A fragment of a mysterious 8th continent is hiding under New Zealand – and it’s twice as old as scientists thought

Zealandia_topography
A map of New Zealandia, outlined in gray.

  • An eighth continent, called Zealandia, is hidden under New Zealand and the surrounding Pacific.
  • Since 94% of Zealandia is submerged, discerning the continent’s age and mapping it is difficult.
  • New research suggests Zealandia is 1 billion years old, about twice as old as geologists thought.
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About 3,500 feet under the south Pacific sits a piece of land 2 million square miles in size – about half as big as Australia.

But scientists can’t agree on whether this submerged land mass, called Zealandia, is a continent or not. A team of geologists declared it one in 2017, but not all researchers are convinced.

“It’s not like a mountain, country, or planet. There is no formal body to approve a continent,” Nick Mortimer, a geologist from New Zealand’s GNS Science who led 2017 group, told Insider.

While the definition of a continent is contentious, Mortimer’s group suggested that a continent should have clearly defined boundaries, occupy an area greater than 386,000 square miles (1 million square kilometers), be elevated above the surrounding ocean crust, and have a continental crust thicker than that oceanic crust.

Zealandia meets all those stipulations.

“If you were to drain the oceans, Zealandia would stand out as a well-defined, high-standing plateau above the ocean floor,” Mortimer said.

He considers it “the thinnest, most submerged and smallest continent.”

The problem, however, was that until recently, the oldest crust and rock ever sampled from Zealandia was just 500 million years old, whereas all the other continents contain crust that is 1 billion years old or more. But a recent study found that part of the submerged continent is twice as old as geologists previously thought, which could boost Mortimer’s argument.

“This new study ticks that final continental box,” Rose Turnbull, a New Zealand geologist who co-authored the study, said in a press release. “There is no longer any doubt that we live on top of a continent.”

How to date a continent

A view of Fiordland National Park
A view of Fiordland National Park on New Zealand’s South Island.

Zealandia, a term geophysicist Bruce Luyendyk coined in 1995, is made up of New Zealand and a collection of submerged chunks of crust that broke off an ancient supercontinent called Gondwana about 85 million years ago.

About 94% of it is underwater – Zealandia sunk under the waves about 30 million to 50 million years after it broke off Gondwana. So it’s a challenging land mass to study.

The geologists behind the recent research looked at 169 chunks of Zealandia granite, which were found under New Zealand’s South and Stewart Islands. Granite forms when magma crystallizes deep within the Earth’s crust.

By extracting microscopic crystals from the granite, the team was able to determine both the age of the crystals themselves and of the crust in which they formed. The results showed that crust was once part of another supercontinent known as Rodinia, which formed between 1.3 billion and 900 million years ago.

In other words, Zealandia’s geologic history starts far earlier than 500 million years ago.

Mapping Zealandia in unprecedented detail

Bathymetric
A bathymetric map of New Zealandia, which shows the shape of the continent under the water.

Part of Turnbull’s mission is to create a 4D map of Zealandia’s western coast – to visualize what that boundary looks like in three dimensions and how it has changed over time.

Last year, Mortimer helped map the shape and depth of the ocean floor surrounding Zealandia – what’s known as a bathymetric map.

The map, part of a global initiative to survey the planet’s entire ocean floor by 2030, also revealed Zealandia’s size and coastlines in unprecedented detail. In addition, Mortimer’s team created a tectonic map showing the locations of the continental and oceanic crusts that make up the submerged land mass.

These new, detailed maps, paired with the discovery that parts of Zealandia are older than geologists realized, offer further evidence that it should be considered the eighth continent, according to Mortimer.

“We hope that Zealandia will eventually make its way onto general world maps, be taught in schools, and become as familiar a name as Antarctica,” he said.

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Earth’s rotation has been slowing since it formed – and that could explain why there’s enough oxygen for us to survive

Clouds above earth
Subtropical stratocumulus clouds above Earth.

  • Earth’s spin has been slowing little by little since it formed about 4.5 billion years ago.
  • That slowing means days are getting longer, which helps some bacteria produce more oxygen.
  • A new study suggests such bacteria produced enough oxygen 2 billion years ago for life to survive.
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Ever since its formation around 4.5 billion years ago, Earth’s rotation has been gradually slowing, and its days have gotten progressively longer as a result.

While Earth’s slowdown is not noticeable on human time scales, it’s enough to work significant changes over eons. One of those changes, according to a new study published Monday, is perhaps the most significant of all: lengthening days boosted the amount of oxygen in Earth’s atmosphere.

As Earth’s days grew longer, blue-green algae, known as cyanobacteria, that emerged and proliferated about 2.4 billion years ago would have been able to produce more oxygen as a metabolic byproduct, the study authors suggest.

“An enduring question in Earth sciences has been how did Earth’s atmosphere get its oxygen, and what factors controlled when this oxygenation took place,” Gregory Dick, a microbiologist at the University of Michigan and co-author of the study, said in a press release.

“Our research suggests that the rate at which Earth is spinning – in other words, its day length – may have had an important effect on the pattern and timing of Earth’s oxygenation,” he added.

Longer days encouraged bacteria to produce more oxygen

the moon surface
The moon as viewed by NASA’s Mariner 10 in 1973.

