Map of Pangaea with Laurasia and Gondwana. 200 mya
|Today part of||Africa
|Tectonic plate||African Plate
South American Plate
Gondwana ( ), or Gondwanaland, was a supercontinent that formed from the unification of several cratons in the Late Neoproterozoic, merged with Laurussia in the Carboniferous to form Pangaea, and began to fragment in the Mesozoic. It was the largest continental landmass on Earth, covering an area of 100,000,000 km2 (39,000,000 sq mi) or 64% of today's continents. Located in the Southern Hemisphere, it incorporated several modern landmasses, including Antarctica, South America, Africa, Madagascar, and Australia, as well as the Arabian Peninsula and the Indian subcontinent, which have now moved entirely into the Northern Hemisphere.
The formation of Gondwana began c. East African orogeny -- the collision of India, Madagascar, and Sri Lanka with East Africa -- and was completed c. with the overlapping Brasiliano and Kuunga orogenies -- the collision of South America with Africa and the addition of Australia and Antarctica, respectively.with the
The continent of Gondwana was named by Austrian scientist Eduard Suess, after the Gondwana region of central northern India which is derived from Sanskrit for "forest of the Gonds". The name had been previously used in a geological context, first by H.B. Medlicott in 1872, from which the Gondwana sedimentary sequences (Permian-Triassic) are also described. The term "Gondwanaland" is preferred by some scientists in order to make a clear distinction between the region and the supercontinent.
The assembly of Gondwana was a protracted process that occurred during the Neoproterozoic and Paleozoic which remains relatively poorly constrained because of the lack of paleo-magnetic data. Several orogenies, collectively known as the Pan-African orogeny, led to the amalgamation of most of the continental fragments of a much older supercontinent, Rodinia. One of those orogenic belts, the Mozambique Belt, formed c. and was originally interpreted as the suture between East (India, Madagascar, Antarctica, and Australia) and West Gondwana (Africa and South America). Three orogenies were recognized during the 1990s: the East African orogeny ( ) and Kuunga orogeny (including the Malagasy orogeny in southern Madagascar) ( ) -- the collision between East Gondwana and East Africa in two steps, and the Brasiliano orogeny ( ) -- the collision between South American and African cratons.
The final stages of Gondwanan assembly overlapped with the opening of the Iapetus Ocean between Laurentia and western Gondwana. During this interval, the Cambrian explosion occurred. Laurentia was docked against the western shores of a united Gondwana for a short period near the Precambrian/Cambrian boundary, forming the short-lived and still disputed supercontinent Pannotia.
The Mozambique Ocean separated the Congo-Tanzania-Bangweulu Block of central Africa from Neoproterozoic India (India, the Antongil Block in far eastern Madagascar, the Seychelles, and the Napier and Rayner Complexes in East Antarctica). The Azania continent (much of central Madagascar, the Horn of Africa and parts of Yemen and Arabia) was an island in the Mozambique Ocean.
The Australia/Mawson continent was still separated from India, eastern Africa, and Kalahari by c. when most of western Gondwana had already been amalgamated. By c. 550 Ma, India had reached its Gondwana position which initiated the Kuunga orogeny (also known as the Pinjarra orogeny). Meanwhile, on the other side of the forming Africa, Kalahari collided with Congo and Rio de la Plata which closed the Adamastor Ocean. c. 540-530 Ma the closure of the Mozambique Ocean brought India next to Australia-East Antarctica and both North and South China were located in proximity to Australia.
Other blocks which helped to form parts of the Southern Cone of South America, including a piece transferred from Laurentia when the west edge of Gondwana scraped against southeast Laurentia in the Ordovician. This is the Cuyania or Precordillera terrane of the Famatinian orogeny in northwest Argentina which may have continued the line of the Appalachians southwards,
As the rest of Gondwana formed, a complex series of orogenic events assembled the eastern parts of Gondwana (eastern Africa, Arabian-Nubian Shield, Seychelles, Madagascar, India, Sri Lanka, East Antarctica, and Australia) c. East African Orogeny c. . Then Australia and East Antarctica were merged with the remaining Gondwana c. in the Kuunga Orogeny.. First the Arabian-Nubian Shield collided with eastern Africa (in the Kenya-Tanzania region) in the
The later Malagasy orogeny at about 550-515 Mya affected Madagascar, eastern East Africa and southern India. In it, Neoproterozoic India collided with the already combined Azania and Congo-Tanzania-Bangweulu Block, suturing along the Mozambique Belt.
The 18,000 km (11,000 mi)-long Terra Australis Orogen developed along Gondwana's western, southern, and eastern margins. Proto-Gondwanan Cambrian arc belts from this margin have been found in eastern Australia, Tasmania, New Zealand, and Antarctica. Though these belts formed a continuous arc chain, the direction of subduction was different between the Australian-Tasmanian and New Zealand-Antarctica arc segments.
