Oceania is a geographical, often geopolitical, region consisting of numerous lands—mostly islands in the Pacific Ocean and vicinity. Ethnologically, the islands that are included in Oceania are divided into the subregions of Melanesia, Micronesia, and Polynesia. The exact scope of Oceania is variably defined: it generally includes New Zealand, is often taken to include parts of Australasia such as Australia and New Guinea, and sometimes all or part of the Malay Archipelago. Most of Oceania consists of island nations composed of thousands of coral atolls and volcanic islands, with small human populations.