments of the North American Great Lakes. Baie Fine is located on the northwestern coast of Georgian Bay of Lake Huron in Ontario , and Huron Bay

Iddefjord - Misplaced Pages Continue

4620-881: The Great Glen Fault which affected the Moine Supergroup and the Dalradian rocks in Scotland and the Shetland Islands through the Walls Boundary Fault , which is the northeast-ward extension of the Great Glen Fault. As mentioned above, the British Isles were separated and belonged to two different tectonic plates: Laurentia ( Scotland and northern and western Ireland ) and Avalonia ( England and Wales and

4730-675: The Maritime Provinces of Canada has been applied to the early Devonian deformation phase in the British Caledonides by analogy with the one that occurred in what is now North America . Late Caledonian orogeny is another term used in reference to this phase. This phase involved a soft docking or soft collision rather an orogen -causing hard continental collision like the Eastern Avalonia docking with Baltica. This orogenic event has been interpreted as

4840-459: The Scandinavian sense of the term, are not universally considered to be fjords by the scientific community, because although glacially formed, most Finnmark fjords lack the steep-sided valleys of the more southerly Norwegian fjords. The glacial pack was deep enough to cover even the high grounds when they were formed. The Oslofjord , on the other hand, is a rift valley , and not glacially formed. The indigenous Māori people of New Zealand see

4950-710: The Scandinavian Caledonides . The first phase that is often included in the Caledonian orogeny is the Finnmarkian Orogeny, which was an early deformation event in Arctic (northern) Norway which preceded the Scandian phase (see below) in this area. Its onset has been dated at c. 500 Ma (Late Cambrian ). It continued to c. 460 Ma and was reactivated in the Scandian phase at ~425–415 Ma. According to van Roermund and Brueckner (2004), there

5060-613: The Straits of Magellan north for 800 km (500 mi). Fjords provide unique environmental conditions for phytoplankton communities. In polar fjords, glacier and ice sheet outflow add cold, fresh meltwater along with transported sediment into the body of water. Nutrients provided by this outflow can significantly enhance phytoplankton growth. For example, in some fjords of the West Antarctic Peninsula (WAP), nutrient enrichment from meltwater drives diatom blooms,

5170-718: The Sudetes Mountains and the Eastern Carpathians, it evolved through the Variscan and the Alpine orogenies, rather than the Caledonian one. The Scandian phase involved a collision between eastern Greenland on the eastern margin of Laurentia and the margin of the Baltoscandian platform of the Fennoscandian peninsula of Baltica. It involved the Scandinavian Caledonides in what is now Norway and

5280-543: The Viking settlers—though the inlet at that place in modern terms is an estuary , not a fjord. Similarly the name of Milford (now Milford Haven) in Wales is derived from Melrfjǫrðr ("sandbank fjord/inlet"), though the inlet on which it is located is actually a ria. Before or in the early phase of Old Norse angr was another common noun for fjords and other inlets of the ocean. This word has survived only as

5390-469: The opening of the Iapetus Ocean between Laurentia, Baltica and Gondwana. Its initial opening phase was between the adjacent Laurentia and Baltica (to the West and East respectively) and caused the two to breakup c. 615 Ma or 590 Ma. Then the part between Laurentia and Gondwana (to the east), opened c. 550 Ma. Further spreading of the Iapetus Ocean also caused Laurentia and Baltica to move away from each other. Baltica drifted northward, too. This involved

5500-419: The Caledonian continental collisions involved another microcontinent, Armorica (southern Portugal , most of the north of France and parts of southern Germany and the Czech Republic ), even smaller than Avalonia. This microcontinent probably did not form one consistent unit, but was instead a series of fragments, of which the current Armorican and Bohemian Massifs are the most important. The ocean between

5610-444: The Caledonian event as one of several episodic phases of mountain building that had occurred during Earth's history . Current understanding has it that the Caledonian orogeny encompasses a number of tectonic phases that can laterally be diachronous , meaning that different parts of the mountain range formed at different times. The name "Caledonian" can therefore not be used for an absolute period of geological time, it applies only to

SECTION 50

#1732780652005

5720-452: The Dalby Group: a) a pervasive slaty cleavage associated with gently to moderately plunging folds which also affected many of the minor igneous intrusions , b) a gently dipping crenulation cleavage associated with small folds verging towards the bedding dip direction. There are several ductile shear zones which run subparallel to the Manx Group northeast-oriented boundary faults which indicate predominantly sinistral shear and possibly

