North America and Europe are now separated by the Atlantic Ocean. Geologists have found clues that may signal the beginning of a cycle where the Atlantic will disappear and the continents will collide and form a new supercontinent. (Map: Google)
Taking a trip from the United States to Europe might be much easier in 220 million years, according to a recent study, which suggests that’s when the Atlantic Ocean could close up, causing North America to collide with Europe.
Australian geologists have detected a new subduction zone–when two oceanic plates collide–forming off the coast of Portugal. It’s the first evidence this previously passive margin in the Atlantic Ocean is now becoming active.
Subduction zones, such as the newly discovered one forming near Iberia, form when one of the dozens of tectonic plates that cover our planet dives and ducks beneath another plate, into the layer located just beneath the surface (the mantle) as the two plates converge.
Illustration of the Wlson Cycle (Used with Permission – Lynn S. Fichter © 1999)
After mapping the ocean floor, the research team found the surface was beginning to fracture, which indicates tectonic activity around the South West Iberia plate margin.
“What we have detected is the very beginnings of an active margin. It’s like an embryonic subduction zone,” said Dr. João Duarte, from Monash University, the study’s lead scientist. “Significant earthquake activity, including the 1755 quake which devastated Lisbon, indicated that there might be convergent tectonic movement in the area. For the first time, we have been able to provide not only evidences that this is indeed the case, but also a consistent driving mechanism.”
The study indicates the subduction zone beginning to form off Portugal’s coast could signal that a new phase of the Wilson Cycle has started. The Wilson Cycle, named for the late Canadian geologist, John Tuzo Wilson, is the periodic opening and closing of the world’s ocean basins, caused by tectonic plate movement.
This cycle is responsible for the joining of continents into supercontinents, which then stabilize and subsequently break up again into individual continents.
Supercontinent Pangaea forms and breaks apart
Over the known history of our planet, a number of these supercontinents have formed and broken up. Pangaea, one of the most famous of these, formed more than 300 million years ago, eventually breaking apart, around 200 million years ago, into the seven continents we’re familiar with today.
The researchers’ findings give other scientists a unique opportunity to observe as a passive margin–the edge of a continental plate that experiences very little tectonic activity–becomes an active margin, which occurs when there is increased tectonic activity because a continental plate is crashing into a nearby oceanic plate, a geological process that takes about 20 million years. Even at this early phase of the process, the new-found subduction zone should provide data that is crucial to refining geodynamic models.
“Understanding these processes will certainly provide new insights on how subduction zones may have initiated in the past and how oceans start to close,” Duarte said.
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