Download Major Australian Landforms and Drainage Basins

Major Australian Landforms and Drainage
Basins
AUSTRALIAN LANDFORMS
Introduction
Australia can be divided up into four main landform divisions. These landforms are:
“W.E.C.C” which means:
*Eastern Highlands
*Western Plateau
*Coastal Plains
*Central Lowlands
Content
Eastern Highlands which is commonly referred to as the Great Dividing Range
covers just 10% of the Australian continent and is three thousand five hundred
kilometres long from Cape York Peninsula to Tasmania. In many places along the
Great Dividing Range it is quite rugged with many valleys and gorges. The Eastern
Highlands is the most fertile region in Australia and mainly consists of young rocks
and has high elevation.
The formation of the Eastern Highlands started when two tectonic plates ran into
each other because of the action of convection currents, which cause the plates to
move. The continuation of the two plates’ movement drove the edges of them
upwards to form peaks of land. All together the Eastern Highlands is a result of
folding and faulting of tectonic plates. This process continues still to this day since
when it was first thought to have started to form in the Pliocene times, 2 million to 5
million years ago. This means the Great Dividing Range is gradually getting higher
and higher!
The Western Plateau incorporates one-third of the Australian continent. The size of
the Western Plateau is 2,700,000 square kilometres, and it is Australia’s largest
drainage division. It is made up of a huge, stable block of ancient igneous and
metaphoric rock, which is up to 3.6 billion years old. Conditions on the western
plateau are quite dry with it usually being arid or semi-arid. Furthermore the plateau
has little vegetation and a low elevation. The large Western Plateau is generally low
lying due to erosion below 500m of elevation. It includes iconic landforms just as:
Uluru, the Olgas, The Great Sandy and Victorian desert.
The Western Plateau was formed when the “Precambrian Western Core Area”,
Precambrian meaning five hundred and forty-two million years ago to four thousand
five hundred and sixty seven years ago, was subdivided by long, straight fractures
called “lineaments”.
These fractures, most obvious in the north and west, outline important rectangular
or rhomboidal blocks, some of which have been raised to form uplands; others have
been depressed to form lowlands or topographic basins.
There are many extensive outcrops of flat-lying Western Plateau that have been
dissected to give rise to striking isolated rock features known variously as plateaus,
mesas, and buttes. Under these circumstances, local joints and bedding planes in the
rocks, combined with the permeable nature of the bedrock, control the local
landforms.
Other features along the large plateau are also extensively and well developed in the
uplands of central Australia. Some of these include the Isa Highlands, and in the
Stirling Range of the southwest. In all of these areas across the vast low-lying plateau
are many types of sandstone and quartzites that underlie the upstanding ridges, the
intervening valleys being eroded in siltstones or shales; and in all these areas the
pattern in plan of ridge and valley reflects the pattern of folding in the underlying
rocks.
In the far southwest, the “Darling Range” forms an up faulted block underlain mainly
by granite but capped by laterite, a reddish, iron-rich product of weathering rock.
The Coastal Plains extend along the eastern edge of the continent. Out of all the
landforms, the Coastal Plains are the most densely populated landform. The Coastal
Plains extend from Queensland to Victoria. The Coastal Plains are flat, low-lying area
on the Australian continent, which is adjacent to the coastline. The Coastal Plains are
also separated from the interior of the continent by mountains and the Great
Dividing Range. The Coastal Plains along the eastern edge of Australia are home to
diverse groups of plant and animal species.
The Coastal Plains are influenced and controlled by their proximity to the sea.
The Coastal Plains along the eastern coast of Australia are made up of much
sedimentary rocks that have formed by ancient marine environmental activity and
have then been uplifted and have made their way through ocean currents to help
form the coastal plain. Another part of it was formed by runoff from precipitation
that slowly flowed down hillsides picking up sediment as it went until it reached the
bottom where it gradually built up to form coastal plains. This process normally
happens on inactive tectonic plates.
The Central Lowlands occupy one-quarter of the continental landmass. It is low-lying
and featureless and is generally 200m above sea level. The Central Lowlands are
made of old rocks and but primarily by sediments. Although the Central Lowlands is
a very flat landform mountains still exist on it. As for its climate and dryness it is
usually very hot and arid to semi-arid conditions. Some of the iconic land formations
on the Central Lowlands are: Simpson Desert, Flinders Range and the Great Artesian
Basin. The Central Lowlands account for 25 percent of the continent and are
characterised by extremely flat, low-lying plains of sedimentary rock. The
sedimentary rocks of the central lowlands were created by sediments, or silt and
biological matter, deposited when the inner part of Australia was covered by an
inland sea millions of years ago.
The Central Lowlands region stretches from Australia's largest river basin, the
Murray-Darling, through the Great Artesian Basin, extending north to the Gulf of
Carpentaria. The Great Artesian Basin is one of the largest artesian groundwater
basins in the world, and covers 1 711 000 square kilometres (km 2). One of the most
significant landforms in the Central Lowlands is Lake Eyre, the lowest point of the
Australian continent, sitting 15 metres below sea level and spreading over almost
10,000 km2. The lowest landforms of the continent are found in this region, with an
average height of less than 200 metres.
DRAINAGE BASINS
Introduction
A drainage basin forms part of the hydrological cycle (water cycle), but unlike the
hydrological cycle, it is an open cycle.
In Australia is divided into twelve drainage basins, which are sub-divided into a total
of seventy-seven water regions. These water regions can be sub-divided into two
hundred and forty-five river basins.
Content
Australian Drainage Basins:
 Indian Ocean
 Western Plateau
 Southwest Coast
 Timor Sea
 Lake Eyre Basin
 South Australian Gulf
 Gulf of Carpentaria
 Murray-Darling Basin
 Tasmania
 Northeast Coast
 Southeast Coast
 Bulloo-Banncannia
Important processes of Drainage Basins:
 A drainage basin forms part of the hydrological cycle (water cycle), but unlike
the hydrological cycle, it is an open cycle.
 A drainage basin is an area of land drained by a main river and its tributaries.
 A Drainage basin is known as an open system because it has:
INPUTS  FLOWS  STORES  FLOWS  STORES  FLOWS  OUTPUTS
 Inputs: Where water enters the system through precipitation (rain or snow).
 Outputs: This is where water is lost through the system by either rivers
carrying it to the sea, by evapotranspiration, evaporation or transpiration
 Stores: Places where the water is held such as in pools and lakes, on the
surface or in the soil and rocks underground. Some other examples are soil
moisture storage or interception of vegetation.
 Flows: Flows or transfers is a process by which water flows through the
system, this can be seen as: infiltration, surface runoff, percolation, through
flow, groundwater flow and stream flow.
 A watershed is defined as a ridge of high land dividing two drainage basin
areas that are drained by different water systems.
 The density of a watershed is measured in this equation:
The total length of the streams in the drainage basins
The total area of the drainage basin
 The tributaries in a drainage basin are small channels that help drain the area
of land.
 The flood plain is a wide, flat valley floor of a river where the silt is deposited
during times of flooding.
 The confluence point in a drainage basin system is the point at which the
river branches off into small channels known as tributaries.
 The river mouth is the place at which the water is directed into the main river
of the drainage basin.