New Zealand is not just a few small islands at the bottom of the world. It is actually part of a fairly large continent 94% of which is under the sea.
This is the conclusion of a paper published this week in GSA Today, the journal of the Geological Society of America.
Eight GNS Science geologists, along with colleagues from Victoria University, the Geological Survey of New Caledonia, and the University of Sydney summarise the evidence that 4.9 million square kilometres of the South West Pacific Ocean is underlain by a submerged continent.
This will not be a surprise to many New Zealand geoscientists, as GNS Science staff and colleagues have long been building the case for Zealandia and it has already been the subject of many books and presentations.
Lead author Nick Mortimer of GNS Science said this latest publication was significant in that it described results of more than 20 years geology and geophysics research in a summary paper that is peer-reviewed.
“Being more than 1 million square kilometres in area, and bounded by well-defined geologic and geographic limits, Zealandia is, by our definition, large enough to be termed a continent," Dr Mortimer said.
It is large and separate enough to be considered an actual continent. Zealandia has a continental crust thickness between 10 km and 30 km, and increasing to more than 40 km under parts of the South Island.
“Based on various lines of geological and geophysical evidence, particularly those accumulated in the last two decades, we argue that Zealandia is not a collection of partly submerged continental fragments but is a coherent 4.9 square million kilometre continent.
“Currently used conventions and definitions of continental crust, continents, and microcontinents require no modification to accommodate Zealandia.”
Zealandia is six times bigger than Madagascar, and about the same area as greater India.
“As well as being the seventh largest geological continent, Zealandia is the youngest, thinnest and most submerged. Zealandia provides a fresh context in which to investigate processes of continental rifting, thinning, and breakup.”
The name Zealandia was first proposed by geophysicist Bruce Luyendyk in 1995 as a collective name for New Zealand, the Chatham Rise, Campbell Plateau, and Lord Howe Rise.
GSA Today has a global audience, and the presence of an extra continent on a map of the Earth will be a genuine surprise to many European, Asian, American, African and Australian geologists. GSA Today publishes 12 science articles per year.