AUSTRALIA, FLAG OF

national flag consisting of a dark blue field (background) with the Union Jack in the canton and six white stars. Its width-to-length ratio is 1 to 2. Thought was given to an all-Australian flag long before confederation was achieved on January 1, 1901. For example, in 1823 a National Colonial Flag displayed four white eight-pointed stars on a red cross on a white field with the Union Jack. From 1831 until as late as the 1920s there was a somewhat similar design known as the Australian Federation Flag, with a blue cross and five white stars. In later years the Eureka Stockade Flag (a white cross with white eight-pointed stars against a blue field) gained popularity after its first hoisting in 1854 during a labour dispute. After the Commonwealth of Australia was formed, thousands of proposals were submitted by the general public in flag design competitions. The winning design, announced on September 3, 1901, is basically still in use today. It has the Union Jack in the canton of a blue field displaying five white multipointed stars in the form of the Southern Cross plus a seven-pointed Commonwealth Star. Minor modifications were made on February 20, 1903, and the flag became official for use on government vessels on May 22, 1909. The same six-star design, with red substituting for the blue background, was established in 1903; although sometimes used on land, this Australian Red Ensign is generally restricted to privately owned vessels. Australian involvement in World War II led to increasing pressure for the selection of the Australian Blue Ensign over the Union Jack as a national flag. The new flag was recognized by law on February 14, 1954, when it was approved by the British sovereign. By the 1980s, however, serious questions were being raised in public, particularly by those who favoured replacement of the monarchy with a republic, about the suitability of this flag for an independent Australia. Veterans, older people, and those of British descent generally favoured retention of the Australian Blue Ensign, but such sentimental and historical ties meant less to younger people and to immigrants from other parts of Europe or from Asia. Many disliked the similarity of the flag to those used by British colonies. Those favouring a new flag could not throw their support behind a single new design, however, because they were split on issues such as the expression of loyalty to the British monarchy and the possible inclusion in a new flag of Aboriginal symbols; therefore, the old flag was retained despite substantial support for a change. Whitney Smith Geologic history The earliest known manifestations of the geologic record of the Australian continent are 4.3-billion-year-old detrital grains of zircon in metasedimentary rocks that were deposited between 3.7 and 3.3 billion years ago. Based on this and other findings, the Precambrian rocks in Australia have been determined to range in age from about 3.7 billion to 570 million years. They are succeeded by rocks of the Paleozoic Era, which extended to 245 million years ago; of the Mesozoic Era, which lasted until 66.4 million years ago; and of the Cenozoic Era, which continues to today. Australia was part of the supercontinents of Pangaea and Gondwanaland (or Gondwana) for millions of years. It finally emerged as a separate continent about 35 million years ago, and it is now at the point of uniting with Southeast Asia. As a continent, Australia thus encompasses two extremes: on the one hand, it contains the oldest known earth material while, on the other, it has stood as a free continent only since about the mid-Cenozoic and is in the processin terms of geologic timeof merging with Asia, so that its life span as a continent will be of short duration. (See also geochronology: Geologic history of the Earth.) General considerations Tectonic framework The map of the structural features of Australia and the surrounding region shows the distribution of the main tectonic units. The primary distinction is between the plates of oceanic lithosphere, generated within the past 160 million years by seafloor spreading at the oceanic ridges, and the continental lithosphere, accumulated over the past 4 billion years. (The lithosphere is the outer rock shell of the Earth that consists of the crust and the uppermost portion of the underlying mantle; see plate tectonics.) The largest area of oldest rocks is the Western Shield, which has been eroded to a low relief. The youngest rocks occur in the growing fold belt of the Banda arcs and in New Guinea at the boundary between the Indian-Australian lithospheric plate and the Eurasian and Pacific plates. The modern fold belts are separated from Australia by a moat (Timor Trough) and a wide shelf (Timor and Arafura seas). The northern half of the Australian margin is completed by the North West Shelf and the Exmouth Plateau on the west and by the Great Barrier Reef and the Queensland Plateau on the east. Precambrian rocks occupy three tectonic environments. The first is in shields, such as the Yilgarn and Pilbara blocks of the Western Shield, enclosed by later orogenic (mountain) belts. The second is as the basement to a younger cover of Phanerozoic sediment (those deposited between 570 million years ago and the present); for example, all the sedimentary basins west of the Tasman Line are underlain by Precambrian basement. The third is as relicts in younger orogenic belts, as in the Georgetown Inlier of northern Queensland and in the western half of Tasmania. Rocks of Paleozoic age occur either in flat-lying sedimentary basins, such as the Canning Basin, or within belts, such as the east-west-trending Amadeus Transverse Zone and north-trending Tasman Fold Belt. Mesozoic and Cenozoic rocks occur in widely distributed (though poorly exposed) basins onshore (Great Artesian Basin) and offshore on the western, southern, and eastern margins, including beneath Bass Strait and in the submerged ground between the Banda arcs/New Guinea and the mainland.