In the western end of Pangaea, the collision between Gondwana and Laurussia closed the Rheic and Palaeo-Tethys oceans. The obliquity of this closure resulted in the docking of some northern terranes in the Marathon, Ouachita, Alleghanian, and Variscan orogenies, respectively. Southern terranes, such as Chortis and Oaxaca, on the other hand, remained largely unaffected by the collision along the southern shores of Laurentia. Some Peri-Gondwanan terranes, such as Yucatán and Florida, were buffered from collisions by major promontories. Other terranes, such as Carolina and Meguma, were directly involved in the collision. The final collision resulted in the Variscan-Appalachian Mountains, stretching from present-day Mexico to southern Europe. Meanwhile, Baltica collided with Siberia and Kazakhstania which resulted in the Uralian orogeny and Laurasia. Pangaea was finally amalgamated in the Late Carboniferous-Early Permian but the oblique forces continued until Pangaea began to rift in the Triassic.
In the eastern end collisions occurred slightly later. The North China, South China, and Indochina blocks rifted from Gondwana during the middle Paleozoic and opened the Proto-Tethys Ocean. North China docked with Mongolia and Siberia during the Carboniferous-Permian followed by South China. The Cimmerian blocks then rifted from Gondwana to form the Palaeo-Thethys and Neo-Tethys oceans in the Late Carboniferous and docked with Asia during the Triassic and Jurassic. Western Pangaea began to rift while the eastern end was still being assembled.
The formation of Pangaea and its mountains had a tremendous impact on global climate and sea levels, which resulted in glaciations and continent-wide sedimentation. In North America, the base of the Absaroka sequence coincides with the Alleghanian and Ouachita orogenies and are indicative of a large-scale change in the mode of deposition far away from the Pangaean orogenies. Ultimately, these changes contributed to the Permian-Triassic extinction event and left large deposits of hydrocarbons, coal, evaporite, and metals.
The break-up of Pangaea began with the Central Atlantic magmatic province (CAMP) between South America, Africa, North America, and Europe. CAMP covered more than seven million square kilometres over a few million years, reached its peak at c. , and coincided with the Triassic-Jurassic extinction event. The reformed Gondwanan continent was not precisely the same as that which had existed before Pangaea formed; for example, most of Florida and southern Georgia and Alabama is underlain by rocks that were originally part of Gondwana, but this region stayed attached to North America when the Central Atlantic opened.
A large number of terranes were accreted to Eurasia during Gondwana's existence but the Cambrian or Precambrian origin of many of these terranes remains uncertain. For example, some Palaeozoic terranes and microcontinents that now make up Central Asia, often called the "Kazakh" and "Mongolian terranes", were progressively amalgamated into the continent Kazakhstania in the Late Silurian. Whether these blocks originated on the shores of Gondwana is not known.
In the Early Palaeozoic the Armorican terrane, which today form large parts of France, was part of either Peri-Gondwana or core Gondwana; the Rheic Ocean closed in front of it and the Palaeo-Tethys Ocean opened behind it. Precambrian rocks from the Iberian Peninsula suggest it too probably formed part of core Gondwana before its detachment as an orocline in the Variscan orogeny close to the Carboniferous-Permian boundary.
Antarctica, the centre of the supercontinent, shared boundaries with all other Gondwana continents and the fragmentation of Gondwana propagated clockwise around it. The break-up was the result of one of the Earth's most extensive large igneous provinces c. , but the oldest magnetic anomalies between South America, Africa, and Antarctica are found in what is now the southern Weddell Sea where initial break-up occurred during the Jurassic c. .
Gondwana began to break up in the early Jurassic following the extensive and fast emplacement of the Karoo-Ferrar flood basalts c. . Before the Karoo plume initiated rifting between Africa and Antarctica, it separated a series of smaller continental blocks from Gondwana's southern, Proto-Pacific margin (along what is now the Transantarctic Mountains): the Antarctic Peninsula, Marie Byrd Land, Zealandia, and Thurston Island; the Falkland Islands and Ellsworth-Whitmore Mountains (in Antarctica) were rotated 90° in opposite directions; and South America south of the Gastre Fault (often referred to as Patagonia) was pushed westward. The history of the Africa-Antarctica break-up can be studied in great detail in the fracture zones and magnetic anomalies flanking the Southwest Indian Ridge.
The Madagascar block and the Mascarene Plateau, stretching from the Seychelles to Réunion, were broken off India; elements of this breakup nearly coincide with the Cretaceous-Paleogene extinction event. The India-Madagascar-Seychelles separations appear to coincide with the eruption of the Deccan basalts, whose eruption site may survive as the Réunion hotspot. The Seychelles and the Maldives are now separated by the Central Indian Ridge.
