This is about active volcanoes in Europe. The occasion is the ongoing volcanic eruption of Cumbre Vieja which is located on the Spanish island La Palma, the most north-western island in the Canaries archipelago.
The island of 85,000 people is a popular tourist destination for Europeans. The volcanic eruption has forced 6,000 people to evacuate their homes.
From the perspective of plate tectonics science, the island isn’t part of Europe. Though La Palma belongs to Spain, the Canary Islands are part of the African plate and are generally considered part of the African continent (Google Maps).
What is it with these plates? Earth's thin outer shell is broken into big pieces called tectonic plates (here is a simplified map of Earth's tectonic plate). These plates fit together like a puzzle. But unlike a puzzle they're not stuck in one place. They are floating on Earth's mantle, a really thick layer of hot flowing rock. Even if plates move very slowly (the fastest plate race along at 15 centimetres per year), their motion has a huge impact on our planet. Especially where tectonic plates meet, earthquakes occur, and volcanoes erupt.
Europe is on the Eurasian Plate. That tectonic plate includes most of the continent of Eurasia (a landmass consisting of the traditional continents of Europe and Asia), with the exceptions of the Indian subcontinent, the Arabian subcontinent, and East Siberia. The border to other tectonic plates runs through the Mediterranean Sea, through the Atlantic Ocean close to Spain, and - in the north - through Iceland. You can imagine it better with a picture.
This is the list of recently active volcanoes in Europe:
Mount Etna, Sicily, Italy, last eruption: February 2021;
Stromboli, Aeolian Islands, Italy, 2019;
Bárðarbunga, Iceland, 2014-2015;
Grímsvötn, Iceland, 2011;
Eyjafjallajökull, Iceland, 2010.
Which volcano will erupt next? You can't really predict it. But forecasts are becoming more reliable. Key to success in short-term volcanic eruption forecasting is recognizing when a volcano moves away from its background level of activity. To do so, volcanologists must collect volcano-monitoring data during times of inactivity. Regarding these background measurements, scientists can better interpret changes caused by magma movement or pressurization, including shifts in seismicity, appearance of ground deformation, and change in character or rate of gas emissions. But: Forecasts remain imperfect.
In the case of Cumbre Vieja a team of experts were monitoring the phenomenon for a while. Tremors had been recorded, and a ground deformation indicated that magma was bubbling beneath the surface. On 15 September, the experts said that it would be possible that this magma could cause a volcanic eruption on the surface in the next few days or weeks. But while the process had intensified, they said there were no clear signs of an imminent eruption. On 19 September, the volcano eruption started. And how long will it last? Nobody really knows. The Canary Islands Volcanology Institute said that the volcanic eruption's aftermath could last up to 84 days. The calculation is based on the length of previous eruptions in the archipelago.