NEWSWEEK
Researchers have uncovered evidence of a lost continent that lies hidden beneath jungles in Southeast Asia, according to a study.
Geoscientists have long suspected that around 155 million years ago a long piece of continent broke off from northwestern Australia and drifted away. The evidence for this is the “void” it left behind—a basin, known as the Argo Abyssal Plain, that lies deep below the ocean off the coast of northwestern Australia.
The structure of the seafloor here indicates that the proposed continent—named Argoland after the abyssal plain—must have drifted off to the northwest, ending up where the islands of Southeast Asia are today.
The proposed Argoland continent extended for more than 3,000 miles from western Australia to north of Papua New Guinea. Researchers were expecting to find a solid continent hidden beneath the islands of Southeast Asia, but no such large continent has been found in the region, only small fragments.
It was suspected that these fragments belonged to Argoland, but they are only a fraction of the size of the proposed continent. In addition, the fragments are surrounded by remnants of oceanic basins dating back to around 205 million years ago—much older than the rock record in the oceanic crust of the Argo Abyssal Plain. This indicates that the fragments drifted away from Australia significantly earlier than Argoland’s proposed split around 155 million years ago.
These older ages had cast doubt on whether these fragments represented parts of Argoland. If they did not, this raised a question: Did Argoland then completely disappear by a process known as subduction? This is when one tectonic plate slides below another plate and sinks into the Earth’s mantle, the geologic layer that lies just below the crust.
To find out, geologists Douwe van Hinsbergen and his colleague Eldert Advokaat of the Netherlands’ Utrecht University have now reconstructed the history of the lost continent for a study published in the journal Gondwana Research.
They told Newsweek: “Our motivation to conduct this research was to see how we could reconcile this information: Why are the fragments smaller, how did we lose such an area of continental crust without leaving a trace, and why do these fragments seem to have left earlier than what we know from the record in Australia?”
If Argoland did disappear by subduction, this would be “bad news” because it would pose a major scientific problem, according to the two geologists. It would indicate that researchers have possibly overlooked entire “lost” continents that were simply subducted into the mantle.
“If continents can dive into the mantle and disappear entirely, without leaving a geological trace at the earth’s surface, then we wouldn’t have much of an idea of what the Earth could have looked in the geological past. It would be almost impossible to create reliable reconstructions of former supercontinents and the earth’s geography in foregone eras,” Van Hinsbergen said in a press release.
He went on: “Those reconstructions are vital for our understanding of processes like the evolution of biodiversity and climate, or for finding raw materials. And, at a more fundamental level, for understanding how mountains are formed or for working out the driving forces behind plate tectonics; two phenomena that are closely related.”
In the latest study, though, the geoscientists determined that Argoland is still present, albeit in a fragmented form.
For the study, Advokaat and Van Hinsbergen used software that enabled them to reconstruct the motion of tectonic plates stretching back hundreds of millions of years.
This work revealed that the proposed continent of Argoland was not one solid block when it broke off from Australia around 155 million years ago. Instead, it appears to have already broken up into a kind of “archipelago” of multiple small continents and intervening ocean basins by this point.
This process is similar to the history of other “lost” continents, such as Zealandia off the coast of eastern Australia and Greater Adria in the Mediterranean region.
“The breakup of Argoland into the ‘Argopelago’ was a process that started more than 200 million years ago,” the two geologists told Newsweek.
The continental fragments that collectively once formed Argoland are now found in Myanmar and the islands of Java, Sulawesi, Borneo and Timor. All of these islands are governed, at least in part, by Indonesia. In the case of Borneo, portions of the territory also belong to Malaysia and Brunei. Timor, meanwhile, is divided between Indonesia and the sovereign state of East Timor. The geologists also conducted fieldwork on several islands to test the models in their study.
“The main implication of this research is that we did not lose continental crust without a trace,” the two researchers said. “Instead, a large area of Argoland consisted of oceanic crust, whose remnants we also found in Southeast Asia. This study thus helps our understanding of processes on Earth such as subduction.”
The continued: “Most of all, it shows that…our reconstructions of Earth’s geography in the past are not missing major ‘lost’ continents. We may have to look a bit, but the remains are still present in the geological record.”
Uncommon Knowledge
Newsweek is committed to challenging conventional wisdom and finding connections in the search for common ground.
Newsweek is committed to challenging conventional wisdom and finding connections in the search for common ground.
