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[[File:Laurasia-Gondwana.svg|thumb|250px|right| A global paleogeographic reconstruction of the Earth in the later [[Triassic]], 220 million years ago.]]
[[File:Gondwana 420 Ma.png|right|250px|Gondwana 420 million years ago. View centred on the South Pole.]]

'''Gondwana''',<ref>{{cite web|title= Gondwana |url= http://dictionary.reference.com/browse/gondwana|work= Dictionary.com|publisher= Lexico Publishing Group|accessdate= 2010-01-18}}</ref><ref>{{cite web|title= Gondwanaland|url= http://www.merriam-webster.com/dictionary/gondwana|publisher= Merriam-Webster Online Dictionary|accessdate= 2010-01-18}}</ref> also called '''Gondwanaland''', was a southern [[supercontinent]]. It formed when [[Pangaea]] broke up, starting 170 [[million]] years ago (mya), in the early [[middle Jurassic]].<ref name="SCAssmbly">{{cite conference |url= http://gsa.confex.com/gsa/2004AM/finalprogram/abstract_78645.htm|title= Paper #207-8 - Linking subduction initiation, accretionary orogenesis and Supercontinent assembly|last= Buchan|first= Craig|date= 2004|conference= 2004 Denver Annual Meeting|publisher= Geological Society of America}}</ref>

The global supercontinent [[Pangaea]] was complete 250 million years ago. Then it split into two smaller supercontinents, which were about the same size. The northern part of Pangaea became [[Laurasia]], and the southern part became Gondwana.<ref>{{Cite web|last= Houseman|first= Greg|url= http://homepages.see.leeds.ac.uk/~eargah/Gond.html|title= Dispersal of Gondwanaland|publisher= [[University of Leeds]]|accessdate=21 Oct 2008}}</ref> Over time, Gondwana drifted [[south]], while Laurasia moved north.

Gondwana included most of the landmasses in today's [[southern hemisphere]], including [[Antarctica]], [[South America]], [[Africa]], [[Madagascar]], [[Australia]]–[[New Guinea]], and [[New Zealand]]. It originally included [[China]], [[Siberia]], [[Arabia]] and the [[Indian subcontinent]], which have now moved entirely into the Northern Hemisphere.

Gondwana itself began to break up in the mid-[[Jurassic]] period, about 170 million years ago.

== History of the name ==
[[File:Nothofagus demis.JPG|thumb|300px|[[Nothofagus]] is a plant [[genus]] that shows a Gondwanan distribution. It first appeared in Gondwana and still exists in parts of Australia, New Zealand, [[New Caledonia]] and [[Chile]]. Fossils have also recently been found in [[Antarctica]].<ref>H.M. Li and Z.K. Zhou 2007. Fossil nothofagaceous leaves from the Eocene of western Antarctica and their bearing on the origin, dispersal and systematics of Nothofagus. ''Science in China''. '''50''': 1525-1535.</ref>]]

Gondwana was named by an [[Austria]]n [[scientist]], [[Eduard Suess]]. He named the supercontinent after the Gondwana region because some of the earliest rock formations of this continent were first investigated in part of the region, in modern [[Odisha]].

The [[adjective]] '''Gondwanan''' is often used in [[biogeography]] to describe where different [[organism]]s live. It is most commonly used when the organisms only live in two or more of the now-separate regions that were once part of Gondwana, including the Antarctic [[flora]]. For example, the [[Proteaceae]], a [[Family (biology)|family]] of [[plant]]s, lives only in southern [[South America]], [[South Africa]], and [[Australia]]. This is called a "Gondwanan distribution" (meaning that the Proteaceae live only in the areas that used to be part of Gondwana). This pattern shows that the Proteaceae have existed for a very long time {{ndash}} since the time that Gondwana existed.

[[Evidence]] of plant and animal distribution supported the ideas of two [[scientist]]s: [[Alfred Russel Wallace]] and [[Alfred Wegener]]. Wallace explained geographical distribution as the result of [[evolution]]. Wegener used geographical distribution as evidence for [[continental drift]].

== Breakup of Gondwana ==
Between 160 and 23 million years ago, Gondwana broke up. [[Africa]] separated from Antarctica around 160 million years ago. Next, it separated from the [[Indian subcontinent]], in the early [[Cretaceous]] period (about 125 million years ago).

About 65 million years ago, Antarctica (then connected to Australia) still had a [[Tropical climate|tropical]] to [[Subtropics|subtropical]] [[climate]], with [[marsupial]] [[fauna]]. About 40 million years ago, Australia-New Guinea separated from Antarctica. This allowed [[Latitude|latitudinal]] [[Ocean current|currents]] to separate Antarctica from Australia, and the first ice began to appear in Antarctica.

