Zealandia in the context of "Microcontinent"

Determining the boundaries between the continents is generally a matter of geographical convention and consensus. Several slightly different conventions are in use. The number of continents is most commonly considered seven (in English-speaking countries) but may range as low as four when Afro-Eurasia and the Americas are both considered as single continents. An island can be considered to be associated with a given continent by either lying on the continent's adjacent continental shelf (e.g. Singapore, the British Isles) or being a part of a microcontinent on the same principal tectonic plate (e.g. Madagascar and Seychelles). An island can also be entirely oceanic while still being associated with a continent by geology (e.g. Bermuda, the Australian Indian Ocean Territories) or by common geopolitical convention (e.g. Ascension Island, the South Sandwich Islands). Another example is the grouping into Oceania of the Pacific Islands with Australia and Zealandia.

There are three overland boundaries subject to definition:

Continental crust is the layer of igneous, metamorphic, and sedimentary rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called sial because its bulk composition is richer in aluminium silicates (Al-Si) and has a lower density compared to the oceanic crust, called sima which is richer in magnesium silicate (Mg-Si) minerals. Changes in seismic wave velocities have shown that at a certain depth (the Conrad discontinuity), there is a reasonably sharp contrast between the more felsic upper continental crust and the lower continental crust, which is more mafic in character.

Most continental crust is dry land above sea level. However, 94% of the Zealandia continental crust region is submerged beneath the Pacific Ocean, with New Zealand constituting 93% of the above-water portion.

New Zealand consists of more than six hundred islands, mainly remnants of a larger land mass now beneath the sea. New Zealand is the sixth-largest island country, and the third-largest located entirely in the Southern Hemisphere. The following is a list of islands of New Zealand.

The two largest islands – where most of the population lives – have names in both English and in the Māori language. They are the North Island or Te Ika-a-Māui and the South Island or Te Waipounamu. Various Māori iwi sometimes use other names, with some preferring to call the South Island Te Waka o Aoraki. The two islands are separated by the Cook Strait. In general practice, the term mainland refers to the North Island and South Island. However, the South Island alone is sometimes called "the mainland" – especially by its residents, as a nickname – because it is the larger of the two main islands.

New Zealand (Māori: Aotearoa) is an island country located in the southwestern Pacific Ocean, near the centre of the water hemisphere. It consists of a large number of islands, estimated around 700, mainly remnants of a larger landmass now beneath the sea. The land masses by size are the South Island (Te Waipounamu) and the North Island (Te Ika-a-Māui), separated by the Cook Strait. The third-largest is Stewart Island (Rakiura), located 30 kilometres (19 miles) off the tip of the South Island across Foveaux Strait. Other islands are significantly smaller in area. The three largest islands stretch 1,600 kilometres (990 miles) across latitudes 35° to 47° south. New Zealand is the sixth-largest island country in the world, with a land size of 268,680 km (103,740 sq mi).

New Zealand's landscapes range from the fiord-like sounds of the southwest to the sandy beaches of the subtropical Far North. The South Island is dominated by the Southern Alps while a volcanic plateau covers much of the central North Island. Temperatures commonly fall below 0 °C (32 °F) and rise above 30 °C (86 °F) then conditions vary from wet and cold on the South Island's west coast to dry and continental a short distance away across the mountains and to the tundra like climate in the Deep South of Southland.

Gondwana (/ɡɒnˈdwɑːnə/ gond-WAHN-ə; Sanskrit: [goːɳɖɐʋɐnɐ]) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia, Zealandia, Arabia, and the Indian subcontinent.

Gondwana was formed by the accretion of several cratons (large stable blocks of the Earth's crust), beginning c. 800 to 650 Ma with the East African Orogeny, the collision of India and Madagascar with East Africa, and culminating in c. 600 to 530 Ma with the overlapping Brasiliano and Kuunga orogenies, the collision of South America with Africa, and the addition of Australia and Antarctica, respectively. Eventually, Gondwana became the largest piece of continental crust of the Paleozoic Era, covering an area of some 100,000,000 km (39,000,000 sq mi), about one-fifth of the Earth's surface. It fused with Laurasia during the Carboniferous to form Pangaea.

A submerged continent or a sunken continent is a region of continental crust, extensive in size but mainly undersea. The terminology is used by some paleogeologists and geographers in reference to some landmasses (none of which are as large as any of the seven generally-recognized continents).

The definition of this term is unclear. If continental fragments and microcontinents smaller than 2,500,000 km (970,000 sq mi), which is approximately one third of the area of mainland Australia, are excluded, then Zealandia (approximately 4,900,000 km or 1,900,000 sq mi) would be the only geological feature which is classifiable as a submerged continent.