Australia and Oceania: Physical Geography

Oceania is a region made up of thousands of islands throughout the Central and South Pacific Ocean. It can be divided into three island groups: continental islands, high islands, and low islands.

Continental Islands

Continental islands were once attached to continents until they were separated by sea level changes and tectonic activity. Tectonic activity is what 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 as a result of tectonic activity.

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 location right below the warm Equator.

High Islands

High islands, also called volcanic islands, are created as volcanic eruptions build up land over time. These eruptions begin under water, when hot magma is cooled and hardened by the ocean. Over time, this activity creates islands with a steep central peak. Ridges and valleys spread outward from the peak 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. They are made of the skeletons and living bodies of small marine animals called corals. Low islands often take the shape of an irregular ring of very small islands, called an atoll. An atoll forms when a coral reef builds up around a volcanic island, then the volcanic island erodes away, leaving a lagoon.

Island Flora and Fauna

The evolution of flora and fauna across the islands of Australia and Oceania is unique. 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, producing multiple species that evolved from a common ancestor. Due to its isolation from the rest of the world, Australia and Oceania have a high number of species that are found nowhere else on Earth.

Plants traveled between islands by riding wind or ocean currents. Birds carried the seeds of fruits and plants and spread them between islands. Ferns, mosses, and some flowering plants rely on spores or seeds that can remain airborne for long distances. Coconut palms and mangroves produce seeds that can float on salty water for weeks at a time.

Birds are very common in Australia and Oceania because they are one of the few animals mobile enough to move from island to island. There are many seabirds and also flightless birds, such as emus and kiwis.

Australia and Oceania is the only place in the world that is home to monotremes—mammals that lay eggs. All monotremes are native to Australia and Papua New Guinea. There are only five living species: the duckbill platypus and four species of echidna.

Many of the most familiar animals native to the region are marsupials, including the koala, kangaroo, and wallaby. Marsupials are mammals that carry their newborn young in a pouch.

Marine Flora and Fauna

Marine realms are large ocean regions where animal and plant life are similar because of shared environmental and evolutionary factors.

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, sea birds and fish, sponges, mollusks, and crustaceans.

The Eastern Indo-Pacific realm surrounds the tropical islands of the central Pacific Ocean. It also has tropical coral formations with a variety of whale, tortoise, and fish species.

Source: Australia and Oceania: Physical Geography
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