5830-411: The Iapetus Ocean orthogonally (at a right angle ). Its drift included an up to 55° counterclockwise rotation with respect to the subduction zone to its north, mainly in the 470–450 Ma timeframe. It moved significantly faster than Baltica but slowed down to a rate comparable to that of the latter in the Late Ordovician when it got close to it. The main phases of the Caledonian orogeny resulted from

5940-427: The Iapetus Ocean outboard the main margin of the Laurentia tectonic plate (the future North America). There two Laurentian landmasses were Scotland and northern and western Ireland . The other parts of the British Isles ( England and Wales and the rest of Ireland) were part of the Avalonia microcontinent. Two parts of Avalonia have been distinguished, a western and an eastern one. The term Western Avalonia refers to

6050-429: The Lakesman terrane and north Wales . Transpression resulted in regionally clockwise transecting sinistral transpressive cleavages which were superimposed on pre-existing structures. Folding northwest of the Iapetus Suture is weak and this northward weakening of deformation may indicate that it is linked with Rheic Ocean subduction rather than Iapetus Ocean closure. The Lake District in north-western England

6160-629: The Limfjord once was a fjord until the sea broke through from the west. Ringkøbing Fjord on the western coast of Jutland is a lagoon . The long narrow fjords of Denmark's Baltic Sea coast like the German Förden were dug by ice moving from the sea upon land, while fjords in the geological sense were dug by ice moving from the mountains down to the sea. However, some definitions of a fjord is: "A long narrow inlet consisting of only one inlet created by glacial activity". Examples of Danish fjords are: Kolding Fjord , Vejle Fjord and Mariager Fjord . The fjords in Finnmark in Norway, which are fjords in

6270-455: The NE into a marine basin which bridged the Avalonia and Laurentia margins. The tectonic contact between the two groups has been correlated either with the Windermere Supergroup (Lake District) turbidites or the Riccarton Group, ( Southern Uplands terrane ).The former hypothesis implies that the Dalby Group was originally deposited on the Manx Group and was subsequently faulted into its present day relationship. The latter one implies that it

6380-413: The Ordovician; these continents were by then further north. It also involved the consumption of both the Iapetus Ocean and the Tornquist Ocean along its northern margin. Avalonia's motion was related to slab pull created by the subduction of the Iapetus Ocean beneath the margin of Laurentia to its northwest and possibly also by ridge push created by the spreading of the Rheic Ocean. It migrated across

6490-425: The Pontesford-Linley fault system and folding in pre-Ashgill strata, uplift of the adjacent Towi Anticline and igneous activity. The main orogenic events or phases of the Caledonian orogenic cycle were related to the final closure of the Iapetus Ocean. They were, in sequential order, the Grampian phase, the docking of Eastern Avalonia with Baltica, the Scandian phase and the Acadian phase. The latter involved: A)

6600-460: The SE and east) ... and each tectonic event throughout this 200 million years can be considered as an orogenic phase." This includes tectonic events which were smaller, localised and predated the more well-known main phases of this orogeny. In this definition, the Taconic and Acadian orogenies in what today is North America are included in the phases of the Caledonian orogeny. Some early phases of deformation and metamorphism are recognised in

6710-420: The Scandinavian sense have been named or suggested to be fjords. Examples of this confused usage follow. In the Danish language some inlets are called a fjord, but are, according to the English language definition, technically not a fjord, such as Roskilde Fjord . Limfjord in English terminology is a sound , since it separates the North Jutlandic Island (Vendsyssel-Thy) from the rest of Jutland . However,

SECTION 60

#1732780652005

6820-407: The Swedish Baltic Sea coast, and in most Swedish lakes. This latter term is also used for bodies of water off the coast of Finland where Finland Swedish is spoken. In Danish, the word may even apply to shallow lagoons . In modern Icelandic, fjörður is still used with the broader meaning of firth or inlet. In Faroese fjørður is used both about inlets and about broader sounds, whereas

6930-412: The Swedish areas by its border. It occurred from the Wenlock Epoch of the Silurian to the Mid Devonian (430–380 Ma). Gee et al. (2013) and Ladenberger et al. (2012) propose a revised onset dating set at 440 Ma, however, there is no consensus about this. The Scandian orogenic event also led to the formation of mountains of Queen Louise Land (or Dronning Louise Land) in north-eastern Greenland . It

