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Transcript of Australian Geography
THAT MAKE AUSTRALIA UNIQUE No country in the world is the same as another, but Australia is particularly rich in physical characteristics that make it unique.
In this section, we focus on the physical environment, including
major landforms and drainage basins,
patterns of climate,
vegetation and natural resources, and
flora and fauna. MAJOR LANDFORMS AND
DRAINAGE BASINS The tectonic forces of folding, faulting and volcanic activity have created many of the major landforms of Australia. Other forces that work on the surface of Australia and give our landforms their present appearance are weathering, mass movement, erosion and deposition. Weathering is the breakdown of bare rock by water and temperature changes at the Earth's surface.
On a continental scale, weathering contributes to the development of only minor landforms.
Its main impact is in the way it converts solid rock into a layer of regolith, or broken rock and soil,
which is more easily moved by other processes. The gravitational movement of rock and soil downslope is called mass movement. This contributes to the appearance of local landforms.
For example, the steep sides of parts of the Blue Mountains are formed by a combination of weathering and mass movement. The main force that has created the present
appearance of our topography is erosion.
Erosion is the wearing away of soil and rock by
natural elements, such as water, ice and wind.
Water erosion by rivers and streams has been
responsible for the carving of many valleys in
Australia's higher areas. Small parts of the Australian
Alps and Tasmania have been eroded by
glaciers during the last Ice Age. Drier parts of
Australia have experienced some wind erosion.
When streams, glaciers and winds slow down,
they deposit or `drop' the load of rock, soil and
particles they have been carrying. This is called
deposition. Many broad coastal and low-lying
inland valleys have been created by stream deposition.
These areas are called ¯flood plains. Wind
deposition has created many sand dunes along
beaches and in desert areas. MAJOR LANDFORM REGIONS The topography or landforms of Australia can be divided into four major regions:
the Coastal Plains,
the Eastern Highlands,
the Central Lowlands and
the Western Plateau. The Coastal Plains around Australia's edge are narrow and discontinuous.
The plains often take the form of river valleys, such as those of the Fitzroy River near Rockhampton and the Hunter Valley near Newcastle.
The Central Lowlands is a vast area of very flat, low-lying land which contains three large drainage basins: the Carpentaria lowlands in the north,
the Lake Eyre basin in the centre,
and the Murray-Darling basin in the south.
The Western Plateau is a huge area of tablelands,
most of which is about 500 metres above sea level.
It includes areas of gibber (or stony) deserts and sandy deserts. There are several rugged upland areas, including the Kimberley and Macdonnell ranges. Using your map of Australia
mark in the four major landform regions 3. Observe the map of Australia's major landform regions.
(a) What are the four major landform regions?
(b) Which region is: (i) the largest? (ii) the smallest?
(c) State the landform region in which each of the
following is located (refer to an atlas if necessary):
(i) Sydney (ii) Alice Springs (iii) Canberra
(iv) Kalgoorlie (v) Cairns (vi) Lake Eyre.
4. Name Australia's largest drainage basin.
5. What is the approximate size of the Murray-Darling drainage basin?
6. The Murray-Darling basin has a large variety of environments. Explain how this would affect the potential for agriculture.
7. Why has the basin developed into such an important irrigation area? RIVERS AND LAKES Permanent rivers and streams flow in only a small proportion of the Australian continent.
In fact, Australia is the driest of all the world's inhabited continents. It has:
· the lowest amount of run-off
· the lowest percentage of rainfall as run-off
· the least amount of water in rivers
· the smallest area of permanent wetlands
· the most variable rainfall and stream flow.
The Murray±Darling is Australia's largest river system. Other significant rivers are:
· the Burdekin River in Queensland
· the Hunter River in New South Wales
· the Murchison, Gascoyne, Ashburton, Fortescue, De Grey, Fitzroy, Drysdale and Ord rivers in thenorth-west region
· the Victoria and Daly rivers in the Northern Territory
· the Leichhardt, Norman, Gilbert and Mitchell
rivers in the Gulf of Carpentaria
· the Tamar, Derwent and Gordon rivers of Tasmania, although these are relatively short.
Australia has many lakes but they hold little water compared with those found on other continents.
The largest are Lake Eyre and Lake Torrens in South Australia. During dry seasons, these become beds of salt and mud.
Yet an inland sea did once exist in this area. It covered about 100000 square kilometres around present-day Lake Eyre
and Lake Frome. South Australia is the driest state and has very few permanent rivers or streams. AUSTRALIA'S PATTERN
OF CLIMATE AND VEGETATION CLIMATE AND RAINFALL The size and location of Australia ensures that it has a wide range of climates. Australia is widely known as the `dry continent'. Around 80 per cent of Australia has a rainfall of less
than 600 mm per year and 50 per cent has less than 300 mm. Not only is the rainfall low but it is highly variable and droughts are a common occurrence. PRESSURE SYSTEMS The main reason Australia is so dry is that much of the continent lies in an area dominated by high pressure for most of the year.
High pressure systems drift from west to east across the continent bringing dry, stable, sinking air.
This results in atmospheric conditions that are not favourable for rainfall TEMPERATURE Variations in temperature occur for several reasons.
One reason is that, at higher latitudes on the Earth's curved surface, solar radiation (heat from the sun)
is spread more widely than at places at lower latitudes The sun's rays that reach the Earth near the Equator
(that is, at low latitudes) have a smaller area to heat than rays
reaching the Earth at higher latitudes.
This explains why Darwin experiences higher temperatures than Melbourne Places inland tend to be warmer in summer and cooler in winter than places on the coast. This is because of the moderating effect of the
oceans on temperature. The oceans heat and cool more slowly than the land and their temperatures vary less throughout the year.
In winter, places near the ocean are warmer than places
inland, whereas in summer they are cooler. AUSTRALIA'S PATTERN OF VEGETATION The size and latitudinal extent of Australia has resulted in a wide variety of vegetation.
The dry climate has resulted in about 40 per cent of Australia being covered by grassland and shrubs.
In higher rainfall areas, trees dominate.
In the medium to high rainfall areas, much of the natural vegetation has been cleared for agricultural and urban development. Wild Life in the Outback!
Biodiversity is having variety in all living things.
Australia is a prime example of this phenomenon.
80% of this nation's plants and animals are found no where else on earth! <iframe src="http://player.vimeo.com/video/15932903?byline=0&portrait=0" width="400" height="300" frameborder="0"></iframe><p><a href="http://vimeo.com/15932903">National Reserve System – Australia’s National Reserve System</a> from <a href="http://vimeo.com/parksaustralia">Parks Australia</a> on <a href="http://vimeo.com">Vimeo</a>.</p>