The Australian desert

The Australian desert is the Southern Hemisphere analog of the Sahara, in that it represents the dry transition between the tropical summer rains and extra-tropical winter rains. Most of the region, however, is more akin to the semi-arid Mediterranean steppes or Sahelian savanna than to the Sahara. Approximately 50% of the Australian continent is arid land and over a quarter is semi-arid. The most important desert regions include the Great Sandy Desert, Gibson Desert, the Great Victoria Desert, the Simpson (Arunta) Desert, and the Sturt Desert (Fig. 18.1).

The desert surface types include sand deserts, stone deserts, mountain and shield deserts, and riverine and clay plains (Fig. 18.2). The largest area, almost 2 million km2, is the sand deserts; these areas are almost devoid of surface water but are generally vegetated and reasonably stable. The stone deserts are the second largest, nearly 1 million km2. These often have integrated drainage basins terminating in large salt lakes, such as Lake Eyre. The shield deserts are relatively featureless, with drainage becoming disconnected in more arid regions and with a few salt lakes. There is relatively little high terrain in Australia; most of the land lies below 600 m. The few mountainous regions generally have elevations between 600 and 1200 m. Those in the central desert tend to enhance the meager rainfall. Many of the soils are deep red, porous sands. Calcareous and siliceous loams, shallow and gray or gray-brown, are associated with salinas; cracking clays of moderate depth occupy alluvial plains and uplands.