7040-452: The Tinure Fault is the surface expression of the Iapetus Suture zone. The Iapetus Suture is the lineament where the Caledonian collision closed the Iapetus Ocean. In Ireland it runs from the estuary of the River Shannon on the Atlantic coast to Clogherhead on the Irish Sea . It crosses this sea and is exposed in the Niarbyl Fault in the southern part of the northern coast of the Isle of Man . In Britain it runs roughly parallel to

7150-463: The accretion of the Armorican terranes with the southern margin of Laurussia in the Carboniferous Variscan orogeny (about 340 million years ago). The Rhenohercynian basin , a back-arc basin , formed at the southern margin of Euramerica just after the Caledonian orogeny. According to these authors, a small rim from Euramerica rifted off when this basin formed. The basin closed when these Caledonian deformed terranes were accreted again to Laurussia during

7260-456: The bedrock. This may in particular have been the case in Western Norway where the tertiary uplift of the landmass amplified eroding forces of rivers. Confluence of tributary fjords led to excavation of the deepest fjord basins. Near the very coast, the typical West Norwegian glacier spread out (presumably through sounds and low valleys) and lost their concentration and reduced the glaciers' power to erode leaving bedrock thresholds. Bolstadfjorden

7370-414: The case of Hardangerfjord the fractures of the Caledonian fold has guided the erosion by glaciers, while there is no clear relation between the direction of Sognefjord and the fold pattern. This relationship between fractures and direction of fjords is also observed in Lyngen . Preglacial, tertiary rivers presumably eroded the surface and created valleys that later guided the glacial flow and erosion of

7480-466: The collision was strongly oblique with sinistral transpression and without substantial crustal thickening . Devonian to Carboniferous rocks rest unconformably on Cambrian to Silurian folded and cleaved rocks. There were igneous intrusions with plutons and batholiths . The terrane has three relief belts. The northern belt and the northernmost part of the Central Belt underwent pure shear deformation with an axial planar cleavage and

7590-419: The combined continental mass of Laurentia, Baltica and Avalonia (called Euramerica, Laurussia or Old Red Continent ) and Armorica is called the Rheic Ocean . The paleogeographic position of the Armorica crustal fragments between the Ordovician and Carboniferous is highly disputed though. There are indications that the Bohemian Massif started moving northward from the Ordovician onward, but many authors place

7700-417: The convergence of Baltica, Laurentia and Avalonia which led to the closure of the Iapetus Ocean. McKerrow et al. (2000) give a definition of the Caledonian orogeny which includes "all the Cambrian , Ordovician , Silurian and Devonian tectonic events associated with the development and closure of those parts of the Iapetus Ocean which were situated between Laurentia (to the NW) and Baltica and Avalonia (to

7810-434: The deeper parts of the fjord the cold water remaining from winter is still and separated from the atmosphere by the brackish top layer. This deep water is ventilated by mixing with the upper layer causing it to warm and freshen over the summer. In fjords with a shallow threshold or low levels of mixing this deep water is not replaced every year and low oxygen concentration makes the deep water unsuitable for fish and animals. In

7920-565: The docking of England and Wales (which were part of eastern Avalonia) with eastern and southern Ireland with Scotland and the rest of Ireland (which were part of Laurentia). B) the amalgamation of terranes of Western Avalonia with the eastern margin of the main landmass of Laurentia (see Acadian orogeny article for this orogeny). During the final part of its northwestward migration, Avalonia converged with Baltica and Laurentia to its northeast and northwest respectively. After its amalgamation with Eastern Avalonia, Baltica converged with Laurentia in

8030-413: The fjord. 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. The deeper, salt layers of Bolstadfjorden are deprived of oxygen and the seabed is covered with organic material. The shallow threshold also creates a strong tidal current. During the summer season, there

8140-408: The fjords . A true fjord is formed when a glacier cuts a U-shaped valley by ice segregation and abrasion of the surrounding bedrock. According to the standard model, glaciers formed in pre-glacial valleys with a gently sloping valley floor. The work of the glacier then left an overdeepened U-shaped valley that ends abruptly at a valley or trough end. Such valleys are fjords when flooded by

