Satellites find two magma reservoirs under Nicaragua’s Masaya volcano

Spanish colonists called it the mouth of hell. Masaya, a volcano in western Nicaragua, has a crater that has glowed with a lava lake on and off for centuries, and about 2 million people live in the region around it. New research suggests what’s happening underneath is more complicated than anyone thought.

A Penn State-led team found evidence of at least two separate magma reservoirs beneath Masaya, behaving in different ways, according to Penn State. The study, published in Geophysical Research Letters, was summarized this month by ScienceDaily.

Watching the ground breathe

The researchers didn’t drill into the volcano. They watched it from space. Using six years of radar data from the European Sentinel-1 satellites, from 2018 to 2024, they tracked tiny rises and falls in the ground, Gizmodo reported.

In plain terms: when magma collects underground, the surface above it swells slightly. When magma drains away or cools, the surface sinks. Satellites can measure those changes down to a fraction of an inch, which turns a volcano’s surface into a kind of pressure gauge.

Two chambers, two stories

Over the central reservoir, about 3 kilometers down, the ground sank roughly 3 centimeters from 2018 to mid-2022, then rose through 2024, according to Gizmodo. The researchers read that rise as possibly reflecting fresh magma entering the deeper store, according to Around Prague’s science coverage.

Around the active Santiago crater, though, the ground kept sinking for the whole period. The team interprets that as a separate, much shallower reservoir, roughly 200 meters deep, acting independently of the deeper one, according to the same reports.

That’s the “double trouble” in Penn State’s headline. One reservoir may be filling while the other drains. A volcano with two plumbing systems doing different things at once is harder to read, and harder to forecast.

What the study did not show

This is the part that matters most for the people living nearby. The authors say the findings do not establish that an eruption is imminent, according to The Sunday Guardian. Some coverage notes that renewed lava activity is possible if inflation continues, and that substantial further inflation may be needed before a return to past lava-lake episodes, according to one report.

Satellite data also has limits. Ground movement shows that something is changing underground, but it doesn’t by itself reveal exactly how much magma is moving or what it will do next. Interpreting a few centimeters of uplift requires models, and models carry assumptions. A single study, however careful, is a starting point for monitoring rather than a prediction.

Why a second chamber matters

Volcano monitoring depends on understanding a system’s plumbing. If scientists assume there’s one reservoir and there are actually two, they might misread the signals: seeing sinking near the crater and concluding the volcano is calming, while a deeper reservoir is quietly refilling.

That’s the practical value of the work. It gives Nicaraguan monitoring agencies a better map of what to watch, and a reason to keep watching both layers. Masaya is one of the most closely studied volcanoes in Central America precisely because it is active and close to large populations.

It also changes the questions scientists will ask next. If the deeper reservoir is refilling, how fast? Is it feeding the shallow one, or are they truly separate? Answers will come from years more data, combined with gas and seismic measurements on the ground. The study’s real contribution is to show where to look.

From the rim

Masaya is also a tourist attraction. Visitors drive up to the crater rim to look down into the glow, and the national park around it is one of the country’s best-known destinations. For guides, park workers and the towns nearby, the volcano is both a livelihood and a hazard, and research like this is part of how those two things are balanced.

Masaya’s hazards are not only lava. The volcano is known for releasing large amounts of volcanic gas, which can affect air quality and crops downwind. Understanding how magma moves beneath it helps explain those emissions, too.

The cheap eye in the sky

There’s a broader story in how this research was done. Sentinel-1 data is freely available, which means scientists can monitor volcanoes in countries that can’t afford dense networks of ground instruments. A team in Pennsylvania can track a volcano in Nicaragua for six years without setting foot on it.

That doesn’t replace people on the ground: seismometers, gas sensors and local experts who know the volcano’s moods. But it adds a layer of watching that didn’t exist a generation ago.

The mouth of hell, it turns out, has at least two throats. The research doesn’t say what they’ll do next. It says, clearly, that both are worth watching.

Sources

• Penn State: two active magma reservoirs indicated at Masaya
• ScienceDaily: something strange beneath a volcano near 2 million people
• Gizmodo: “mouth of hell” volcano may hide a second magma chamber
• Around Prague: satellites reveal two magma sources
• The Sunday Guardian: what the satellite data reveals about eruption risks
• Above the Norm News: hidden magma reservoirs expanding

Photos

• “Volcano Pacaya In Guatemala, Central America” by GreensandBlues, Envato Elements (featured image)