New Zealand part of sunken 'lost continent'

New Zealand sits atop a previously unknown continent -- mostly submerged beneath the South Pacific -- that should be recognised with the name Zealandia, scientists said today.

Researchers said Zealandia was a distinct geological entity and met all the criteria applied to Earth's seven other continents -- elevation above the surrounding area, distinctive geology, a well-defined area and a crust much thicker than that found on the ocean floor.

In a paper published in the Geological Society of America's Journal, GSA Today, they said Zealandia measured five million square kilometre (1.9 million square miles) and was 94 percent underwater.

The paper's authors said it had only three major landmasses, New Zealand's North and South Islands to the south, and New Caledonia to the north.

The scientists, mostly from the official New Zealand research body GNS Science, said Zealandia was once part of the Gondwana super-continent but broke away about 100 million years ago.

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

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

Lead author Nick Mortimer said scientists have been gathering data to make the case for Zealandia for more than 20 years.

But their efforts had been frustrated because most of it was hidden beneath the waves.

"If we could pull the plug on the oceans, it would be clear to everybody that we have mountain chains and a big, high-standing continent," he told TVNZ.

While there is no scientific body that formally recognises continents, Mortimer said he wanted Zealandia to become an accepted part of how the Earth is viewed.

"What we hope is that Zealandia will appear on world maps, in schools, everywhere," he said.

"I think the revelation of a new continent is pretty exciting."