8250-489: The formation of sea ice. The study of phytoplankton communities within fjords is an active area of research, supported by groups such as FjordPhyto, a citizen science initiative to study phytoplankton samples collected by local residents, tourists, and boaters of all backgrounds. An epishelf lake forms when meltwater is trapped behind a floating ice shelf and the freshwater floats on the denser saltwater below. Its surface may freeze forming an isolated ecosystem. The word fjord

8360-498: The hypotheses that arc rocks were eroded and thus have not been preserved, that the arc was displaced by lateral movement along strike-slip faults or that this is due to flat–slab subduction , which reduces magmatism rates. Nelison et al. (2009) propose an Iapetus Ocean subducting slab breakoff model to account for the intrusive rocks in the Grampian terrane being emplaced post-subduction. However, Miles at al. (2016) note that

8470-477: The ice cap receded and allowed the ocean to fill valleys and lowlands, and lakes like Mjøsa and Tyrifjorden were part of the ocean while Drammen valley was a narrow fjord. 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. After the ice age

8580-641: The intrusive rocks in the Trans-Suture Suite and in all the terranes in the region are similar in age and geochemistry. Thus, they argue that the common mechanism for the whole region involved an Iapetus Ocean slab which did not just break off. It also peeled back below the Iapetus Suture for c. 100 km to the SE below Avalonia. Thus they invoke a model of slab drop-off caused by lithospheric mantle delamination . The Lakesman terrane covers

8690-446: The level of the original sea level. In Eidfjord, Eio has dug through the original delta and left a 110 m (360 ft) terrace while lake is only 19 m (62 ft) above sea level. Such deposits are valuable sources of high-quality building materials (sand and gravel) for houses and infrastructure. Eidfjord village sits on the eid or isthmus between Eidfjordvatnet lake and Eidfjorden branch of Hardangerfjord. Nordfjordeid

8800-471: The main fjord. The mouth of Fjærlandsfjord is about 400 m (1,300 ft) deep while the main fjord is 1,200 m (3,900 ft) nearby. The mouth of Ikjefjord is only 50 m (160 ft) deep while the main fjord is around 1,300 m (4,300 ft) at the same point. During the winter season, there is usually little inflow of freshwater. Surface water and deeper water (down to 100 m or 330 ft or more) are mixed during winter because of

8910-497: The marine limit. Like freshwater fjords, the continuation of fjords on land are in the same way denoted as fjord-valleys . For instance Flåmsdal ( Flåm valley) and Måbødalen . Outside of Norway, the three western arms of New Zealand 's Lake Te Anau are named North Fiord, Middle Fiord and South Fiord. Another freshwater "fjord" in a larger lake is Western Brook Pond , in Newfoundland's Gros Morne National Park ; it

9020-405: The most extreme cases, there is a constant barrier of freshwater on the surface and the fjord freezes over such that there is no oxygen below the surface. Drammensfjorden is one example. The mixing in fjords predominantly results from the propagation of an internal tide from the entrance sill or internal seiching. The Gaupnefjorden branch of Sognefjorden is strongly affected by freshwater as

9130-569: The mountainous regions, resulting in abundant snowfall to feed the glaciers. Hence coasts having the most pronounced fjords include the west coast of Norway, the west coast of North America from Puget Sound to Alaska, the southwest coast of New Zealand, and the west and to south-western coasts of South America , chiefly in Chile . Other regions have fjords, but many of these are less pronounced due to more limited exposure to westerly winds and less pronounced relief. Areas include: The longest fjords in

9240-462: The mouths and overdeepening of fjords compared to the ocean are the strongest evidence of glacial origin, and these thresholds are mostly rocky. Thresholds are related to sounds and low land where the ice could spread out and therefore have less erosive force. John Walter Gregory argued that fjords are of tectonic origin and that glaciers had a negligible role in their formation. Gregory's views were rejected by subsequent research and publications. In

9350-747: The north of England down to the Wensleydale in North Yorkshire and crosses the Irish Sea passing by the Island of Anglesey off Wales . Its continuation in eastern Ireland is the Leinster terrane. The combined terrane is termed Leinster-Lakesman terrane. It lies on the southern margin of the Iapetus Suture . It includes the Lake District and the Isle of Man . The Acadian Orogeny affected

9460-448: The northern margin of Gondwana ( Amazonia and northwest Africa) close to the original position of Baltica which had been to its north. Its rifting involved the opening and spreading of the Rheic Ocean to its south, which separated it from Gondwana. This rifting and opening were coeval with and may be related to subduction onset in the Iapetus Ocean. The drift of Avalonia was towards the positions where Baltica and Laurentia had been in

