Scientists have announced the discovery of a Greenland-size continent that was born from Gondwana. Naming it Greater Adria, they claim that about 120 million and 100 million years ago, geologic forces slowly shoved this continental land mass underneath what is now southern Europe.
According to geologists, the continents were once joined together in one supercontinent, Pangea, which then split into two fragments: Laurasia in the north that became Europe, Asia, and North America, and Gondwana in the south that became Africa, Antarctica, South America, and Australia.
A study reported in September 2019 stated that the newly found continent was already half-submerged to start with, but as it rumbled toward the Earth’s mantle (the rocky inner layer of our planet), its top layer got peeled away and it began jutting up to form mountains that can be seen in some 30 European countries.
Scientists explain the subduction by comparing it to the act of shoving an arm clothed with a sweater below a table’s edge. As the arm is pushed under the table, the sweater sleeve stays behind, getting folded and jutting upward. The folded sleeve, they say, is the equivalent of the upper few kilometres of Adria’s crust, becoming Eurasian mountain belts like the Apennines in Italy, the Dinarides in Bosnia and Herzegovina, the Swiss Alps, the Zagros mountains of Iran, and the Himalayas; the arm is the plate that is sunk in the mantle, hundreds or even thousands of kilometres below the earth’s surface.
The study was based on a decade-long-work involving aggregating geological data from countries across Europe, North Africa, and western Asia.
Importance of magnetic rocks
Naturally occurring magnets in the Earth’s crust are seen as a way of tracing tectonic-plate movements. When hot lava cools at the boundary between two shifting plates, it traps rocks containing magnetic minerals that align with the Earth’s magnetic fields at the time. The rocks keep that alignment. Scientists say they can use their orientation to calculate where those magnets were on the planet.
The researchers looked at magnetic rocks from some 2,300 ancient sites across the Mediterranean region. The data was used to make computer simulations of the movements of Earth’s tectonic plates before, during, and after Greater Adria’s descent into the mantle. They concluded that the continent broke off of what is now Africa 220 million years ago, and then probably turned into a string of archipelagos. It further splintered away from what became the Iberian Peninsula later.
At that time, Adria probably looked like modern-day Zealandia, the minicontinent that underpins New Zealand’s north and south islands. Only 7 per cent of Zealandia is said to be above sea level.