Continent Europe and Asia together as a single continent, dubbed "Eurasia". In this model, the world is divided into six continents, with North America and South America considered separate continents. Geologists use the term "continent" in a different manner from geographers. In geology a continent is defined by continental crust: a platform of metamorphic and igneous rock, largely of granitic composition. Some geologists restrict the term 'continent' to portions of the crust built around stable Precambrian "shield", typically 1.5 to 3.8 billion years old, called a craton. The craton itself is an accretionary complex of ancient mobile belts (mountain belts) from
Australia (continent) in urban centres. West Papua, a province of Indonesia, is home to an estimated 44 uncontacted tribal groups. Australia, the largest landmass in the continent, is highly urbanised, and has the world's 13th-largest economy with the second-highest human development index globally. Australia also has the world's 9th largest immigrant population. The first settlers of Australia, New Guinea, and the large islands just to the east arrived between 50,000 and 30,000 years ago. Archaeological terminology for this region has changed repeatedly. Before the 1970s, the single Pleistocene landmass was called "Australasia", derived from the Latin "australis", meaning "southern", although this word