Satellite observations show that thecreated major disruptions of in the air. Giving birth to violent. Winds that accelerated as they rose in altitude. When they reached the — a layer of our atmosphere located between 60 and 1,000 kilometers above sea level — the mission Ionospheric Connection Explorer ( ), passing over South America, recorded them at over 720 km/h. Quite simply, the strongest winds recorded by the mission above 200 kilometers altitude.
The ionosphere impacted from all sides
These extreme winds also affected thecirculating in the ionosphere. These currents – classically fed by winds from the lower atmosphere – thus reached five times their normal peak power. They also radically changed direction. Beginning to flow west for a short time. So far, only could have had such an effect.
This work confirms that the ionosphere can be affected by events that occur onas well as by phenomena that occur in space — the , for example. Because changes can affect our signals and in particular, it is important for researchers to be able to continue to better understand the phenomena that cause them.
How big was the eruption of the Hunga Tonga-Hunga Ha’Apai volcano? Decryption
Like the shock wave it generated, the eruption of the Hunga Tonga-Hunga Ha’Apai volcano erupted around the world. Firstly for its magnitude, which allows it to be referenced as a major eruption in the first part of the 21st century.and century. For the damage caused afterwards, even if the balance sheet in Tonga is still largely incomplete. Finally, for its manifestations of a planetary order, right up to us at the other end of the world… But for all that, where does it rank in relation to the major eruptions on our planet?
Article ofpublished on 01/25/2022
Ais, by definition, an impressive natural phenomenon. But for a small-scale eruption, like that of in Reunion which has just ended, to an eruption that could cause global climatic disturbances, there is a big difference in explosiveness.
In order to be able to compare them, Newhall and Self created the Volcanic Explosivity Index (or VEI) in 1982, a scale which makes it possible to estimate theof one from different parameters. This assessment is mainly based on the of tephras emitted at the time of the paroxysm, which corresponds to the fragmented during the most violent event of the eruption, and on the height of the associated volcanic plume. However, this VEI is not the result of a calculation, but rather of an estimate: the approach is therefore somewhat subjective. But this scale is logarithmic, that is to say that the index increases by one value when the volume of tephra emitted is ten times greater, which allows a certain largesse. Thus, two eruptions from the same VEI are not strictly equivalent, but this scale makes it possible to fairly reasonably classify the eruptions between them. For example, those of are classically of a VEI between 0 and 1, when the eruption of 600,000 years ago in Yellowstone in the United States is 8, the highest index of this scale!
Video animation showing the VEI of some historical eruptions. © Taype Studios
The eruptive column of January 14 above the Tongan volcano, the day before the paroxysm, reached 20 kilometers in altitude. This already made this event an eruption of a certain magnitude, since the limit between theand the which is called the and which is located about 15 kilometers above sea level at this latitude, requires a certain flow to be crossed. But Wellington’s VAAC (the information center for of ash in this sector of the globe) warns that the next day’s eruptive column reaches an altitude of about 30 kilometers! Satellite data confirmed this, some even suggesting a maximum altitude of 35 kilometers!
#hunga Tonga-Hunga Ha’apai #volcano (Tonga) activity update: latest measurements confirmed 30 km column height containing 0.4 Tg SO2 – According to the Ozone Mapping and Profiler Suite (OMPS) lidar-based satellite, measuring the glo…https://t.co/Wt4vgsd6mD
— VolcanoDiscovery (@volcanodiscover) January 17, 2022
It is comparable to the 34 kilometers of the paroxysm of the eruption of Pinatubo in the Philippines, on June 15, 1991, just like the umbrella formed by the spreading of the plume in thewhose diameter reaches about 500 kilometers for these two eruptions. But the few centimeters of ash fall on the of Tonga are incomparable to the total darkness in which much of the island of Luzon found itself in broad daylight during the ! And if a large part of the ash from this eruption in Tonga fell back into the Pacific Ocean, thus annihilating the estimate of a reliable volume for this eruption, it appears that the VEI here is necessarily weaker than the 6 of the Pinatubo.
The little ash linked to this activity, relative to the significant height of the eruptive plume, is explained by the mechanism at work at the level of the eruptive mouth. This one being under water, the contact betweenand the sea water engenders the a large amount of water vapour. Gas is therefore added to the eruption! In short, volcanic eruptions under shallow water are complicated by seawater which makes them more explosive! More explosive therefore, but not necessarily more emitting …
By comparing this eruption in Tonga with that of Chaitén in Chile, in May 2008, which is a VEI 4, we also realize there the deficit of ashes emitted by the volcano Hunga Tonga-Hunga Ha’Apai. Indeed, if the height of the eruptive plume is slightly less for the Chilean volcano, the thickness of the ash deposit of its paroxysm is 30 centimeters at 65 kilometers from the volcano! To go further, we can also estimate thedeployed at the time of the eruption. James Garvin, a scientist from the thus estimated that the had released an energy equivalent to 10 megatons, the equivalent of 500 Hiroshima bombs! This is comparable with the explosion of Mount Saint Helens in the United States, in May 1980, which is estimated at a VEI 5.
In view of these comparisons, the VEI of the eruption in Tonga is therefore very probably between 4 and 5, which makes it a very violent eruption, but not cataclysmic. And if on a human scale, it is an important event, on a planetary scale, it is much less so!
An impact over a large area
Unlike Chaitén or Mount Saint Helens, this eruption was felt several thousand kilometers away.indeed spread throughout the Pacific Ocean and the sound of the explosion was heard as far as Alaska, more than 8,500 kilometers away! This is reminiscent of the eruption of Krakatau in Indonesia, in August 1883, estimated at a VEI 6 with an eruptive plume that reached about 50 kilometers in altitude. The sound of the paroxysm was heard almost throughout the Indian Ocean, from Australia to Rodrigues Island, a small island near . The tsunami was gigantic, with several tens of meters high on the coasts of and Sumatra, which explains the very heavy toll associated with this eruption: 36,000 victims at least! This tsunami is the consequence of the of the volcano which peaked at about 800 meters high in the ocean, which is to date the most likely hypothesis to explain the tsunamis of the eruption in Tonga…
Chile: Video that shows a strong swell at Las Coloradas on Isla del Rey, in the municipality of Corral where the tsunami arrives after the wave has traveled 9,500 km since the explosion of the underwater volcano Hunga Tonga-Hunga-Ha ‘apai, Tonga.pic.twitter.com/Pp3qAhyWKM
— Rebecca Rambar (@RebeccaRambar) January 15, 2022
Finally, it is also appropriate to ask whether this eruption could be the cause of. Because the scale release significant amounts of carbon dioxide a gas that combines with water in the atmosphere to form micro-droplets of . This constitutes a kind of veil which reflects part of the solar radiation, which can modify the if these quantities of gas are significant. The eruptions of Krakatau in 1883 and Pinatubo in 1991 are for example associated with climatic disturbances for a few months or years. But in the case of the eruption in Tonga, the quantity of sulfur dioxide emitted was estimated at 400,000 tonnes, which is too little to have climatic consequences.