What is Gondwana? What is Gondwana? By Stephanie Pappas, Live Science Contributor | June 7, 2013 03:52pm ET MORE The breakup of the Pangaea supercontinent. Credit: U.S. Geological Survey Gondwana was an ancient supercontinent that broke up about 180 million years ago. The continent eventually split into landmasses we recognize today: Africa, South America, Australia, Antarctica, the Indian subcontinent and the Arabian Peninsula. The familiar continents of today are really only a temporary arrangement in a long history of continental movement. Landmasses on Earth are in a constant state of slow motion, and have, at multiple times, come together as one. These all-in-one supercontinents include Columbia (also known as Nuna), Rodinia, Pannotia and Pangaea (or Pangea). Gondwana was half of the Pangaea supercontinent, along with a northern supercontinent known as Laurasia. The creation of Gondwana Gondwana's final formation occurred about 500 million years ago, during the late Ediacaran Period.

By this time, multicellular organisms had evolved, but they were primitive: The few fossils left from this period reveal segmented worms, frond-like organisms and round creatures shaped like modern jellyfish. In this world, Gondwana conducted its slow grind to supercontinent status. Bits and pieces of the future supercontinent collided over millennia, bringing together what are now Africa, India, Madagascar, Australia and Antarctica. This early version of Gondwana joined with the other landmasses on Earth to form the single supercontinent Pangaea by about 300 million years ago. About 280 million to 230 million years ago, Pangaea started to split. Magma from below the Earth's crust began pushing upward, creating a fissure between what would become Africa, South America and North America. As part of this process, Pangaea cracked into a northernmost and southernmost supercontinent. The northern landmass, Laurasia, would drift north and gradually split into Europe, Asia and North America. The southern landmass, still carrying all those bits and pieces of the future southern hemisphere, headed southward after the split. This supercontinent was Gondwana.

Gondwana's breakup During Gondwana's stint as the southerly supercontinent, the planet was much warmer than it was today — there was no Antarctic ice sheet , and dinosaurs still roamed the Earth. By this time, it was the Jurassic Period , and much of Gondwana was covered with lush rainforest. The great supercontinent was still under strain, however. Between about 170 million and 180 million years ago, Gondwana began its own split, with Africa and South America breaking apart from the other half of Gondwana. About 140 million years ago, South America and Africa split, opening up the South Atlantic Ocean between them. Meanwhile, on the eastern half of the once-supercontinent, Madagascar made a break from India and both moved away from Australia and Antarctica. Australia and Antarctica clung together longer; in fact, Antarctica and Australia didn't make their final split until about 45 million years ago. At that point, Antarctica started to freeze over as Earth's climate cooled, while Australia drifted northward.

(Today, the Australian continent still moves north at a rate of about 1.2 inches (3 centimeters) a year.) Gondwana theory The exact mechanisms behind Gondwana's split are still unknown. Some theorists believe that "hot spots," where magma is very close to the surface, bubbled up and rifted the supercontinent apart. In 2008, however, University of London researchers suggested that Gondwana instead split into two tectonic plates , which then broke apart. The existence of Gondwana was first hypothesized in the mid-1800s by Eduard Suess, a Viennese geologist who dubbed the theoretical continent "Gondwanaland." Suess was tipped off by similar fern fossils found in South America, India and Africa (the same fossils would later be found in Antarctica). At the time, plate tectonics weren't understood, so Suess didn't realize that all of these continents had once been in different locations. Instead, he developed a theory of sea level rise and regression over time that would have linked together the southern hemisphere continents with land bridges.

Suess got the name Gondwanaland from the Gondwana region of central India, where geological formations match those of similar ages in the southern hemisphere. Follow Stephanie Pappas on Twitter and Google+ . Follow us @livescience , Facebook & Google+ . Original article on LiveScience.com. Editor's Recommendations Facts About Pangaea The breakup of the Pangaea supercontinent. Credit: U.S. Geological Survey About 300 million years ago, Earth didn't have seven continents, but instead one massive supercontinent called Pangaea, which was surrounded by a single ocean called Panthalassa. The explanation for Pangaea's formation ushered in the modern theory of plate tectonics , which posits that the Earth's outer shell is broken up into several plates that slide over Earth's rocky shell, the mantle. Over the course of the planet's 3.5 billion-year history, several super continents have formed and broken up, a result of churning and circulation in the Earth's mantle , which makes up most of planet's volume. This breakup and formation of supercontinents has dramatically altered the planet's history. "This is what's driven the entire evolution of the planet through time.

This is the major backbeat of the planet," said Brendan Murphy, a geology professor at the St. Francis Xavier University, in Antigonish, Nova Scotia. History More than a century ago, the scientist Alfred Wegener proposed the notion of an ancient supercontinent, which he named Pangaea (sometimes spelled Pangea), after putting together several lines of evidence. The first and most obvious was that the "continents fit together like a tongue and groove," something that was quite noticeable on any accurate map, Murphy said. Another telltale hint that Earth's continents were all one land mass comes from the geologic record. Coal deposits found in Pennsylvania have a similar composition to those spanning across Poland, Great Britain and Germany from the same time period. That indicates that North America and Europe must have once been a single landmass. And the orientation of magnetic minerals in geologic sediments reveals how Earth's magnetic poles migrated over geologic time, Murphy said. In the fossil record, identical plants, such as the extinct seed fern Glossopteris, are found on now widely disparate continents.

And mountain chains that now lie on different continents, such as the Appalachians in the United States and the Atlas Mountains in Morocco, were all part of the Central Pangaea Mountains, formed through the collision of the supercontinents Gondwana and Laurussia. Pangaea formed through a gradual process spanning a few hundred million years. Beginning about 480 million years ago, a continent called Laurentia, which includes parts of North America, merged with several other micro-continents to form Euramerica. Euramerica eventually collided with Gondwana, another supercontinent that included Africa, Australia, South America and the Indian subcontinent. About 200 million years ago, the supercontinent began to break up. Gondwana (what is now Africa, South America, Antarctica, India and Australia) first split from Laurasia (Eurasia and North America). Then about 150 million years ago, Gondwana broke up. India peeled off from Antarctica, and Africa and South America rifted, according to a 1970 article in the Journal of Geophysical Research . Around 60 million years ago, North America split off from Eurasia.