9570-448: The ocean was about 150 m (490 ft) at Notodden . The ocean stretched like a fjord through Heddalsvatnet all the way to Hjartdal . Post-glacial rebound eventually separated Heddalsvatnet from the ocean and turned it into a freshwater lake. In neolithic times Heddalsvatnet was still a saltwater fjord connected to the ocean, and was cut off from the ocean around 1500 BC. Some freshwater fjords such as Slidrefjord are above

9680-443: The ocean. Thresholds above sea level create freshwater lakes. Glacial melting is accompanied by the rebounding of Earth's crust as the ice load and eroded sediment is removed (also called isostasy or glacial rebound). In some cases, this rebound is faster than sea level rise . Most fjords are deeper than the adjacent sea ; Sognefjord , Norway , reaches as much as 1,300 m (4,265 ft) below sea level . Fjords generally have

9790-696: The opening of the Tornquist Ocean which separated it from the northern margin of Gondwana to the south. The onset of Baltica rifting and the Tornquist Ocean opening are difficult to date due to insufficient palaeomagnetic data but must have occurred in similar times as those of Laurentia and the Iapetus Ocean. Either in the Late Precambrian or Early Ordovician , the Avalonia microcontinent started to drift northwestward from

9900-677: The outer Hebrides , causing thrusting in the Northern Highlands which culminated in the development of the Moine Thrust Belt , Ben Hope Thrust and Naver- Sgurr Beag Thrust (435–420 Ma) and led to igneous intrusion in Galloway and the Southern Uplands (c. 400 Ma) in Scotland and the enlargement of the Lake District batholith in northern England . All this spanned the Iapetus Suture zone (see below). It also caused northeast trending strike-slip faults, such as

10010-423: The outlet follow the Norwegian naming convention; they are frequently named fjords. Ice front deltas developed when the ice front was relatively stable for long time during the melting of the ice shield. The resulting landform is an isthmus between the lake and the saltwater fjord, in Norwegian called "eid" as in placename Eidfjord or Nordfjordeid . The post-glacial rebound changed these deltas into terraces up to

10120-439: The outlet of fjords where submerged glacially formed valleys perpendicular to the coast join with other cross valleys in a complex array. The island fringe of Norway is such a group of skerries (called a skjærgård ); many of the cross fjords are so arranged that they parallel the coast and provide a protected channel behind an almost unbroken succession of mountainous islands and skerries. By this channel, one can travel through

10230-465: The place name Fiordland . 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. In Norway and Iceland, the usage is closest to the Old Norse, with fjord used for both a firth and for

10340-624: The rest of Ireland). The Early Devonian Acadian event in this area saw the amalgamation of these landmasses to form the British Isles as they are now. This occurred through NW-dipping subduction of Avalonian oceanic crust beneath the southern margins of the Laurentian landmasses. Since the 1980s the term Acadian , which referred to the Late Silurian to Early Devonian orogeny in the Northern Appalachians , and

10450-497: 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. 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. Thresholds at

10560-528: The same regional cleavage suggesting that they are roughly coeval. There is ductile deformation in some localities and a broad shear zone in the Langness Peninsula which deform the primary cleavage and are thought to have formed during or soon after the main deformation phase. The Dalby Group was overthrust onto the Manx Group, probably in the early Devonian. During the final stage of the Iapetus Ocean closure its turbidites were deposited from

10670-641: The same regions typically are named Sund , in Scandinavian languages as well as in German. The word is related to "to sunder" in the meaning of "to separate". So the use of Sound to name fjords in North America and New Zealand differs from the European meaning of that word. The name of Wexford in Ireland is originally derived from Veisafjǫrðr ("inlet of the mud flats") in Old Norse, as used by

10780-487: The seaward margins of areas with fjords, the ice-scoured channels are so numerous and varied in direction that the rocky coast is divided into thousands of island blocks, some large and mountainous while others are merely rocky points or rock reefs , menacing navigation. These are called skerries . The term skerry is derived from the Old Norse sker , which means a rock in the sea. Skerries most commonly formed at

10890-466: The south of the suture) which were at the Laurentia and Avalonia margins respectively. The emplacement of the plutons occurred after the subduction of the Iapetus Ocean ended. The Southern Uplands terrane is thought to be an accretionary wedge . Deep marine sedimentation here in response to subduction begun 455 Ma and marked the switch from an initial SE-dipping Iapetus subduction under Avalonia to

