Sur cette photo prise depuis la Station spatiale internationale le lendemain de l’éruption du volcan Hunga Tonga-Hunga Ha’Apai, on découvre un impressionnant panache de cendres. Les chercheurs du Jet Propulsion Laboratory (JPL, États-Unis) précisent qu’il s’est accompagné d’une importante émission de vapeur d’eau. © Nasa

“We have never seen anything like it! »

When a volcano erupts, there are lava flows and plumes of smoke. But when said volcano is a submarine volcano, there can also be ejection into the atmosphere of water vapour. And in the case of the Hunga Tonga-Hunga Ha’Apai volcano, which erupted last January, it was colossal amounts of water vapour.

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[EN VIDÉO] Explosive eruption in the Tonga Islands
The eruption of the Hunga Tonga-Hunga Ha’Apai volcano produced very violent explosions and columns of ash 20 to 30 kilometers high.

Last January, a underwater volcano with an extended name — baptized Hunga Tonga-Hunga Ha’Apai — erupted in the Pacific. A tsunami followed which affected nearly 90,000 people in the Tonga Islands. The sound of this powerful eruption circled the Earth ! And today, researchers from Jet Propulsion Laboratory (JPL, USA) tell us that the anger of the volcano also projected an absolutely colossal quantity of water vapor into the tunes. Enough to fill nearly 60,000 Olympic swimming pools!

“We have never seen anything like it”comments Luis Millan, researcher at JPL, in a communicated. According to his figures, it is no less than 146 teragrams, or 146 billion kilograms of water vapor that the Hunga Tonga volcano sent directly into the stratosphere — and even a little above — the layer of the atmosphere that is between 15 and 50 kilometers above the ground. This is almost four times more than what was ejected by the eruption of Mount Pinatubo (Philippines) in 1991. And no less than 10% of the total quantity of water vapor already present at this level of the atmosphere .

This is all the more remarkable as it remains rare for volcanic eruptions inject water vapor into the stratosphere. Almost 20 years since the NASA take readings. And that had only happened two other times. During the event of Kasatochi (Alaska) in 2008 and during the eruption of Calbuco (Chile) in 2015. In proportions very far from being comparable, in addition. The excess water vapor had quickly dissipated. This time, it could persist for up to ten years.

Consequences for life on Earth?

Researchers attribute the phenomenon to a kind of position “ideal” of Boiler of the volcano some 150 meters deep. Deeper and the pressure of the ocean would have attenuated the eruption. Shallower and there would have been much less superheated water to form steam.

The problem is that the presence of water vapour in the atmosphere is not so neutral and innocent as it might seem at first glance. Because in the stratosphere, water vapor tends to produce radicals that carry electrons “singles”. What makes them highly reagents. They tend to destroy theozone. But stratospheric ozone is the one that protects life from radiation ultraviolet harmful that comes to us from Sun.

Water vapor also plays a fairly direct role on thegreenhouse effect. It is even a rather effective greenhouse gas. Because it can absorb radiation infrared emitted by our Earth over a wide range of frequencies. Thus the eruption of the Hunga Tonga volcano and the massive injection of water vapor that followed should have at least a one-time effect — potentially several years all the same, once the carbon dioxide sulfur refreshing dissipated — on average temperatures. Raising them a little more. As for a possible longer-term significant effect on the global warming anthropogenic, scientists remain divided for the time being.

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