Life and climate Having one massive landmass would have made for very different climactic cycles. For instance, the interior of the continent may have utterly dry, as it was locked behind massive mountain chains that blocked all moisture or rainfall, Murphy said. But the coal deposits found in the United States and Europe reveal that parts of the ancient supercontinent near the equator must have been a lush, tropical rainforest, similar to the Amazonian jungle, Murphy said. (Coal forms when dead plants and animals sink into swampy water, where pressure and water transform the material into peat, then coal.) "The coal deposits are essentially telling us that there was plentiful life on land," Murphy told Live Science. Pangaea existed for 100 million years, and during that time period several animals flourished, including the Traversodontidae , a family of plant-eating animals that includes the ancestors of mammals. During the Permian period , insects such as beetles and dragonflies flourished. But the existence of Pangaea overlapped with the worst mass extinction in history, the Permian-Triassic (P-TR) extinction event.

Also called the Great Dying, it occurred around 252 million years ago and caused most species on Earth to go extinct. The early Triassic period saw the rise of archosaurs, a group of animals that eventually gave rise to crocodiles and birds, and a plethora of reptiles. And about 230 million years ago some of the earliest dinosaurs emerged on Pangaea, including theropods, largely carnivorous dinosaurs that mostly had air-filled bones and feathers similar to birds. Cycle in history The current configuration of continents is unlikely to be the last. Supercontinents have formed several times in Earth's history, only to be split off into new continents. Right now for instance, Australia is inching toward Asia, and the eastern portion of Africa is slowly peeling off from the rest of the continent. Geologists have noticed that there is a quasi-regular cycle in which supercontinents form and break up every 300 to 400 million years, but exactly why is a mystery, Murphy said. But most scientists believe that the supercontinent cycle is largely driven by circulation dynamics in the mantle, according to a 2010 article in the Journal of Geodynamics . Beyond that, the details get fuzzy.

While the heat formed in the mantle likely comes from the radioactive decay of unstable elements, such as uranium, scientists don't agree on whether there are mini-pockets of heat flow within the mantle, or if the entire shell is one big heat conveyor belt, Murphy said. Follow Tia Ghose on Twitter and Google+ . Follow LiveScience @livescience , Facebook & Google+ . Additional resources Pangea | supercontinent | Britannica.com supercontinent Pangea, also spelled Pangaea, in early geologic time , a supercontinent that incorporated almost all the landmasses on Earth . Paleogeography and paleoceanography of (top) Early Permian and (bottom) early Late Permian times. Adapted from C.A. Ross and J.R.P. Ross, Cushman Foundation for Foraminiferal Research, Special Publication 24 Pangea was surrounded by a global ocean called Panthalassa, and it was fully assembled by the Early Permian Period (some 299 million to 272 million years ago).

The supercontinent began to break apart about 200 million years ago, during the Early Jurassic Period (201 million to 174 million years ago), eventually forming the modern continents and the Atlantic and Indian ocean s. Pangea’s existence was first proposed in 1912 by German meteorologist Alfred Wegener as a part of his theory of continental drift . Its name is derived from the Greek pangaia, meaning “all the Earth.” The land on Earth is constantly moving. Over millions of years, the continents broke apart from a … Encyclopædia Britannica, Inc. The land and seas on Earth are constantly moving. Over the course of millions of years, the … Created and produced by QA International. © QA International, 2010. All rights reserved. During the Early Permian, the northwestern coastline of the ancient continent Gondwana (a paleocontinent that would eventually fragment to become South America , India , Africa , Australia , and Antarctica ) collided with and joined the southern part of Euramerica (a paleocontinent made up of North America and southern Europe ).

With the fusion of the Angaran craton (the stable interior portion of a continent) of Siberia to that combined landmass during the middle of the Early Permian, the assembly of Pangea was complete. Cathaysia, a landmass comprising the former tectonic plates of North and South China , was not incorporated into Pangea. Rather, it formed a separate, much smaller, continent within the global ocean Panthalassa. Similar Topics Laurasia The mechanism for the breakup of Pangea is now explained in terms of plate tectonics rather than Wegener’s outmoded concept of continental drift, which simply stated that Earth’s continents were once joined together into the supercontinent Pangea that lasted for most of geologic time. Plate tectonics states that Earth’s outer shell, or lithosphere , consists of large rigid plates that move apart at oceanic ridges , come together at subduction zones , or slip past one another along fault lines . The pattern of seafloor spreading indicates that Pangea did not break apart all at once but rather fragmented in distinct stages. Plate tectonics also postulates that the continents joined with one another and broke apart several times in Earth’s geologic history.

The first oceans formed from the breakup, some 180 million years ago, were the central Atlantic Ocean between northwestern Africa and North America and the southwestern Indian Ocean between Africa and Antarctica. The South Atlantic Ocean opened about 140 million years ago as Africa separated from South America. About the same time, India separated from Antarctica and Australia, forming the central Indian Ocean. Finally, about 80 million years ago, North America separated from Europe, Australia began to rift away from Antarctica, and India broke away from Madagascar . India eventually collided with Eurasia approximately 50 million years ago, forming the Himalayas . During Earth’s long history, there probably have been several Pangea-like supercontinents. The oldest of those supercontinents is called Rodinia and was formed during Precambrian time some one billion years ago. Another Pangea-like supercontinent, Pannotia, was assembled 600 million years ago, at the end of the Precambrian. Present-day plate motions are bringing the continents together once again. Africa has begun to collide with southern Europe, and the Australian Plate is now colliding with Southeast Asia .

