CARING FOR OUR COUNTRYOutcomes:

By the end of this topic you should be able to:

•Describe how Australia’s land surfaces have undergone continuous weathering and erosion at rates that are very slow in comparison to worldwide averages

•Explain why soil is a resource that requires careful management

•Explain the relationship between salinity or soils and water

•Explain the effect of ecessive use of fertilisers and the long term consequences

•Describe the importance of the maintenance of environmental flows and natural processes

•Describe the results of the industrial Revolution on the atmosphere and hydrosphere

•Describe the depletion of the ozone layer

•Describe the rehabilitation and safe use odf previously contaminated sites

TOPIC OVERVIEW

There are 7 parts to this topic1. Australia’s land surfaces exhibit the effects of long

periods of weathering and erosion2. Soil as a resource that requires careful

management3. Salinity of soils and water4. The effect of excessive use and long term

consequences of using some pesticides5. Maintenance of environmental flows and natural

processes in water6. The results of the Industrial Revolution on the

atmosphere and hydrosphere7. Rehabilitation and safe use of previously

contaminated sites

PART 1-LESSON 1The Development of Australian Soils

INTRODUCTION The Australian

continent is very old and because of that soils are highly leached and often mineral deficient. Farmers going back as early as the first settlers have had to alter the natural environment in order to grow crops. This has caused significant damage to the environment

INTRODUCTION

Today attempts are being made to reverse some of these negative results and to prevent further damage.

INTRODUCTION

Farmers are not the only ones who have created problems for our environment. Our cities and industry also have negative effects on the environment.

INTRODUCTION

For example mining can damage and destroy environments. Towns produce huge amounts of waste that needs to be disposed of. And the burning of fossil fuels in automobiles and industry is changing the worlds climate.

INTRODUCTION

Such environmental issues are often segmented in today's news headlines. These problems are being addressed however are/should we take them seriously and are we moving fast enough?

THE DEVELOPMENT OF AUSTRALIAN SOILS

Australia has some of the oldest exposed rocks in the world. This is because the Australian continent has been tectonically stable for a long time.

Why has Australia been stable for so long?

POOR SOILS

Australia is located in the centre of the Indo-Australian plate. Because of this, it prevents most of the continent from coming into other continents which we know causes surface changing processes such as: uplift, mountain building, volcanism and earthquakes.

POOR SOILS

As a result of this stability, Australian rocks have had a very long time to weather and erode into soils leaving a very low relief terrain.

POOR SOILS

Lack of weathering and erosion results in a reduction of new sediments being transported to replenish old soils.

POOR SOILS

Leeching is another contributor. This is the process where soluble nutrients are transported from top layers to lower layers often into ground water where plants are unable to access them.

POOR SOILS

The ancient Australian soils have experienced weathering and leeching for up to 300 million years removing nutrients and producing fragile soils with low fertility.

Does Australia have areas of good soil?

GOOD SOILS

What causes good soils? In the Northern Hemisphere recent periods of glaciations has dumped large amounts of freshly ground up rocks which weather to create fertile soil.

GOOD SOILS

Most of Australia’s better soils are a result of recent volcanism. About 40 million years ago Australia passed over a hot spot which created small volcanoes along the East coast.

GOOD SOILS

These volcanoes are now extinct however as they erode, basalt and other volcanic rocks produce very fertile soils. Extinct volcanoes and their basaltic lavas can be found from Cairns to Melbourne.

COMPARISON OF AUSTRALIAN SOILS

Soil Characteristic Basalt derived soil (Eastern Australia)

Deeply Weathered Lateritic Soil (Western Australia)

Colour Black Red

Nutrients Present Nitrates, Phosphates None

Minerals Magnesiuum, zircon, iron

Iron and Aluminium

Structure Blocky Thin, sandy under hardened crust

Water Retention Good Poor

Organic Content High Little or none

Age Less than 10 million years

Up to 300 million years

REFLECTION

Long periods of leeching nutrients from the soil, low relief of the country and continental stability for hundreds of millions of years have all contributed toward the low fertility of Western Australian soils.

Recent volcanic activity (10-20mya) along the East Coast of Australia has resulted in black fertile soils.

HOMEWORK

Read pages 109-110 HSC Spotlight Text

Update Electronic vocabulary

Complete ‘To Think About’ page 110-112

Complete DOT Point 1.1 pg 54