Geologists Discover New 'Embryonic' Subduction Zone: America and Europe Collide

Our planet Earth is constantly changing. Continents shift and move across oceans as the plates continuously flow beneath one another. Now, scientists have discovered a new subduction zone forming off of the coast of Portugal. The new findings heralds the beginnings of a cycle that will eventually see the Atlantic Ocean close as continental Europe moves closer to America.

Subduction zones are areas where one of the tectonic plates the cover Earth's surface dives beneath another plate and into the mantle, the layer just below the crust. This movement can cause continents to shift and oceans to disappear--or grow larger--over millions of years. Yet not all subduction zones are always active.

The recently discovered subduction zone in the Atlantic Ocean was actually inactive until relatively recently. Geologists discovered the first evidence that a passive margin in the Atlantic Ocean is becoming active. More specifically, the researchers mapped the ocean floor and found that it was beginning to facture. This indicated that tectonic activity around the apparently passive 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 João Duarte, the lead author of the new study, in a news release. "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."

This newly active subduction zone could signal the start of a new phase of the Wilson Cycle, in which plate movements breakup supercontinents, open oceans, stabilize them and then form new subduction zones which close the oceans and bring the scattered continents back together. In theory, the newly active zone could pull Iberia toward the United States over approximately 220 million years.

Yet we shouldn't be so surprised that these shifts are occurring. After all, our planet has constantly changed throughout the billions of years of its history. The supercontinent, Pangaea, broke up to eventually form the continents that we know today. And the break-up and reformation of supercontinents has occurred at least three times over more than four billion years.

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

The findings are published in the journal Geology.