Warning as massive La Palma volcano 'much bigger than previously thought'

A volcano that last erupted in 2021 and destroyed more than 3,000 properties has magma underneath it much bigger than previously thought.

When the Cumbre Vieja volcano, on the Canary Island of La Palma, erupted more than 7,000 people were forced to leave their homes as the lava closed in. It was the first eruption on the island since 1971 and the longest-ever recorded on the island.

Now a study has shown that the amount of magma under the volcano – that is also known as ‘Tajogaite’ – has been underestimated.

‌The study has been led by the Volcanological Institute of the Canary Islands (Involcan) and the Environment Area of the Institute of Technology and Renewable Energies (ITER) together with the Complutense University of Madrid.

The main technique of the research was the use of receiver functions, a method that allows the seismic waves generated by eruptions to be studied in order to map the structure of the earth’s crust and upper mantle down to depths of 31 miles (50 kilometres). 

Using this method the researchers have been able to discern the velocities of the seismic waves at depth which has allowed the identification of the different geological layers that make up the volcano.

‌The research was first published on May 8 and it offered a “plain language summary”.

It said: “Oceanic volcanic islands have a complex internal structure. 

“Our study is important to understand volcanic activity in its geodynamic context better. 

“The last eruption occurred in the Cumbre Vieja volcanic complex on La Palma Island (2021) and had an unexpected magnitude in terms of lava volume, explosivity, and a significant impact on the economy and society of the island.”

The summary goes on to say that depths of up to 50km were analysed closely by looking at the recordings of teleseismic events such as earthquakes.

It added: “We used an advanced inversion technique to study the structure of the crust and the upper mantle beneath the volcano. 

“The most relevant finding is a zone of anomalous low seismic velocities extending from 13 to 37 km depth.

“This zone is likely to host partial melt and magma chambers and extends over a much wider and thicker volume than expected from previous studies.”