Pangaea

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The supercontinent Pangaea in the early Mesozoic (at 200 Ma) Pangaea 200Ma.jpg
The supercontinent Pangaea in the early Mesozoic (at 200 Ma)

Pangaea or Pangea ( /pænˈə/ [1] ) was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. [2] It assembled from earlier continental units approximately 335 million years ago, and began to break apart about 175 million years ago. [3] In contrast to the present Earth and its distribution of continental mass, Pangaea was centred on the Equator and surrounded by the superocean Panthalassa. Pangaea is the most recent supercontinent to have existed and the first to be reconstructed by geologists.

Contents

Origin of the concept

Alfred Wegener c. 1924-1930 Alfred Wegener ca.1924-30.jpg
Alfred Wegener c. 1924–1930
World map of Pangaea created by Alfred Wegener to illustrate his concept Alfred Wegener - Pangaea.jpg
World map of Pangaea created by Alfred Wegener to illustrate his concept

The name "Pangaea/Pangea" is derived from Ancient Greek pan ( πᾶν , "all, entire, whole") and Gaia ( Γαῖα , "Mother Earth, land"). [4] [9] The concept that the continents once formed a contiguous land mass was hypothesised by, with corroborating evidence, Alfred Wegener, the originator of the scientific theory of continental drift, in his 1912 publication The Origin of Continents (Die Entstehung der Kontinente). [10] He expanded upon his hypothesis in his 1915 book The Origin of Continents and Oceans (Die Entstehung der Kontinente und Ozeane), in which he postulated that, before breaking up and drifting to their present locations, all the continents had formed a single supercontinent that he called the "Urkontinent".

The name "Pangea" occurs in the 1920 edition of Die Entstehung der Kontinente und Ozeane, but only once, when Wegener refers to the ancient supercontinent as "the Pangaea of the Carboniferous". [11] Wegener used the Germanized form "Pangäa," but the name entered German and English scientific literature (in 1922 [12] and 1926, respectively) in the Latinized form "Pangaea" (of the Greek "Pangaia"), especially due to a symposium of the American Association of Petroleum Geologists in November 1926. [13]

Wegener originally proposed that the breakup of Pangaea was due to centripetal forces from the Earth's rotation acting on the high continents. However, this mechanism was easily shown to be physically implausible, which delayed acceptance of the Pangaea hypothesis. [14] Arthur Holmes proposed the more plausible mechanism of mantle convection, [15] which, together with evidence provided by the mapping of the ocean floor following the Second World War, led to the development and acceptance of the theory of plate tectonics. This theory provides the now widely-accepted explanation for the existence and breakup of Pangaea. [16]

Evidence of existence

The distribution of fossils across the continents is one line of evidence pointing to the existence of Pangaea. Snider-Pellegrini Wegener fossil map.svg
The distribution of fossils across the continents is one line of evidence pointing to the existence of Pangaea.

The geography of the continents bordering the Atlantic Ocean was the first evidence suggesting the existence of Pangaea. The seemingly close fit of the coastlines of North and South America with Europe and Africa was remarked on almost as soon as these coasts were charted. The first to suggest that these continents were once joined and later separated may have been Abraham Ortelius in 1596. [17] Careful reconstructions showed that the mismatch at the 500 fathoms (3,000 feet; 910 meters) contour was less than 130 km (81 mi), and it was argued that this was much too good to be attributed to chance. [18]

Additional evidence for Pangaea is found in the geology of adjacent continents, including matching geological trends between the eastern coast of South America and the western coast of Africa. The polar ice cap of the Carboniferous Period covered the southern end of Pangaea. Glacial deposits, specifically till, of the same age and structure are found on many separate continents that would have been together in the continent of Pangaea. [19]

Fossil evidence for Pangaea includes the presence of similar and identical species on continents that are now great distances apart. For example, fossils of the therapsid Lystrosaurus have been found in South Africa, India and Antarctica, alongside members of the Glossopteris flora, whose distribution would have ranged from the polar circle to the equator if the continents had been in their present position; similarly, the freshwater reptile Mesosaurus has been found in only localized regions of the coasts of Brazil and West Africa. [20]

