Australian Geology

Australian geology is very interesting.

Australia is the world’s oldest, flattest and driest populated continent.


The main reason for its fantastic landscape and impressive rock formations is its geological stability.

Group of Rounded Granite Boulders, Part of Devil's Marbles, Northern Territory, Australia
Devil's Marbles. Poster by AllPosters. Click on thumbnail to buy

Australian Geological Stability
Away from tectonic plate boundaries, volcanoes don’t erupt and mountain ranges don’t rise. In contrast to the neighbouring geologically active New Zealand, Australian continent hasn’t changed, other than eroded, since the uplift of the Great Dividing Range 80 million years ago.

Barren Landscape on Desert Highway, Australia
Australian geology. Poster by AllPosters. Click on thumbnail to buy

This geological stability has given erosion a lot of time to flatten the land and expose some of the world's oldest rocks and most strange rock formations, like Twelve Apostles in Victoria, Remarkable Rocks and Murphy’s Haystacks in South Australia, pinnacles in Nambung National Park and Wave Rock in Western Australia; and Devil’s Marbles, Kata Tjuta and the world’s largest monolith Ayers Rock in Uluru Kata Tjuta National Park in the Northern Territory.

Uluru (Ayers Rock) with Desert Vegetation
Uluru. Poster by AllPosters. Click on thumbnail to buy

Australian Red Desert Soil
These fantastic rock formations are often surrounded by the reddest soils you have probably ever seen. It’s so beautiful and it makes the whole landscape so colourful, particularly when the sun sets.

Outback Road, Menindee, New South Wales, Australia, Pacific
Australian geology. Poster by AllPosters. Click on thumbnail to buy

So why is it? Why is it that in Europe the soils are black and in Australia they are red? It’s because of the climate. Soil is the product of rock erosion, and the erosion is caused by weathering. In cold climate, like in Europe and most of the North America, the main form of weathering is physical, such as jointing, frost wedging, and in places the impact of ancient glaciers. In hot climate like in Australia and in south-eastern USA, the weathering is chemical. Reactions like hydrolysis, hydration and oxidation happen – and the red colour is a result of oxidation, more exactly – iron oxides, just like rust.

If you are interested in Australian geology, there is one exellent book. It explains everything about Australia's Precambrian as well as Gondwanan - past, through every period, and it also mentions places (and has photos of) where in Australia you can see the different features. It explains a lot of geology that you see when you travel around in Australia.

It's got great photos and it is written in a language that is easy to understand. So it is not like a boring, hard-to-understand geology book, it is really reader friendly.


History of Australian Geology

Australia in the Geological Time Scale
During most of the Precambrian Eon all the world's continents were joined in the supercontinent Pangaea. At the end of Precambrian, Pangaea broke up and formed two different supercontinents - the northern Laurentia, and the southern Gondwana. Australia was part of Gondwana continent roughly from Cambrian Period until the end of Mesozoic - the era of dinosaurs (it started breaking off in the Jurassic Period and was completely separated only during the Cenozoic Era).

Artist's Concept of the Formation of the Solar System
Poster by AllPosters. Click on thumbnail to buy

Australian Geology during Precambrian
Precambrian is the oldest eon in the Earth's history, and Australia's oldest rocks are some large old shields (cratons) in South and Western Australia. Australian precambrian rocks also contain some large orebodies and some evidence of glaciation. Western Australia's famous stromatolites and Banded Iron Formations also originate from this time.

Artist's Concept Showing How the Surface of Earth Appeared During the Hadean Eon
Poster by AllPosters. Click on thumbnail to buy

Australian Geology during Phanerozoic
The next eon, Phanerozoic, started with Cambrian Period evolution when an amazing amount of species evolved during only a few millions of years, something that came to be called the , and the rocks we have from this period suddenly showed a big change in fossils. It was a big step in animalCambrian Explosion. The eastern third of Australia was under the ocean, and shallow seas covered much of central Australia, where many Cambrian fossils can be found in sedimentary rocks in places like MacDonnells Ranges in Northern Territory and Flinders Ranges in South Australia.

