Geologists have lengthy identified that round 155 million years in the past, a 5000 km lengthy piece of continent broke off western Australia and drifted away. They will see that by the ‘void’ it left behind: a basin hidden deep under the ocean referred to as the Argo Abyssal Plain.
The underwater function additionally lends its title to the newly fashioned continent: Argoland. The construction of the seafloor exhibits that this continent will need to have drifted off to the northwest, and will need to have ended up the place the islands of Southeast Asia are situated at this time. However surprisingly, there isn’t a massive continent hidden beneath these islands, solely the remnants of small continental fragments which might be additionally surrounded by a lot older oceanic basins. So what occurred to Argoland? Geologists at Utrecht College have now managed to reconstruct the historical past of the misplaced continent. Because it seems, Argoland is in fragments, however continues to be there. “In any other case, we’d have been confronted with a serious scientific downside.”
Geologists differentiate the earth’s crust into the heavier oceanic crust and lighter continental crust. These lighter continents could also be partially hidden under sea degree, as was additionally the case with one other ‘misplaced’ continent, Higher Adria. Like Argoland, it additionally consisted of various fragments separated by slim ocean basins, which finally turned a part of a single tectonic plate. In some unspecified time in the future previously, Higher Adria plunged into the earth’s mantle, however the prime layer stayed behind and was folded to type the mountains of Southern Europe. Argoland, nevertheless, left no such hint within the type of folded rock strata.
Traces from foregone eras
“If continents can dive into the mantle and disappear totally, with out leaving a geological hint on the earth’s floor, then we wouldn’t have a lot of an concept of what the earth might have seemed within the geological previous. It could be virtually unimaginable to create dependable reconstructions of former supercontinents and the earth’s geography in foregone eras”, explains Utrecht College geologist Douwe van Hinsbergen. “These reconstructions are very important for our understanding of processes just like the evolution of biodiversity and local weather, or for locating uncooked supplies. And at a extra basic degree: for understanding how mountains are fashioned or for understanding the driving forces behind plate tectonics; two phenomena which might be intently associated.”
Van Hinsbergen and his colleague Eldert Advokaat had been interested by what the geology of Southeast Asia might inform about Argoland’s destiny. “However we had been actually coping with islands of knowledge, which is why our analysis took so lengthy. We spent seven years placing the puzzle collectively”, says Advokaat. “The scenario in Southeast Asia may be very totally different from locations like Africa and South America, the place a continent broke neatly into two items. Argoland splintered into many various shards. That obstructed our view of the continent’s journey.”
However that was till he realised that the fragments arrived at their present places at across the identical time, which clarified how they as soon as linked collectively. The shards fashioned a collage: Argoland is hidden beneath the inexperienced jungles of enormous components of Indonesia and Myanmar.
That splintering is typical for the microcontinent. There was by no means a single clearly delineated and coherent continent of Argoland, however reasonably an ‘Argopelago’ of microcontinental fragments separated by older oceanic basins. In that it resembles Higher Adria, which by now has virtually totally subducted into Earth’s mantle, or Zeelandia, the largely submerged continent east of Australia. “The splintering of Argoland began round 300 million years in the past”, Van Hinsbergen provides.
The puzzle that Advokaat and Van Hinsbergen have solved matches seamlessly between the neighbouring geological methods of the Himalayas and the Philippines. Their detective work additionally explains why Argoland is so fragmented: the break-up accelerated round 215 million years in the past, because the continent shattered into skinny splinters. The geologists performed area work on a number of islands, together with Sumatra, the Andaman Islands, Borneo, Sulawesi and Timor, to check their fashions and decide the age of key rock strata.