The geological subsurface of large parts of Australia was created in the ancient times. This old land mass of the Australian shield was part of the former great continent Gondwana. Since the disintegration of Gondwana in the Jura, the Australian plaice has drifted in a south-easterly direction and has since been an independent continent. The construction of this continent is relatively easy, because it consists of only three large areas, the Western Australian Shield, the Central Australian Depression and the Eastern Australian Highlands (Fig. 2).
According to smber, the Western Australian Shield extends west from about 135 ° E. L. and thus covers more than half of the continent. It consists mainly of tabular lands that are at heights between 300 and 500 m. With a few exceptions, these table countries are semi-desert or desert-like in character. In its central part, the Great Sand Desert, the Gibson Desert and the Great Victoria Desert follow from north to south.
The space between the Great Victoria Desert and the Indian Ocean is finally occupied by the Nullabor Plain, a semi-desert-like treeless flat land. The table lands of the Australian Shield are interspersed with mountains, for example the MacDonnel chain in central Australia, all of which only reach low mountain heights of around 500 m. The Central Australian Depression consists of several basin landscapes that represent flat-hilly plains. They are mostly less than 150 m and are crossed by many, usually dry river beds. In the north, around the Carpentariagolf, is the first basin of the same name.
The Great Artesian Basin occupies the center of the continent. It is the driest basin with the Simpson Desert, in which the sand dunes reach heights of up to 60 m, in the northern part and Lake Eyre in the southern part.
In the very south of the Central Australian Depression lies the Murray Basin, which is almost enclosed by mountains and is traversed by the largest Australian rivers.
The mountain ranges of the East Australian Highlands, the Great Dividing Range, extend over 3000 km parallel to the Pacific coast of Australia. These landscapes are characterized by steep drops both to the coast and inland, as well as deeply cut rivers. The majority of the mountain ranges are low mountain ranges. Only in the south, in the Canberra area, do they have a high mountain character. Here, in the Snow Mountains, is Mount Kosciusko (2230 m), the highest mountain in Australia.
The only major river in Australia with constant water is the Murray in southeast Australia. It rises in the Snowy Mountains. West of Adelaide it flows into the Indian Ocean after 2,589 km.
The longest river, however, is the Darling River with 2720 km , which, however, carries very little, sometimes no water at all in dry years.
In the Great Dividing Range there are still a number of rivers that flow into the Pacific after a few hundred kilometers. The numerous smaller rivers originating in the Great Artesian Basin mostly end in Lake Eyre, which is 14 m above sea level. d. M. and thus represents the deepest point in Australia.
This largest lake in Australia is located in the driest and hottest region on the continent. The rivers that flow into the lake have therefore dried up for months and rarely fill it. Due to the high evaporation, Lake Eyre is a salt lake, the area of which varies between 15000 and 8500 km². There are numerous other salt lakes in central Australia.
Australia is the driest continent on earth. The Tropic of Capricorn divides Australia into a northern part with a tropical climate and a central and southern part with a subtropical and, in the far south, a temperate climate (Fig. 6). The tropical north has high temperatures all year round and receives significant rainfall averaging 1500 mm per year. The precipitation falls almost exclusively in the summer rainy season from November to April.
However, they decrease rapidly to the south inland. Even 1000 km south of Darwin, only 350 mm fall per year. In the subtropics, the central coastal areas of the continent are on the Pacific coast in the east (e.g. Brisbane) and on the coast of the Indian Ocean in the west (e.g. Perth).
With around 1100 mm of precipitation per year, there is no pronounced dry season in these areas. In the over 2000 m high mountain regions of the Great Dividing Range, up to 3500 mm of precipitation falls per year, in the south in winter as snow.
The annual temperature differences range between an average of 25 °C in January (summer) and 15 °C in July (winter), so they are relatively small. The south of Australia around Sydney and Melbourne has a temperate climate that is comparable to the European Mediterranean climate. Mild, humid winters alternate with warm, dry summers. The areas of Central Australia, the so-called Outback, have a special climatic position. Characteristic here are high temperature fluctuations between day and night and extreme drought. Temperature “jumps” from frosty minus degrees in the night to a hot 40 °C the next day are not unusual in the outback.
The vegetation of Australia is fundamentally different from that of other continents. Around 2200 plant species have only evolved in Australia, which means they are endemic. In the always humid tropical north and northeast, tropical rainforests still grow .
To the south inland, tree, bush and grass savannas join with increasing drought. They then pass into the Australian bush, the scrub, which dominates large parts of the inhospitable interior. It consists mainly of evergreen hardwood and shrub plants.
In the central parts of the continent, the scrub eventually turns into deserts and semi-deserts with tufted grasses (Spinifex).
Characteristic endemic plants of Australia are above all the diverse species of eucalyptus. What they all have in common is the ability to shed their bark rather than their leaves during dry or cold spells. Bottle trees and grass trees, casuarinas and, above all, diverse acacia species are characteristic of Australia.