By Richie Keoghan

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The Unique Australian Environment. By Richie Keoghan. Gondwana. All the countries were joined together more than 200 million years ago and started to drift apart due to the tectonic plates in the earths core. They are constantly moving apart. - PowerPoint PPT Presentation

Text of By Richie Keoghan

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By Richie KeoghanThe Unique Australian Environment1All the countries were joined together more than 200 million years ago and started to drift apart due to the tectonic plates in the earths core. They are constantly moving apart. The name of all the continents joined together is Pangaea. Science tells us that the Continents of Australia, India, South America, Africa, and Antarctica, existed together as a separate landmass as long as 650 million years ago. And as these continents only began to break up some 130 million years ago, this great supercontinent had a life of around 520 million years; making it perhaps the most important geological structure of the last billion years.

Gondwana2Gondwanaland is named after the Upper Palaeozoic and Mesozoic formations of the Gondwana district of central India, which display a number of shared geologic features (the "Gondwana beds"). In the late nineteenth century, on the basis of comparative geological evidence, the Austrian geologist, Edward Suess, suggested that the continents of Africa, South America, Australia and India were once part of a single supercontinent, which he called "Gondwanaland".

Gondwana3Pangaea was the supercontinent that existed during the Paleozoic and Mesozoic eras about 250 million years ago, before the component continents were separated into their current configuration.The Pangaea theory is one that states that all present continents were once together and collectively known as a 'supercontinent' called a Pangaea. The word 'Pangaea' means 'all lands' in Greek, accurately defining the way the continents were 200 millions years ago before it split up. These split-up pieces drifted slowly apart and became the way they are today. Even until now, the shape of the Earth surface is still changing, and it will be forever, as long as the mantle underneath the Earth's crust gets heated and convection currents in the magma keeps dragging the plates.


Map of Pangaea

5Laurasia was located in the north after Pangaea split into two separate supercontinents, the other being Gondwanaland in the south. Laurentia is another name for the North American craton, the large and very old chunk of rock that North America rests on. The "basement complex" (the metamorphic and igneous rock below the sedimentary layer) of Laurentia is 1.0 - 3.0 billion years old, and was created in a tectonically active setting, under great pressure and temperature. Its constituent rocks are all igneous oxides, like granite. Like the other continents, Laurentia gets pushed around by ocean spreading, bumping into them and occasionally forming supercontinents like Pangaea. Laurentia is named after the Laurentian craton, another name for the North American craton Laurasia6

Map of Laurasia7

The continental drift theoryhas said to have started over 200 million years ago.Timeline8Plates are giant slabs of solid rock. They move a few centimetres every year due mainly to the pull of the subducting edges of plates at convergent plate margins, the 'push' of ridges at mid-ocean ridges, and convection of heat from Earth's interior. The entire surface of the planet is covered with these plates and they collide, slide, and separate from each other at their boundaries. Their movements are associated with volcanism, mountain building, and earthquakes. The plates are formed of the crust and the underlying attached solid rock of the upper mantle (the lithosphere)Tectonic plates9The continents are still moving roughly 6 centimetres every year. The Atlantic continues to widen while the Pacific is slowly shrinking. The Mediterranean will eventually close up and it is predicted that in another 60 million years, Australia will have moved north as far as the equator.Continental Drift10Most of Australia's known dinosaurs are from the Early Cretaceous. Because Australia was within the Antarctic Circle, some of its dinosaurs show adaptations to life in seasonal darkness with small size and large eyes. Large Early Cretaceous Australian dinosaurs included the sauropod Austrosaurus, the plant-eater Muttaburrasaurus, and the large meat-eater Rapator. Smaller dinosaurs included the hypsilophodontids Leaellynasaura, Atlascopcosaurus, and Fulgurotherium; the theropod Kakuru; and the armored Minmi. All these dinosaurs are much different than their relatives on other continents.

Animals in Australia11Many other plants and animals lived on Gondwana. We have found many different fossil species on continents that were part of Gondwana, and more are being found every year. The ancestors to modern marsupials, reptiles, birds, amphibians, and many plants such as ginkgoes, cycads, many pines, and flowering plants appear in the fossil record from GondwanaFlora and Fauna on Gondwana12Dinosaurs roamed freely all over Gondwanaland.The break up of Gondwana began during the time that Dinosaurs were the dominant land animals (in the Cretaceous - 120 million years ago), but it was such a slow process that they were unlikely to be affected by it. Continents break up and move apart at about the same speed you fingernails grow at (about 6 cm per year in the case of Australia and Antarctica breaking apart); by the time Australia had completely broken away from Antarctica, all dinosaurs (except birds) were extinct.Dinosaurs on Gondwana13All animals and plants have to change or adapt all the time to survive. These changes are very slow, but can be seen by looking at the fossil record. During the cold times in Gondwana (around 270 million years ago), only animals and plants that were able to survive in cold environments were able to survive there, but once the continent warmed up other animals were able to live there, and cold-adapted animals either had to find mountain tops to live on (where it stayed cold), or adapt to the new warm environments. As plants were unable to migrate, they changed or died as a result.Adaption14It appears that humans walked throughout most of Africa and Asia, and crossed into America through the Bering Strait while it was frozen during a particularly cold winter. Humans built rafts and boats that allowed them to colonise Australia, New Guinea, New Zealand and the Pacific Islands. The exact timing of this colonisation, and where it all began is still being worked on by anthropologists and archaeologists. Humans appear to have developed from an ape-like ancestor, Spread of humans15 Bibliography16