Paleomagnetic study of apparent polar wandering paths also support the theory of a supercontinent. Geologists can determine the movement of continental plates by examining the orientation of magnetic minerals in rocks; when rocks are formed, they take on the magnetic properties of the Earth and indicate in which direction the poles lie relative to the rock. Since the magnetic poles drift about the rotational pole with a period of only a few thousand years, measurements from numerous lavas spanning several thousand years are averaged to give an apparent mean polar position. Samples of sedimentary rock and intrusive igneous rock have magnetic orientations that are typically an average of the "secular variation" in the orientation of magnetic north because their remanent magnetizations are not acquired instantaneously. Magnetic differences between sample groups whose age varies by millions of years is due to a combination of true polar wander and the drifting of continents. The true polar wander component is identical for all samples, and can be removed, leaving geologists with the portion of this motion that shows continental drift and can be used to help reconstruct earlier continental positions. [21]

The continuity of mountain chains provides further evidence for Pangaea. One example of this is the Appalachian Mountains chain, which extends from the southeastern United States to the Caledonides of Ireland, Britain, Greenland, and Scandinavia. [22]

Formation

Appalachian orogeny Appalachian orogeny.jpg
Appalachian orogeny

Pangaea is only the most recent supercontinent identified in the geologic record. The forming of supercontinents and their breaking up appears to have been cyclical through Earth's history. There may have been several others before Pangaea.

Paleomagnetic measurements help geologists determine the latitude and orientation of ancient continental blocks, and newer techniques may help determine longitudes. [23] Paleontology helps determine ancient climates, confirming latitude estimates from paleomagnetic measurements, and the distribution of ancient forms of life provides clues on which continental blocks were close to each other at particular geological moments. [24] However, reconstructions of continents prior to the breakup of Pangea, including the ones in this section, remain partially speculative, and different reconstructions will differ in some details. [25]

Previous supercontinents

The fourth-last supercontinent, called Columbia or Nuna, appears to have assembled in the period 2.0–1.8 billion years ago (Ga). [26] [27] Columbia/Nuna broke up and the next supercontinent, Rodinia, formed from the accretion and assembly of its fragments. Rodinia lasted from about 1.3 Ga until about 750 million years ago, but its exact configuration and geodynamic history are not nearly as well understood as those of the later supercontinents, Pannotia and Pangaea. [28]

According to one reconstruction, [29] when Rodinia broke up, it split into three pieces: the supercontinent of Proto-Laurasia, the supercontinent of Proto-Gondwana, and the smaller Congo craton. Proto-Laurasia and Proto-Gondwana were separated by the Proto-Tethys Ocean. Next Proto-Laurasia itself split apart to form the continents of Laurentia, Siberia, and Baltica. Baltica moved to the east of Laurentia, and Siberia moved northeast of Laurentia. The splitting also created two new oceans, the Iapetus Ocean and Paleoasian Ocean. [30] Most of the above masses coalesced again to form the relatively short-lived supercontinent of Pannotia. This supercontinent included large amounts of land near the poles and, near the equator, only a relatively small strip connecting the polar masses. Pannotia lasted until 540  Ma, near the beginning of the Cambrian period and then broke up, giving rise to the continents of Laurentia, Baltica, and the southern supercontinent of Gondwana. [31]

Formation of Euramerica (Laurussia)

In the Cambrian period, the continent of Laurentia, which would later become North America, sat on the equator, with three bordering oceans: the Panthalassic Ocean to the north and west, the Iapetus Ocean to the south, and the Khanty Ocean to the east. In the Earliest Ordovician, around 480 Ma, the microcontinent of Avalonia – a landmass incorporating fragments of what would become eastern Newfoundland, the southern British Isles, and parts of Belgium, northern France, Nova Scotia, New England, South Iberia, and northwest Africa – broke free from Gondwana and began its journey to Laurentia. [32] Baltica, Laurentia, and Avalonia all came together by the end of the Ordovician to form a landmass called Euramerica or Laurussia, closing the Iapetus Ocean. The collision also resulted in the formation of the northern Appalachians. Siberia sat near Euramerica, with the Khanty Ocean between the two continents. While all this was happening, Gondwana drifted slowly towards the South Pole. This was the first step of the formation of Pangaea. [33]

