The drill ship JOIDES Resolution. Photo: ANU

A two-month long expedition to solve the mysteries of Zealandia, a “lost” undersea landmass, begins today.

The expedition is led by Australian National University and is part of the International Ocean Discovery Program (IODP), which encompasses 23 countries from around the world.

Zealandia consists of 1.9 million square miles, and extends from the south of New Zealand north to New Caledonia and west to the Kenn Plateau off Rockhampton.

It was connected as a part of Australia until about 75 million years ago, when it began to break away and move northeast where it settled 53 million years ago. This was also around the same time that the Pacific Ring of Fire – an area known to have many earthquakes and volcanic eruptions – began to form.

The landmass has only gained significant attention from researchers within the last two decades, so little is known about its origin or geologic history.

Earlier this year, the Geological Society of America published a paper that presented an argument that Zealandia should receive “continent” status. In the paper, the authors listed four key attributes of continents and how Zealandia meets the criteria.

Zealandia is almost completely submerged by the South Pacific, and would be a connector between the islands of New Zealand and New Caledonia if the ocean didn’t act as a barrier.

"The continental crust of Zealandia was thinned by stretching before it separated from Australia so that it lies lower than Australia," said Rupert Sutherland, co-chief scientist from Victoria University of Wellington. "Zealandia's continental crust is thicker than the surrounding oceanic crust, and so it lies higher than that."

For the ANU-led expedition, researchers will work with a drill ship, JOIDES Resolution, to drill and collect sediment and rock cores, which they hope will help answer questions about how Zealandia formed, and how the area has been affected over time. The team will analyze the samples on board the ship, and on shore.

They also hope to better understand the global tectonic configuration that began around the time of the Ring of Fire formation.

“Scientists will study the cores on board and onshore to address problems in fields such as climate and oceanographic history, extreme climates, sub-seafloor life, plate tectonics and earthquake-generating zones, and the dynamics of island arcs and ocean basins,” explained ANU in a release.

"As Australia moved north and the Tasman Sea developed, global circulation patterns changed and water depths over Zealandia fluctuated. This region was important in influencing global changes," said Jerry Dickens, co-chief scientist, of Rice University.

Preliminary results are expected to be shared at the end of September when the ship docks in Hobart.

Map of Zealandia. Photo: Nick Mortimer, GNS Science, Dunedin