In March 2022, thousands of earthquakes rattled São Jorge Island in Portugal's Azores archipelago after a huge body of magma (molten rock) surged upward from deep underground, according to a new study led by researchers at UCL (University College London). The magma traveled from more than 20 kilometers beneath Earth's surface before stopping just 1.6 kilometers below the island, narrowly avoiding an eruption.

Researchers found that much of the magma's rise happened quietly, with relatively little seismic activity during its ascent. Most of the earthquakes struck only after the magma stopped moving upward. The enormous intrusion unfolded within just a few days and involved enough magma to fill roughly 32,000 Olympic-sized swimming pools.

Lead author Dr. Stephen Hicks of UCL Earth Sciences said: "This was a stealthy intrusion.…