Collision of Gondwana with Euramerica

The second step in the formation of Pangaea was the collision of Gondwana with Euramerica. By the middle of the Silurian, 430 Ma, Baltica had already collided with Laurentia, forming Euramerica, an event called the Caledonian orogeny. Avalonia had not yet collided with Laurentia, but as Avalonia inched towards Laurentia, the seaway between them, a remnant of the Iapetus Ocean, was slowly shrinking. Meanwhile, southern Europe broke off from Gondwana and began to move towards Euramerica across the Rheic Ocean. It collided with southern Baltica in the Devonian. [34]

By the late Silurian, Annamia and South China split from Gondwana and started to head northward, shrinking the Proto-Tethys Ocean in their path and opening the new Paleo-Tethys Ocean to their south. In the Devonian Period, Gondwana itself headed towards Euramerica, causing the Rheic Ocean to shrink. In the Early Carboniferous, northwest Africa had touched the southeastern coast of Euramerica, creating the southern portion of the Appalachian Mountains, the Meseta Mountains, and the Mauritanide Mountains, an event called the Variscan orogeny. South America moved northward to southern Euramerica, while the eastern portion of Gondwana (India, Antarctica, and Australia) headed toward the South Pole from the equator. North and South China were on independent continents. The Kazakhstania microcontinent had collided with Siberia. (Siberia had been a separate continent for millions of years since the deformation of the supercontinent Pannotia in the Middle Carboniferous.) [35]

The Variscan orogeny raised the Central Pangean Mountains, which were comparable to the modern Himalayas in scale. With Pangea now stretching from the South Pole across the equator and well into the Northern Hemisphere, an intense monsoon climate was established, except for a perpetually wet zone immediately around the central mountains. [36]

Formation of Laurasia

Western Kazakhstania collided with Baltica in the Late Carboniferous, closing the Ural Ocean between them and the western Proto-Tethys in them (Uralian orogeny), causing the formation of not only the Ural Mountains but also the supercontinent of Laurasia. This was the last step of the formation of Pangaea. Meanwhile, South America had collided with southern Laurentia, closing the Rheic Ocean and completing the Variscian orogney with the formation the southernmost part of the Appalachians and Ouachita Mountains. By this time, Gondwana was positioned near the South Pole, and glaciers were forming in Antarctica, India, Australia, southern Africa, and South America. The North China block collided with Siberia by Jurassic, completely closing the Proto-Tethys Ocean. [37]

By the Early Permian, the Cimmerian plate split from Gondwana and headed towards Laurasia, thus closing the Paleo-Tethys Ocean, but forming a new ocean, the Tethys Ocean, in its southern end. Most of the landmasses were all in one. By the Triassic Period, Pangaea rotated a little, and the Cimmerian plate was still travelling across the shrinking Paleo-Tethys until the Middle Jurassic. By the late Triassic, the Paleo-Tethys had closed from west to east, creating the Cimmerian Orogeny. Pangaea, which looked like a C, with the new Tethys Ocean inside the C, had rifted by the Middle Jurassic, and its deformation is explained below. [38]

Life

An early Mesozoic ammonite from Pangaea Ammonite - Toarcien moyen 09.jpg
An early Mesozoic ammonite from Pangaea
The four floristic provinces of the world at the Permian-Carboniferous boundary, 300 million years ago The World of the Carboniferous-Permian boundary.svg
The four floristic provinces of the world at the Permian-Carboniferous boundary, 300 million years ago

Pangaea existed as a supercontinent for 160 million years, from its assembly around 335 million years ago (Early Carboniferous) to its breakup 175 million years ago (Middle Jurassic). [3] During this interval, important developments in the evolution of life took place. The seas of the Early Carboniferous were dominated by rugose corals, brachiopods, bryozoans, sharks, and the first bony fish. Life on land was dominated by lycopsid forests inhabited by insects and other arthropods and the first tetrapods. [39] By the time Pangaea broke up, in the Middle Jurassic, the seas swarmed with molluscs (particularly ammonites), [40] ichthyosaurs, sharks and rays, and the first ray-finned bony fishes, while life on land was dominated by forests of cycads and conifers in which dinosaurs flourished and in which the first true mammals had appeared. [41] [42]

