For a week, a series of earthquakes struck the island of São Jorge in the Portuguese Azores. More than 12,000 tremors have been recorded, and around 2,000 smaller quakes were reported early on with magnitudes of up to 3.5.
According to Volcano Discovery, the swarm is likely caused by a magnetic intrusion at 10-15 km depth and could indicate renewed eruptive activity in the future.
On Wednesday, the region’s seismic surveillance center raised the volcanic alert to four, meaning a “real possibility” of a volcanic eruption.
Volcanic eruption refers to the emission of volcanic material from the Earth’s surface with explosive force, ejecting pyroclastic materials into the atmosphere, which fall back to Earth as ash and sometimes lava flows.
The last time a volcano erupted on the island was in 1808, when a series of eruptions occurred along the south-central part of the island.
“Annually, São Jorge has a few earthquakes — and now we’re talking about thousands,” said Joao Fontiela, a seismologist working on the island. He said that he is currently setting up monitoring stations around the islands to continue to monitor developments.
CIVISA stated “no evidence that a volcanic eruption was imminent,” but that the possibility of an eruption should not be overlooked since the seismic swarms are abnormal.
Meanwhile, the island’s emergency strategy was activated, and preparations are in order to evacuate São Jorge’s 8,400 residents if need be. An estimated 1,250 people already left the island on Wednesday and Thursday alone.