Australia: The Land Where Time Began

A biography of the Australian continent 

Aridification of Australia  

Prior to the Middle Miocene there would have been places in Australia where there were some arid land, possibly seasonal, but from the Middle Miocene on, there has been a steady progression towards aridification of the continent, interrupted by wet spells of varying length, but with each dry phase more of the continent was pushed past the point of no return. With each dry phase more refuge areas would have been lost, and of those that remained, many would become increasingly isolated, unable to provide the species that could repopulate areas that had experienced a wet phase because of the intervening stretches of desert. The ultimate dry spell occurred between 18,000 and 15,000 years ago, at the height of the most recent glacial maximum, when 85 % of the continent was covered by dunefields.

The latitude of the Australian continent at the present is the main factor leading to aridification, being situated in the mid-latitude high-pressure zone. Another contributing factor to the aridity of the continent is the presence of the Great Dividing Range along the eastern seaboard, forcing the southeast trade winds to rise soon after they pass the coast with the result that they lose much of their moisture as rain on the eastern, seaward side of the ranges. This has placed the rest of the continent, most of the landmass, in a rain shadow. Before the rise of the Eastern Uplands rain would have been brought by these winds to much of the inland.

On the west coast, a cold ocean current, the West Coast Drift (the Capes Current) increases the aridity present to the north of Perth. The aridity of the Australian interior is also favoured by the compactness of the landmass and distance of many regions from the sea.

The later Tertiary was a time when the climate of the interior was humid, and in the Quaternary there were alternating periods of wet and dry conditions. The widespread sand dunes that now cover such as large area of the continent were developed during these arid phases. Another result of these arid phases was the formation of many playas, that are often salt-encrusted, along the rivers that flowed episodically and at their termini. During these arid phases the drainage systems, that were previously well integrated, were dismembered and disrupted by aridity. The authors suggest warping may have contributed to the modification of these drainage systems (Twidale & Campbell, Source 5).

Sources & Further reading

  1. After the Greening, The Browning of Australia, Mary E. White, Kangaroo Press, 1994
  2. Twidale, C.R. & Campbell, E.M., 2005, Australian Landforms: Understanding a Low, Flat, Arid, and Old Landscape, Rosenberg Publishing Pty Ltd.
Author: M. H. Monroe
Last updated 02/04/2020


Aridification of Australia
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