The evolution of life in this interval of time reflected conditions created by the assembly of Pangaea. The assembly of most of the continental crust into one landmass reduced the extent of sea coasts. Increased erosion from uplifted continental crust increased the importance of floodplain and delta environments relative to shallow marine environments. Continental assembly and uplift also meant an increasingly arid climate over much of the surface of the Earth. This favored the evolution of amniotes and seed plants, whose eggs and seeds were better adapted to dry climates. [39] The early drying trend was most pronounced in western Pangaea, which became an epicenter for the evolution and geographical spread of amniotes. [43]

Coal swamps are typically a feature of perpetually wet regions close to the equator. The assembly of Pangaea disrupted the intertropical convergence zone and created an extreme monsoon climate that reduced the deposition of coal to its lowest level in the last 300 million years. During the Permian, coal deposition was largely restricted to the North and South China microcontinents, which were among the few areas of continental crust that had not joined with Pangaea. [44] The extremes of climate conditions in the interior of Pangaea are reflected in bone growth patterns of pareiasaurs and in the growth patterns in gymnosperm forests. [45]

Early Triassic Lystrosaurus fossil from South Africa Lystrosaurus cf. oviceps - National Museum of Natural History - IMG 1984.JPG
Early Triassic Lystrosaurus fossil from South Africa

The lack of oceanic barriers is thought to have favored cosmopolitanism, in which species show a wide geographical distribution. Cosmopolitanism was also driven by mass extinctions, including the Permian–Triassic extinction event, the most severe in the fossil record, and also the Triassic–Jurassic extinction event. These events resulted in disaster fauna showing little diversity and high cosmopolitanism. These include Lystrosaurus , which opportunistically spread to every corner of Pangaea following the Permian-Triassic extinction event. [46] On the other hand, there is evidence that many Pangaean species were provincial, with a limited geographical range, in spite of the lack of geographical barriers. This may be due to the strong variations in climate by latitude and season produced by the extreme monsoon climate. [47] For example, cold-adapted pteridosperms (early seed plants) of Gondwana were blocked from spreading throughout Pangaea by the warming climate, and northern pteridosperms ended up dominating Gondwana in the Triassic. [48]

Mass extinctions

The tectonics and geography of Pangaea may have worsened the Permian-Triassic extinction event or other extinctions. For example, the reduced area of continental shelf environments may have left marine species vulnerable to extinction. [49] However, no evidence for a species-area effect has been found in more recent and better characterized portions of the geologic record. [50] [51] Another possibility is that reduced sea-floor spreading associated with the formation of Pangaea, and the resulting cooling and subsidence of oceanic crust, may have reduced the number of islands that could have served as refugia for marine species. Species diversity may have already been reduced prior to mass extinction events due to mingling of species possible when formerly separate continents were merged. However, there is strong evidence that climate barriers continued to separate ecological communities in different parts of Pangaea. The eruptions of the Emeishan Traps may have eliminated South China, one of the few continental areas not merged with Pangaea, as a refugium. [52]

Rifting and break-up

The breakup of Pangaea over time Pangaea to present.gif
The breakup of Pangaea over time

There were three major phases in the break-up of Pangaea.

Opening of the Atlantic

The first phase began in the Early-Middle Jurassic (about 175 Ma), when Pangaea began to rift from the Tethys Ocean in the east to the Pacific in the west. The rifting that took place between North America and Africa produced multiple failed rifts. One rift resulted in a new ocean, the North Atlantic Ocean. [22]

The Atlantic Ocean did not open uniformly; rifting began in the north-central Atlantic. The South Atlantic did not open until the Cretaceous when Laurasia started to rotate clockwise and moved northward with North America to the north, and Eurasia to the south. The clockwise motion of Laurasia led much later to the closing of the Tethys Ocean and the widening of the "Sinus Borealis", which later became the Arctic Ocean. Meanwhile, on the other side of Africa and along the adjacent margins of east Africa, Antarctica and Madagascar, new rifts were forming that would lead to the formation of the southwestern Indian Ocean that would open up in the Cretaceous.

