Zealandia is a long, narrow microcontinent that is mostly submerged in the South Pacific Ocean.

A microcontinent is a landmass that has broken off from a main continent. Zealandia broke off from Antarctica about 100 million years ago, and then from Australia about 80 million years ago.

Zealandia is about half the size of Australia, but only 7 percent of it is above sea level. Most of that terrestrial land makes up the two large islands of the country of New Zealand, the North Island and the South Island. Stewart Island, just south of the South Island, and many smaller islets are also a part of Zealandia. New Caledonia, a collection of islands governed by France, makes up the northern tip of Zealandia.

Zealandia generally enjoys a mild, temperate climate. Its largest islands have glaciers, the largest being Tasman Glacier on the South Island. Activity from the last glacial period also carved out many fjords and valleys. The tropical climate of New Caledonia, on the other hand, has more in common with Oceania and the South Pacific.

Volcanic Activity

Zealandia is a very tectonically active region. Part of the microcontinent is on the Australian plate, while the other part is on the Pacific plate.

The northern part of Zealandia is very volcanic. There are six major areas with active volcanoes, the largest being the Taupo Volcanic Zone on the North Island. Geothermal activity caused by the interaction of the Australian and Pacific plates also means there are many natural geysers and hot springs scattered throughout Zealandia.

Both the North and South Islands have volcanic mountain ranges running through their centers. The North Island is dominated by the North Island Volcanic Plateau, while the primary mountain range of the South Island is the Southern Alps. Both mountain ranges are slowly getting higher through a process called tectonic uplift.

Underwater Zealandia

The submerged part of Zealandia is rich in mineral deposits, although New Zealand's government strictly controls undersea mining activity. There are also many natural gas fields scattered throughout Zealandia. The Maui natural gas field in the Tasman Sea is the largest.

Underwater Zealandia is of value to science as well as business. During glacial periods, sea levels fell, and more of Zealandia was above water. Zealandia's submerged fossils provide valuable clues to life during those time periods.