Topography is a term that refers to the characteristics of land in terms of slope, elevation and orientation. The study of topography is crucial in gaining an understanding of the land and its uses. A landform is an individual topographic feature, which can be as minor as a cliff or a sand dune, or as major as a peninsula or a mountain range. In focusing on a topographic landform it is possible to ascertain information on environmental quality, agriculture and hydrology, such as determining weather patterns, managing soil erosion and understanding drainage characteristics.
The Australian continent, with the exception of Antarctica, is the lowest, flattest and driest of the seven continents. The continent can be broken into four major landform regions: the Coastal Plains, the Eastern Highlands, the Central Lowlands and the Western Plateau. These landform regions have been created by movements in the Earth's crust, river erosion and changes in climate and sea level. Within these major areas, there are smaller topographic regions with distinctive landforms. See image 1
The Coastal Plains are a narrow strip of land along the eastern coast of Australia that extends from Queensland to Victoria. This area is flat and has relatively high rainfall. It is therefore well suited to building large cities. Australia's largest cities, including Sydney, Melbourne and Brisbane, are all located along the coastal plains. See image 2
The Eastern Highlands, also known as the Great Dividing Range, are a series of hills, valleys and mountains located to the west of the coastal plains. The range extends north to the Cape York Peninsula in Queensland and south to Tasmania. The Eastern Highlands are called the Great Dividing Range because they divide rivers in Queensland, New South Wales and Victoria into eastward-flowing and westward-flowing rivers. See image 3
The mountains and hills in the Eastern Highlands were created through a number of processes. Most were created through folding and faulting. Folded mountains are created when two tectonic plates collide with one another, causing the land to deform, while fault mountains are created when the crust breaks into pieces, allowing some parts to be uplifted. Some of the mountains are volcanic, such as the Warrumbungle Range in central New South Wales and the Glass House Mountains in northern Queensland. (Refer Chapter 5) The Eastern Highlands are also home to a number of gorges, or valleys with cliff walls. These gorges were carved into soft areas of rock by streams and rivers.
The Eastern Highlands are the highest part of Australia. Australia's highest point, Mount Kosciuszko in southern New South Wales, is located in the Eastern Highlands. The Eastern Highlands are tall enough to affect the weather in the rest of their region. They cause rain to fall upon the coastal plains and keep the central lowlands dry. Compared with mountain ranges in the rest of the world, however, the Eastern Highlands are not very high at all. Mount Kosciuszko is less than half the height of Mount Blanc, the highest mountain in Europe, and four times smaller than Mount Everest, the highest mountain in the world.
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 (km2). 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.
The Central Lowlands also receive the least amount of rain a year out of all the regions, less than 125 millimetres per year, and contain large deserts and salt plans. The Sturt Stony Desert (29 750km2), the Strzelecki Desert (80 250km2), and the Simpson (176 500km2) Desert are all located in the Central Lowlands. The Simpson contains the world's largest sand ridge desert. The 30-metre high dunes consist of red sand ridges extending for hundreds of kilometres. The dunes are held in position by vegetation. See image 4
The Western Plateau topographic region covers approximately one third of the continent, or about 2 700 000 square kilometres. This region of arid land includes significant parts of Western Australia, South Australia and the Northern Territory. The western plateau comprises a massive block of igneous and metaphoric rock, with some rocks being over 3.6 billion years old. The region is regarded as relatively flat, as the average elevation is less than 500 metres. This is due to erosion, which has affected this region for millions of years.
There are some mountain ranges located on the Western Plateau found in areas with erosion-resistant rocks. Located within the Western Plateau are the MacDonnell, Musgrave and Flinders ranges. Flinders Range is South Australia's largest mountain range, stretching over 430 kilometres from Port Pirie to Lake Callabonna. The Flinders Ranges began to form around 800 million years ago due to stretching of the Earth's crust.
There are also numerous plateaux, or flat areas of rock, that lie within the region, including the Kimberley Plateau, the Pilbara Plateau and Arnhem Land. The Kimberley Plateau is located in the northern part of Western Australia and spans 424 517 square kilometres. The Western Plateau region also contains a number of gorges, including Stanley Gorge, Chasm Gorge, Katherine Gorge and Ormiston Gorge.
Within the Western Plateau are a number of large, free-standing rocks, including Kata Tjuta, Mt Connor and Uluru. Uluru, also referred to as Ayers Rock, is a large sandstone rock formation located in the Northern Territory. It reaches a height of 346 metres and has a circumference of eight kilometres. The Pitjantjatjara people, an Aboriginal group in the region, named the landmark Uluru and it is of great spiritual and cultural significance. See image 5
Approximately 70% of the Western Plateau is composed of deserts. The Great Victoria (650 000 km2), Gibson (310 800 km2) and the Great Sandy (415 000 km2) are just a few of the deserts found in the region. Numerous salt lakes are found within the Western Plateau, which signify areas of internal drainage.