Zealandia has only begun been acknowledged as a continent in its own right recently. It is about 5 million square kilometres, but almost 95% of it is underwater. The islands of New Zealand are the main landmasses of the continent that peak above sea level.

Now the research ship Joides Resolution will make a series of six trips into the Tasman Sea, beginning on 27 July. They aim to extract cores of sediment from 300 to 800 metres deep, working at water depths of up to 5,000 metres.

It's hoped that these 'fossil sediments' will reveal more about the history of the elusive continent, and the origin of New Zealand itself.

"Some 50 million years ago a massive shift in plate movement happened in the Pacific Ocean," said Jamie Allan of the US's National Science Foundation, which is funding the mission alongside the International Ocean Discovery Programme (IODP).

"It resulted in the diving of the Pacific Plate under New Zealand, the uplift of New Zealand above the waterline and the development of a new arc of volcanoes."

This shift was one of the largest in recent geological time. Extracting deep sediment from it, which has not been attempted on this scale before, could reveal information about how very large tectonic events happen.

"If you go way back, about 100 million years ago, Antarctica, Australia and Zealandia were all one continent," said expedition co-chief scientist Gerald Dickens of Rice University in the US.

"Around 85 million years ago, Zealandia split off on its own, and for a time, the seafloor between it and Australia was spreading on either side of an ocean ridge that separated the two."

The research will also help to make better forecasts of climate change. Studying the evolution of the Earth's climate in this part of the world will help fill in a lot of missing data on how life in the oceans reacted to varying carbon levels in the past tens of millions of years. Better historical data will help to create more solid projections for the future.

"This expedition will answer a lot of lingering questions about Zealandia," Dickens said.

Joides Resolution
Joides Resolution, the research ship that will be used on the mission. IODP