Within the next 250 million years, Africa and the Americas will merge with Eurasia to form a supercontinent that approaches Pangean proportions. The episodic assembly of the world’s landmasses has been called the supercontinent cycle or, in honour of Wegener, the Wegenerian cycle (see plate tectonics: Supercontinent cycle ). Map showing the future world as projected to appear in about 250 million years. Earth’s present-day … Adapted from C.R. Scotese, The University of Texas at Arlington Learn More in these related articles: Historical perspective [This Dynamic Earth, USGS] Tectonic plates [115 k] The belief that continents have not always been fixed in their present positions was suspected long before the 20th century; this notion was first suggested as early as 1596 by the Dutch map maker Abraham Ortelius in his work Thesaurus Geographicus. Ortelius suggested that the Americas were "torn away from Europe and Africa . . .

by earthquakes and floods" and went on to say: "The vestiges of the rupture reveal themselves, if someone brings forward a map of the world and considers carefully the coasts of the three [continents]." Ortelius' idea surfaced again in the 19th century. However, it was not until 1912 that the idea of moving continents was seriously considered as a full-blown scientific theory -- called Continental Drift -- introduced in two articles published by a 32-year-old German meteorologist named Alfred Lothar Wegener. He contended that, around 200 million years ago, the supercontinent Pangaea began to split apart. Alexander Du Toit, Professor of Geology at Witwatersrand University and one of Wegener's staunchest supporters, proposed that Pangaea first broke into two large continental landmasses, Laurasia in the northern hemisphere and Gondwanaland in the southern hemisphere. Laurasia and Gondwanaland then continued to break apart into the various smaller continents that exist today. In 1858, geographer Antonio Snider-Pellegrini made these two maps showing his version of how the American and African continents may once have fit together, then later separated.

Left: The formerly joined continents before (avant) their separation. Right: The continents after (aprés) the separation. (Reproductions of the original maps courtesy of University of California, Berkeley.) Wegener's theory was based in part on what appeared to him to be the remarkable fit of the South American and African continents, first noted by Abraham Ortelius three centuries earlier. Wegener was also intrigued by the occurrences of unusual geologic structures and of plant and animal fossils found on the matching coastlines of South America and Africa, which are now widely separated by the Atlantic Ocean. He reasoned that it was physically impossible for most of these organisms to have swum or have been transported across the vast oceans. To him, the presence of identical fossil species along the coastal parts of Africa and South America was the most compelling evidence that the two continents were once joined. In Wegener's mind, the drifting of continents after the break-up of Pangaea explained not only the matching fossil occurrences but also the evidence of dramatic climate changes on some continents.

For example, the discovery of fossils of tropical plants (in the form of coal deposits) in Antarctica led to the conclusion that this frozen land previously must have been situated closer to the equator, in a more temperate climate where lush, swampy vegetation could grow. Other mismatches of geology and climate included distinctive fossil ferns (Glossopteris) discovered in now-polar regions, and the occurrence of glacial deposits in present-day arid Africa, such as the Vaal River valley of South Africa. The theory of continental drift would become the spark that ignited a new way of viewing the Earth. But at the time Wegener introduced his theory, the scientific community firmly believed the continents and oceans to be permanent features on the Earth's surface. Not surprisingly, his proposal was not well received, even though it seemed to agree with the scientific information available at the time. A fatal weakness in Wegener's theory was that it could not satisfactorily answer the most fundamental question raised by his critics: What kind of forces could be strong enough to move such large masses of solid rock over such great distances?

Wegener suggested that the continents simply plowed through the ocean floor, but Harold Jeffreys, a noted English geophysicist, argued correctly that it was physically impossible for a large mass of solid rock to plow through the ocean floor without breaking up. Rejoined continents [48 k] Undaunted by rejection, Wegener devoted the rest of his life to doggedly pursuing additional evidence to defend his theory. He froze to death in 1930 during an expedition crossing the Greenland ice cap, but the controversy he spawned raged on. However, after his death, new evidence from ocean floor exploration and other studies rekindled interest in Wegener's theory, ultimately leading to the development of the theory of plate tectonics. Plate tectonics has proven to be as important to the earth sciences as the discovery of the structure of the atom was to physics and chemistry and the theory of evolution was to the life sciences. Even though the theory of plate tectonics is now widely accepted by the scientific community, aspects of the theory are still being debated today. Ironically, one of the chief outstanding questions is the one Wegener failed to resolve: What is the nature of the forces propelling the plates?

Scientists also debate how plate tectonics may have operated (if at all) earlier in the Earth's history and whether similar processes operate, or have ever operated, on other planets in our solar system. The Pangea Supercontinent By Amanda Briney, Contributing Writer Pangea, also spelled Pangaea, was a supercontinent that existed on the Earth millions of years ago and covered about one-third of its surface. A supercontinent is a very large landmass that is made up of more than one continent. In the case of Pangea nearly all of the Earth's continents were connected into one large landmass. It is believed that Pangea began forming about 300 million years ago, was fully together by 270 million years ago and began to separate around 200 million years ago. The name Pangea is ancient Greek and means "all lands." The term began being used in the early 20th century after Alfred Wegener noticed that the Earth's continents looked like they fit together like a jigsaw puzzle.

He later developed his theory of continental drift to explain why the continents looked the way they did and first used the term Pangea at a symposium in 1927 focused on that topic. Formation of Pangea Due to mantle convection within the Earth's surface new material constantly comes up between the Earth's tectonic plates at rift zones , causing them to move away from the rift and toward one another at the ends. continue reading below our video 10 Facts About the Titanic That You Don't Know In the case of Pangea, the Earth's continents were eventually moved so much over millions of years that they combined into one large supercontinent. Around 300 million years ago the northwestern part of the ancient continent of Gondwana (near the South Pole), collided with the southern part of the Euramerican continent to form one very large continent. Eventually the Angaran continent, located near the North Pole, began to move south and it collided with the northern part of the Euramerican continent to form the large supercontinent, Pangea, by about 270 million years ago.

