Earlier this year, a team of geologists published a paper arguing that a new, mostly sunken landmass called Zealandia should be classified as our planet's eighth continent. Now a collective of scientists from 12 countries has returned from a two-month expedition exploring this subsea mystery. The result of extensive seafloor analysis is hoped to reveal new insights into the Earth's dynamic geological past.

"Zealandia, a sunken continent long lost beneath the oceans, is giving up its 60 million-year-old secrets through scientific ocean drilling," says Jamie Allan, one of the researchers affiliated with the mission. "This expedition offered insights into Earth's history, ranging from mountain-building in New Zealand to the shifting movements of Earth's tectonic plates to changes in ocean circulation and global climate."

The expedition traveled to six separate sites to drill sediment cores from the ocean floor. Samples were obtained at water depths up to 1,250 meters (4,101 ft), offering data that reveals the climate and geographic changes the drowned continent has undergone over 70 million years.

Thousands of fossil specimens were gathered during the research that clearly indicated that Zealandia was not always an undersea land. It was generally suspected that the continent slipped under water about 80 million years ago when it broke away from Australia and Antarctica.

"That is still probably accurate, but it is now clear that dramatic later events shaped the continent we explored on this voyage," says Rupert Sutherland, co-chief scientist on the expedition.

Those "dramatic later events" have been revealed to be a stretch of significant volcanic activity between 40 and 50 million years ago. Resulting in the formation of what is known as the "Pacific Ring of Fire," this major geological shift buckled the seabed of the sunken continent.

Other discoveries from the expedition reveal clues as to how certain species of flora and fauna have migrated across the globe.

"The discovery of microscopic shells of organisms that lived in warm shallow seas, and of spores and pollen from land plants, reveal that the geography and climate of Zealandia were dramatically different in the past," adds co-chief scientist Gerald Dickens.

The treasure trove of data gathered by the expedition will help strengthen global climate models, allowing for profiles of the past 60 million years that ultimately lead to better future predictions. The team suggests the data will help solve a problem scientists have been facing in producing accurate climate models of the planet around 50 million years ago.

"When the community does climate modeling for the Eocene Epoch [56 to 33.9 million years ago], this is the area that causes consternation, and we're not sure why," said Dickens. "It may be because we had continents that were much shallower than we thought. Or we could have the continents right but at the wrong latitude. The cores will help us figure that out."

Despite being 94 percent submerged, Zealandia reminds us that there are still plenty of undiscovered and unexplored mysteries on our remarkable planet

Source: National Science Foundation (1), (2)

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