Science & Technology

Zealandia Secrets Brought to the Surface by Research Voyage – Upends Previous Theory

Current seafloor drilling has revealed that the ‘hidden continent’ of Zealandia — a area of continental crust twice the measurement of India submerged beneath the southwest Pacific Ocean — skilled dramatic elevation adjustments between about 50 million and 35 million years in the past. Credit score: Worldwide Ocean Discovery Program, JOIDES Decision Science Operator

Contemporary proof of how the continent of Zealandia was created has been printed by a world group of scientists co-led by Te Herenga Waka—Victoria College of Wellington’s Professor Rupert Sutherland.

The analysis each upends the earlier concept and establishes a brand new geological idea.

Professor Sutherland from the College’s College of Geography, Atmosphere and Earth Sciences was a part of the group of predominantly GNS Science researchers that made world headlines in 2017 after they introduced Zealandia ought to rely as a brand new fully-fledged continent, Earth’s seventh and smallest.

New Zealand to the south and New Caledonia to the north are the solely main land plenty of the in any other case largely underwater Zealandia, which, at 4.9 million sq. kilometers, is about two-thirds the measurement of Australia.

Its continental crust is usually between 10 and 30 kilometers thick, which is thinner than the 30 to 45 kilometers of the six different continents, but thicker than oceanic crust, which is about seven kilometers thick.

The primary scientific drilling expedition to Zealandia in 1972 hypothesized it was underwater after its crust was stretched, thinned and ripped away from the historical supercontinent of Gondwana (which included Australia and Antarctica) about 85 million years in the past.

Though proof stays compelling that this was no less than a part of the case, new samples collected and examined by Professor Sutherland and his colleagues throughout a nine-week Tasman Sea voyage beneath the auspices of the Worldwide Ocean Discovery Program point out a key extra issue: Zealandia’s subsequent modification throughout the formation of the Pacific Ring of Fireplace about 50 million years in the past.

The Pacific Ring of Fireplace is a zone of volcanoes and earthquakes that end result from the geological strategy of subduction, the place a tectonic plate sinks again deep into the Earth. The method by which the zone shaped has at all times been a thriller.

“We suggest {that a} ‘subduction rupture occasion’ propagated round the entire of the western Pacific at the moment,” says Professor Sutherland. “We advise the course of was related to an enormous super-slow earthquake that resurrected historical subduction faults that had lain dormant for a lot of hundreds of thousands of years. This idea of ‘subduction resurrection’ is a brand new concept and will assist clarify a spread of various geological observations.”

On account of the Pacific Ring of Fireplace, “issues that had been in 1,000 meters of water got here up to sea stage after which subsided down to be greater than 1,000 meters deep once more,” he says. “The everlasting results included the New Caledonia Trough that comes all the manner to Taranaki.”

Professor Sutherland’s group included greater than 30 scientists from New Zealand, the United States, Italy, Spain, New Caledonia, China, the Netherlands, Germany, Brazil, Japan, the United Kingdom, and South Korea. He co-led it with Professor Gerald Dickens from Rice College in Texas in the United States.

They used a 300-tonne drill to make six boreholes up to 900 meters beneath the sea flooring, from which rock and sediment cores had been collected and analyzed for clues about the timing and size of Zealandia’s uplift.

“We used fossils from three of the websites to present that northern Zealandia turned a lot shallower and sure even had land areas between 50 and 35 million years in the past. At about the identical time, two different websites subsided into deeper water, after which the entire area subsided by no less than a kilometer to its current depth,” says Professor Sutherland.

The group’s proof reveals that occasions reminiscent of the creation of the Pacific Ring of Fireplace “can dramatically alter the geography of continents, and the sedimentary file preserved on Zealandia will assist us determine in additional element how and why it occurred, and what the penalties had been for vegetation, animals, and regional local weather.”

Reference: “Continental-scale geographic change throughout Zealandia throughout Paleogene subduction initiation” by R. Sutherland, G.R. Dickens, P. Blum, C. Agnini, L. Alegret, G. Asatryan, J. Bhattacharya, A. Bordenave, L. Chang, J. Collot, M.J. Cramwinckel, E. Dallanave, M.Ok. Drake, S.J.G. Etienne, M. Giorgioni, M. Gurnis, D.T. Harper, H.-H.M. Huang, A.L. Keller, A.R. Lam, H. Li, H. Matsui, H.E.G. Morgans, C. Newsam, Y.-H. Park, Ok.M. Pascher, S.F. Pekar, D.E. Penman, S. Saito, W.R. Stratford, T. Westerhold and X. Zhou, 6 February 2020, Geology.

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