There are two major components to this story that, at first glance, don’t seem to have a lot to do with each other. The first is that Earth’s spin is slowing down. Earth’s rate of rotation is slowing because the moon exerts a gravitational pull on the planet. As the moon gradually pulls away from Earth, it imperceptibly slows down how fast our planet rotates.

Research suggests that Earth’s days are lengthening by 1.8 milliseconds every century. In our planet’s infancy, days may have been as brief as 6 hours. About 1.4 billion years ago, days were just 18 hours long.

The second component is something known as the Great Oxidation Event – when cyanobacteria emerged in such great quantities that Earth’s atmosphere experienced a significant rise in oxygen between 2.4 billion and 2 billion years ago.

Without this event, scientists think life as we know it could not have emerged.

Researchers still aren’t sure why the event happened when it did and not sometime earlier in Earth’s history, but the new study may help connect the dots.

In the Middle Island Sinkhole in Michigan’s Lake Huron, there are mats of microbes similar to the cyanobacteria responsible for the Great Oxidation Event.

In these lake-bed mats, purple cyanobacteria that produce oxygen via photosynthesis compete with white microbes that metabolize sulfur. At night, the white microbes rise to the top of the microbial mat and munch their their sulfur. When day breaks, and the sun rises high enough in the sky, the white microbes retreat and the purple cyanobacteria rise to the top.

“Now they can start to photosynthesize and produce oxygen,” study co-author Judith Klatt said in the release. “However, it takes a few hours before they really get going, there is a long lag in the morning. The cyanobacteria are rather late risers than morning persons, it seems.”

This means the window of daytime in which the cyanobacteria can pump out oxygen is very limited – and it was this fact that caught the attention of researchers at the University of Michigan. They wondered if changing day length over Earth’s history had an impact on cyanobacteria’s photosynthesis.

“It’s possible that a similar type of competition between microbes contributed to the delay in oxygen production on the early Earth,” Klatt said.

cyanobacteria bloom baltic sea nasa 2015 closeup 8
A cyanobacteria bloom in the Baltic Sea, 2015.

To test this hypothesis, Klatt and Dick’s team performed experiments and measurements on the Michigan lake bed microbes, both in their natural environment and in a lab. They also created models based on their results that linked sunlight to microbial oxygen production, and microbial oxygen production to Earth’s history.

“Intuition suggests that two 12-hour days should be similar to one 24-hour day. The sunlight rises and falls twice as fast, and the oxygen production follows in lockstep,” Arjun Chennu, a marine scientist with the Leibniz Centre for Tropical Marine Research in Germany and study co-author, said in the release.

“But the release of oxygen from bacterial mats does not, because it is limited by the speed of molecular diffusion. This subtle uncoupling of oxygen release from sunlight is at the heart of the mechanism,” he said.

These results were incorporated into global models of oxygen levels, and the team found that lengthening days were linked to the increase in Earth’s oxygen – not just the Great Oxidation Event, but also a second atmospheric oxygenation called the Neoproterozoic Oxygenation Event that occurred between 550 to 800 million years ago.

“We show that there is a fundamental link between day length and how much oxygen can be released by ground-dwelling microbes,” Chennu said. “It’s pretty exciting. This way we link the dance of the molecules in the microbial mat to the dance of our planet and its moon.”

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The biggest volcano eruptions in recorded history

  • The Volcanic Explosivity Index (VEI) ranks volcano eruptions by size and power.
  • The scale goes from VEI-0 to VEI-8 and measures ash, lava, and rock ejected.
  • VEI-1 is a gentle eruption that can happen frequently. Italy’s Mt. Stromboli has been erupting almost continuously for 2,000 years.
  • VEI-6s are colossal eruptions every 100 years. The 1883 explosion of Krakatoa was the most famous of these.
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Following is a transcript of the video.

Earth has had a dramatic history, filled with its share of angry outbursts. Here’s how the largest volcanic eruptions measure up.

The Volcanic Explosivity Index (VEI) ranks eruptions by size and power. The scale goes from VEI-0 to VEI-8. It measures ash, lava, and rock ejected.

VEI-0 are usually a steady trickle of lava instead of an explosion. An example is the Hawaiian volcano of Kīlauea.

Next is VEI-1, a gentle eruption that can happen frequently. Italy’s Mt. Stromboli has been erupting almost continuously for 2,000 years.

VEI-2s consist of several mild explosions a month. Indonesia’s Mount Sinabung has been erupting since 2013.

VEI-3 are catastrophic eruptions that happen every few months. Lassen Peak in Northern California had a VEI-3 in 1915.

VEI-4s happen about every other year. In 2010, Iceland’s Eyjafjallajökull grounded thousands of flights.

At VEI-5 things start getting more dramatic. Both Mt. Vesuvius (79 AD) and Mt. St. Helens (1980) were VEI-5s.

VEI-6s are colossal eruptions every 100 years. The 1883 explosion of Krakatoa was the most famous of these.

VEI-7 eruptions occur every 1,000 years. The most recent was Indonesia’s Mt. Tambora in 1815.

VEI-8 is a devastating explosive eruption every 50,000 years. The Yellowstone Caldera would reach this level if it were to erupt.

Let’s all just keep our cool.

EDITOR’S NOTE: This video was originally published on November 1, 2017.

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