Break-up of Gondwana

The second major phase in the break-up of Pangaea began in the Early Cretaceous (150–140 Ma), when the landmass of Gondwana separated into multiple continents (Africa, South America, India, Antarctica, and Australia). The subduction at Tethyan Trench probably caused Africa, India and Australia to move northward, causing the opening of a "South Indian Ocean". In the Early Cretaceous, Atlantica, today's South America and Africa, finally separated from eastern Gondwana (Antarctica, India and Australia). Then in the Middle Cretaceous, Gondwana fragmented to open up the South Atlantic Ocean as South America started to move westward away from Africa. The South Atlantic did not develop uniformly; rather, it rifted from south to north.

Also, at the same time, Madagascar and India began to separate from Antarctica and moved northward, opening up the Indian Ocean. Madagascar and India separated from each other 100–90 Ma in the Late Cretaceous. India continued to move northward toward Eurasia at 15 centimeters (6 in) a year (a plate tectonic record), closing the eastern Tethys Ocean, while Madagascar stopped and became locked to the African Plate. New Zealand, New Caledonia and the rest of Zealandia began to separate from Australia, moving eastward toward the Pacific and opening the Coral Sea and Tasman Sea.

Opening of the Norwegian Sea and break-up of Australia and Antarctica

The third major and final phase of the break-up of Pangaea occurred in the early Cenozoic (Paleocene to Oligocene). Laurasia split when North America/Greenland (also called Laurentia) broke free from Eurasia, opening the Norwegian Sea about 60–55 Ma. The Atlantic and Indian Oceans continued to expand, closing the Tethys Ocean.

Meanwhile, Australia split from Antarctica and moved quickly northward, just as India had done more than 40 million years before. Australia is currently on a collision course with eastern Asia. Both Australia and India are currently moving northeast at 5–6 centimeters (2–3 in) a year. Antarctica has been near or at the South Pole since the formation of Pangaea about 280 Ma. India started to collide with Asia beginning about 35 Ma, forming the Himalayan orogeny, and also finally closing the Tethys Seaway; this collision continues today. The African Plate started to change directions, from west to northwest toward Europe, and South America began to move in a northward direction, separating it from Antarctica and allowing complete oceanic circulation around Antarctica for the first time. This motion, together with decreasing atmospheric carbon dioxide concentrations, caused a rapid cooling of Antarctica and allowed glaciers to form. This glaciation eventually coalesced into the kilometers-thick ice sheets seen today. [53] Other major events took place during the Cenozoic, including the opening of the Gulf of California, the uplift of the Alps, and the opening of the Sea of Japan. The break-up of Pangaea continues today in the Red Sea Rift and East African Rift.

Climate change after Pangaea

The breakup of Pangaea was accompanied by outgassing of large quantities of carbon dioxide from continental rifts. This produced a Mesozoic CO2 High that contributed to the very warm climate of the Early Cretaceous. [54] The opening of the Tethys Ocean also contributed to the warming of the climate. [55] The very active mid-ocean ridges associated with the breakup of Pangaea raised sea levels to the highest in the geological record, flooding much of the continents. [56]

The expansion of the temperate climate zones that accompanied the breakup of Pangaea may have contributed to the diversification of the angiosperms. [57]

See also

Related Research Articles

The PaleozoicEra is the earliest of three geologic eras of the Phanerozoic Eon. It is the longest of the Phanerozoic eras, lasting from 541 to 251.902 million years ago, and is subdivided into six geologic periods : the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian. The Paleozoic comes after the Neoproterozoic Era of the Proterozoic Eon and is followed by the Mesozoic Era.

Phanerozoic Fourth and current eon of the geological timescale

The Phanerozoic Eon is the current geologic eon in the geologic time scale, and the one during which abundant animal and plant life has existed. It covers 541 million years to the present, and it began with the Cambrian Period when animals first developed hard shells preserved in the fossil record. The time before the Phanerozoic, called the Precambrian, is now divided into the Hadean, Archaean and Proterozoic eons.

Supercontinent Landmass comprising more than one continental core, or craton

In geology, a supercontinent is the assembly of most or all of Earth's continental blocks or cratons to form a single large landmass. However, some earth scientists use a different definition, "a grouping of formerly dispersed continents", which leaves room for interpretation and is easier to apply to Precambrian times although at least about 75% of the continental crust then in existence has been proposed as a limit to separate supercontinents from other groupings.

