Titanic collisions, deep recesses, gaping faults: it is difficult to imagine that under our feet lie for miles deep the remains of a formidable tectonic waltz, danced for millions of years by pieces of floating earth crust on an unstable coat.

To know how this rock or rock came to the surface, what were his previous lives, is part of the job of geologists, thanks to whom we now know that Norway was one day in the southern hemisphere and France in the tropics.

A considerable advance has been made in this discipline with the discovery, by an international team of an entire continent, called Grand Adria.

Douwe van Hinsbergen
Douwe van Hinsbergen

We rewind a great stroke of 240 million years: at the time, all of the immersed lands are spread over two supercontinents, resulting from the dislocation of Pangea: Laurasia in the North (including the future generally Asia, Europe and North America), Gondwana to the south (South America, Africa, Oceania, Antarctica). In the north of Gondwana, pieces break away from the current Maghreb to begin a rise to the north. Among them, future pieces of Spain and the south of France, and a big piece now in pieces: The Grand Adria.

Engulfed by Europe

120 million years later, when it is the size of Greenland, the inevitable happens: the Grand Adria hits the European continent. At each shock its winner and loser. Here, Europe takes over, and the Great Adria literally plunges into the bowels of the earthly mantle. Escaping the subduction, some pieces of the upper crust scraped on the surface of the Grand Adria nevertheless managed to stay on the surface.

It is the analysis of these pebbles, scattered over dozens of countries but especially concentrated in the south of Italy and on the Croatian coast, which allowed, after ten years, to confirm the existence of this continent which was only a hypothesis, and to reconstruct its trajectory.

Why so much time? Because it was not until the development of powerful software to process as much data, and especially because the area concerned, the Mediterranean basin, is known as a real headache for geologists. "The Mediterranean is a geological bazaar: everything is bent, broken and piled up", explained this week to the journal Science the Dutch geologist Douwe van Hinsbergen, principal author of the study published at the beginning of September in Gondwana Research. A big bazaar in which he and his team managed to find the missing pieces of an even bigger puzzle, that of continental drift.

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