In 1969, a giant earthquake off the coast of Portugal sparked a devastating tsunami that puzzled the scientific community. Unlike the known earthquake zones around the globe, this natural phenomenon seemed to come from the middle of nowhere. There were no signs of a tectonic shift at the time.

After puzzling it over for a few years, Michael Purdy (now executive VP of Research at Columbia Univeristy) sketched out his best guess of what happened in 1975.

Today, João Duarte a marine geologist from the Instituto Dom Luiz at the University of Lisbon in Portugal has stumbled across the same explanation.

“It sounds wild, it sounds crazy, but it was not my idea,” Duarte told Maya Wei-Haas, a science staff writer for National Geographic. “[Purdy] drew in 1975 the result I have in my numerical model—it’s mind-blowing.”

So, what’s the cause that took 50 years to confirm? Duarte presented his computer simulations at the European Geosciences Union meeting:

A tectonic plate in the Iberian Sea seems to be slowly peeling apart. The bottom layers of the tectonic plate have begun moving downward, away from the top layers, in what is called a subduction zone.

For those of us who need to brush up on our geology homework, this is a really significant discovery! Never before have scientists been able to capture the beginnings of an oceanic tectonic plate peeling like this. We’ve only seen the after effects of long-gone shifts.

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Lost? Here’s a quick summary of plate tectonics. 

• “Plate tectonics is the theory that Earth’s outer shell is divided into several plates that glide over the mantle, the rocky inner layer above the core. The plates act like a hard and rigid shell compared to Earth’s mantle.” (2)
• Before scientists understood plate tectonics, they used to explain natural geological phenomenons with continental drift theory.
• Earth has 9 major tectonic plates: North American, Pacific, Eurasian, African, Indo-Australian, Australian, Indian, South American and Antarctic.
• When two plates pull apart, hot magma escapes and forms a new crust at the ridge. When two plates combine, one slides beneath the other (subduction zone). Two plates can also “grind” against each other, in opposite directions, which can cause earthquakes.

Other scientists’ simulations predict that tectonic movements like this will eventually cause the Atlantic Ocean to shrink and decrease the distance between Europe and the Americas. Of course, this is a slow, painstaking process which would make drying paint seem fascinating.

Duarte speculates that the subduction zone formed because of water stuck within the layers of the tectonic plate, which may have serpentinized into soft minerals that eventually led to the separation of the bottom layer. But at this stage, speculation is as close as the world has to learning more.

Until then, Duarte and his team are in the process of submitting their research for publication to spark further research and discussion. Duarte told National Geographic that if his work is accepted, he plans to send the first copy to Michael Purdy.

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