It should be noted however that there was another separate landmass, Cathaysia, which was made up of north and south China that was not a part of the larger Pangea landmass. Once it was completely formed, Pangea covered around one-third of the Earth's surface and it was surrounded by an ocean that covered the rest of the globe. This ocean was called Panthalassa. Break-Up of Pangea Pangea began to break up about 200 million years ago as a result of the movement of the Earth's tectonic plates and mantle convection. Just as Pangea was formed by being pushed together due to the movement of the Earth's plates away at rift zones, a rift of new material caused it to separate. Scientists believe that the new rift began due to a weakness in the Earth's crust. At that weak area, magma began to push through and create a volcanic rift zone. Eventually the rift zone grew so large that it formed a basin and Pangea began to separate. In the areas where Pangea began to separate, new oceans formed as Panthalassa rushed into the newly opened areas. The first new oceans to form were the central and southern Atlantic.

About 180 million years ago the central Atlantic Ocean opened up between North America and northwestern Africa. Around 140 million years ago the South Atlantic Ocean formed when what is today South America separated from the west coast of southern Africa. The Indian Ocean was the next to form when India separated from Antarctica and Australia and about 80 million years ago North America and Europe separated, Australia and Antarctica separated and India and Madagascar separated. Over millions more years, the continents gradually moved to their current positions. Evidence for Pangea As Alfred Wegener noticed in the early 20th century, the Earth's continents seem to fit together like a jigsaw puzzle in many areas around the globe. This is the significant evidence for the existence of Pangea millions of years ago. The most prominent place where this is visible is the northwestern coast of Africa and the eastern coast of South America. In that location the two continents look like they were once connected, which they in fact were during Pangea. Other evidence for Pangea includes fossil distribution, distinctive patterns in rock strata in now unconnected parts of the world and the distribution of the world's coal.

In terms of fossil distribution, archaeologists have found matching fossil remains if ancient species in continents are separated by thousands of miles of ocean today. For example matching reptile fossils have been found in Africa and South America indicating that these species at one time lived very close to each other as it is not possible to them to have crossed the Atlantic Ocean. Patterns in rock strata are another indicator for the existence of Pangea. Geologists have discovered distinctive patterns in rocks in continents that are now thousands of miles apart. By having matching patterns it indicates that the two continents and their rocks were at one time one continent. Finally the world's coal distribution is evidence for Pangea. Coal normally forms in warm, wet climates. However geologists have found coal under Antarctica's very cold and dry ice caps. If Antarctica were a part of Pangea it is likely that it would have been in another location on the Earth and the climate when the coal formed would have been very different than it is today. Many Ancient Supercontinents Based on the evidence scientists have found in plate tectonics, it is likely that Pangea was not the only supercontinent to exist on the Earth.

In fact, archaeological data found in matching rock types and searching for fossils shows that the formation and break-up of supercontinents like Pangea are a cycle throughout the Earth's history ( Lovett, 2008 ). Gondwana and Rodinia are two supercontinents that scientists have discovered that existed prior to Pangea. Scientists also predict that the cycle of supercontinents will continue. Currently the world's continents are moving away from the Mid-Atlantic Ridge toward the middle of the Pacific Ocean where they will eventually collide with one another in about 80 million years (Lovett, 2008). To see a diagram of Pangea and how it separated, visit the United States' Geological Survey's Historical Perspective page within This Dynamic Earth . Think the Earth | 012 Earthrium ←Back The formation of supercontinents The Earth was born around 4.6 billion years ago, after which it has continued to evolve for a considerable length of time. Based on evidence found in rock formations, it is thought that by 4.4 billion years ago oceans and continents had already formed.

Research into such things as plate tectonics and plume tectonics (see Part 4: Earthquakes around the world) have advanced to the stage where it is has been concluded that from around two billion years ago, so-called supercontinents containing all the present-day continents were forming every 400-500 million years. Recent studies have revealed quite a lot of detail about the formation and breaking up of these supercontinents up to around 600 million years ago. This is due to advances in a field of study known as paleomagnetism, which involves looking into the extent of continental drift by searching for rock formations that contain records of the Earth's magnetic field over time and then measuring the ages of these rock formations. The images used in this edition of Earthrium were provided by Dr. Ronald Blakey, a geologist at Northern Arizona University. Well then, just what kind of supercontinents existed on Earth all those years ago? The following is a brief description of the supercontinents we currently know existed. Neuna Neuna was the Earth's first supercontinent and was formed around 1.9 billion years ago.

We know that it broke up soon after it formed, but it is difficult to determine what form it took. The name Neuna was given to the continent by the Harvard University geologist Dr. Paul Hoffman, and is an acronym that derives from Northern Europe and North America. Traces of the orogenic activity of 1.9 billion years ago can still be found in various locations around the world, and on the basis of these it is thought that most of the landmass that currently makes up the continent of North America was once part of the Neuna supercontinent. Rodinia This supercontinent is thought to have existed from between one billion and 700 million years ago. It is now thought that before it started breaking apart, there was a major ice age that froze the entire surface of the Earth, including the ocean in the vicinity of the equator. Because when viewed from space the Earth would probably have resembled a huge lump of white snow, this theory has been labeled the Snowball Earth hypothesis. According to one theory, during the Neuna and Rodinia periods there existed another supercontinent known as Colombia (1.5 billion years ago), although at this stage little is known about this supercontinent.

Gondwana Gondwana was a new supercontinent that formed after Rodinia broke up. Most of it is thought to have been located in the southern hemisphere. If you click on "600 million years ago" at the bottom of the globe at left you'll notice a large continent in the form of a single landmass in the southern hemisphere. The supercontinent of Gondwana included the present-day continents of Africa, South America, Australia, and Antarctica, as well as the Indian subcontinent. Pangaea The supercontinent of Pangaea formed around 290 million years ago. It began to break apart some 250 million years ago, eventually separating into the six continents that exist today. Two hundred and fifty million years ago was also when the Earth's most severe extinction event occurred. It is thought that this extinction event is probably closely related to the break up of Pangaea, and extensive research is currently being carried out around the world to determine the exact relationship between the two events. Supercontinents of the future We know that at present the continents are all drifting in the direction of Asia.

