Killer Tsunami in Greenland possibly induced through Landslide


Image: YouTube

Four people are missing and nearly a dozen homes were flooded after a rare tsunami struck the west coast of Greenland on Saturday. Initial reports attributed the giant wave to a magnitude four earthquake, but speculation is emerging that the highly-localized tsunami was actually produced by a massive landslide.

The tsunami, which struck on Saturday evening, has left two people seriously injured, many homes damaged, and a small, isolated community in shock. “It’s hard to believe what happened last night,” noted Greenland’s Prime Minister Kim Kielsen in a Facebook post. “After the earthquake in Nuugaatsiaq we were made aware that the forces of nature can suddenly change…what happened is tragic and my thoughts are with everyone from Nuugaatsiaq.”

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Killer Tsunami in Greenland Possibly Triggered by Landslide

About Tsunami
A tsunami (from Japanese: 津波, “harbour wave”; English pronunciation: /tsuːˈnɑːmi/) or tidal wave, also known as a seismic sea wave, is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater explosions (including detonations of underwater nuclear devices), landslides, glacier calvings, meteorite impacts and other disturbances above or below water all have the potential to generate a tsunami. Unlike normal ocean waves which are generated by wind, or tides which are generated by the gravitational pull of the Moon and Sun, a tsunami is generated by the displacement of water.
Tsunami waves do not resemble normal undersea currents or sea waves, because their wavelength is far longer. Rather than appearing as a breaking wave, a tsunami may instead initially resemble a rapidly rising tide, and for this reason they are often referred to as tidal waves, although this usage is not favoured by the scientific community because tsunamis are not tidal in nature. Tsunamis generally consist of a series of waves with periods ranging from minutes to hours, arriving in a so-called “internal wave train”. Wave heights of tens of metres can be generated by large events. Although the impact of tsunamis is limited to coastal areas, their destructive power can be enormous and they can affect entire ocean basins; the 2004 Indian Ocean tsunami was among the deadliest natural disasters in human history with at least 230,000 people killed or missing in 14 countries bordering the Indian Ocean.
Greek historian Thucydides suggested in his late-5th century BC History of the Peloponnesian War, that tsunamis were related to submarine earthquakes, but the understanding of a tsunami’s nature remained slim until the 20th century and much remains unknown. Major areas of current research include trying to determine why some large earthquakes do not generate tsunamis while other smaller ones do; trying to accurately forecast the passage of tsunamis across the oceans; and also to forecast how tsunami waves interact with specific shorelines.

A video captured by Olina Angie K. Nielsen shows the panicked moment when the wave hit the village. In classic tsunami fashion, the ocean appears to move inland, flooding dwellings and damaging structures, and then receding back into the ocean. Helicopters and medical staff were dispatched to the village, and some 39 residents have been evacuated. At least four people are missing, but concerns of aftershocks have delayed attempts to recover the bodies.

Initially, the tsunami was attributed to a magnitude four earthquake, but as geologist Dave Petley points out at the Landslide Blog, the large—but highly isolated—tsunami may have been caused by a landslide:

Killer Tsunami in Greenland Possibly Triggered by Landslide

It appears that the local seismological bureau recorded the event as a magnitude 4.0 earthquake, with the tsunami striking a few minutes later. Greenland is not a particularly seismically-active area, and as far as I can tell this earthquake has not been recorded more widely. This, combined with the localised nature of the tsunami, suggest that the cause is most likely to have been a very large landslide, either from the fjord walls or under the water (or maybe both).

Peter Voss, a geologist with the National Geological Surveys for Denmark and Greenland (GEUS), told the Greenland Broadcasting Corporation that his team detected a signal suggestive of an earthquake, but that a landslide can’t be ruled out. He theorizes that a major slope from a mountain triggered the waves. “The slump has made a large part of the mountain collapse into the fjord and has created this wave,” he told GBC.

Allison Bent, a seismologist with Natural Resources Canada, told the CBC that, “Based on the magnitude, we suspect it wasn’t the earthquake itself that triggered the tsunami, but in all likelihood, the earthquake triggered an underwater landslide, and that is what triggered the tsunami,” she said.

Michael MacFerrin from the Geological Survey of Denmark and Greenland Copenhagen, Denmark, says the landslide theory makes sense given Greenland’s geology.

“For the most part, Greenland is not a very seismically active area,” he told Gizmodo. “Its geology is composed primarily of old, metamorphic rocks and as far as I know is typically very stable (compared to, say, Iceland). Earthquakes in Baffin Bay (off the coast of NW Greenland) are quite rare, and it isn’t a region known to have tsunami warning systems anywhere. So this would likely have come as a rather large surprise to anyone there. From initial reports it seems very plausible it was caused by a landslide (either into the water somewhere in the fjord, or subsurface under the water), but I really don’t know without any data.”

The recent disaster is a reminder that Greenland is not immune to tsunamis. Back in 2000, a tsunami slammed into Disco Bay, also on Greenland’s west coast.

[Nunatsiaq Online, CBC, Landslide Blog]