SOUTH AUSTRALIA, a state of the Commonwealth of Australia, occupying 380,070 sq. miles (12.78%) in the central southern portion of the continent. Its southern boundary is the coast-line whose absolute length (1,540 m.) somewhat belies its geographical significance.
Situated athwart the junction line of the great western plateau and the great central plains of Australia, and having also special features of its own, South Australia falls into a number of different physical areas though its relief is nowhere so marked as that of the eastern States and there is relatively little land above 2,000 ft. (a) The north-west quarter is occupied by the south-western extension of the western plateau. (b) The north-eastern quarter is occupied by the Lake Eyre de pression, with its horseshoe of mud and marsh-filled depressions ("Lakes" Frome, Callabonna, Blanche, Gregory, Eyre [3,700 sq. miles], Torrens) surrounding the northern Flinders Ranges. (c) Southwards from these lies an area where recent (Pliocene) cross patterned warping and faulting, elevation and submergence have provided the most decisive features of the State:—Mount Lofty– Flinders Range, the northern part of Yorke Peninsula, the Spencer Gulf–Lake Torrens (semi-drowned) valley; the Flinders–Barrier spur or ridge, the extremities of the peninsulas, Kangaroo Island and perhaps also—though it is older—the Gawler Range. (d) South and east of this lies the Murray and south-eastern lowland plain, the western fringe of the great Murray (Tertiary sea-basin) lowland and the counterpart of the Lake Eyre basin in the north.
The coasts are alternately rocky and cliff-bound (e.g., Bight, Jervis Peninsula) and again low, sandy and backed by dunes. Their general inhospitality is due partly to uplift in relatively recent geological times. Most distinguished is the granite coast from Cape Jervis to Port Elliot, and most curious the long "hall" of the Coorong. (See further : AUSTRALIA : Geomorphology, Soils, Drainage.) The Murray has some 500 miles of its lower course in South Australia. Its total fall in South Australia is only 57 ft. and its outflow to the sea, through Lake Alexandrina (q.v.) and over a sandy bar, is meagre.
The north-eastern corner of the State (I i8,000 sq. miles) forms part of the Great Artesian Basin, the water-bearing beds lying at (average) depths of 4,000-5,000 ft. in the north-east but shal lowing until, along the edge of the W. Australian platform, the waters well up in a line of remarkable "mound-springs." The soft strata of the Lower Murray basin also yield plentiful supplies, often of good quality, from depths of 50-35o ft. and, towards the extreme south-east (Penola–Millicent) the underground water table intersects the surface and has resulted in extensive swamps and coastal lagoons. Boring westwards of Oodnadatta has re
vealed good supplies and the results of recent prospecting in the vast western interior (northwards from the transcontinental rail way line) are reported to have been encouraging. The yield of the north-east bores is, however, diminishing: one well 5,458 ft. deep yields now only 5o gallons a day.
South Australia lies wholly within the temperate zone but the greater part of the north lies in that "No Man's Land" between northern and southern rainfall and shares the aridity or erratic regime of the continent's interior. Av. ann. temps. range from c. 7o° F in the north-east to c. 56° in the extreme south, but much greater extremes are experienced in the north and in the interior generally than in the coastal parts espe cially towards the south-east. So with rainfall. Apart from occasional descents of northern (monsoonal) summer rains into the north and north centre of the State, the rain falls in winter and is heaviest (2o-25 in.) and most reliable over the central south and south-east coastal areas. Inland (northwards) the average amounts rapidly die away and practically all the areas north of lat. 31° 5o' S.—and in the east, north of the River Murray—have less than io in., and the extreme interior has only c. 5 in. (Oodnadatta, 4•97 in.) and this extremely erratic. The wettest portions are in the extreme south-east (25-30 in.) and in southern Eyre's Peninsula; the central highlands and, to a less extent, Spencer Gulf, induce heavier precipitation and cause a long tongue of higher rainfall (2o-25 in. in the S., with 40 in. in the hills east of Adelaide, to 15-10 in. in the N.) to extend far into the interior. (See also PORT AUGUSTA; ADE LAIDE ; and inf.) Population, Settlement and General Economic Develop ment.—Comparatively long settled, possessing a climate mainly temperate, with little of the sensational in her development, South Australia shows few unusual features as regards population. With an area 12.78% of that of the Commonwealth, the population in 1933 of 580,987 represents 8.76% of that of the Common wealth's total, nearly 54% (312,629) being metropolitan. The increase, if not at a very high rate, has been remarkably steady (1928 pop. was 575,800), and due to natural causes and to immi gration in about equal proportions. The average density is low (1.52 per sq. mile) and this, as well as the distribution, exhibits clearly the effect of physical and also of historical circumstances.