If this trend continues, the first thing that will happen, some 50 million years from now, is that Australia will collide with the Japanese archipelago. Next, some 200 to 300 million years in the future according to one theory, Africa and the Arabian peninsula, and then America will merge with Asia, possibly forming a single supercontinent known as Amasia. From Seimei to chikyu no rekishi (History of life and the Earth) by Shigenori Maruyama and Yukio Isozaki (Iwanami Shoten) Although the speed at which the continents are moving is less than 1cm a year, by compressing time we hope we have brought home the fact that the Earth is a planet on which the landmasses are continually shifting. Australia Separates from Antarctica Australia Separates from Antarctica The Rifting Begins The Jurassic was the period when the process of separation of Australia by passive margin rifting began, eventually giving rise to the isolated continent of today. This process gave rise to many of the geological features and landforms of the continent.

At the start of the formation of Gondwana Australia collided with Antarctica and no other major landmasses followed it, the other collisions occurred on other edges of Antarctica. So Australia spent its whole time with Gondwana on the outer edge of the supercontinent. Early in the Jurassic , a wide belt of continental crust was uplifted along the east coast. Comprising this raised crust are the now mostly submerged Lord Howe Rise & Norfolk Rises, the submerged Queensland Plateau, the islands of New Caledonia and New Zealand and the submerged Campbell Plateau to the south of New Zealand. New Zealand is actually more like a sub-continent, much of its area being submerged. It was previously believed that the pre-sea floor spreading continents could be fitted together at the edges of their continental shelves. It has now been found that stretching of the continental crust preceded the start of rifting that separated the land masses. Based on this improved knowledge of how the landmasses fitted together in Gondwana, it places Australia adjacent to the present Wilkes Land of Antarctica.

India, a much larger landmass than present-day India, including the crust folded up in the Himalayas and subducted under them, was connected to Antarctica adjacent to the present West Australian coast. Beginning 160 million years ago stretching of the continental crust began. The first upwelling of sea floor crust, basalt, is estimated to have occurred when the rift valley was about 600 km wide and the inner 360 km of crust had stretched and thinned. Because of the thinning of the crust it becomes lighter and isostatic adjustment caused the thinned crust to rise, allowing the underlying hot lithosphere to rise closer to the surface. When the thickness of the crust was reduced from about 40 km to 10 km, the pressure changes caused the upper lithosphere to become molten and the magma was forced up at the thinnest point in the stretched crust. The continued emergence of basalt pushed the separated sections of crust apart, as sea floor continues to be added at mid-ocean ridges. The first part of the continent to begin separation at this time was the West Australian end. About 20 % of the continent is thought to have separated during the first phase. .

During this first phase of rifting, from 160 to 132 million years ago, Middle Jurassic to Early Cretaceous , a small fragment of crust, Argoland , moved away from a section of the northwest coast of Western Australia occupied by the Canning Basin , by active seafloor spreading, allowing the sea to flood the basin. The seafloor that resulted from this spreading is known as the Argo Abyssal Plain . Plant material was deposited in the troughs associated with the rifting and was the source of the Northwest Shelf's oil and gas deposits. Early in the Cretaceous, India rotated away from Australia, the sea entered the proto-Indian Ocean rift. At this time the Darling Scarp, the edge of the Yilgarn Block , becomes a prominent feature of Western Australia. This is partly because there was some crustal uplift, but also because the crust seaward of the Scarp was warped down. By about 150 Ma the coastline of Antarctica was close to the South Pole. At this time the western end of Tethys was connected to the proto-Pacific Ocean.

From the northeast margin of Gondwana slivers of continental crust in the area of Australia's Northwest Shelf, and the New Guinea region, then the eastern tip of Gondwana, are believed to have been rifted to the northwest, beginning in about the Permian . These fragments are thought to possibly be in South Tibet and a number of places in Southeast Asia. There is very little evidence known of their journey away from Australia across Tethys. (Hill, 1994). Movement of these fragments has been suggested to have occurred later rather than earlier, maps in Hill (1994) show them as possible islands, and it has been assumed that most of them started rifting about 167 Ma, after the Callovian seafloor spreading event along that part of the coast of Gondwana. It is believed the fragments attached to the southeastern section of what was then the Asian continent to form Sundaland, which was a promontory. It is still in the equatorial zone. Possible 'stepping-stone' links connecting the Asian mainland with the Australian section of Gondwana are indicated on the maps in Hill (1994) as a group of hypothetical islands.

The palaeogeography of the area is believed to have probably changed dramatically since then. At about 150 Ma a strip of terrain separated the present coast of eastern Australia from the proto-Pacific Ocean. This terrain is now marked by the Lord Howe Rise, Queensland Plateau and New Caledonia. In the Early to Mid Jurassic the breakup of Gondwana was preceded by a major thermal event that produced basaltic magmatic activity over a wide area, comprised of the dolerites of Tasmania and southeast Australia, Karoo dolerites in South Africa and in Antarctica, the Ferrar Super Group, Dufek Intrusion. Movement between west Gondwana (Africa-South America) and east Gondwana (Madagascar, Greater India and Australia) had begun by 150 Ma. Strike-slip movement dominated the breakup, which formed narrow basins, and it is believed there may have been land connecting the 2 major fragments periodically. According to Wilcox & Stagg (1990), it was about this time that rifting along the southern margin of Australia began (Hill, 1994).

By 140 Ma much of the gap between Africa and the the block composed of Antarctica, Madagascar, Greater India and Australia was covered by a narrow expanse of ocean. The fragments of crust that had separated from the northeastern edge of Gondwana had moved towards the Equator. Rifts continued to form along the western and southern margins of Australia, separating Australia from Antarctica and Greater India. Accumulation of sediments in East Antarctica is mostly recycled palynomorphs (Truswell, 1983). Along the southern margin of Australia, as rifting progressed, there was initial extension, northwest to southeast, of about 300 km which was accomplished by 120 Ma. New Zealand was part of the landmass along the margins of East Antarctica and southeast Australia.

