A Terrifying Megatsunami Devastated Greenland. Then Scientists Discovered The Unusual Cause

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It sounds like something from the dim and distant past. A freak wave known as a megatsunami crashing onto frozen shores, carving a path of destruction as it rolls onto the land. But this isn’t some historical occurrence. It happened in 2017 in Greenland, and the reasons behind it are as shocking as they are incredible.

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What makes this event so interesting isn’t just its size, it’s the footage captured showing the wave hitting the western shores of Greenland. Because tsunamis occur so quickly, there’s often no time for those involved to record what’s happening. But in this age of connected technology, residents of the remote area managed to do just that.

Image: Hermann Fritz

And then there’s the question of what caused the giant wave. Locals were baffled at first by the sudden surge of water. But after digging deeper into the geology of the area, scientists realized that something unprecedented had created the megatsunami. And now they’re monitoring the area to see if it’s likely to happen again.

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The megatsunami hit the coast near a small fishing village called Nuugaatsiaq. It was Saturday evening and the inhabitants didn’t know what was coming. More than 80 people lived in the settlement – the wave killed four of them and injured dozens more. In addition, 11 houses were washed away by the oncoming waters.

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The village didn’t bear the full brunt of the tsunami, though. Nuugaatsiaq is in fact some 12 miles away from the source of the giant wave. And that meant its force was depleted by the time that it reached the village. When it was at its peak, it would have been an even more terrifying sight to behold.

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There’s no footage of the wave when it was at its largest, but scientists have published a report that suggests that it was truly enormous. In fact, there’s a very good chance that this wave was one of the biggest ever recorded. And as a result, it would have been the sort of thing only usually seen in disaster movies.

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You see, the crest of the wave is estimated to have been more than 300 feet high. That would put it at somewhere around the same height as a 25-story building. Prior to it reaching Nuugaatsiaq, however, much of the wave’s energy had been lost when it hit a fjord. If that hadn’t happened, the end result could have been even more catastrophic.

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But what was it that caused such a massive wave? Well, to begin with scientists thought that the answer was obvious. Around the same time as the wave was hitting the shores of Greenland, a seismic event was recorded. So it looked like an earthquake was to blame for the giant wave that hit Nuugaatsiaq.

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Image: U.S. Navy photo by Photographer’s Mate 2nd Class Philip A. McDaniel

Tsunamis are created when a large volume of water is disturbed for some reason. And more often than not the cause is a large undersea earthquake. Perhaps the most infamous tsunami of recent times, the 2004 Indian Ocean tsunami, was created in this way. The earthquake that caused that destruction measured around nine on the Richter scale.

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However, the seismic event that scientists believed had triggered the megatsunami in Greenland measured just four on the same scale. And then another piece of evidence was discovered, which pointed to the real cause of the wave. It was an event so massive that it fooled seismic devices into registering that there had been an earthquake.

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To the south of the village where the tsunami hit the land, scientists spotted the telltale marks of a landslide. The cliffs around Karrat Fjord were now concave. And by the looks of it, an enormous amount of rock had plummeted into the waters below. But was that an effect of the earthquake or something else?

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The landslide was truly enormous. It was at least 3,000 feet long, in fact, and 900 feet across. Dave Petley, the University of Sheffield’s the pro-vice-chancellor, subsequently studied images of the area that the landslide had originated in. And he wrote on the American Geophysical Union’s The Landslide Blog that the slip would have been “high in volume.”

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Indeed, the landslide was so enormous that it fooled the region’s seismic detectors. There was no earthquake, but the amount of material that fell from the cliff face was enough to register on the seismometers that track earthquake activity in the area. But what made the landslide happen if there was no earthquake?

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Well, one theory suggests that global warming could have been the trigger. You see, it isn’t just rocks that make up the cliffs in the Western Greenland. A good portion of the material in them is ice. And as global temperatures become higher, that ice becomes more unstable, which could lead to more landslides like this one.

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While the summer months in Greenland do carry with them the risk of landslides, as warmer temperatures melt the ice sheets and permafrost, it’s rare that the outcome is something as massive as this tsunami. Melting ice can destabilize slopes, though, and if the temperatures keep rising then there’s going to be even more melting ice.

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And the danger hasn’t passed for Western Greenland just yet. Next to the site of the original landslide there is another unstable slope. And if that cliff slips into the sea as well, then there’s a good chance that there’ll be another large tsunami as well. Possibly one more devastating than the wave that hit Nuugaatsiaq, in fact.

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Naval ships and helicopters have consequently been deployed to the area in order to keep an eye on the site. Denmark’s Joint Arctic Command, which was in charge of the search and rescue operation after the first megatsunami, has also warned that a second catastrophic event may occur.

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For the people of Nuugaatsiaq, though, it’s unlikely that life is going to be returning to normal any time soon. Boats and debris were pushed inland by the force of the wave, and many people are now consequently without homes. At the last census 84 people were registered as living in the village. At least 39 of them have been evacuated in the wake of the tragedy.

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If scientists’ theories about the cause of the landslide turn out to be true, then this probably isn’t going to be the last time that we hear about a landslide causing a tsunami. The conditions in Western Greenland suggest that similar events could be almost inevitable. And while this catastrophe might have been rare in recent times, there’s a terrifying chance that it could become commonplace.

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Costas Synolakis is a tsunami researcher from the University of Southern California in Los Angeles. He wasn’t involved in the project to study what happened in Greenland, but speaking to Nature, he had a worrying premonition for the future. “Earlier, we didn’t really believe such extremes were possible,” Synolakis said. “But with global warming and sea level rise, such landslides are going to be far more common.”

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