The
Australian Shield, also called the Western Australian
Shield or
Western Plateau, occupies more than half of the continent of Australia. The word shield is used because it refers to ancient, molten rock which has cooled and solidified. The Australian Shield has a characteristic depth of 4.5 km and an estimated age of 2.8 to 3.5 billion years. In places younger
sedimentary rock covers the shield's
Precambrian surface.