Europe, America to collide, say geologists

Geologists have spotted a new subduction zone off the coast of Portugal that is slowly tugging Europe toward the New World.

Rodrigo Cabrita/Diario de Noticias/AP
A woman prays at Lisbon's 14th-century Carmo Convent, in 2005, during a mass remembering the victims of the 1755 earthquake that destroyed most of the city. The convent is one of the last remnants of one of the strongest earthquakes ever to hit western Europe.

If Christopher Columbus had been willing to wait just a few hundred million years, he could have simply walked to the New World.

That's because geological forces are slowly tugging Europe toward the Americas, with an estimated time of arrival of about 220 million years from now. 

In a study published in the current issue of the journal Geology, a team led by researchers at Monash University in Melbourne, Australia, say that they have discovered the first signs of the eventual closing of the Atlantic Ocean, in the form of an "embryonic" subduction zone off the coast of Portugal

Subduction zones form when one tectonic plate begins to slide underneath another. The geologists, who mapped the ocean floor and found a spot where it was just beginning to fracture, say that this new subduction zone could signal the beginning of a new phase in the Wilson Cycle, a series of events, named for the Canadian geophysicist John Tuzo Wilson, who found that the planet's ocean basins periodically open and close over millions of years.

This breakup and reforming of the world's continents has happened at least three times already, say geologists.

"What we have detected is the very beginnings of an active margin - it's like an embryonic subduction zone," said Monash University's João Duarte, the study's lead author, in a press release. 

This collision of plates, which can be considered young only on a geological time scale, could have triggered the devastating 1755 Lisbon earthquake, a temblor that is believed to have killed some 60,000 people, reduced the Portuguese capital to rubble, and birthed the modern science of seismology.

"Significant earthquake activity, including the 1755 quake which devastated Lisbon, indicated that there might be convergent tectonic movement in the area," said Dr. Duarte. "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."

Observing how this new subduction zone forms – a process that geologists say will take about 20 million years before it becomes full-blown – could yield new data about how continents are made.

"Understanding these processes will certainly provide new insights on how subduction zones may have initiated in the past and how oceans start to close," Dr. Duarte said.

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