Oceanian realm located on terrain feature Insular Oceania
The Oceanian realm is one of the World Wildlife Fund (WWF) biogeographic realms, and is unique in not including any continental land mass. It has the smallest land area of any of the WWF realms.
This realm includes the  islands of the Pacific Ocean in Micronesia, the Fijian Islands, the Hawaiian islands, and Polynesia (with the exception of New Zealand). New Zealand, Australia, and most of Melanesia including New Guinea, Vanuatu, the Solomon Islands, and New Caledonia are included within the Australasian realm.
Conversely, New Guinea, New Caledonia, the Solomon Islands and New Zealand are included in the Oceanian realm in the classification scheme developed by Miklos Udvardy in 1975.The Juan Fernández Islands have been included in both the Oceanian and Temperate South American realms. Despite only being a few hundred miles removed from the South American coast, the islands have strong Hawaiian and southeast Polynesian biogeographic influences, and the presence of an endemic insect and plant family. The uninhabited French territory of Clipperton Island, 1,000 kilometers off the coast of Mexico, has also been associated with the realm.Geology
Oceania is geologically the youngest realm. While other realms include old continental land masses or fragments of continents, Oceania is composed mostly of volcanic high islands and coral atolls that arose from the sea in geologically recent times, many of them in the Pleistocene. They were created either by hotspot volcanism, or as island arcs pushed upward by the collision and subduction of tectonic plates. The islands range from tiny islets, sea stacks and coral atolls to large mountainous islands, like Hawaii and Fiji.