A 4.3-magnitude earthquake struck the Canary Island of El Hierro on Saturday, the largest to date since the National Geographic Institute sounded the alarm in July, when it began registering unusual seismic activity there.

There were no injuries, though the tremor, which struck at 9.34pm, was felt throughout El Hierro. It was especially intense in the southern town of El Pinar, the closest part of the island to the epicenter, located a kilometer offshore and 13 kilometers deep.

Experts believe that these tremors could be the prelude to a volcanic eruption, a phenomena that has not occurred in the Canary Islands since 1971 in La Palma. El Hierro's last volcanic eruption was in 1793.