The Rangitata Orogeny is thought to have caused this landmass to reach its greatest extent in the Early Cretaceous (Stevens, 1989), in Hill, 1994), By 132 million years ago the position of the South Pole had shifted, bringing Australia's most southerly point at the time, somewhere near the Queensland-New South Wales border to about 80o South. By 120 million years ago the South Pole was close to Tasmania. In the second phase of separation, 132-96 million years ago, the remainder of Australia separated. During this phase, India started rotating northwestward from Australia. As a result of this the Perth Basin subsided allowing the sea to flow in. Australia was joined to Antarctica along the eastern edge of that continent. What is now Australia's east coast was then it's southern coast. In the first phase of rifting the West Australian end of the rift had opened up as far as the Great Australian Bight. In the second phase rifting shifted direction. It was now the eastern Australian end that opened forming the Otway Basin and Torquay Basin .

About 15 million years later rifting of an arm of the Tasman Sea formed the Gippsland Basin . During the second phase of separation Australia rotated to the northwest, so that the southern (now eastern) end of the rift opened. In the second phase of rifting, 132-96 million years ago, the remainder of the continent separated. This rotation squeezed the West Australian section, forcing thinner basin crust, with overlying sediments, against the solid Yilgarn Block . This resulted in the heaving up of the Stirling Ranges . By 130 Ma, the last 3 continents had begun to separate. There were still no significant water gaps between them (Powell et al., 1988), and Australia and Antarctica were moving apart at a rate of only a few mm per year. The separation between Australia and Antarctica had begun about 132 Ma at the southwest margin of the Exmouth Plateau, progressing to the south then to the east along Australia's southern margin. At about this time the South Atlantic had begun to open, opening from the south to the north (Nurnberg & Muller, 1991).

At this time of great tectonic activity that was tearing apart the previously stable landmasses, as with Gondwana, the sea level was rising. Added to the easier access to the interconnected basins that characterised much of Australia from down warping and rifting, this rising sea level resulted in large areas of the continent being swamped. In the modern north of Australia the sea entered the Carpentaria Basin , starting a process of inundation that saw a vast area of the interconnected inland basins being flooded. This epicontinental sea, the Eromanga Sea , reached as far inland as the middle of the Eromanga Basin . By its peak, between 115 and 110 million years ago all the inland basins were covered by a single, huge sea. Australia then consisted of 4 islands. The part of the sea that had entered the rift forming between Antarctica and Australia was connected to the Eromanga Sea by its extension into the Eucla Basin . By 120 Ma, there were wide expanses of water on the African east coast and between India and Antarctica and Western Australia, Australia still being attached to Antarctica.

As the continental extension between Antarctica and Australia continued slowly, the direction of the extension changed from NW-SE to NNE-SSW. In the east movement of 120 km resulted in the formation of the Gippsland and Bass Basins (Wilcox & Stagg, 1990) (in Hill, 1994). At about 110 Ma large parts of the Australian continent were submerged beneath a marine transgression, the Eromanga Sea , that peaked in the Aptian, about 116-113 Ma. Rifting along the southeastern ('Australian') edge of Gondwana, leading to the opening of the Tasman Sea (Stevens, 1989), as well as the western margin of New Zealand. The Antarctic Peninsula and adjacent areas of West Antarctica were affected by rifting and crustal blocks rotating locally. Though it continued until about 100 Ma it didn't have a significant effect on the overall geography (Storey et al., 1988).

At this time the widening gap as Australia rifted from Antarctica allowed the proto-Indian Ocean to enter at the western end to begin the formation of the Southern Ocean (Hill, 1994). After 110 Ma, the Eromanga Sea gradually receded until the continent was once again above water by the end of the Cretaceous . There is some evidence, though not conclusive, of winter ice on the Eromanga Sea during the Early Cretaceous . Drop stones, indicative of ice, have been found in fine-grained deposits in eastern parts of the Northern Territory and northwestern Queensland. These fine-grained sediments are of marine origin, deposited on a shallow marine margin of the Carpentaria Basin . Marine sediments were deposited under the Eromanga Sea , and fresh water sediments following the return of fresh water drainage after the retreat of the Eromanga Sea, formed capping rocks above the Jurassic sandstones of the GAB . After 160 Ma, when the crustal stretching began, and 90 Ma, when ocean floor spreading began, Tasmania moved 130 km. Tasmania was on a separate crustal plate, moving independently of the other 2 continents.

The South Tasman Rise behaved like a 4th plate. When Australia began drifting, Tasmania followed. Phase 3 - Sea Floor Spreading By 100 Ma the sea had submerged some rift zones around New Zealand, as a result of subsidence and erosion lowering the surrounding landmasses, but in the south there was still a land connection to Antarctica (Stevens, 1989). It is thought the Eastern Highlands of Australia may have begun to be uplifted about this time, associated with the opening of the Tasman Sea (Wellman, 1987). Before 96 Ma, India had been moving at a slow pace as it moved northwest. About 96 mya, the spreading ridges that had been pushing India's plate stopped functioning and the abandoned ridges are now the Lost Dutchman and Dirk Hartog submarine ridges. Prior to 96 mya India had been moving at only a few mm/year. After 96 Ma it picked up pace to 15-20 cm/year, and changed direction, it now headed north. About 55- 50 mya it collided with Asia.

India stopped moving away from Australia at 45 Ma as the spreading ridge in the Wharton Undersea Basin powering its movement became inactive. When India started its faster movement, sea floor spreading began in the rift between Australia and Antarctica, but moved very slowly while India was moving towards Asia. Throughout the period from 96 to 45 mya the rift grew at only 4 mm/year, Australia travelling only about 500 km. After 45 mya it moved at about 6-7 cm/year until the present. Sea floor spreading, as opposed to stretching of the crust, began in the rift about 96 mya but the Southern Ocean connection wasn't complete because of the presence of the extension zone. The rift valley still contained river deltas, brackish swamps and fresh water lakes. Throughout the slow phase of movement, a land connection was maintained via Tasmania. Beginning at 96 mya, rifting between Australia and the Lord Howe-New Zealand Subcontinent began. The Tasman Sea started opening from south to north, beginning from the South Tasman Rise. The New Zealand section was still connected to Australian crust by the Campbell Plateau. Tasman Sea spreading stopped during the India sprint to Asia.