East Gondwana, comprising Antarctica, Madagascar, India, and Australia, began to separate from Africa. East Gondwana then began to break up c.  The Indian Plate and the Australian Plate are now separated by the Capricorn Plate and its diffuse boundaries. During the opening of the Indian Ocean, the Kerguelen hotspot first formed the Kerguelen Plateau on the Antarctic Plate c. and then the Ninety East Ridge on the Indian Plate at c. . The Kerguelen Plateau and the Broken Ridge, the southern end of the Ninety East Ridge, are now separated by the Southeast Indian Ridge.when India moved northwest from Australia-Antarctica.
Separation between Australia and East Antarctica began c. with sea-floor spreading occurring c. . A shallow seaway developed over the South Tasman Rise during the Early Cenozoic and as oceanic crust started to separate the continents during the Eocene c. global ocean temperature dropped significantly. A dramatic shift from arc- to rift magmatism c. separated Zealandia, including New Zealand, the Campbell Plateau, Chatham Rise, Lord Howe Rise, Norfolk Ridge, and New Caledonia, from West Antarctica c. .
The opening of the South Atlantic Ocean divided West Gondwana (South America and Africa), but there considerable debate over the exact timing of this break-up. Rifting propagated from south to north along Triassic-Early Jurassic lineaments, but intra-continental rifts also began to develop within both continents in Jurassic-Cretaceous sedimentary basins; subdividing each continent into three sub-plates. Rifting began c. at Falkland latitudes, forcing Patagonia to move relative to the still static remainder of South America and Africa, and this westward movement lasted until the Early Cretaceous . From there rifting propagated northward during the Late Jurassic c. or Early Cretaceous c. most likely forcing dextral movements between sub-plates on either side. South of the Walvis Ridge and Rio Grande Rise the Paraná and Etendeka magmatics resulted in further ocean-floor spreading c. and the development of rifts systems on both continents, including the Central African Rift System and the Central African Shear Zone which lasted until c. . At Brazilian latitudes spreading is more difficult to assess because of the lack of palaeo-magnetic data, but rifting occurred in Nigeria at the Benue Trough c. . North of the Equator the rifting began after and continued until c. .
As the age of mammals commenced, the continent of Australia-New Guinea began gradually to separate and move north (55 Mya), rotating about its axis to begin with, and thus retaining some connection with the remainder of Gondwana for about 10 million years.
About 45 Mya, the Indian subcontinent collided with Asia, buckling the crust and forming the Himalayas. At about the same time, the southernmost part of Australia (modern Tasmania) finally separated from Antarctica, letting ocean currents flow between the two continents for the first time. Antarctica became cooler and Australia became drier because ocean currents circling Antarctica were no longer directed around northern Australia into the subtropics.
The opening of the Drake Passage, the separation of South America from West Antarctica, during the Oligocene at c. also caused climate changes. Immediately before this separation, South America and East Antarctica were not connected directly. However, the many microplates of the Antarctic Peninsula remained near southern South America, acting as "stepping stones" and allowing continued biological interchange and stopped oceanic current circulation. When the Drake Passage opened, a barrier was no longer present to force the cold waters of the Southern Ocean to be exchanged with warmer tropical water. Instead, a cold circumpolar current developed and Antarctica became what it is today: a frigid continent that locks up much of the world's fresh water as ice. Sea temperatures dropped by almost 10 °C, and the global climate became much colder.
By about 15 Mya, the collision between New Guinea (on the leading edge of the Australian Plate) and the southwestern part of the Pacific Plate pushed up the New Guinea Highlands, causing a rain shadow effect which drastically changed weather patterns in Australia, drying it out.
Later, South America was connected to North America via the Isthmus of Panama, cutting off a circulation of warm water and thereby making the Arctic colder, as well as allowing the Great American Interchange.
The adjective "Gondwanan" is in common use in biogeography when referring to patterns of distribution of living organisms, typically when the organisms are restricted to two or more of the now-discontinuous regions that were once part of Gondwana, including the Antarctic flora. For example, the plant family Proteaceae, known from all continent in the Southern Hemisphere, has a "Gondwanan distribution" and is often described as an archaic, or relict, lineage. The distributions in Proteaceae is, nevertheless, the result of both Gondwanan rafting and later oceanic dispersal.
During the late Paleozoic, Gondwana extended from a point at or near the South Pole to near the Equator. Across much of Gondwana, the climate was mild. During the Mesozoic, the world was on average considerably warmer than it is today. Gondwana was then host to a huge variety of flora and fauna for many millions of years. The laurel forest of Australia, New Caledonia, and New Zealand have a number of other related species of the laurissilva de Valdivia, through the connection of the Antarctic flora as gymnosperms and deciduous angiosperm Nothofagus. Corynocarpus laevigatus is called the bay of New Zealand, Laurelia novae-zelandiae belongs to the same genus Laurelia. The sempervirens tree niaouli grows in Australia, New Caledonia, and New Zealand.
New Caledonia and New Zealand ecoregions became separated from Australia by continental drift 85 million years ago. The islands still retain plants that originated in Gondwana and spread to the Southern Hemisphere continents later. However, strong evidence exists of glaciation during the Carboniferous to Permian time, especially in South Africa.