The Great Dividing Range, often referred to as the Eastern Highlands, is Australia’s most substantial topographic feature. It runs parallel to the eastern coast, profoundly influencing the nation’s climate, hydrology, and biological diversity. As one of the world’s longest mountain chains, this ancient range acts as a natural divider that shapes the environment and provides a foundation for understanding the continent’s unique geography.
Defining the Great Dividing Range
The Great Dividing Range is a complex system of uplands, plateaus, and mountain ranges, not a single, continuous chain of peaks. Stretching over 3,500 kilometers, it is the longest mountain range situated entirely within a single country. It begins at the Cape York Peninsula in Queensland, follows the eastern coastline south through New South Wales, and terminates near the Grampians region in Victoria.
The range traverses Queensland, New South Wales, Victoria, and the Australian Capital Territory. The Snowy Mountains region, located within this system, is home to the continent’s highest point, Mount Kosciuszko, which reaches 2,228 meters. The range’s width varies significantly, spanning from roughly 160 kilometers to over 300 kilometers in places.
Geological History and Formation
The Great Dividing Range’s origins date back to the Paleozoic era, with initial formation beginning over 300 million years ago. Unlike younger ranges formed by continental plate collision, the GDR is primarily the result of crustal uplift and long-term erosion. Original mountains, formed around 500 million years ago, were eventually eroded down to a near-level plain.
The current topography is attributed to the Kosciuszko Uplift, which occurred in stages starting in the Late Cretaceous period. This uplift along the continent’s eastern edge was triggered by the break-up of Gondwana and the formation of the Tasman Sea. A later upward push occurred approximately 50 million years ago as Australia moved north over a mantle anomaly.
This history of uplift and weathering explains the range’s generally rounded profile and lower elevations compared to younger mountain chains. The exposed rock, including limestone, sandstone, and quartzite, testifies to the immense duration of erosive forces. This combination of gradual uplift and relentless weathering produced the complex system of plateaus and escarpments seen today.
Climate and Hydrological Influence
The Great Dividing Range functions as a substantial barrier along the eastern coast, significantly influencing Australia’s climate and water resources. It acts as a watershed, dictating the flow of nearly all major eastern and southern Australian river systems. The range separates short, fast-flowing rivers running east to the Pacific Ocean from the longer systems that drain west toward the arid interior.
This topographic barrier is responsible for the pronounced rain shadow effect across eastern Australia. Moisture-laden winds from the Pacific are forced upward, cooling and condensing their water vapor. This results in high rainfall and lush environments on the eastern, or windward, slopes.
Once the air passes over the crest, it descends, warming and drying out, creating a significantly drier climate on the western, or leeward, slopes. The western slopes are the primary runoff-generating region for the Murray-Darling Basin, the continent’s largest river system. Rainfall on the eastern side can exceed 1,200 millimeters annually, while the western reaches may receive less than 300 millimeters.
The water flowing from the western slopes feeds the headwaters of the Darling and Murrumbidgee rivers, which feed the Murray River. This water is vital for inland agricultural areas and provides drinking water for millions. In the south, the Australian Alps capture winter snowmelt, providing a reliable source of water for irrigation and hydroelectric power.
Ecosystems and Unique Biodiversity
The Great Dividing Range’s length and varying elevations create a mosaic of distinct ecosystems, supporting unique biological diversity. Habitats range from tropical rainforests in northern Queensland to temperate rainforests and alpine regions in the south. The range’s dense forests, including the carbon-dense Mountain Ash forests in Victoria, play a significant role in storing carbon.
The Gondwana Rainforests of Australia, a World Heritage Area, record plant and animal evolution, featuring species with ancient lineages. These areas provide a refuge for species that evolved in cooler, wetter conditions. Endemic species, found nowhere else, have evolved in the varied climate zones and isolation provided by the range.
Specific fauna illustrates this uniqueness, such as the Alpine Pygmy-possum, which hibernates through harsh winters in the high country. Other endemic amphibians, like the Magnificent Brood Frog and the Painted Spadefoot Toad, are restricted to certain microclimates. The range provides habitat for over 70 percent of Australia’s threatened species, acting as a climate refuge. The diverse flora also includes wet sclerophyll forests and snow gum woodlands, adapted to specific rainfall and temperature gradients.