The Coral Sea Basin was forming between Australia and New Guinea at this time. There was volcanic activity along the Queensland coast as it is today, the coast was much further out at the time the volcanoes were active. The now submerged Queensland Plateau was still part Queensland at the time. In the earlier part of the Cretaceous there was also volcanic activity on the Lord Howe Rise. After 96 Ma the volcanic arc moved away from Queensland until now it lies 3000 km east, passing through present-day New Zealand. In the past 96 million years the only volcanic activity n the Australian continent has been when the continent passed over "hot spots". By 90 Ma an extension of the proto- Southern Ocean extended as far east as Tasmania, following a period of seafloor spreading between Australia and Antarctica to the NNW. The ocean to the south of New Zealand in the Tasman Sea had opened as a result of seafloor spreading. This had the result of isolating New Zealand and New Caledonia from the rest of Gondwana (Stevens, 1989).

It has been suggested that there may have been a land link between New Zealand and New Caledonia that lasted until about 70 Ma, but evidence for this link has not yet been found. From about 90 Ma to about 60 Ma there was subaerial volcanism in the open ocean to the west of Australia on the northern edge of the Broken Ridge Platform (Rea et al., 1990). It has been suggested this may have provided a stepping stone for floral migration. The seafloor was now spreading between northeastern Australia and eastern New Guinea that resulted in the formation of the Coral Sea Basin by the close of the Palaeocene . Continental fragments that were moved to the west by movements of the Pacific Plate after the close of the Palaeocene to become part of the islands of eastern Indonesia (Pygram & Symonds, 1991) are thought to have resulted from seafloor spreading in the vicinity of eastern New Guinea at this time (Hill, 1994). By the Late Cretaceous nearly the whole of the continent was above sea level, but the sea was still present in the Perth and Carnarvon Basins .

As was happening worldwide during the hot, humid Late Cretaceous , there was a great amount of erosion occurring. 96 mya was also the time when the eastern margin of the continent underwent significant uplift to form the Great Dividing Range , a reaction to pressure from the Tasman Sea Rift. A strip of crust at the edge of the continent warped down, exaggerating the height of the Divide still further. As a result of the steeper gradient erosion in the eastward flowing rivers increased, carving out great gorges. By the Late Cretaceous , about 84 Ma, Australia was separated from Antarctica by a seaway about 100 km wide. Tasmania was still connected to Antarctica. Bass strait consisted of river flood plains, swamps and lakes. The sediment laid down in the Bass Basin at this time indicate the river and lake origin. As the Tasman Sea widened, the New Caledonia Trough developed between the Lord Howe Rise and the Norfolk Rise. The New Zealand Subcontinent was still subsiding. In the Late Cretaceous , 85-65 Ma, Tasmania was still connected to Antarctica by the stretched crust of the South Tasman Rise.

A hot and humid climate is indicated by the presence at the time of widespread deep chemical erosion. A lot of the sediment from this period was carried to the margins of the continent, so deep sedimentary deposits didn't form to make rocks. 80 Ma. At this time India and Madagascar had been isolated by a surrounding ocean and now became separated from each other. Tasmania was still close to Antarctica, but attached to Australia by the Bassian Plain, later to become Bass Strait, that at this time was composed mostly of lowland environments where that were depocentres for the sediments derived from higher ground to the north and south, and carried there by rivers. It was eventually flooded in the Oligocene - Miocene (Hill, 1994). 70 Ma. On the Australian continent the presence of widespread, thick, weathered profiles indicate the climate was probably uniformly humid, and remained tropical for much of the Late Cretaceous (G.E. Wilford, R.P. Langford & E.M. Truswell, unpublished data).

In Hill (1994).There are few clastic sediments known from 70 Ma and earlier Late Cretaceous on and around the Australian continent, an exception being the southern margin that was tectonically active. As the end of the Cretaceous the climate cooled. The Terminal Cretaceous Event , probably the widely blamed meteorite, was associated with a mass extinction around the world, but apparently except for Australia. The Australian and New Zealand fossil record doesn't display signs of a mass extinction at 65 Ma. Early in the Palaeocene epoch, between 65 and 58 Ma. At this time the oceans were warm, the abyssal water around Australia was 12-15o C, it is now 2o C. Without much of a temperature gradient between the surface and deeper water, ocean circulation was slow. Between 55 and 50 mya, the spreading in the Tasman Sea and the Corel Sea Basin stopped. An expanse of oceanic crust separated Australia from Antarctica by the start of the Oligocene , about 36.6 Ma.

To the west and east of the rift zone spreading ridges had formed, extending the seafloor, spreading into the Indian Ocean and south of Tasmania, across the Tasman Sea to south of the Campbell Plateau, forming the Pacific-Antarctic Ridge that separates the Antarctic and Pacific Plates. 60 Ma. By this time the expansion of the Tasman Sea had stopped. Australia continued drifting north. Widespread erosion and deposition of sediments occurred across Australia, believed to be associated with one or more cooling events, and probably ice accumulation, in the early Cenozoic. Very sandy channels formed in the east, while in the west wide expanses of swampy alluvial channels formed (G. E. Wilford, R. P. Langford & E. M. Truswell, unpublished data) . The same conditions occurred intermittently until about the Early Oligocene . (Hill, 1994). 50 Ma. It was at about this time that the Transantarctic Mountains were thrust up (Fitzgerald and Gleadow, 1988), leading to the increased accumulation of snow and ice, a feature of Antarctica for much of the Cenozoic. 40 Ma.

The movement of the Pacific Plate changed direction at this time to a more WNW direction, eventually colliding with the Australian Plate in New Guinea. From the Mid Oligocene onwards the collision resulted in mountain building and subduction of the Australian Plate beneath Sundaland (Pigram & Symonds, 1991). The spreading rate between Australia and Antarctica had increased about 44 Ma, as the Australian Plate moved to the north, resulting in the formation of a deep marine strait between Tasmania and Antarctica by 38 Ma (Kennett, 1980). This allowed the Circum Antarctic Current to form, which resulted in the increased cooling of Antarctica and the adjacent oceans. Microcontinental blocks linked the Antarctic Peninsula to the tip of South America up until about this time, since then plate movements and seafloor spreading associated with the opening of the Scotia Sea has separated them. It is not known exactly when the Drake Passage, the expanse of sea between the Antarctic Peninsula and southern South America, opened. Lawver et al.

