An island in the Atlantic narrowly escaped a hidden eruption - scientists have discovered

In the spring of 2022, a powerful seismovolcanic crisis began on São Jorge. Researchers concluded that it was caused by the introduction of magma: it rose from a depth of more than 20 kilometres and stopped about 1.6 kilometres below the island. The surface rose by about 6 centimetres in places, confirming the magma's entry into the upper crust.

Details

The most important thing about this work is the nature of the magma uplift. The authors note that much of its journey was almost "quiet": at the very beginning there was no strong seismic pattern, which is usually expected before an eruption. The main series of earthquakes unfolded after the magma stopped rising further.

Scientists believe that the Pico do Carvão fault zone played a key role. It both helped the magma move upwards and possibly released gases and fluids to the sides. Because of this, the pressure in the magma was reduced and its ascent stopped. The authors figuratively describe the fault as a "mainline and a leak" at the same time.

During the crisis, authorities prepared for possible evacuation. On 23 March 2022, the Azores Civil Protection Service activated the regional civil protection plan because of the situation at São Jorge.

However, no official mass evacuation of the entire island was announced. Smithsonian Global Volcanism Programme with reference to the Azorean Civil Protection Service reported that as of 22 March there were no official evacuation orders, although vulnerable people, including patients of the medical centre in Velas, were moved to other parts of the island.

At the same time, some residents left on their own. The same Smithsonian Global Volcanism Programme, citing news reports, indicates that about 1,250 people left the island on 23-24 March. Also, the U.S. Consulate in Ponta Delgada conveyed the position of the Azor regional government: travelling to São Jorge should be postponed and an evacuation order may be issued if the situation worsens.

Why it matters

The work shows that large magmatic intrusions can occur very quickly and do not always give classic early signals. This makes predicting eruptions more difficult, especially at island volcanoes and in areas of active faults.

The study also helps us understand how volcanic islands grow in general. Even if there is no eruption, magma can change the structure of the island underground and gradually participate in its formation. The authors believe that such cases are particularly important for volcanic risk monitoring systems.

Background

São Jorge is part of the Azores archipelago, where volcanism and active tectonic faults combine. In 2022, the island experienced tens of thousands of small earthquakes in a short time, raising serious fears of a possible eruption. A new study explains why it never happened.

Source

The study is published in Nature Communications in 2026. It was prepared by an international team of scientists led by UCL researchers and partners from Spain and other countries.