Hi, my name's Shona. I'm from Geoscience Australia and today we're in our Education
Centre to introduce the geography of Australia. We're going to use this wonderful big colourful
map behind me. It's one of my favourite maps, and it uses colours to represent the height of the
land that we call topography and different colours used for the depths of the oceans.
We're going to zoom in and have a look at Australia and the continent that we are part of.
Can you see the coastline is just here? It's quite faint. That's quite deliberate because
the orange actually represents the total continent
and the edge of our continent is actually covered with ocean at the moment.
If we were to go back to the last ice age, maybe 20,000 years ago when sea levels were lower,
all of the orange would have been land. People were living in these areas and indigenous people
could walk to New Guinea and Tasmania. It was all part of one landmass. Things have changed
since then and things will keep changing as sea levels go up and down over long periods of time.
So to think about the physical geography we're going to consider three regions. In the west
part of the country, with the bright orange colours representing slightly higher land and
plateaus and this is where some of the oldest rocks in the continent are found and some of
the oldest rocks in the world. They're over three billion years old. It's been land for a very long
time. It's very stable and weathered and worn down and there's lots of red looking rocks, red looking
sand from the iron that's in those rocks as they've worn down, it's dry, it's desert as well.
Our next region is in the middle. The main feature here is Lake Eyre and it has rivers
flowing into it, but most of the time they don't have any water in. Lake Eyre is a salt lake
and only occasionally fills with water. It's also our lowest point on the continent,
about 15 metres below sea level. The third region is the eastern highlands all
along the east coast, the Great Dividing Range, as we call it, but when you look at this compared to
other mountain ranges in the world it's actually not that big. These hills and plateaus were added
to the continent quite recently, within the last 200 million years when tectonic forces
caused the rocks to be lifted up along this edge and that gave us the current shape of Australia.
The highest point, Kosciuszko, is down here. Some of you might have climbed Kosciuszko.
Did you need special equipment? Did you need oxygen because it was such a high mountain?
No. It's actually only 2228 metres above sea level to get all the way to the top
and that's not very big compared to Everest over eight kilometres above sea level.
Now, in Australia our lack of major big mountain ranges is a problem because we don't have lots of
places that make lots of rainfall that would feed rivers into our inland and provide water supply
and transportation routes for people to live in the inland. The Murray-Darling river system
has low flows and is unreliable. That's not the same as the Mississippi River
system in the United States or many others. The last feature we're going to look at is
the Great Australia Bight, the southern edge of the continent. Now Australia and Antarctica
were together for many, many millions of years and they took a long time to separate and about
34 million years ago they finally separated and Australia has been moving northwards ever since.
And that's moved us into drier parts, drier latitudes within the world. And that's another
reason why we are such a low rainfall continent. So, to sum up, Australia is a low, a dry,
an old and a red continent with really relatively few people living in it.