Ancient Tsunami Struck the Falkland Islands, Scientists Speculate

Nature

Scientists are speculating that the Falkland Islands could experience a major tsunami in the future. They think that an ancient tsunami occurred from seafloor slope failures located at the British Overseas Territory’s southern side in the recent past. Computer models showed how underwater landslides could have sent waves that are at least ten metres in height to crash on to the coastline.

The ancient tsunami seems to happen only once in roughly a million years. Uisdean Nicholson, a geologist from the Heriot-Watt university, said that more research is needed to understand how such an event occurs and to comprehend the time scales.

The landslides were found to occur on a steeply inclined terrain at the edge of Burdwood Bank seafloor’s raised region. The scientists collected seismic data that showed repeated sediment failure, wherein silt, sand, and mud tumbled downslope into deeper waters. For significant events to occur, 100 km3 of material needs to be moved, which is roughly the size of Edinburgh.

The scientists estimate the age of the sediments and calculate the frequency of slope failures from exploratory drilling. Scientific expeditions and oil companies were involved in the investigation, including the University College London and the BGS or British Geological Survey. They discovered that three to four “Edinburgh-sized” slope slides have occurred within the past three million years.

 Certain earthquakes that cause tsunamis have been found to trigger ocean tsunamis by either depressing down or pushing up the water column above ruptures on the seafloor. In addition, sudden slumping of the sediment in landslides underwater also create the same effect. The biggest tsunami or worst tsunami that modern mankind can experience could come from these conditions. Scientists can gauge tsunami locations from such conditions. A search for “tsunami Wikipedia” can generate a lot of information, such as a list of tsunamis in history.

The September 2018 tsunami is a good example. This occurred in Sulawesi, Indonesia. It was caused by an earthquake that triggered submarine slope failures, which then caused waves that are two metres high to crash into Palu City. In 1998, another submarine landslide triggered a 15 metre-high tsunami in Papua New Guinea; the resulting tsunami death toll was 2,200.

 Tsunamis that are induced by landslides under the water can be very big; however, they quickly fall off with distance. The Falklands are around 150 kilometers from the Burdwood Bank. Nonetheless, the computer modelling showed how larger slope failures may cause 10-metre tsunamis at Port Stanley, the capital, and 40-metre tsunamis on the southern shoreline.

 Dave Tappin, professor at the BGS, reiterated that ancient tsunamis should not alarm the people. Their team studies both modern events, such as the most recent tsunami 2019, as well as prehistoric ones, to better understand how tsunamis are generated as well as predict future hazards.

 Burdwood Bank is a particularly prolific “landslide factory.” It is speculated that this may be due to the SAF or Sub-Antarctic Front, which is the northernmost jet or branch of the ACC or Antarctic Circumpolar Current. The latter is the most powerful water movement known on Earth. The locations where the SAF skirts the Burwood Bank can accelerate in some places, making it highly erosive. The SAF picks up sediment from one location then dumps it elsewhere. The accumulation site is called the Burdwood Drift, which is a high and steep slope.

 The emplaced sand and silt have been found to be accumulating again, although current data does not allow predictions of when the next slide could happen. Internal instabilities may eventually activate a slide, as well as shaking from an earthquake. It is worth noting that the bank is close to some tectonic plate boundaries.

 A future direction of research may involve digging on some areas in the Falklands in order to determine the presence of ancient tsunami deposits.

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