11000-419: The steady cooling of the surface and wind. In the deep fjords, there is still fresh water from the summer with less density than the saltier water along the coast. Offshore wind, common in the fjord areas during winter, sets up a current on the surface from the inner to the outer parts. This current on the surface in turn pulls dense salt water from the coast across the fjord threshold and into the deepest parts of

11110-455: 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. Overall, phytoplankton abundance and species composition within fjords is highly seasonal, varying as a result of seasonal light availability and water properties that depend on glacial melt and

11220-809: The westernmost part of the microcontinent which amalgamated the east coast of the main part of the Laurentia tectonic plate (what is now North America) to the west in the area of the northern Appalachians and the Maritimes . Eastern Avalonia refers to a) the part which amalgamated with Baltica , b) England a Wales and eastern and south-eastern Ireland which amalgamated with Scotland and the north and west of Ireland (which were part of Laurentia). The easternmost part of Eastern Avalonia amalgamated with Baltica through an oblique soft docking governed by dextral strike-slip convergence and shear , rather than through an orogen-causing hard continental collision . This

11330-429: The world are: Deep fjords include: Caledonian orogeny The Caledonian orogeny was a mountain-building cycle recorded in the northern parts of the British Isles , the Scandinavian Caledonides , Svalbard , eastern Greenland and parts of north-central Europe. The Caledonian orogeny encompasses events that occurred from the Ordovician to Early Devonian , roughly 490–390 million years ago ( Ma ). It

11440-713: Was a distinct orogenic event which was separate and slightly younger than that of the Finnmarkian one, which they dated at 455 Ma. They named it the Jämtlandian Orogeny . It involved the Seve Nappe Complex of the Swedish Caledonides in central Sweden , which is interpreted as the stretched outermost edge of Baltica. Contrary to the previous opinion that it had been subducted beneath an oceanic island arc , they propose that it involved

11550-627: Was accompanied by late stage igneous intrusions . The event caused a major unconformity in Shropshire with considerable erosion before the deposition of sediments in the Llandovery Epoch of the Silurian (444–443 Ma). There was no break in sediments in the area until the end of the Early Devonian , which was caused by the Acadian Orogeny in the British Isles . It was associated with dextral (right-lateral) strike-slip movement in

11660-589: Was adopted in German as Förde , used for the narrow long bays of Schleswig-Holstein , and in English as firth "fjord, river mouth". The English word ford (compare German Furt , Low German Ford or Vörde , in Dutch names voorde such as Vilvoorde, Ancient Greek πόρος , poros , and Latin portus ) is assumed to originate from Germanic * ferþu- and Indo-European root * pertu- meaning "crossing point". Fjord/firth/Förde as well as ford/Furt/Vörde/voorde refer to

11770-546: Was at the north-western margin of the English part of Eastern Avalonia which converged and collided with Scotland and was thus involved in the Acadian phase. Generally, Acadian deformation metamorphosed mudrocks throughout various geologic formations of the district into slates by creating slaty cleavages . The Early Palaeozoic rocks in the Isle of Man in the Irish Sea crop out close to or probably on Iapetus suture . The island lies immediately to its SE. The island

11880-535: Was caused by the closure of the Iapetus Ocean when the Laurentia and Baltica continents and the Avalonia microcontinent collided. The orogeny is named for Caledonia , the Latin name for Scotland . The term was first used in 1885 by Austrian geologist Eduard Suess for an episode of mountain building in northern Europe that predated the Devonian period . Geologists like Émile Haug and Hans Stille saw

11990-522: Was not related to the Iapetus Ocean. It also has been argued that, although the Acadian orogeny in the British Isles involved the Iapetus Ocean closure, its driving force was actually a push from the south caused by the northward subduction of the Rheic Ocean which lied to the south of Avalonia and separated it from Gondwana . The closure of this ocean involved the (early) Eo-Variscan collision of Gondwana-related terranes in which Eastern Avalonia

12100-465: Was peripherally involved. Subduction of the Iapetus Ocean occurred beneath the Midland Valley terrane of Scotland. There is a Trans-Suture Suite of intrusive plutons which straddle both sides of the trace of the Iapetus Suture in the Southern Uplands terrane of Scotland (to the north of the suture) and the Lakesman-Leinster terrane of northern England and eastern Ireland (to

#4995