Australia | The Land Down Under
Australia’s first settlers were a dark-skinned race of hunters and food-gatherers who arrived via raft or canoe from southeast Asia probably 50,000 to 60,000 years ago. At the time of European settlement the aboriginal population numbered between 300,000 and one million people, whose complex and distinctive culture was shaped by a severe environment. They had no agriculture and used only stone age tools.
Geography of Australia
Australia is distinguished by being the largest island in the world and the smallest continent. Australia is the only continent occupied by one nation. It is, of course, and island, and is only 2% smaller than continental United States. Its population is around 22 million, compared to over 300 million inhabiting the United States. Australia is the sixth largest country in area after Russia, Canada, China, the US and Brazil. The coast of Australia is washed by the indian ocean on the west and the southern Pacific Ocean on the east. The shoreline extends 23,000 miles.
About 40 percent of Australia is north of the Tropic of Capricorn. It lies 6,467 miles from the west coast of the United States. Australia is also one of the oldest and flattest of the continents. Australia's average elevation is about 900 ft compared to around 2,200 ft as a world average. Rocks from the Murchison River area of Western Australia date to 4.2 billion years ago, and rocks from the northwest corner of Western Australia contain the oldest remains of life, fossil bacteria-like organisms 3.5 billion years old. Australia is tectonically quite, without much volcanic or severe earthquake activity.
There are three major structural divisions of the Australian continent. These are the stable Western Shield, the gently warped Central Basin, and the Eastern Uplands.
The Western Shield is one vast ancient crustal block about 980 ft above sea level. It emerges from Western Australia's coastal plain and covers about half the continent. A famous outcrop which interrupts monotony of the plateau is Ayers Rock in the central desert. It is a huge monolith, commonly regarded as the largest in the world. The Western Shield makes up most of the 1 million square miles that is covered by windblown sand. Much of it, including the Nullabor Plain, is without a river.
The Central Basin is a great lowland belt extending from the Gulf of Carpentaria in the north to the coast of Victoria in the south. it averages 490 feet above sea level. Much of the drainage is internal, to Lake Eyre in South Australia, a 540,000 square mile tectonic depression that dates back 200 million years and was much larger in the Tertiary and Pleistocene. Usually, lake Eyre is a dry saltpan, but it fills with water after heavy rains, most recently in 1988. Its basin at the lowest point is 50 feet below sea level. Cretaceous fossils indicate that the Central Basin was covered by the sea relatively recently in geological history. Gibber-strewn plains cover 100,000 square miles around the Simpson Desert.
The Eastern Uplands (of Highlands), which average around 3,000 feet in elevation, extend along the eastern rim of the continent from Cape York to Tasmania. The Highlands were differentially uplifted in the Tertiary and are more commonly referred to as the Great Dividing Range. This range hugs the edge of the continent 31 to 248 miles from the eastern coast. Rivers to the east drain into the Pacific Ocean, whereas poorly watered western slopes drain internally or into Australia's largest river system, the Murray-Darling. The southeastern area of the Great Dividing Range is known as the Australian Alps and includes Australia's highest peak, Mount Kosciuszko which peaks at 7,308 feet. The region contains the only areas of Australia to be glaciated during the Pleistocene.