Rodinia Hypothetical neoproterozoic supercontinent from between about a billion to about three quarters of a billion years ago

Rodinia was a Neoproterozoic supercontinent that assembled 1.1–0.9 billion years ago and broke up 750–633 million years ago. Valentine & Moores 1970 were probably the first to recognise a Precambrian supercontinent, which they named 'Pangaea I'. It was renamed 'Rodinia' by McMenamin & McMenamin 1990 who also were the first to produce a reconstruction and propose a temporal framework for the supercontinent.

Laurasia Northern supercontinent that formed part of the Pangaea supercontinent

Laurasia, was the more northern of two large landmasses that formed part of the Pangaea supercontinent from around 335 to 175 million years ago (Mya), the other being Gondwana. It separated from Gondwana 215 to 175 Mya during the breakup of Pangaea, drifting farther north after the split and finally broke apart with the opening of the North Atlantic Ocean c. 56 Mya. The name is a blend of Laurentia and Asia.

Tethys Ocean Mesozoic ocean between Gondwana and Laurasia

The Tethys Ocean, also called the Tethys Sea or the Neo-Tethys, was an ocean during much of the Mesozoic Era located between the ancient continents of Gondwana and Laurasia, before the opening of the Indian and Atlantic oceans during the Cretaceous Period.

Panthalassa Prehistoric superocean that surrounded Pangaea

Panthalassa, also known as the Panthalassic Ocean or Panthalassan Ocean, was the superocean that surrounded the supercontinent Pangaea, the latest in a series of supercontinents in the history of Earth. During the Paleozoic–Mesozoic transition c. 250 Ma it occupied almost 70% of Earth's surface. Its ocean floor has completely disappeared because of the continuous subduction along the continental margins on its circumference. Panthalassa is also referred to as the Paleo-Pacific or Proto-Pacific because the Pacific Ocean developed from its centre in the Mesozoic to the present.

Iapetus Ocean Ocean that existed in the late Neoproterozoic and early Paleozoic eras

The Iapetus Ocean was an ocean that existed in the late Neoproterozoic and early Paleozoic eras of the geologic timescale. The Iapetus Ocean was situated in the southern hemisphere, between the paleocontinents of Laurentia, Baltica and Avalonia. The ocean disappeared with the Acadian, Caledonian and Taconic orogenies, when these three continents joined to form one big landmass called Euramerica. The "southern" Iapetus Ocean has been proposed to have closed with the Famatinian and Taconic orogenies, meaning a collision between Western Gondwana and Laurentia.

Pannotia Hypothesized Neoproterozoic supercontinent from the end of the Precambrian

Pannotia, also known as the Vendian supercontinent, Greater Gondwana, and the Pan-African supercontinent, was a relatively short-lived Neoproterozoic supercontinent that formed at the end of the Precambrian during the Pan-African orogeny, during the Cryogenian period and broke apart 560 Ma with the opening of the Iapetus Ocean, in the late Ediacaran and early Cambrian. Pannotia formed when Laurentia was located adjacent to the two major South American cratons, Amazonia and Río de la Plata. The opening of the Iapetus Ocean separated Laurentia from Baltica, Amazonia, and Río de la Plata.

Avalonia Microcontinent in the Paleozoic era named for the Avalon Peninsula in Newfoundland

Avalonia was a microcontinent in the Paleozoic era. Crustal fragments of this former microcontinent underlie south-west Great Britain, southern Ireland, and the eastern coast of North America. It is the source of many of the older rocks of Western Europe, Atlantic Canada, and parts of the coastal United States. Avalonia is named for the Avalon Peninsula in Newfoundland.

Caledonian orogeny Mountain building event caused by the collision of Laurentia, Baltica and Avalonia

The Caledonian orogeny was a mountain-building era recorded in the northern parts of the British Isles, the Scandinavian Mountains, 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 was caused by the closure of the Iapetus Ocean when the continents and terranes of Laurentia, Baltica and Avalonia collided.

Variscan orogeny Collision of tectonic plates resulting in the creation of mountains

The Variscan or Hercynianorogeny was a geologic mountain-building event caused by Late Paleozoic continental collision between Euramerica (Laurussia) and Gondwana to form the supercontinent of Pangaea.

