Te Riu-a-Māui/Zealandia is the planet's youngest, smallest, thinnest and most submerged continent.
Te Riu-a-Māui/Zealandia is the planet's youngest, smallest, thinnest and most submerged continent.
Scientists have reconstructed the 100-million-year story of the lost continent that Aotearoa sits upon, in a series of maps charting the formation of Te Riu-a-Māui/Zealandia.
Being nearly completely underwater – New Zealand represents the largest portion of it above sea level – what is the world’s youngest, smallest and thinnest continent is largely invisible to us.
But, if we drained the oceans, we could see it unfurling some 4.9 million sq km across the South Pacific.
New Zealand sits upon the ancient, and only recently recognised, continent of Zealandia. Image / GNS Science
Scientists had known about it for decades, but were reluctant to state, unequivocally, that the lost continent physically existed.
But it did: and for a relatively brief point in the Earth’s history its sprawling mass once stood above the waves, dispersing animals and plants from here to New Caledonia and the east of Australia.
Most groups of dinosaurs, including the towering titanosaurs, roamed its rolling, mountainless, low-lying landscape.
Scientific papers and reports hinted at the presence of an eighth continent, spanning back to 1910, when improved bathymetric maps showed our country wasn’t just a few chunks of land jutting from an otherwise deep bath of abyssal ocean crust.
By the mid-2000s, GNS Science geologists including Dr Hamish Campbell and Dr Nick Mortimer began publishing research describing Zealandia’s physical boundaries and composition.
Yet it wasn’t until 2017 that a paper, led by Mortimer, somehow made Zealandia a real place and instantly captured the world’s attention, generating more than 16,000 news articles that reached nearly a billion people.
Zealandia is the planet's smallest continent.
Now, in a series of 15 maps presented in a recently-published study, scientists have reconstructed its evolution, from the mid-Cretaceous period 98 million years ago, to now.
Over that time, the landmass drifted north from polar latitudes, with the southernmost areas climbing from around 80°S to 50°S.
“The work is also useful to those studying hazards, both faults and volcanoes, as understanding how these systems have evolved through time is important for understanding how things work at present,” said study lead author and GNS sedimentologist Dominic Strogen.
“Especially in somewhere with an active plate boundary, like Aotearoa New Zealand.”
“It’s incredible how far we have come with our understanding about Te Riu-a-Māui, much of which was once almost entirely unknown.”
Strogen and his colleagues hoped the maps would provide helpful introductory material for people interested in how our continent – once part of the supercontinent Gondwana - formed.
This map shows Te Riu-a-Māui/Zealandia as still part of the Gondwana super-continent, around 98 million years ago. Image / GNS Science
For the wider geoscience community, the maps offered large-scale context for any number of more detailed geological studies.
This work was also very useful to paleobiologists, who are interested in how species moved into Te Riu-a-Māui from other regions and then within the continent, long before Aotearoa comprised two main islands.
“The geological evidence suggests that the land we now know as Aotearoa New Zealand, was never fully submerged,” Strogen said.
While there’d been attempts to make reconstructed paleogeographic maps of the continent two decades ago, these had been “essentially cartoon in nature” and were drawn very approximately.
This map shows the continent after having broken off from other land masses, and shifting northward, around 77 million years ago. Image / GNS Science
“In the past they would create these kinds of maps by moving paper cut-outs on a light table, new software has become available to allow us to do this digitally, and to bring in far more datasets to constrain the maps.”
The big step forward, he said, was how his team had been able to move around the blocks that formed Zealandia – and all their data – in a rigorous and repeatable way.
“It also allows us to make changes, either to the blocks or to how they move through time and re-draw the maps accordingly, especially as new data become available.”
Te Riu-a-Māui/Zealandia as it was 57 million years ago. Image / GNS Science
A lot of that data wasn’t new and drew upon work by countless geoscientists over the last 150 years.
“The more we discover, the more we can add,” Strogen said.
Te Riu-a-Māui/Zealandia as it appeared 30 million years ago. Image / GNS Science
“You can look at tiny parts of this map and identify large or small chunks of work over the years that are represented by more detail within the maps, and also areas where we still don’t know enough and the maps are poorly constrained.
“Our scientists have contributed across the spectrum to the richness of data types that constrain the maps, from large scale seismic mapping to pollen and microfossils.
“The total accumulation of our knowledge of the past shapes these maps.”
The team was encouraging feedback from other geoscientists to help improve and refine the models.
“The first step to improving upon something is getting it down on the page, for everyone to debate and improve upon.”
These insights come after Mortimer was recently awarded a $100,000 James Cook Research Fellowship from Royal Society Te Apārangi to produce updated reviews of Zealandia’s geological make-up and ancestry.
The continent four million years ago - pictured largely submerged as it remains today. Image / GNS Science
These will include a research publication for geoscientists, as well as a book explaining the continent’s origins and discovery, alongside Māori perspectives.
“It has taken hundreds of years for the science behind the discovery of this continent to mature, and there is still much to explain and communicate about the continent’s exploration, framework, and beginnings,” he told the Herald last year.
Particularly, the funding would enable to write a much-needed update of his most cited research paper, published back in 2004.