(1985) has suggested that it opened some time between 64 and 34 Ma, but Barker & Burrell (1977) have suggested it was more like 30-25 Ma. In (Hill, 1994). About 42 Ma there was a possible stepping stone island, about 2000 km west of Perth near Broken Ridge, where limestone and chert were exposed It is thought to have lasted only a short time (Tea et al., 1990). By 30 Ma the last impediment to the movement of water around Antarctica was removed when the connection between the tip of South America and Antarctica and between Tasmania and Antarctica was broken. The formation of the circum-Polar curren t now developed. This allowed the freezing of the Antarctica continent by shielding it from the warmer water of the adjacent oceans. After 50 Ma Australia began to move more rapidly and by 45 Ma the last connection with Antarctica was broken.

From about 38 - 36 Ma, in the Early Oligocene , a change in the Australian climate occurred, becoming much drier, and duricrusts formed over much of the continent, as the large-scale ice sheets became established in East Antarctica. Evidence for this climatic shift was found in 1988 in the cores of the Ocean Drilling Program (G. E. Wilford, R. P. Langford & E. M. Truswell, unpublished data). McDougall & Duncan (1988) suggest that from about 30 Ma a series of volcanic islands between the Australian continent and New Caledonia could have influenced plant migration in the Neogene , though the evidence for a land connection is lacking. The only island of this series that has not been submerged is Lord Howe Island, a bit over 6 million years old. The submerged islands forming seamounts in the Tasman Sea (McDougall & Duncan, 1988). 20 Ma. By this time Australia had drifted far enough north for its northernmost parts to move into the zone of influence of the tropical monsoon climate. This led to the formation in well-drained coastal soils of bauxite deposits.

A number of rivers that were active in the early Tertiary under this climate regime, but were less active when the rainfall declined resulting in less erosion, which was reduced further by partly duricrusted soil surfaces. There were many lakes at this time. Volcanism occurred sporadically along the northern margin of the Australian Plate as it continued pushing north into Southeast Asia. One result of the northward movement with the accompanying volcanic activity was the formation of islands between Australia and Asian mainland. 10 Ma. By now the increasing aridity was being caused in Australia, especially in the interior, by the greatly expanding ice sheets in Antarctica. This led to reduced erosion and deposition. A similar effect has recently been found to be responsible for the decades long drought across southern Western Australia and Victoria, in this case by the contraction of the weather systems closer to Antarctica that previously brought winter rain to the southern parts of the continent. The rain-bearing clouds no longer reach as far north as they did previously, many completely missing the Australian continent. (Catalyst, ABC TV).

As the Indo-Australian Plate moves northeast the volcanic activity continues on its northern margin in the mountainous island of New Guinea that bears the brunt of the collision with the Pacific Plate, as well as along the subduction zone known as the Pacific "Ring of Fire". Mary E. White, After the Greening, The Browning of Australia, Kangaroo Press, 1994 Hill, Robert S., (ed.), 1994, History of the Australian Vegetation, Cambridge University Press. McDougall, I., & Duncan, R. A., 1988, Age Progressive Volcanism in the Tasmantid Seamounts, Earth and Planetary Science Letters, 89, 207-20. Veevers, J. J (ed.), 2000, Billion-year earth history of Australia and neighbours in Gondwanaland, GEMOC Press Sydney. Scotese, C.R. & Denham, C.R.. Users' Manual for Terra Mobilis; Plate Tectonics for the Macintosh. Wilcox, J.B.

& Stagg, H.M.J., 1990, Australia's southern margin: a product of oblique extension, Tectonophysics, 173, 269-81. Truswell, E.M., (1983), Geological implications of recycles palynmorphs in continental shelf sediments around Antarctica. In Antarctic Earth Science, ed. R.L.Oliver, R.R.James & J.B.Jags, pp. 394-9. Canberra, Australian Academy of Science. Stevens, G.R., 1989, The nature and timing of biotic links between New Zealand and Antarctica in Mesozoic and early Cenozoic times. In Origins and Evolution of the Antarctic Biota, ed. J.A.Crame, Geological Society Special Pubication, 47, 141-66. Powell, C .McA., Roots, S.R. & Veevers, J.J., 1988, Pre-breakup continental extension in East Gondwanaland and the early opening if the eastern Indian Ocean, Tectonophysics, 155, 261-83.

Nurnberg, D. & Muller, R.D., 1991, The tectonic evolution of the South Atlantic from Late Jurassic to present, Tectinophysics, 91, 27-53. Storey, B.C., Dalzeil, I.W.D., Garrett, S.W., Grunow, A.M., Pankhurst, R.J. & Vennum, W.R., 1988. West Antarctica in Gondwanaland: crustal blocks, reconstruction and breakup processes, Tectonophysics, 155, 381-90. Rea et al., D.K., Pehn, J., Driscoll, N.W, et al., 1990, Palaeoceanography of the eastern Indian Ocean from ODP log 121 drilling on Broken Ridge. Geological Society of America Bulletin, 102, 679-90. Pigram, C.J. & Symonds, P.A., 1991, A review of the timing of the major tectonic events in the New Guinea Orogen.

South East Asian Journal of Earth Sciences, 6, 307-18. Fitzgerald, R.G. & Gleadow, A.J.W., 1988, Fission-track geochronology , tectonics and structure of the Transantarctic Mountains in northern Victoria Land, Antarctica. Chemical Geology (Isotope Geoscience Sections), 73, 169-98. Lawver, L.A., Sclater, J.G.and Meinke, L., 1985, Mesozoic and Cenozoic reconstruction of the South Atlantic.Tectonophysics, 114, 233-54. Barker P.F. & Burrell, J.1977, The opening of the Drake Passage. Marine Geology, 25, 15-34. Links

Question: What name is given to the southern landmass formed by the splitting of a single world continent over 200 million years ago?
Answer: GONDWANALAND