For years, João Duarte has puzzled over a seemingly boring underwater expanse off the coast of Portugal. In 1969, this site spawned a massive earthquake that rattled the shore and sparked a tsunami. But you would never know why just from looking at the broad, featureless surface of the seabed. Duarte, a marine geologist from the Instituto Dom Luiz at the University of Lisbon, wanted to find out what was going on.
Now, 50 years after the event, he may finally have an answer: The bottom of the tectonic plate off Portugal’s coast seems to be peeling away from its top. This action may be providing the necessary spark for one plate to start grinding beneath another in what’s known as a subduction zone, according to computer simulations Duarte presented in April at the European Geosciences Union meeting.
If confirmed, the new work would be the first time an oceanic plate has been caught in the act of peeling—and it may mark one of the earliest stages of the Atlantic Ocean shrinking, sending Europe inching toward Canada as predicted by some models of tectonic activity. (Find out what scientists think will happen when Earth’s tectonic plates grind to a halt.)
“It’s certainly an interesting story,” says the University of Oslo’s Fabio Crameri, who was not part of the research team but who attended the EGU lecture. Duarte presented some strong arguments, he says, but he cautions that the model needs further testing—not an easy feat when your data comes from a natural process that works at the speed at which fingernails grow.
“It’s a big statement,” Duarte says of the conclusions, acknowledging that he and his team still have work to do. “Maybe this is not the solution to all the problems. But I think we have something new here.”
The tectonic parade
Earth’s tectonic plates are constantly in a slow-motion march, with some edges pulling apart and others colliding. At least three times in our planet’s 4.54-billion-year history, the ever-shifting landmasses glommed into mighty supercontinents, only to eventually reverse course and break apart. Subduction zones are major driving forces behind this tectonic conveyor belt, as they pull oceanic crust and upper mantle down to depth, recycling the rocks and dragging continents around in the process. (Learn more about the possible future supercontinent, Pangaea Proxima.)..Read More at National Geographic