Paleo-Tethys Ocean Ocean on the margin of Gondwana between the Middle Cambrian and Late Triassic

The Paleo-Tethys or Palaeo-Tethys Ocean was an ocean located along the northern margin of the paleocontinent Gondwana that started to open during the Middle Cambrian, grew throughout the Paleozoic, and finally closed during the Late Triassic; existing for about 400 million years.

The Proto-Tethys or Theic Ocean was an ancient ocean that existed from the latest Ediacaran to the Carboniferous.

Cimmeria (continent) Ancient string of microcontinents that rifted from Gondwana

Cimmeria was an ancient continent, or, rather, a string of microcontinents or terranes, that rifted from Gondwana in the Southern Hemisphere and was accreted to Eurasia in the Northern Hemisphere. It consisted of parts of present-day Turkey, Iran, Afghanistan, Pakistan, Tibet, China, Myanmar, Thailand, and Malaysia. Cimmeria rifted from the Gondwanan shores of the Paleo-Tethys Ocean during the Carboniferous-earliest Permian and as the Neo-Tethys Ocean opened behind it, during the Permian, the Paleo-Tethys closed in front of it. Cimmeria rifted off Gondwana from east to west, from Australia to the eastern Mediterranean. It stretched across several latitudes and spanned a wide range of climatic zones.

Geological history of Earth The sequence of major geological events in Earths past

The geological history of Earth follows the major events in Earth's past based on the geological time scale, a system of chronological measurement based on the study of the planet's rock layers (stratigraphy). Earth formed about 4.54 billion years ago by accretion from the solar nebula, a disk-shaped mass of dust and gas left over from the formation of the Sun, which also created the rest of the Solar System.

Gondwana Neoproterozoic to Cretaceous landmass

Gondwana or Gondwanaland was a supercontinent that existed from the Neoproterozoic and began to break up during the Jurassic, with the final stages of breakup, including the opening of the Drake Passage separating South America and Antarctica occurring during the Paleogene. Gondwana was not considered a supercontinent by the earliest definition, since the landmasses of Baltica, Laurentia, and Siberia were separated from it.

Laurentia A large continental craton that forms the ancient geological core of the North American continent

Laurentia or the North American Craton is a large continental craton that forms the ancient geological core of North America. Many times in its past, Laurentia has been a separate continent, as it is now in the form of North America, although originally it also included the cratonic areas of Greenland and also the northwestern part of Scotland, known as the Hebridean Terrane. During other times in its past, Laurentia has been part of larger continents and supercontinents and itself consists of many smaller terranes assembled on a network of Early Proterozoic orogenic belts. Small microcontinents and oceanic islands collided with and sutured onto the ever-growing Laurentia, and together formed the stable Precambrian craton seen today.

The geology of the North Sea describes the geological features such as channels, trenches, and ridges today and the geological history, plate tectonics, and geological events that created them.

A paleocontinent or palaeocontinent is a distinct area of continental crust that existed as a major landmass in the geological past. There have been many different landmasses throughout Earth's time. They range in sizes, some are just a collection of small microcontinents while others are large conglomerates of crust. As time progresses and sea levels rise and fall more crust can be exposed making way for larger landmasses. The continents of the past shaped the evolution of organisms on Earth and contributed to the climate of the globe as well. As landmasses break apart, species are separated and those that were once the same now have evolved to their new climate. The constant movement of these landmasses greatly determines the distribution of organisms on Earth's surface. This is evident with how similar fossils are found on completely separate continents. Also, as continents move, mountain building events (orogenies) occur, causing a shift in the global climate as new rock is exposed and then there is more exposed rock at higher elevations. This causes glacial ice expansion and an overall cooler global climate. Which effects the overall global climate trend of Earth. The movement of the continents greatly affects the overall dispersal of organisms throughout the world and the trend in climate throughout Earth's history. Examples include Laurentia, Baltica and Avalonia, which collided together during the Caledonian orogeny to form the Old Red Sandstone paleocontinent of Laurussia. Another example includes a collision that occurred during the late Pennsylvanian and early Permian time when there was a collision between the two continents of Tarimsky and Kirghiz-Kazakh. This collision was caused because of their askew convergence when the paleoceanic basin closed.

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