Researchers using satellite data found two magma chambers filling beneath Masaya volcano, known as the Mouth of Hell, though the study identified no immediate dangers for nearby residents.
Penn State University scientists tracked ground movement at Nicaragua’s Masaya volcano and reported clear signs that magma is shifting and accumulating below the surface. The active peak sits only 13 miles from Managua, a capital of two million people, and draws thousands of tourists each year to its lava-filled Santiago crater.
Daily Mail reporting on the new paper in Geophysical Research Letters describes a plumbing system more complex than earlier maps suggested, with one reservoir refilling after years of drainage and a second, shallower chamber also showing activity.
Lead author Lizzie Johnson put the stakes plainly.
"Having a thorough understanding of Masaya’s volcanic activity and its related hazards is critical."
The team relied on Sentinel-1 satellite passes that scan the site every 12 days and measure tiny rises and falls in the ground. Between 2018 and mid-2022, the area around the Masaya Central Reservoir, just north of Santiago crater, sank about 1.2 inches. From 2022 to 2024, that same ground began to lift.
Johnson explained what the pattern usually means.
"When it's subsiding, that means that there's probably magma draining away from the volcano, but once the ground starts uplifting again, that can mean that there's potentially new magma moving in."
At the same time, the ground directly around Santiago crater and its lava lake kept deflating across the full six-year window. That steady drop pointed researchers toward a second, shallower reservoir roughly 656 feet below the surface that is also active and losing volume.
Johnson tied the two signals together.
"This indicates that the plumbing system is more complex and could be due to decreasing magma in a second, shallower reservoir."
The study itself did not identify any immediate eruption threat. Masaya last produced a major lava flow in 1772. Over the past 50 years it has generated several explosions, and so far those blasts have caused no injuries.
That record is not the whole picture. The volcano’s persistent degassing regularly produces dangerously high concentrations of sulphur dioxide. Johnson noted the ongoing gas hazard even while the lava-flow history remains distant.
"Although Masaya last produced a major lava flow in 1772, its persistent degassing often produces dangerously high concentrations of sulphur dioxide volcanic gas."
Proximity keeps the risk live. Managua’s two million residents live within easy reach of any major change in activity. Tourists continue to crowd the Santiago crater overlook. A serious eruption in that setting would not be an abstract geology problem.
Co-author Dr. Young Cheol Kim stressed the value of steady observation rather than one-off snapshots.
"Doing continuous monitoring allows us to understand the baseline activity and identify if things are changing."
He added the obvious next step if the baseline shifts.
"And then if there is a need to warn people, we can do that in a timely manner."
The researchers want more measurements to sharpen the picture of how Masaya behaves and to improve eruption forecasts. The satellite record already shows the system is not simple: one chamber drained and then refilled, while a second shallow chamber deflated for years. That complexity is exactly why baseline data matters.
Volcanoes do not wait for convenient politics or perfect models. When magma moves under a capital and a tourist draw, the sober response is continuous measurement, clear public information, and no wishful thinking about the ground beneath people’s feet.
