An underwater tsunami occurred after the collapse of an Antarctic glacier, let’s find out what it is.
An “underwater tsunami” as high as an apartment building has been observed in Antarctica due to a glacier calving. Let’s find out more about this phenomenon.
In recent years, unfortunately, the great natural tragedies are remembered above all with earthquakes and, for those who live on the coasts, with tremendous tsunamis. Documentaries of all kinds have been made and even an extraordinary film like The Impossible which retraced the consequences of a tsunami. However, the tsunami, which in scientific literature is indicated with the Japanese word tsunami , indicates an anomalous wave motion of the sea of frightening dimensions caused most often by an underwater earthquake or near the coast and in rarer cases by other events that favor one sudden movement of a large mass of water such as: a landslide, an underwater volcanic eruption or the fall of a meteorite or asteroid.Climate change is bringing about various situations, very dangerous, with submarine tsunamis or internal tsunamis no longer caused by earthquakes.
This is the case that occurred recently in Antarctica following the collapse of the William Glacier .
Although the latter do not cause huge wave fronts, they are capable of displacing a large amount of water in every way and can be found in oceans and lakes, but are not seen on the surface. The front area of the William Glacier had a height of forty meters above sea level and the amount of ice that detached had an area of 78,000 square meters , comparable to ten football fields. As Professor Michael Meredith , lead study lead author of the Polar Oceans group at BAS and who was in the vicinity of William Glacier at the time of the collapse, explained:
We were lucky to be in the right place at the right time. Many glaciers end up in the sea and their ends regularly split into icebergs. This can cause large waves on the surface, but we know it also creates waves within the ocean. When they break, they cause the sea to mix affecting life in the sea. Our serendipitous timing shows how much more we need to learn about these remote environments and how much they matter to our planet.
Large tsunamis usually start in the deep ocean where a large volume of water can be displaced. As the wave approaches the shore, it gets higher and higher. The first indicator of an approaching tsunami after an earthquake is water receding or moving away from the coast. The area flooded by a tsunami can extend inland for hundreds of meters, devastating vast surfaces. It should be considered that, in retreating towards the sea, the return wave carries most of the material invested on the coast towards the open sea. The maximum heights of the tsunami wave observed immediately before breaking on the coast are of the order of thirty meters, but the highest known wave reached perhaps sixty meters.
How long does a tsunami last?
Tsunami waves can attack the coast and be dangerous for hours on end, with waves arriving every 5-60 minutes . The first wave may not be the largest and followed by three or four waves that increase in size. After the first wave hits the coast, it often travels farther out to sea until the seabed is exposed. The next wave then rushes ashore within minutes and carries with it a lot of debris that has been pulled up by the previous waves. When waves enter ports, very strong and dangerous water currents are generated which can easily break the moorings of ships, and when tsunamis enter rivers or other waterways, holes can form and travel inland .
Despite its speed, the large wavelength of tsunamis makes the period of these waves very long. Thus it can happen that many minutes pass between the arrival of one wave and another and that the tsunami lasts several hours with all that follows.
The most devastating tsunami ever
The tsunami with the highest waves ever reached the one that occurred in Alaska on July 9, 1958 in Lituya Bay went down in history as the highest tsunami in the world with a wave 525 meters high.
Its height is comparable to the Empire State Building or ten times that of Niagara Falls
This mega-tsunami was caused by an earthquake with a magnitude of 7.8 which, triggering a series of landslides, allowed the creation of the enormous wave. Despite the dizzying height of its waves, it only claimed five lives who happened to be with their boat in the bay.
From a geological point of view, the Lituya tsunami made it possible to confirm the existence of mega-tsunamis , up until then only hypothesized and never directly observed.
However the largest tsunami ever was probably seen by dinosaurs and not humans.
Waves a kilometer and a half high. A tsunami of unimaginable violence, the one unleashed sixty-six million years ago, by the fall of the asteroid that caused the extinction of the dinosaurs. After much research on the subject, a team of scientists from three American universities, Michigan, MIT and Princeton , has finally studied and confirmed the waves that followed the impact on the earth of Chicxclub, the fourteen kilometer asteroid that crashed on the current Yucatán , Mexico. It went from hundreds of meters, to tens, up to small waves of just four meters and American researchers regarding the large impact, have elaborated a computer simulation to analyze the ten minutes following the fall of the asteroid, whichit generated a crater with a diameter of 180 kilometers and a depth of 1.5 kilometers . It is possible to just image the effect of the tsunami on the mainland.
- An underwater tsunami occurred after the collapse of an Antarctic glacier, what it is (scienzenotizie.it)
- Tsunami, how long it lasts and why it happens (esquire.com)