So far, we don’t know much about the world’s disputed “lost continent,” but a group of scientists set out to change that.
For two months, a team of 32 scientists from the International Ocean Discovery Program explored a region—being called Zealandia—that lies just east of Australia. Zealandia is roughly the size of India and is only now being explored because for many years it sat unknown, at depths ranging from 8,000 to 13,000 feet below the sea. The researchers collected a host of data, including by drilling into seabed, retrieving 8,202 feet of sediment cores.
In these cores, the team found records of life in the region dating back millions of years.
“More than 8,000 specimens were studied, and several hundred fossil species were identified,” said Gerald Dickens, the expedition’s co-chief scientist, in a press release. According to Dickens, one of the most significant findings made so far was that Zealandia was likely much shallower than it is now.
“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,” Dickens added.
Scientists aren’t quite sure exactly how and when Zealandia separated from Australia. Experts are divided on whether or not it should be considered a continent at all.
In an interview with National Geographic earlier this year, Northwestern geologist Christopher Scotese described the region as continental but “not a continent.” For him, the distinction boils down to the widely held definition of a continent as a landmass above and surrounded by water. Other scientists say the fact that Zealandia is submerged shouldn’t overshadow its geologically distinct nature.
According to the National Science Foundation, what scientists do know is that the region sits above two tectonic plates—the Australian plate and the Pacific plate—and that it broke off from Australia roughly 40 to 50 million years ago. When this happened, the Pacific plate was lodged under the Australian plate, creating a subduction zone. It’s thus one of several large features in the “Ring of Fire,” a region of intense seismic and volcanic activity.
“This is a crucial part of our history. Zealandia was part of Australia and ripped away for reasons we don’t understand very well,” said Jamie Allen, the program director for the National Science Foundation’s Division of Ocean Sciences.
The collected sediments provide a bank of paleoclimate data that Allen described as being like “tape recorders” of the region’s history.
Based on the characteristics of microorganisms fossilized deep within the region’s crust, scientists can determine how warm the water was and when. This provides an indication of how shallow or deep Zealandia was over its million-year history. Understanding how life on Earth responded to these changes can help scientists model how massive seismic and volcanic activity could influence climate in the years to come.
That Zealandia was once much shallower also provides a theory for how plants and animals dispersed throughout the Pacific in the past.
“If you have an understanding of why Earth’s climate changed in the past, that helps you model it for the future,” said Allen.
The expedition’s scientists have yet to release more details about their findings. They plan to study the huge reservoir of collected information over the coming year and publish their results.