Australiais the smallest of the geographiccontinents, though not of geological continents. New Zealand is not on the same continental shelf and so is not part of the continent of Australia but is part of the submerged continent Zealandia. Zealandia and Australia together are part of the wider region known asOceaniaorAustralasia. Oceania(sometimesOceanica) is ageographical, oftengeopolitical,regionconsisting of numerous landsmostlyislandsin thePacific Oceanand vicinity. Consisting of Australia, New Zealand, New Guinea, and the south Pacific islands, Oceania is a highly diverse region. From the vast dry bushland of Western Australia to the dense rain forest of the tiny Solomon Islands, Oceania also includes mountains, jungles, and swamplands. The boundaries of Oceania are defined in a number of ways. Most definitions include parts ofAustralasiasuch asAustralia,New Zealand, and New Guinea, and all or part of theMalay Archipelago. Ethnologically, the islands that are included in Oceania are divided into thesubregions ofMelanesia,Micronesia, andPolynesia.