WorldWide Drilling Resource

Discovering the Secrets of our Hidden Continent Compiled by Bonnie Love, Editor, WorldWide Drilling Resource ® In 2017, Zealandia was confirmed as a continent by the Geological Society of America. Located in the southwest Pacific Ocean, the newly identified continent includes the country of New Zealand, as well as the New Caledonia territory. Once a part of the ancient supercontinent Gondwana, Zealandia is a mass of continental crust about half the size of Australia, surrounding New Zealand. Why did it take so long to find this lost continent? Unlike most continents, 94% of Zealandia is immersed below sea level. Recent improvements and more detailed seafloor maps have brought the youngest, thinnest, and most submerged continent into focus. Expedition co-chief scientist Gerald Dickens, a professor of earth, environmental, and plan- etary science at Rice University explained, “If you go way back, about 100 million years ago, Antarctica, Australia, and Zealandia were all one continent. 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.” A research team of more than 30 scientists from 12 countries boarded the JOIDES Resolution, one of the world’s most sophisticated scientific drill ships, in search of clues about the history of this hidden continent. Sponsored by the National Science Foundation and its global partners in the International Ocean Discovery Program (IODP), the expedition to explore Zealandia set sail in early summer 2017. The goal of the nine-week voyage was to drill and collect core samples from the ancient seafloor to see what it can teach us about the earth during that time period. “Zealandia . . . is giving up its 60 million-year-old secrets through scientific ocean drilling,” said Jamie Allan, program director in the U.S. National Science Foundation's Division of Ocean Sciences. “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,” he stated. The team of scientists drilled into the seafloor at six sites in water depths of more than 4000 feet and collected more than 8200 feet of cores filled with sed- iment from millions of years ago. According to Dickens, significant new fossil discoveries were made. These fossils prove Zealandia was not always as deep beneath the ocean as it is today. “More than 8000 specimens were studied, and several hundred fossil species were identified,” he explained. “The discovery of microscopic shells of organisms that lived in warm shallow seas, and of spores and pol len from land plants, reveal that the geography and cl imate of Zealandia were dra- matical ly different in the past.” These findings provide clues to how plants and animals dispersed and evolved in the South Pacific. Expedition co-chief scientist Rupert Sutherland of Victoria University of Wellington in New Zealand said, “The discovery of past land and shallow seas now provide an explanation. There were pathways for animals and plants to move along.” So, why did the continent sink? According to Sutherland, the core sam- ples clearly show signs of major geo- graphic changes and volcanic eruptions on the continent, which were related to the formation of the Pacific Ring of Fire, a chain of undersea volcanoes, ocean trenches, seamounts, and hydrothermal vents which formed 40-50 million years ago. The only way to find out more is with continued research. Gerald Dickens and Rupert Sutherland, co-chief scien- tists for the operation. Photo by Tim Fulton, IODP JRSO. Photo of the first core of the expedi- tion by Kristina Pascher & IODP. ENV WorldWide Drilling Resource ® 7 JULY 2018 Photo of quiet rig floor at dusk by Tim Fulton, IODP JRSO.