The deep oceans of the South Pacific have been hiding a secret for millions of years. In the waters surrounding New Zealand, scientists recently discovered the planet's seventh continent, the majority of which now lies a kilometer underwater. Now researchers have started to unravel its secrets, by drilling down into the rock and studying what they find.
“Zealandia, a sunken continent long lost beneath the oceans, is giving up its 60 million-year-old secrets through scientific ocean drilling,” said Jamie Allan, project director of the expedition. “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.”
During the nine-week voyage, the researchers drilled down deep into the seabed to sample the rocks that make up Zealandia. At six sites they bored down at depths of 1,250 meters (4,101 feet), and collected over 2,500 meters (8,202 feet) worth of sediment and rock samples. This impressive record of the region's geology recorded how the geology, volcanism, and climate on the drowned continent has altered during the past few tens of millions of years.
When looking through these samples, the researchers discovered something highly significant. They found the remains of hundreds of fossils, covering a wide array of species from the microscopic shells of creatures that prefer warm shallow oceans to deep continental shelves, to the spores of land plants. This hinted at a past for Zealandia that is vastly different to the subaquatic watery land we see today.
It seems that the continent was once riding high above the waves, and was no doubt a haven for a whole host of animals and plants at the time. They suspect that as the continent split from Australia and Antarctica some 80 million years ago, it set into action a chain of events that eventually culminated in the land mass slowly sinking beneath the waves, leaving just the islands of New Zealand and a few others peaking above the surface.
And this, it turns out, could help explain how some of the wildlife in the South Pacific ended up where it is today despite being separated by vast tracts of deep ocean.
“Big geographic changes across northern Zealandia, which is about the same size as India, have implications for understanding questions such as how plants and animals dispersed and evolved in the South Pacific,” remarked Rupert Sutherland, co-author of the study published in The Geological Society of America. “The discovery of past land and shallow seas now provides an explanation. There were pathways for animals and plants to move along.”
The research will now focus on how the movement of the tectonic plates moved and caused the landmass to sink.