Researchers Propose A Peeling Tectonic Plate To Explain Peculiar Portugal Quakes

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Portuguese researchers have put forward a new hypothesis to explain what’s happening underneath the Atlantic off the coast of Portugal. At a recent conference, they presented numerical simulations that suggest the bottom of the oceanic plate is peeling away from the top. If so, this might be the beginning of a new subduction zone and the possible eventual reunification of North-America and Europe into a single continent.

This peeling phenomenon, known technically as delamination, was proposed to explain several features related to the region, known as the Horseshoe abyssal plain. As the name suggests, it is a flat region about 4.8 kilometers (3 miles) under water. It has no known tectonic fault, so geologically it shouldn’t be particularly active. Yet it is, and researchers think delamination may be the answer.

Two major quakes shook the region over the last 300 years. First was the Great Lisbon earthquake of 1755, one of the deadliest in history, which took the lives of between 10,000 and 100,000 people. The latest is the 1969 Portugal earthquake, a 7.9 magnitude event where 13 people (11 in Morocco and two in Portugal) perished.

The latter has led to international interest in the region, with many researchers investigating the area. In 2012, researchers used seismic waves to study the region. They found evidence of a curious dense structure deep below the crust. The presence of this mass was shown in a subsequent study from a different team, and other researchers have identified tiny quakes emanating from the mass that stretches 250 kilometers (155 miles) below the Earth’s crust.

Researchers have been considering a possible explanation for decades. Dr João Duarte, a marine geologist at the University of Lisbon, and colleagues ran numerical simulations to show that a peeling tectonic plate is certainly possible. Duarte presented the findings at the European Geosciences Union meeting last month.

“It’s a big statement,” Duarte told National Geographic. “Maybe this is not the solution to all the problems. But I think we have something new here.”

Although the research is yet to be submitted for peer review, it has started several discussions in geological circles about the likelihood of such an event.

The idea is certainly in line with another hotly debated scenario about the cyclical formation of a super-ocean every billion years or so. In that hypothesis, the Atlantic ocean should stop expanding in the future and begin to sink underneath the continental plates. Evidence of a delaminated oceanic plate would provide great support for the super-ocean cycle hypothesis.

[H/T: National Geographic]

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