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Avalonia was a
microcontinent Continental crustal fragments, partially synonymous A synonym is a word, morpheme A morpheme is the smallest meaningful lexical item in a language. A morpheme is not a word. The difference between a morpheme and a word is that a morpheme bou ...
in the
Paleozoic The Paleozoic (or Palaeozoic) Era ( ; from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Eu ...
era An era is a span of time defined for the purposes of chronology Chronology (from Latin ''chronologia'', from Ancient Greek , ''chrónos'', "time"; and , ''wikt:-logia, -logia'') is the science of arranging events in their order of occurrence ...

era
. Crustal fragments of this former microcontinent underlie south-west
Great Britain Great Britain is an island An island (or isle) is an isolated piece of habitat that is surrounded by a dramatically different habitat, such as water. Very small islands such as emergent land features on atoll An atoll (), ...

Great Britain
, southern
Ireland Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic. It is separated from Great Britain to its east by the North Channel (Great Britain and Ireland), North Channel, the Irish Sea ...

Ireland
, and the eastern coast of
North America North America is a continent A continent is any of several large landmasses. Generally identified by convention (norm), convention rather than any strict criteria, up to seven geographical regions are commonly regarded as continen ...

North America
. It is the source of many of the older rocks of
Western Europe Western Europe is the western region of Europe Europe is a continent A continent is any of several large landmasses. Generally identified by convention (norm), convention rather than any strict criteria, up to seven geographical r ...

Western Europe
, Atlantic Canada, and parts of the coastal
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

United States
. Avalonia is named for the
Avalon Peninsula The Avalon Peninsula (french: Péninsule d'Avalon) is a large peninsula A peninsula ( la, paeninsula from 'almost' and 'island') is a landform A landform is a natural or artificial feature of the solid surface of the Earth or other planet ...

Avalon Peninsula
in
Newfoundland Newfoundland and Labrador (, ) is the easternmost provinces and territories of Canada, province of Canada, in the country's Atlantic Canada, Atlantic region. It is composed of the island of Newfoundland (island), Newfoundland and the continental ...
. Avalonia developed as a
volcanic arc A volcanic arc is a chain of volcano A volcano is a rupture in the crust of a planetary-mass object A planet is an astronomical body orbit In physics, an orbit is the gravitationally curved trajectory of an physical body, obj ...
on the northern margin of
Gondwana Gondwana () or Gondwanaland was a supercontinent In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (g ...

Gondwana
. It eventually
rift In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear Fault (geology), downfaulted depression, called a graben, or more commonly ...

rift
ed off, becoming a drifting microcontinent. The
Rheic Ocean The Rheic Ocean was an ocean which separated two major palaeocontinents, Gondwana and Laurussia (Laurentia-Baltica-Avalonia). One of the principal oceans of the Palaeozoic, its Suture (geology), sutures today stretch from Mexico to Turkey and its ...
formed behind it, and the
Iapetus Ocean The Iapetus Ocean (pronounced ) was an ocean that existed in the late Neoproterozoic and early Paleozoic eras of the geologic timescale (between 600 and 400 million years ago). The Iapetus Ocean was situated in the southern hemisphere, between the ...
shrank in front. It collided with the continents
Baltica Baltica is a paleocontinent A paleocontinent or palaeocontinent is a distinct area of continental crust 350px, The thickness of Crust (geology)#Earth's crust, Earth's crust (km) Continental crust is the layer of Igneous rock, igneous, Sedim ...
, then
Laurentia Laurentia or the North American Craton is a large continental craton A craton (, , or ; from el, κράτος ''kratos'' "strength") is an old and stable part of the continental lithosphere, which consists of Earth's two topmost layers, the ...
, and finally with Gondwana, ending up in the interior of
Pangea Pangaea or Pangea () was a supercontinent In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology ...

Pangea
. When Pangea broke up, Avalonia's remains were divided by the rift which became the
Atlantic Ocean
Atlantic Ocean
.


Development

The early development of Avalonia is believed to have been in
volcanic arc A volcanic arc is a chain of volcano A volcano is a rupture in the crust of a planetary-mass object A planet is an astronomical body orbit In physics, an orbit is the gravitationally curved trajectory of an physical body, obj ...
s near a
subduction zone Subduction is a geological process in which the oceanic lithosphere A lithosphere ( grc, λίθος [] for "rocky", and [] for "sphere") is the rigid, outermost shell of a terrestrial planet, terrestrial-type planet or natural satellite. O ...
on the margin of
Gondwana Gondwana () or Gondwanaland was a supercontinent In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (g ...

