Australia

The continent's oldest rocks are in the Western Australian shield in southwest Australia. The basement (underlying) rocks in this area have not been folded since the Archean eon over three billion years ago, when the planet was still very young. The nucleus of this shield (called the Yilgarn craton) comprising 230,000 sq mi (59,570,000 ha), consists mostly of granite with belts of metamorphic rock like greenstones, rich in economic mineral deposits as well as intrusions of formerly molten rock.

The Yilgarn craton does not quite extend to the coast of Western Australia. It is bounded on the west by the Darling Fault near Perth. To the south and east the craton is set off by the Frazer Fault from somewhat younger rocks that were metamorphosed between 2.5 billion and two billion years ago. Both fault lines are 600 mi (960 km) long and are considered major structures on the continent.

Along the north coast of Western Australia near Port Hedland is another nucleus of ancient rocks, the Pilbara Craton. The Pilbara craton is composed of granites over three billion years old as well as volcanic, greenstone, and sedimentary rocks. The Hammersley Range just south of the Pilbara Craton is estimated to contain billions of tons of iron ore reserves.