The Story of Your Place: South-West Australia

What makes it unique?

Our Earth is more than 4 billion years old.

We have some of the oldest bits of the earth’s surface right on our doorstep.

Pilbara = 3.4 billion years old

Darling plateau = 2.5 – 2.9 billion years old Some volcanic

islands are just a couple of million years old.

Tiny Zircon crystals found in the North West are the oldest known bits of the earth’s crust. 4.3 billion years old.

Click here, then drag the arrow to see how australia moved.

• 40 million years ago Australia broke away from Antarctica and started to drift North to where it is today.

• It’s still moving North at the same rate as your finger nails grow each year.

In Perth we live on sand many KMs deep.

A craton is an area of the planet’s crust that has been stable for more than 1.5 billion years.

The Yilgarn Craton is a big old lump of granite that pokes through to the surface at spots where, for example, you find boulders in the Perth hills.

This is sediment ground down out of the old Yilgarn Craton to our east as well as the remains of shells and marine animals from thousands of years ago.

Ernest Hodgkin’s Swanland by Anne Brearley (UWA Press).

What makes us a biological Island?

What stops plants and animals moving south and west?

The sea

What stops plants and animals moving North and East?

The hot and inhospitable desert

Some life, such as mulga and salt bush, can exist in the drier country, but most of the plants and animals around here stay put in the south-west corner where the rainfall is above 300 ml per year. Look at the

chart.Where does rainfall drop below 300ml per year?

Ernest Hodgkin’s Swanland by Anne Brearley (UWA Press).

Plants in Australia manage to grow out of deeply weathered and exhausted sandy, soils that are many, many millions of years old.

These beautiful little sundew plants, that you might notice on the ground in the bush, or say, King’s Park, tell a story about our soils in south-western Australia.

In Europe the soils are no older than forty-five thousand years old

The Sundew(click here to find out more)

There are more than 50 known species of Sundews (Drosera) in Australia, and forty two of those are confined to WA. In fact the greatest concentration of sundews in the world is found here in south-west Australia.

Sundews are plants that eat insects. These little plants glisten with drops of what smells like nectar on hairy stems and leaves. But what smells like nectar is actually a sticky solution of enzymes full of bacteria. Insects land on the sundew to drink, they are caught in the fluid, and the enzymes and bacteria digest them, and feed them to the plant.

This system of collecting nutrients means that sundews can out-compete many other plants in places where nutrients are not readily come by in the soil.

Next time you see the sticky little plants on the ground, remember that you are looking at a plant which speaks the nature of the land here.

Sundew catching a fly

More species of bird-pollinated flower grow in the south-west than in any other place on earth.

Birds have good eyesight and in the competition to attract pollinators the plants with the most visually impressive flowers proliferate. That’s why we have so many bright and impressive flowers.

Our isolation has led to the evolution of unique groups of living things.

Did you know..........

The Kangaroo Paw draws wattle-birds and honey eaters to come and drink nectar from the flower. Because of the arching shape of the flowers the stamen brushes the bird as it sticks its beak in the flower. Its beak is long to reach deep inside the flower. The bird then carries the pollen far away and ensures genetic diversity in the seeds.

The flower’s beautiful shape is bound up with the shape of local birds and their long beaks.

Our state’s floral emblem is an example of the way in which when you take hold of one thing in nature, you find that it is hitched to everything else in the universe.

This is a surface stream of warm, low-salinity water that travels at 2km per hour down the WA coast, often against the wind, from northern Australia, past Perth. It goes a long way. Like the Gulf Stream in England, this thermal conveyor belt keeps our waters warm. Its strength depends on the amount of tropical water flowing through the Indonesian islands from the Pacific Ocean. In winter there can be as much as 5oC difference between the colder offshore waters and the middle of the Leeuwin Current.Much of our winter rainfall comes from evaporation of this warm current.

On every other continental west coast in temperate latitudes you find cold water marine currents, rising from the ocean depths they bring nutrients and plankton to the surface, attracting fish, birds and marine mammals.Not here.We are different. We have the Leeuwin Current

The red and orange on this satellite image show the warm Leeuwin Current moving down the coast.

When you go snorkeling on Rottnest you get to see an interesting intermingling of tropical and temperate plants, molluscs and fish. It is thanks to this ocean current that tropical marine conditions get closer to the South pole on the WA coast than any other place on earth… for which Rottnest snorkellers can give thanks!

Homework Task• Go to a natural place close to where you live.• Do the same exercise that you did at the start of this

class. Record your perceptions in your book.• Use a digital camera and/or mobile phone to take pictures,

video and/or record sounds at this place. These should help to convey what the place means to you and what you find interesting. There are no ‘right’ things to take pictures of record, its your perceptions that are important.

• Interview people of different ages (your family or other people who live in the area) to find out what they feel about your chosen area, what they use it for and if possible how it has changed and any stories about its history.

• Email me 1 or 2 of your photos before next lesson.• Save the rest of your work as you will need it to complete

the assessment task at the end of this module.• This assessment task will be to:

– Produce a multimedia ‘document’ that expresses what a natural environment

in Western Australia means to you.

Maps taken from Ernest Hodgkin’s Swanland by Anne Brearley (UWA Press). All photos copyright Tom Wilson.