Over 2,000 years ago, Plato wrote of a land called Atlantis, where a mighty empire disappeared beneath the waves after a series of “exceedingly violent earthquakes and floods”. His story inspired plenty of nonsense over the centuries that followed, but now it seems Plato was onto something. New research shows that the Lost Continents are real and have had a big impact on human life, but not in the way Plato imagined.
Douwe van Hinsbergen, a geologist at Utrecht University in the Netherlands, has explored one of the most spectacular of these lost continents, known as Greater Adria. In an article published in early September in the Gondwana Research journal, he and his colleagues studied the rocks around and under the Mediterranean Sea to reveal the full extent of Greater Adria for the first time. ” It’s enormous ! About the approximate size and shape of Greenland,” he says.
If you don’t remember seeing Greater Adria on a map, there’s a reason for that. It is completely buried – not under the ocean, but under southern Europe. About 140 million years ago, the two continents began to collide. Greater Adria was razed and buried in the process and sank beneath what is now Italy, Greece and the Baltics.
And Greater Adria is not unique. New studies of the Earth’s mantle show probable traces of lost continents in the past. Analysis of ancient rocks suggests that nearly all of Earth’s earliest continents may have disappeared, taking with them much of the history of life on this planet. Evidence of how life first arose may be lost somewhere down there in the depths.
But the lost continents are not entirely lost. Like lost civilizations, they leave traces, if you know how to look for them. Van Hinsbergen notes that rocks from Greater Adria were scraped and incorporated into the Alps, while whole chunks became embedded in southern Italy and Croatia. Even parts of Greater Adria that have been pushed tens of kilometers into the mantle, the layer below the crust, continue to influence modern Europe.
Under enormous heat and pressure and over tens of millions of years, the limestone rocks of Greater Adria turned into marble. Friction between Greater Adria and Europe then brought the sunken rocks to the surface, where people found and mined them. “This is where the marble that the Romans and Greeks used for their temples came from,” says van Hinsbergen.
Plato was literally standing on the remains of a real Atlantis. He just had no idea.
Earth’s hidden eighth continent
Greater Adria remained unknown for a long time because it was almost completely obliterated and obscured. But at least one other lost continent has lurked in plain sight.
Maps of the ocean floor show a large elevated region surrounding the New Zealand Islands, a formation known as Zealandia. Two years ago, a team led by geologists Nick Mortimer of GNS Science, a geological research company, and Rupert Sutherland of Victoria University of Wellington, both in New Zealand, combined these maps with measurements of surface gravity and analysis of seafloor samples to show that Zealandia is much more than a lump in the ocean: it’s a single, continuous continent, the world’s eighth (or seventh, if you group Europe and Asia as Eurasia), about two-thirds the size of Australia and more than twice as large as Greater Adria.
Like Greater Adria, Zealandia has been overlooked because it is a low-rider. A few hundred million years ago, during the age of the dinosaurs, it was a proud part of the great supercontinent known as Gondwana. “Then it split 85 to 100 million years ago,” says Sutherland. “It has stretched and thinned, causing elevation to drop, and it has also been affected by the development of the ‘Pacific Ring of Fire,’ an area of volcanic activity that borders the ocean. Peaceful.
These insults conspired to sink Zealandia beneath the waves. Today it is 94% underwater, with the islands of New Zealand and New Caledonia being its only major outposts of dry land. During its long existence, however, additional parts of Zealandia likely arose above sea level. The resulting islands would have provided crucial stepping stones for life to migrate across the southwest Pacific and could help explain the unusual plants and animals found there.
Sutherland recently led an ocean drilling project to find the lost history of Zealandia, the geological equivalent of sending a submarine to explore the Titanic. He plans to reveal the results soon, “hopefully by the end of the year.”
Lands that come and go
It now appears that Zealandia and Greater Adria are just two recent examples of what was once a regular Atlantis-like process. According to Derrick Hasterok, a geophysicist from the University of Adelaide, the continents have not always been stable elements of our planet. At the beginning of our planet’s history, more than 2 billion years ago, they were fragile and transient things, which collapsed, fractured or simply eroded easily.
The surprising reason for all this instability? Radioactivity. Earth was born with far more radioactive elements than it has now (many of them have since decayed), says Hasterok, and those elements accumulate preferentially in continental rocks. When the first continents formed, they sowed the seeds of their own demise. The only way he knows they ever existed is by the curious lack of high-radioactivity rocks in modern continents. These rocks do not exist, because the continents on which they lived are long gone.
“I imagine that a crust producing high heat is produced, and then the radioactivity heats it inside until it melts, or the crust becomes soft and collapses,” Hasterok said in an email.
No one will ever know what kinds of events took place on those early continents. But the most recent past is always present, and van Hinsbergen finds ways to read it. He created an “Atlas of the Underworld” to document what happened to parts of the earth’s crust that were pulled into the mantle. He is now trying to match the Atlas with surface geology studies, such as the new map of Greater Adria, to produce more accurate reconstructions of how continents have moved and collided in the past.
All this is more than an intellectual exercise. Just as Greater Adria brought marble to the surface in Europe, other continental collisions dug up valuable ores and minerals. “We hope this will lead to the exploration of new deposits,” van Hinsbergen said. “The world needs more copper and rare earths for the green revolution. It might help us find them.
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