Inland Australia was once a large prehistoric sea. A new computer modeling technique shows how the sea disappeared.
[Music plays while ‘sci files’ logo appears on screen. Didgeridoo music plays during animation of Australia breaking away from the Antarctic].
Narrator: This recreation of Australia breaking away from the Antarctic is 100 million years racing before your eyes. And it reveals for the first time the puzzle of the disappearance of Australia’s great inland sea.
[Image shows close up of Dr Louis Moresi]
Dr Louis Moresi: The puzzling thing about the Australian plate is that about 100 million years ago when sea levels everywhere were at their lowest Australia was actually flooded. But then 20 million years or so later sea levels were much higher but Australia was actually dry.
[Images move through various aerial views of Australian landscape]
Narrator: Like all continents Australia is a thin crust of the lightest rock material, only about 20 to 50 kilometres deep, that drifts and bobs in response to the vast churning of the earth’s internal heat engine. And the shifting and collision of tectonic plates creates mountain ranges and volcanoes. But this didn’t answer the question of why the inland sea disappeared.
[Image changes to inside CSIRO laboratory]
So CSIRO scientists created a computer model of the changes that have occurred ever since Australia broke away from the Antarctic.
[Image shows Dr Louis Moresi sitting at computer]
And for the first time were able to see just how much it has drifted, bobbed and bent.
[Image shows close up of Dr Louis Moresi]
Dr Louis Moresi: Well we took all the available data and we took a conceptual model of how we think that the earth operates and we combined those two to make a computer program which would be capable of modelling how the earth works.
[Images shows waves crashing on rocks]
Narrator: Millions of years ago the Australian plate was sucked down by some 350 metres by a second tectonic plate shown in purple.
[Image changes to animation of map of Australia]
This allowed the seas to flood low lying areas.
[Arrow on animation points to sea water flooding inland Australia]
Then as the continent drifted north, gradually escaping from the influence of the underlying plate, the shallow seas that had covered it disappeared.
[Animation shows Australia drifting away from Antarctic. Image then changes to show open ocean]
Later when sea levels rose the sediment left behind by the seas made the land surface high enough to remain dry.
[Image changes to aerial view of Australian desert landscape. Image then changes to inside a laboratory. Image then changes to show arid mining landscape]
This animation not only shows for the first time how Australia was formed, it is expected to be a valuable tool in the hunt for oil and minerals, helping geologists better understand how a particular piece of ground was formed and what lies below.
[Music plays as ‘sci files’ logo appears on screen with the words 1999 CSIRO]
