The Oceania region includes thousands of islands throughout the Central and South Pacific Ocean divided into three island groups.

Continental Islands

Continental islands were once attached to continents until they were separated by sea level changes and tectonic activity. Tectonic activity causes earthquakes by the movement and collision of different plates of the Earth’s crust.

Australia, Zealandia, and New Guinea are continental islands with mountain ranges or highlands. These highlands are fold mountains, created as tectonic plates pressed together and pushed land upward. New Zealand and Papua New Guinea also have volcanic features.

Australia’s landscape is dominated by the Outback, a region of deserts. New Zealand’s glaciers are a result of the islands’ high elevations and proximity to cool, moisture-bearing winds. Papua New Guinea’s highland rain forests are a result of the island’s high elevations, proximity to tropical, moisture-bearing winds, and the warm Equator.

High Islands

High islands, also called volcanic islands, are created as volcanic eruptions build up land over time. These eruptions begin underwater when hot magma is cooled and hardened by the ocean. This activity creates islands with a steep central peak. Ridges and valleys spread outward toward the coastline.

The island region of Melanesia is a major part of the “Ring of Fire,” a string of volcanoes around the boundary of the Pacific Ocean.

Low Islands

Low islands are also called coral islands, made of the skeletons and living bodies of small marine animals called corals. Low islands may form an irregular ring of very small islands, called an atoll, when a coral reef builds up around a volcanic island, then the volcanic island erodes away, leaving a lagoon.

Island Flora and Fauna

Many plants and animals reached the islands from southern Asia during the last glacial period, when sea levels were low. After sea levels rose, species adapted to the environment of each island. Due to their isolation, Australia and Oceania have a high number of unique species.

Plants traveled between islands by riding wind or ocean currents. Birds carried the seeds of fruits and plants. Other species include ferns, mosses, flowering plants, coconut palms, and mangroves.

Birds are very common in Australia and Oceania because they can move from island to island. There are seabirds and flightless birds such as emus and kiwis.

Australia and Papua New Guinea are the native homes of all monotremes, which are mammals that lay eggs. The only living species are the duckbill platypus and four species of echidna.

Many animals native to the region are marsupials, including the koala, kangaroo, and wallaby. Marsupials are mammals that carry their newborns in a pouch.

Marine Flora and Fauna

The Temperate Australasia realm is one of the world’s richest areas for seabirds such as the albatross and petrel.

The Central Indo-Pacific realm includes the world’s two largest coral formations—the Great Barrier Reef and the New Caledonia Barrier Reef. These reefs have extensive biodiversity, with many species of whales and dolphins, sea turtles, sponges, mollusks, and crustaceans.

Source: Australia and Oceania: Physical Geography
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