Scientists have discovered that a tectonic plate off Portugal’s coast might be shearing into two layers.
In 1969, an earthquake in the location spawned a tsunami, and 200 years before that, an 8.7 magnitude quake struck the area, destroying the capital city of Lisbon and killing 100,000 people, according to Joao Duarte, a marine geologist from the Instituto Dom Luiz at the University of Lisbon.
Because of these two quakes, scientists have been puzzled as to why as they didn’t occur near any fault or cracks in the Earth’s crust.
Some scientists are theorizing that the crust in this area might be peeling into two layers, creating a new subduction zone, which is when one tectonic plate is rammed under another one, according to an abstract of their findings.
If confirmed, this 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 Europe’s slow crawl toward Canada https://t.co/mqoSxNkc9T
— National Geographic (@NatGeo) May 7, 2019
“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,” said National Geographic.
The University of Oslo’s Fabio Crameri said that while “it’s certainly an interesting story,” the hypothesis needs more testing.
“It’s a big statement,” Duarte noted. “Maybe this is not the solution to all the problems. But I think we have something new here.” He added that it’s not clear how subduction zones actually start, saying it’s an unsolved problem.
About 90 percent of the world’s earthquakes take place in the Pacific Ring of Fire that spans around the Pacific Ocean, going from New Zealand all the way around to the southern tip of South America, encompassing Indonesia, Japan, Alaska, the West Coast of the United States, and more.
— Live Science (@LiveScience) May 7, 2019
Around the Atlantic Ocean, however, tectonic plates pull apart and form a new crust.
National Geographic noted that the 1969 earthquake hit a relatively flat area under the ocean’s surface.
“It’s like the plains of Kansas under 4.8 kilometers [three miles] of water,” geologist Marc-André Gutscher of the French University of Western Brittany, told the outlet.
In 2018, a researcher at University of Lisbon’s Instituto Dom Luiz published a high-resolution image of the region, showing signs of activity.
“Now we are 100 percent sure it’s there,” Duarte told the outlet.
Live Science pointed out that Duarte and his team are not the first to propose this idea, adding that it has not yet been published in a peer-reviewed journal.
In 1755, an earthquake that is known as the “Great Lisbon earthquake” hit off the coast of the city, causing a series of fires and a tsunami that killed tens of thousands.
“This earthquake occurred on All Saint’s Day while many of the 250,000 inhabitants of Lisbon were in Church. Stone buildings swayed violently and then collapsed on the population. Many who sought safety on the river front were drowned by a large tsunami. Fire ravaged the city. One quarter of Lisbon’s population perished. This earthquake had a profound effect on the intellectual outlook of Europe,” said the U.S. Geological Survey.
At the time, the event was discussed by a number of Enlightenment philosophers, the New World Encyclopedia says.
“Owing to a stroke of luck, the royal family escaped unharmed from the catastrophe. King Joseph I of Portugal and the court had left the city, after attending mass at sunrise, fulfilling the wish of one of the king’s daughters to spend the holiday away from Lisbon. After the catastrophe, Joseph I developed a fear of living within walls, and the court was accommodated in a huge complex of tents and pavilions in the hills of Ajuda, then on the outskirts of Lisbon,” says the entry for the quake.