US researchers have published a disturbing study concerning part of Alaska. By causing glaciers to retreat faster, global warming is weakening the fjords. In one area in particular, a large mass threatens to collapse, which could cause a tsunami with the highest waves reaching 300 meters in height.
From retreating glaciers to tsunamis
The retreat of glaciers feeds many fears in the overwhelming majority of the polar (and mountainous) regions of the globe. However, the consequences of this decline can sometimes turn out to be rather unexpected. A team of researchers from the Ohio State University (United States) evokes in particular a scenario which has all the disaster film. According to them, Alaska is likely to see a megatsunami occur. In their study published in the journal Geophysical research letters in October 2020, scientists explain that they had analyzed satellite images of the region, concerning the period 1999-2020. When a glacier gradually withdraws from a valley, the slopes (which until then benefited from the support of the mass of ice) are weakened. Also, the risk of ground movements large-scale become very important.
One of the first signs of this type of risk is the appearance of some kind of indentation scar at the top of the slope. We can also mention a slow downward movement of the ground. A trigger event such as an earthquake, heavy precipitation or even rapid snowmelt can then cause a complete rupture of the ground. As a result, the mass of rocks and sediment slides into the valley (fjord) and can trigger a huge tsunami.
Waves 300 meters high
Through their images, the US researchers have highlighted the downward movement of part of a slope of Barry Arm Fjord, in Prince William Sound (Alaska). You should know that in 2019, an inhabitant of the area had spotted a landslide. Nevertheless, this recess is much older as evidenced by a photograph dating from 1957 studied by scientists. However, team members agree on a acceleration of the process between 2010 and 2017. However, this acceleration heralds a future break in the slope.
Scientists have thought about several scenarios thanks to their models. The most pessimistic concerns a rupture of the slope and the sliding of the entire mass of rock and sediment. However, this mass represents a volume of almost half a billion cubic meters. By sliding in the waters of Barry Arm Fjord, the mass in question will therefore be at the origin of a giant tsunami, the highest waves of which could measure 300 m high and spinning at a speed between 25 and 40 m / s.
Obviously, this event would be a disaster for the inhabitants villages in Prince William Bay. It is also a very touristic area and a popular fishing spot. However, researchers are unable to predict when this tsunami will occur, but can at least delimit the risk areas.