A Species of Pirania, a Primitive Sponge That Populated the Ocean Floors 505 Million Years Ago
Cambrian animal. Poster by AllPosters. Click on thumbnail to buy

During Ordovician, the eastern third of Australia was still under the ocean, although Cape York and Gulf Savannah had emerged from the water. Across central Australia, a shallow sea called Larapinta Seaway crossed the continent from west to east and divided it to a southern and a northern half. In the south, near Canberra, volcanoes were erupting.

Trilobite Fossil (Niobides Armatus), Ordovician Period, 480 M.Y.A., Bolivia
Ordovician fossil. Poster by AllPosters. Click on thumbnail to buy

During Silurian, the uplift of eastern Australia continued and most of Queensland now emerged from the water while New South Wales, Victoria and Tasmania remained under the water. In central and Western Australia, sand dunes formed and sediments were laid, that later turned to sedimentary rocks that carry the first evidence of an animal on the land in Australia.

Fossil Sipunculid Worms (Lecthyalus Gregarius), Silurian Period, 420 M.Y.A., Illinois, USA
Silurian fossil. Poster by AllPosters. Click on thumbnail to buy

During Devonian, eastern Australia emerged from the water, and there was a lot of volcanism in Victoria, New South Wales and eastern and north Queensland. In Western Australia, sediments that later formed the limestones and sandstones of the Kimberley region were deposited.

A Late Devonian Ichthyostega Emerges from Waters of a Floodplain
Devonian. Poster by AllPosters. Click on thumbnail to buy

Carboniferous period was named after the carbon-bearing coal deposits that formed in the Northern Hemisphere where the climate was much warmer than in the southern Gondwanaland. Fossils from these times represent a cold climate flora and fauna with no coral reef. Australia was freezing cold, covered in ice and geologically active with a lot of volcanism. It was during this period as Australia's youngest mountain range, the Great Dividing Range, was formed.

A Pair of Carnivorous Dimetrodon Explore an Early Permian Landscape
Permian. Poster by AllPosters. Click on thumbnail to buy

In the end of Permian Period the climate got warmer and after Permian Extinction - the world's largest mass extinction where 80% of species were wiped out, it was time for the era of dinosaurs. It was the Mesozoic Era and Australia continued being geologically active throughout it, with active volcanism, and the climate continued being warm and tropical.

Coelophysis Dinosaurs Walk Amongst a Forest
Triassic. Poster by AllPosters. Click on thumbnail to buy

Mesozoic started with the Triassic period and the first - Triassic - dinosaurs. However, it was only the beginning of dinosaur history and there were not so many types of dinosaurs.

A Carnivorous Allosaurus Confronts a Giant Diplodocus Herbivore During the Jurassic Period on Earth
Jurassic. Poster by AllPosters. Click on thumbnail to buy

But Jurassic was really the time when the dinosaurs evolved into many different species and there started to be many different types of dinosaurs.

A Albertaceratops Wanders a Cretaceous Forest
Cretaceous. Poster by AllPosters. Click on thumbnail to buy

During the next, Cretaceous period, there were a lot of different species of dinosaurs, but the end of the period saw another mass extinction - the famous extinction of dinosaurs.

A Pack of Dire Wolves Crosses Paths with Two Mammoths During the Upper Pleistocene Epoch
Cenozoic. Poster by AllPosters. Click on thumbnail to buy

Only after that did the mammals get a chance to start flourishing, and Cenozoic is the era of mammals. Only now did Australian geology become inactive (volcanism also stopped with the exception of Glasshouse Mountains). And it was only now that Australia was completely separated from Gondwana continent.

Jurassic Park Movie


Jurassic Park is one of the world's most successful movies ever made. It was based on the 1990 novel Jurassic Park written by Michael Crichton. The science fiction adventure movie was filmed on Hawaii and in California, and came out in 1993. The scene is a fictional island in central America, in an amusement park with cloned dinosaurs. I won't say any more, you watch the rest of the thriller!

     

The movie was so popular that in 1997 The Lost World was added, to be followed by Jurassic Park III in 2001.

 


 













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