One of history’s deadliest volcanoes is showing renewed signs of unrest decades after its last eruption.
Mount Pelée sits on the Caribbean island of Martinique, roughly 1,500 miles southeast of Florida and along heavily traveled air routes connecting the region with the US.
The volcano's most notorious eruption struck in 1902, when a superheated cloud tore through Saint-Pierre and killed approximately 30,000 people within minutes and more recently between 1929 and 1932.
Now, experts have reported a sharp increase in seismic activity, detecting 124 earthquakes between July 24 and July 31, nearly three times the 45 recorded the previous week.
The Martinique Volcanological and Seismological Observatory said 331 volcanic earthquakes were detected throughout July, averaging approximately 85 each week.
Such earthquakes can occur when rising magma or pressurized fluids push against and fracture solid rock beneath a volcano, although seismic activity alone does not mean an eruption will follow.
A major eruption could unleash scorching clouds of gas, ash and rock across northern Martinique, while a towering ash plume could force airlines to reroute or cancel flights across parts of the Caribbean.
Fine volcanic ash can severely damage aircraft engines, reduce visibility and travel hundreds or even thousands of miles when powerful winds carry it high into the atmosphere.
However, officials have not warned that an eruption is imminent, and there is currently no indication that Florida faces a direct threat.
Since May, scientists have also detected several inches of ground movement around Mount Pelée’s summit. The ground is currently shifting at a rate of nearly half an inch per month, although that movement slowed slightly during the latest four-week period.
Experts said the deformation is consistent with a pressurized source roughly 0.6 miles beneath the summit that is causing the volcano to swell from within.
The Martinique Volcano and Seismology Observatory said in an alert: 'The probability of eruptive activity in the short term remains low.
However, considering the observations accumulated over the past months and years, an evolution of the situation in the medium term (weeks to months) cannot be excluded.'
The alert level for Mount Pelée is currently at YELLOW, which means the volcano is showing signs of elevated unrest, an advisory level or decreasing activity after a higher alert.
Nearly all of the earthquakes recorded this week were shallow, striking between half a mile and just over one mile beneath Mount Pelée’s summit.
Experts noted that none of the earthquakes have been felt by people on the ground, as they have only reached a magnitude 1.
The tremors were concentrated inside the same network of superheated water and steam that has driven much of the volcano’s unrest since seismic activity began increasing in 2019. But scientists found that one earthquake stood out.
That tremor struck approximately three miles below sea level, just west of the volcano’s summit domes and significantly deeper than the main cluster.
The quake occurred in a critical zone between the bottom of Mount Pelée’s hydrothermal system and the upper reaches of the magma reservoir below.
Scientists closely monitor that area because earthquakes at such depths can be triggered by hot fluids and gases moving between the two systems.
One deep earthquake does not signal that an eruption is imminent, but repeated tremors in that zone could provide an important clue about what is happening beneath the volcano.
Meanwhile, the ground around Mount Pelée’s summit continues to swell outward.
Ground swelling is a sign of a volcano eruption because rising magma fills underground chambers, increasing pressure and pushing the surface upward.
It is currently moving at a rate of nearly half an inch per month, slightly slower than during the previous four-week period.
Scientists believe the swelling is being driven by a pressurized source approximately half a mile beneath the summit.
The slight slowdown is encouraging, but scientists will need to monitor the volcano for several more weeks before determining whether the pressure is truly easing.
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