ARTICLES
What’s Australia made of?
Geologically, it Depends on the State you’re In
By Alan Collins, Bo Yang and Grant Cox
We think of Australia as a solid landmass, but it’s actually more
like a jigsaw puzzle that has been put together over many millions
of years.
These cratons are really proto-continents, or “wannabe-
continents”. They are made of the same materials continents are
made of, but quite small compared to the modern landmasses.
They are the earliest jigsaw puzzle pieces.
The problem with working out how Australia formed is that the
evidence is often buried, making access to geological materials
quite difficult.
What Australia is made of geologically depends on the state
you're in...
But now new techniques, new drill holes and the re-evaluation
of older samples are reshaping our understanding of how and
when Australia formed, and the results are not what you’d expect.
An ocean and mountains once existed in the west and centre
of Australia, and the eastern states are latecomers – they’re
relatively new to the continent.
Australia has only been a unique continent for around 55 million
years. However, the rocks and minerals beneath us date back to
an earlier time. These give clues as to the composite nature of
the lands that make Australia.
Bo Yang examining precious rocks from deep beneath the
Northern Territory in the Darwin Core store of the Northern
Territory Geological Survey. Alan Collins.
The world’s oldest known material – some unprepossessing
grains of sand – are found in Western Australia. These are 4,374
million years old, nearly as ancient as the planet Earth itself. Building ‘the lucky country’
Between Perth and Kalgoorlie lies an ancient piece of the Earth
called the Yilgarn craton. This is dated between 3,700 and 2,600
million years old. Further north, centred around the iron-ore towns
of Newman and Tom Price, lies an equally old terrane called the
Pilbara craton. We now know that in Earth’s middle age, sometime between
1,800-1,300 million years ago, three contributing continents came
together to form part of what we now recognise as Australia.
At the time, each was still linked to rocks that are now found
elsewhere in the world.
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SCIENCE EDUCATIONAL NEWS VOL 67 NO 1