Missing Continent Is Found 155 Million Years After It Vanished

The continent of Argoland, which seemingly vanished after splitting from Australia 155 million years ago, has finally been discovered, according to a new study.

Continental splits usually leave traces in ancient fossils, rocks, and mountain ranges. But up until now, scientists had been unable to find where Argoland had ended up.

Now, researchers at Utrecht University in the Netherlands report that they've uncovered the mysterious landmass hidden under the eastern islands of Southeast Asia.

The discovery could help explain something known as the Wallace line, which is an imaginary boundary that separates Southeast Asian and Australian fauna.

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"We were literally dealing with islands of information, which is why our research took so long. We spent seven years putting the puzzle together," said the study author Eldert Advokaat, a geologist at Utrecht University, in a press release.

Argoland shattered into continental ribbons

It took some careful detective work to find where Argoland had gone after breaking off from what would become Australia. Scientists had found bits of "ribbon continents" around Southeast Asia but could not piece them back together, Advokaat told Live Science.

"Nothing fit," he said.

Finally, they had an epiphany: What if Argoland started off as a series of continent fragments rather than a solid chunk?

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"The situation in Southeast Asia is very different from places like Africa and South America, where a continent broke neatly into two pieces," Advokaat said in the press release.

"Argoland splintered into many different shards. That obstructed our view of the continent's journey," he said.

Working from this hypothesis, they found that Argoland hadn't really disappeared. It had survived as a "very extended and fragmented ensemble" under the islands to the east of Indonesia.

With this work, they were finally able to bring Argoland's journey over the past 155 million years back to life. You can see Argoland, in green, drifting below.

Because it's not a solid mass but rather a series of microcontinents separated by the ocean floor, Advokaat and his Utrecht University colleague Douwe van Hinsbergen coined a new term to define the Argoland more precisely: an "Argopelago."

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Their findings were published October 19 in the peer-reviewed journal Gondwana Research.

A barrier that divides marsupials and tigers in Southeast Asia

The research may not only tell us how our planet came to be the way it is today.

It could also help scientists better understand the bizarre Wallace line, an invisible barrier that runs through the middle of Indonesia and separates mammals, birds, and even early human species in the Southeast Asian islands, Advokaat told Live Science.

The barrier has puzzled scientists because of how starkly it separates the island's wildlife. To the west of the line are placental mammals such as apes, tigers, and elephants — which are also found in Southeast Asia. But these are almost absent to the east, where you can find marsupials and cockatoos — animals typically associated with Australia.

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This could be because Argoland carried its own wildlife away from the future Australia before it smashed into Southeast Asia.

"Those reconstructions are vital for our understanding of processes like the evolution of biodiversity and climate, or for finding raw materials," van Hinsbergen said.

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