The Cumbre Vieja volcano, an area of the Spanish island of La Palma in the Canary archipelago, resumed its eruptive activity yesterday 19 September, with the opening of several vents along a 150 meter fracture at approximately 600-800 meters above sea level.
For several days now we had been witnessing earthquakes and swelling of the ground, which had led the authorities to evacuate around 5000 people from the affected area.
The site of the eruption is located in the south-west of the island, where in 1949 another volcano, San Juan, had already erupted. La Palma, together with Tenerife, is a geologically young island and is home to several volcanoes; the last eruption was that of the Teneguía volcano, in 1971.
But what does an eruption have to do with the work of an astrophysicist? It has something to do with it, especially if it's a solar physicist like me.
You should in fact know that La Palma hosts several telescopes, grouped in the Roque de Los Muchachos Observatory (north of the island) and among these telescopes there are the Swedish Tower Telescope, one of the largest solar telescopes in world, and the Italian TNG telescope (Telescopio Nazionale Galileo) which is used to study the planets and minor bodies of the solar system and to observe galaxies and objects of cosmological interest. As regards the TNG, we know directly from its director, Ennio Poretti, that it remained operational despite the eruption, constantly monitored.
Also in Tenerife, on the Teide volcano, at around 2500 m above sea level, there is an observatory with various telescopes, including the German VTT (Vacuum Tower Telescope), where I went for three observation campaigns and which provided me with the observations of an erupting solar filament (similar to volcanoes!) on whose interpretation I based my doctoral thesis and two scientific works.
But why do we build telescopes on islands, especially volcanic ones?
Because, especially with regard to solar telescopes with which we observe during the day, it is very important to try to find places where the atmosphere is particularly stable. In fact, the air around the telescope, heating up under the beating sun and rising upwards, generates turbulences which degrade the observations and greatly affect their sharpness.
The sea, which the islands are surrounded by, thanks to its high heat capacity, tends to stabilize the atmosphere.
Furthermore, in addition to the fact that volcanoes are still mountains and therefore it is possible to build high up, avoiding thick layers of atmosphere above the telescopes, they also have slopes that are less steep than the mountains themselves and on which it is easier to build.
Image credits: Ennio Poretti
