Image copyright AFP Image caption Mount Cook, the highest peak of New Zealand - and Zealandia

You think you know your seven continents? Think again, as there's a new contender hoping to join that club.

Say hello to Zealandia, a huge landmass almost entirely submerged in the southwest Pacific.

It's not a complete stranger, you might have heard of its highest mountains, the only bits showing above water: New Zealand.

Scientists say it qualifies as a continent and have now made a renewed push for it to be recognised as such.

In a paper published in the Geological Society of America's Journal, researchers explain that Zealandia measures five million sq km (1.9m sq miles) which is about two thirds of neighbouring Australia.

Image copyright GNS

Some 94% of that area is underwater with only a few islands and three major landmasses sticking out above the surface: New Zealand's North and South Islands and New Caledonia.

You might think being above water is crucial to making the cut as a continent, but the researchers looked at a different set of criteria, all of which are met by the new kid in town.

elevation above the surrounding area

distinctive geology

a well-defined area

a crust thicker than the regular ocean floor

Image copyright ESA/NASA Image caption New Zealand as captured from space by astronaut Tim Peake

The main author of the article, New Zealand geologist Nick Mortimer, said scientists have been researching data to make the case for Zealandia for more than two decades.

"The scientific value of classifying Zealandia as a continent is much more than just an extra name on a list," the researchers explained.

"That a continent can be so submerged yet unfragmented" makes it useful for "exploring the cohesion and breakup of continental crust".

So how then to get Zealandia into the canon of continents? Should text books authors get nervous again? After all, just a few years ago, Pluto got kicked off the list of planets, changing what had been taught in schools for decades.

There is in fact no scientific body that formally recognises continents. So it could only change over time if future research accepts Zealandia on par with the rest so that eventually we might be learning about eight, not seven, continents.