New maps reveal details about the size and shape of Earth's lost 8th continent, Zealandia, which disappeared under the Pacific Ocean

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New maps reveal details about the size and shape of Earth's lost 8th continent, Zealandia, which disappeared under the Pacific Ocean

A map of Zealandia, outlined in gray. World Data Center for Geophysics & Marine Geology / National Geophysical Data Center, NOAA

 

About 3,500 feet under the south Pacific waves sits a lost eighth continent.

 

Scientists confirmed that the submerged land mass, named Zealandia, was its own continent in 2017. But they hadn't been able to map its full breadth until now.

 

On Monday, researchers from GNS Science in New Zealand announced that they'd mapped the shape and size of the continent in unprecedented detail. They put their maps on an interactive

 

website so that users could virtually explore the continent.

 

"We've made these maps to provide an accurate, complete, and up-to-date picture of the geology of the New Zealand and southwest Pacific area — better than we have had before," Nick

 

Mortimer, who led the work, said in a statement.

 

Mortimer and his colleagues mapped the bathymetry surrounding Zealandia — the shape and depth of the ocean floor — as well as its tectonic profile, showing where Zealandia falls across

 

tectonic-plate boundaries.

 

The maps reveal new information about how Zealandia formed before it became submerged underwater millions of years ago.

An underwater continent nearly 2 million square miles in size

 

Zealandia's area is nearly 2 million square miles (5 million square kilometers) — about half the size of Australia.

 

But only 6% of the continent is above sea level. That part underpins New Zealand's north and south islands and the island of New Caledonia. The rest is underwater, which makes Zealandia

 

challenging to survey.

 

To better understand the submerged continent, Mortimer and his team mapped both Zealandia and the ocean floor around it. The bathymetric map they created (below) shows how high the

 

continent's mountains and ridge rise toward the water's surface.

 

A bathymetric map of Zealandia, which shows the shape of the continent under the water. GNS Science

 

It also depicts coastlines, territorial limits, and the names of major undersea features. The map is part of a global initiative to map the planet's entire ocean floor by 2030.

 

The second map the GNS scientists made (below) reveals the types of crust that make up the underwater continent, how old that crust is, and major faults. The continental crust — the older,

 

thicker kind of Earth's crust that forms landmasses — is shown in red, orange, yellow, and brown. The oceanic crust, which is generally younger, is in blue. Red triangles show where volcanoes are.

 

A tectonic map of Zealandia, which shows the types and age of the crust, major faults, and volcanoes that make up the continent. GNS Science

 

This map also reveals where Zealandia sits across various tectonic plates, which of those plates are being pushed under the other in a process known as subduction, and how quickly that

 

movement is happening.

 

Studying the tectonic machinations that underpin Zealandia today can reveal clues about how the continent formed in the first place.

Zealandia's 85 million-year-old origins

 

The concept of Zealandia is 25 years old. Geophysicist Bruce Luyendyk coined the term in 1995.

 

Luyendyk previously told Business Insider that he never intended for the term to describe a new continent. Rather, the name originally referred to New Zealand and a collection of submerged

 

chunks of crust that broke off the ancient supercontinent Gondwana about 85 million years ago.

 

"The reason I came up with this term is out of convenience," Luyendyk said. "They're pieces of the same thing when you look at Gondwana. So I thought, 'Why do you keep naming this collection of

 

pieces as different things?'"

 

Gondwana formed when Earth's ancient supercontinent, Pangea, split into two fragments. Laurasia in the north became Europe, Asia, and North America. Gondwana in the south dispersed to

 

form modern-day Africa, Antarctica, South America, and Australia.

 

"If we could pull the plug on the world's oceans, it would be quite clear that Zealandia stands out," he told Science News in 2017, adding, "If it wasn't for the ocean level, long ago we'd have recognized Zealandia for what it was — a continent."

A map of Pangea 200 million years ago, with tectonic plate boundaries in white. Wikimedia Commons

 

Geologic forces continued to rearrange these land masses, and Zealandia was forced under the waves about 30 million to 50 million years after it broke off Gondwana as the largest tectonic plate

 

— the Pacific Plate — slowly subducted beneath it.

These maps show Zealandia is a continent like the other 7

Until 2017, Zealandia was classified as a "microcontinent," like the island of Madagascar. But according to Mortimer, Zealandia ticks all the boxes for continent status: It has clearly defined

 

boundaries, occupies an area greater than 386,000 square miles (1 million square kilometers), is elevated above the surrounding ocean crust, and has a continental crust thicker than that oceanic

 

crust.

 

 

These new maps therefore offer further evidence that the underwater land mass should be considered the eighth continent, Mortimer added.

 

 

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