Gondwana

Gondwana or Gondwanaland was a supercontinent that existed from the Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic (about 180 million years ago), with the opening of the Drake Passage, separating South America and Antarctica occurring during the Eocene. Gondwana was not considered a supercontinent by the earliest definition, since the landmasses of Baltica, Laurentia, and Siberia were separated from it.

It was formed by the accretion of several cratons. Eventually, Gondwana became the largest piece of continental crust of the Paleozoic Era, covering an area of about 100,000,000 km2 (39,000,000 sq mi), about one-fifth of the Earth's surface. During the Carboniferous Period, it merged with Euramerica to form a larger supercontinent called Pangaea. Gondwana (and Pangaea) gradually broke up during the Mesozoic Era. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia, the Indian Subcontinent, Zealandia, and Arabia.

The formation of Gondwana began c. 800 to 650 Ma with the East African Orogeny, the collision of India and Madagascar with East Africa, and was completed c. 600 to 530 Ma with the overlapping Brasiliano and Kuunga orogenies, the collision of South America with Africa, and the addition of Australia and Antarctica, respectively.

Regions that were part of Gondwana have shared floral and zoological elements that persist to the present day.

Formation
The assembly of Gondwana was a protracted process during the Neoproterozoic and Paleozoic, which however remains incompletely understood 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 800 to 650 Ma 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 (650 to 800 Ma) and Kuunga orogeny (including the Malagasy Orogeny in southern Madagascar) (550 Ma), the collision between East Gondwana and East Africa in two steps, and the Brasiliano orogeny (660 to 530 Ma), the successive collision between South American and African cratons.

The last 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 continent Australia was still separated from India, eastern Africa, and Kalahari by c. 600 Ma, when most of western Gondwana had already been amalgamated. By c. 550 Ma, India had reached its Gondwanan position, which initiated the Kuunga orogeny (also known as the Pinjarra orogeny). Meanwhile, on the other side of the newly 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. 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. 750 to 530 Ma. First the Arabian-Nubian Shield collided with eastern Africa (in the Kenya-Tanzania region) in the East African Orogeny c. 750 to 620 Ma. Then Australia and East Antarctica were merged with the remaining Gondwana c. 570 to 530 Ma in the Kuunga Orogeny.

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-long (11,000 mi) 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.