At the time of this writing, there are about 40 erupting volcanoes around the world, according to data from the United States Institute of Geological Studies, which lists them. Most eruptions represent only small flows or thin plumes of smoke. But sometimes, volcanic eruptions reveal their thunderous and devastating power.
A 90 m tsunami at its point of origin
On January 15, the Tongan island of Hunga Tonga exploded, 2,000 km northwest of the New Zealand coast. That evening, the column of smoke rose more than 50 km high, five times higher than an airliner. The crackle of the eruption was heard as far away as New Zealand.
A study to be published in the specialized journal Ocean Engineering now estimates that the tsunami wave resulting from this eruption was up to 90 m at its point of origin, a height equivalent to that of Notre-Dame de Paris. In question, a double shock wave, both maritime and atmospheric. The waves circled the globe, with waves recorded as far away as the Mediterranean. Of the five known victims of the disaster, two were also killed thousands of kilometers away, on the Peruvian coast. The other three are Tongans.
In total, almost 6,660 million cubic meters of water have been moved. In early August, another study, published in the scientific journal Shock Wavescalculated that the eruption caused an explosion equivalent to 61 Mt of TNT, more than the “Tsar Bomba”, the most powerful of nuclear bombs.
A lack of volcanic risk monitoring
How to explain that this disproportionate eruption is ultimately less deadly than other natural disasters, such as the tsunami that hit Japan in 2011? First, it took place in the middle of the Pacific Ocean, in an uninhabited area. By the time the tsunami hit the Tonga archipelago, 70 km away, the wave was no more than 1.50 m. Above all, the relief of the seabed affects the shape and size of the waves, and therefore the destruction on land.
For the researchers behind these studies, it is above all necessary to improve the monitoring and warning systems for natural disasters linked to volcanism. While earthquakes are perfectly recorded all over the globe, underwater volcanoes or in remote areas are very poorly observed.