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Land and Resources

Geology

Australia was once part of the enormous landmass Gondwanaland, which earlier formed part of the supercontinent Pangaea. Much of its geological history is remarkably ancient; the oldest known rock formations date from 3 billion to 4.3 billion years ago.

The great plateau of western Australia is underlain by a vast, stable shield of Precambrian metamorphic and igneous rocks, ranging in age from 570 million to 3 billion years old. These form the core of the ancestral continent, which, with Antarctica, had split off from Gondwanaland during the Jurassic Period, less than 200 million years ago, and had begun drifting eastward. Australia began to assume its modern configuration by the Eocene Epoch, some 50 million years ago, when Antarctica broke away and drifted southward.

The thick sedimentary rocks of the Great Dividing Range were deposited in a long, broad north-south depression, or geosyncline, during an interval that spanned most of the Paleozoic Era (570 million to 225 million years ago). Compressive forces buckled these rocks at least twice during the era, forming mountain ranges and chains of volcanoes. However, the volcanoes have long since become extinct, and as a result the mountain ranges are extremely eroded.

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