During the [[Eocene-Oligocene extinction event]] about 34 million years ago, levels of [[carbon dioxide]] were about 760 [[parts per million]].<ref>{{cite web|url=http://www.physorg.com/news172072921.html |title=New CO2 data helps unlock the secrets of Antarctic formation |publisher=Physorg.com |accessdate=2011-07-26}}</ref> They had been decreasing from earlier levels, which were in the thousands of parts per million.

Around 23 million years ago, the [[Drake Passage]] opened between Antarctica and South America, resulting in the [[Antarctic Circumpolar Current]] that completely isolated Antarctica. Models of the changes suggest that decreasing levels of carbon dioxide became more important.<ref>{{Cite journal| title = Rapid Cenozoic glaciation of Antarctica induced by declining atmospheric CO<sub>2</sub> | journal = Nature | volume = 421 | pages = 245–9 | date = 2003 | url = http://www.nature.com/nature/journal/v421/n6920/abs/nature01290.html | doi = 10.1038/nature01290 | accessdate = 19 October 2009 | issue=6920| pmid = 12529638| s2cid = 4326971 | last1 = Deconto | first1 = Robert M. | last2 = Pollard | first2 = David | bibcode = 2003Natur.421..245D }}</ref> The ice began to spread through Antarctica, replacing the [[forest]]s that had covered the continent. Since about 15 million years ago, Antarctica has been mostly covered with ice.<ref name="Trewby">{{Cite book| editor = Trewby, Mary | title = Antarctica: an encyclopedia from Abbott ice shelf to zooplankton | year = 2002 | publisher = Firefly Books | isbn = 1-55297-590-8 }}</ref> Around six million years ago, the Antarctic [[ice cap]] reached the size it is today.

== Submerged former lands ==
There are several submerged (underwater) lands in the [[Indian Ocean]], off the west of [[Australia]]. They are under more than {{convert|1.5|km|mi|abbr=off}} of water. Their rocks show that they used to be part of Gondwana. They are not the type of rocks that are usually found in the [[ocean]], like [[basalt]]. Instead, they are typical land rocks, like [[granite]], [[sandstone]], and [[gneiss]]. They also have the type of [[fossils]] that are now found on [[continent]]al areas. Recently, two of these sunken [[island]]s were found to the west of [[Perth, Western Australia]].<ref name=Sydney>Sunken islands could cause tectonic shift in Gondwana story. ''University of Sydney'' [http://sydney.edu.au/news/84.html?newsstoryid=8188]</ref> These islands are almost the size of [[Tasmania]], and have flat tops. This shows they were once at [[sea level]] before being submerged underwater. It also shows that when India began to break away from [[Australasia]] in the early [[Cretaceous]] period, the islands formed part of the last link between the two present-day continents.<ref name=Perth>Scientists find two 'sunken islands' off WA – part of Gondwana land link. ''Perth Now'' [http://www.perthnow.com.au/news/special-features/scientists-find-two-sunken-islands-off-wa-part-of-gondwana-land-link/story-e6frg163-1226194474355]</ref>

=== Naturaliste Plateau ===
The Naturaliste Plateau is a submerged land off of [[Western Australia]].<ref>{{Cite web |url=http://www-a.ga.gov.au/oceans/sa_Ntrlst.jsp |title=Naturaliste Plateau – regional setting. Geoscience Australia |access-date=2011-11-20 |archive-date=2012-07-23 |archive-url=https://archive.is/20120723061357/http://www-a.ga.gov.au/oceans/sa_Ntrlst.jsp |url-status=dead }}</ref> It has an [[area]] of 90,000 [[square kilometre]]s (34,749 [[square mile]]s).

The Naturaliste Plateau may have deposits of [[oil]]. When it was above land during the [[Mesozoic]] [[era]], it had a tropical climate which might have been perfect for creating [[coal]], oil and [[natural gas]].

=== Kerguelen microcontinent ===
{{Main|Kerguelen Plateau}}
The '''Kerguelen Plateau''' is a submerged [[microcontinent]] in the southern [[Indian Ocean]]. It is about {{convert|3000|km|mi|abbr=off}} to the [[southwest]] of [[Australia]], and extends for more than {{convert|2200|km|mi|abbr=off}} in a [[northwest]]-[[southeast]] direction. It is under deep water, but a small part of the plateau is above sea level, forming the Australian [[Heard Island and McDonald Islands]], and the [[France|French]] [[Kerguelen Islands]]. The islands are part of a [[large igneous province]] (LIP) which started when Gondwana started to break up, 130 million years ago in the [[Lower Cretaceous]] period.

[[Volcanic activity]] occurs sometimes on the Heard and McDonald islands.<ref>UT Austin scientist plays major role in study of underwater “micro-continent”. ''University of Texas.'' [http://www.utexas.edu/news/1999/05/28/nr_continent/] {{Webarchive|url=https://web.archive.org/web/20101129113402/http://www.utexas.edu/news/1999/05/28/nr_continent/ |date=2010-11-29 }}</ref>

== References ==
{{Reflist}}

[[Category:Gondwana| ]]

Gondwana - Revision history

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