On Sunday, September 19 at 15.12 o’clock local time (14:12 UTC), Cumbre Vieja, a volcano located in El Paso municipality on the Canary Island of La Palma, Spain, started to erupt. As soon as eruption began, Europe’s Sentinel-5 Precursor (S5P) satellite detected and recorded the resulting sulphur dioxide (SO2) cloud forming over the islands The S5P measurements are continuously processed at EOC and thereby constantly reveal the volcanic emissions as they evolve.
There were indications of an impending eruption already on September 11. Earthquakes deep under the volcano slowly migrated to the surface, signalling the upward movement of magma. Over 25,000 earthquakes measuring up to 3.5 on the Richter scale were recorded over a ten day period. The Cumbre Vieja area is the Canary Islands’ most volcanically active region. The last eruptions occurred here 50 and around 70 years ago. The current eruption takes place from at least seven main eruptive vents, together with strong lava outflows and gas emissions.
Just 20 minutes after the first eruption the TROPOMI sensor on S5P provided the first measurements of SO2 concentration above the island, and all subsequent measurements are being continuously analysed. The UVN spectrometer has a spatial resolution of 3.5 × 5.5 kilometres, and in addition to SO2 it measures every day, worldwide, other atmospheric trace gases such as ozone and nitrogen dioxide.
In total, more than 50 tons of SO2 have been emitted so far. The height of the SO2 cloud layer could also be retrieved using a new scientific algorithm developed at EOC and optimized in the framework of the ESA S5P+I: SO2 LH project. The development of value added products and visualisation of the sulphur dioxide emissions take place as part of the DLR “inpuls” project.
On September 23 the volcano went though a more explosive phase. The lava flow reached nearby houses and destroyed several hundred of them, So far, no casualties have been reported. Around 300 people had to be evacuated from the immediate danger zone and up to 10,000 more may have to follow. The alert phase has been raised to its highest level.
Almost concurrently with Cumbre Vieja, Etna volcano on the Italian island of Sicily erupted on September 21, 2021, producing a gas and ash plume that rose to an altitude of 9 km. The SO2 cloud can be seen in the animation of daily SO2 measurements. SO2 is a naturally occurring trace gas in Earth’s atmosphere. The largest source of atmospheric SO2 is fossil fuel combustion in power stations and other industrial plants. In addition, volcanos introduce SO2 into the lower troposphere (passive degassing) and into the high stratosphere (explosive eruptions).
The caustic gas not only endangers the environment and population near the volcano, but also the passengers and crew of commercial aircraft if it penetrates aircraft cabins. Aircraft engines can be damaged as well. Timely detection and recording of the presence of SO2 helps to minimize these dangers and show where dangerous concentrations of gas and ash can be expected. So far, flights to the islands continue.