2023-12-20 11:51:50
After weeks of seismic activity, the earth finally opened up to spew streams of lava into Iceland. During the night from Monday to Tuesday, a new volcanic eruption took place southwest of the capital Reykjavik and 3 km from the small town of Grindavik, whose 4,000 inhabitants have been evacuated since November 11 and the announcement of the imminent arrival of this new eruption.
Along with molten rock, volcanoes release gases, ash and debris that can affect the climate. We might believe that volcanoes promote global warming since they emit greenhouse gases, particularly CO2. And yet, according to NASA data, our human activities release more than 100 times what all the world’s volcanoes can emit! Volcanoes really don’t have much impact on global warming, which remains a human specialty.
On the other hand, among all the gases that escape during eruptions, there is also sulfur. In the atmosphere, this sulfur oxidizes with water vapor and then forms tiny droplets of sulfuric acid which are called aerosols and which can then block the sun’s rays. They form a sort of shield against the sun. There is therefore a cooling effect.
Volcanic winter
Not all breakouts are equal. During small eruptions, we can observe a drop in temperature of one or two degrees, very localized and only for a few days, or even no drop in temperature. But with a huge volcano, which sends its sulfur high into the atmosphere, the winds can circulate sulfuric acid aerosols for weeks or even years around the globe and cause a real volcanic winter. The drop in temperatures after a major eruption is one of the ways scientists can explain the end of the dinosaurs.
Atmospheric pollution
The type of magma currently flowing in Iceland is very rich in iron and titanium. Two ores which trap a lot of sulfur in the liquid state. This eruption near Grindavik could therefore potentially have a cooling effect. Fortunately, despite a three and a half kilometer crack, and the very impressive images of these molten lava geysers that we can see on the internet, the flow has calmed down a lot: it is now a modest eruption, according to Olgeir Sigmarsson, research director at the CNRS magma and volcanoes laboratory.
According to him, on the other hand, it is the pollution that we will have to monitor. “ When the lava then cools and crystallizes, there is an emission of a second generation of volatile elements, that is to say molecules which escape into the atmosphere. These are often elements from the halogen family: fluorine and chlorine. They will in turn release a lot of metals which can be toxic in quantity, such as cadmium, arsenic, rare earths, etc. » So local populations will have to be careful, because the risk of these small eruptions is rather a risk for health and the environment.
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