Gondwana
. Some material may have accreted from volcanic island arcs which formed further out in the ocean and later collided with Gondwana as a result of plate tectonic movements. The igneous activity had started by 730 million years ago and continued until around 570 million years ago, in the late
Neoproterozoic The Neoproterozoic Era is the unit of geologic time Geology (from the Ancient Greek Ancient Greek includes the forms of the used in and the from around 1500 BC to 300 BC. It is often roughly divided into the following periods: ...
. In the early
Cambrian The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These peri ...
, the supercontinent Pannotia broke up and Avalonia drifted off northwards from Gondwana. This independent movement of Avalonia started from a latitude of about 60° South. The eastern end of Avalonia collided with
Baltica Baltica is a paleocontinent A paleocontinent or palaeocontinent is a distinct area of continental crust 350px, The thickness of Crust (geology)#Earth's crust, Earth's crust (km) Continental crust is the layer of Igneous rock, igneous, Sedim ...
, a continental plate occupying the latitudes from about 30°S to 55°S, as Baltica slowly rotated counterclockwise towards it. This happened at the end of the Ordovician and during the Llandovery epoch, Early Silurian. In the late Silurian and lower Devonian, the combined Baltica and Avalonia collided progressively, with
Laurentia Laurentia or the North American Craton is a large continental craton A craton (, , or ; from el, κράτος ''kratos'' "strength") is an old and stable part of the continental lithosphere, which consists of Earth's two topmost layers, the ...
, beginning with the long extremity of Avalonia which is now attached to North America. The result of this was the formation of Euramerica. At the completion of this stage, the site of Britain was at 30°S and Nova Scotia at about 45°S. This collision is represented by the Caledonian orogeny, Caledonian folding or in North America as an early phase in the Acadian orogeny. In the Carboniferous, the new continent and another terrane, Armorican terrane, Armorica which included Iberian plate, Iberia, drifted in from Gondwana, trapping Avalonia between it and the continent so adding Iberia/Armorica to Euramerica. This was followed up by the arrival of Gondwana. The effects of these collisions are seen in Europe as the Variscan orogeny, Variscan folding. In North America it shows as later phases of the Acadian orogeny. This was happening at around the Equator during the later Carboniferous, forming Pangaea with Avalonia near its centre but partially flooded by shallow sea. In the Jurassic, Pangaea split into Laurasia and Gondwana, with Avalonia as part of Laurasia. In the Cretaceous, Laurasia broke up into
North America North America is a continent A continent is any of several large landmasses. Generally identified by convention (norm), convention rather than any strict criteria, up to seven geographical regions are commonly regarded as continen ...

North America
and Eurasia with Avalonia split between them. Iberia was later rotated away again as the African part of Gondwana strike-slipped past it. This last movement caused the Alpine orogeny including the raising of the Pyrenees during the Miocene and Pliocene. As a result of this, part of Avalonia is now to be found on each side of the Straits of Gibraltar.


Consequences

The Avalonian part of
Great Britain Great Britain is an island An island (or isle) is an isolated piece of habitat that is surrounded by a dramatically different habitat, such as water. Very small islands such as emergent land features on atoll An atoll (), ...

Great Britain
almost exactly coincides with England and Wales. Elsewhere in Europe, parts of Avalonia are found in the Ardennes of Belgium and north-eastern France, north Germany, north-western Poland, south-eastern
Ireland Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic. It is separated from Great Britain to its east by the North Channel (Great Britain and Ireland), North Channel, the Irish Sea ...

Ireland
, and the south-western edge of the Iberian Peninsula. Part of the British-Belgian section formed an island in the Carboniferous, affecting the disposition of coalfields; this is known by names such as the 'London-Brabant Island'. Its bulk had an effect on the geological structure between the Ardennes and the English Midlands by influencing the subsequent crustal folding resulting from the Variscan collision. In Canada, Avalonia comprises the
Avalon Peninsula The Avalon Peninsula (french: Péninsule d'Avalon) is a large peninsula A peninsula ( la, paeninsula from 'almost' and 'island') is a landform A landform is a natural or artificial feature of the solid surface of the Earth or other planet ...

Avalon Peninsula
of southeast
Newfoundland Newfoundland and Labrador (, ) is the easternmost provinces and territories of Canada, province of Canada, in the country's Atlantic Canada, Atlantic region. It is composed of the island of Newfoundland (island), Newfoundland and the continental ...
, southern New Brunswick, part of Nova Scotia, and Prince Edward Island. In the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

United States
, Avalonia consists of northern coastal Maine, all of Rhode Island, and other sections of coastal New England.


See also

*Mistaken Point, Newfoundland and Labrador


References


External links


Map showing Avalonia in the Ordovician Period
* {{Continents of the world Historical continents Ordovician geology Paleozoic Europe Paleozoic North America Geology of England Geology of Nova Scotia Geology of New Brunswick Geology of Newfoundland and Labrador Geology of Wales Terranes Ordovician England Ordovician Nova Scotia Ordovician New Brunswick Ordovician Newfoundland and Labrador