Two hidden magma sources discovered beneath Nicaragua's Masaya volcano

Satellite data reveals complex plumbing system near capital, raising new questions about eruption forecasting

By LineZotpaper

Published20 October 2026

Read Time2 min

Scientists at Penn State have uncovered evidence of two previously unrecognized magma sources beneath Nicaragua's active Masaya volcano, a popular tourist destination that sits within 13 miles of roughly 2 million people. The discovery, based on six years of satellite observations and published in Geophysical Research Letters, reveals that the volcano's underground magma system may be considerably more complicated than previously understood, with separate reservoirs behaving in opposite ways.

Using interferometric synthetic aperture radar (InSAR) data from the European Space Agency's Sentinel-1 satellite, researchers tracked subtle changes in ground elevation around Masaya between 2018 and 2024. The measurements revealed that one part of the caldera initially sank before beginning to rise, potentially indicating fresh magma entering a deep reservoir. At the same time, the ground around the active Santiago crater and its lava lake continued to sink throughout the study period, suggesting a separate, shallower magma reservoir was losing magma.

"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," said lead author Lizzie Johnson, who earned her bachelor's degree in geosciences from Penn State in May. "At the same time, the area directly around the active Santiago crater deflated over the entire study period independently of the transition to inflation of the main reservoir. This indicates that the plumbing system is more complex and could be due to decreasing magma in a second, shallower reservoir."

Although Masaya last produced a major lava flow in 1772, it is closely monitored because of its persistent degassing, which often produces dangerously high concentrations of sulfur dioxide. Young Cheol Kim, who completed his doctorate in geosciences at Penn State this summer, emphasized the importance of continuous monitoring. "Doing continuous monitoring allows us to understand the baseline activity and see if things are changing," he said. "And then if there is a need to warn people, we can do that in a timely manner."

The researchers stressed that their observations did not indicate any immediate danger to surrounding communities. The findings, however, could improve hazard monitoring not only at Masaya but at other volcanoes with persistent lava lakes and complex underground magma systems.

Analysis

Why This Matters

Roughly 2 million people live within 13 miles of Masaya, and the caldera is a national park and major tourist destination. Understanding its magma system is essential for public safety and hazard preparedness.
The discovery of two distinct magma reservoirs behaving in opposite ways challenges existing models of how magma moves beneath volcanoes, potentially improving eruption forecasting for Masaya and similar volcanoes worldwide.
Elevated sulfur dioxide levels from persistent degassing already pose health risks; knowing the volcano's baseline activity helps distinguish normal behavior from signs of an impending eruption.

Background

Masaya is a geologically complex volcano near Managua, Nicaragua, featuring multiple overlapping craters and calderas. While it has not produced a major lava flow since 1772, it is one of the few volcanoes in the world with a persistent lava lake and continuous degassing. Scientists have studied Masaya for years, but the movement of magma through its underground reservoirs and passageways has remained poorly understood. The satellite-based InSAR technique allows researchers to detect tiny ground deformations that suggest changes in magma storage below.

Key Perspectives

Penn State researchers: The team, led by Lizzie Johnson and Young Cheol Kim, sees the two-reservoir system as evidence that Masaya's plumbing is more complex than previously thought. They emphasize that continuous satellite monitoring is essential to establish baseline activity and recognize when behavior departs from normal. Local authorities and communities: While the study does not indicate immediate danger, the findings underscore the need for ongoing hazard monitoring. Nicaragua's authorities must balance tourism at the popular national park with public safety, especially given the volcano's proximity to the capital. Volcanology community: The discovery has implications beyond Nicaragua. Other volcanoes with lava lakes and complex underground systems may exhibit similar dual-reservoir behavior. The study calls for further long-term geodetic and modeling studies to improve hazard mitigation globally.

What to Watch

Continued satellite observations of Masaya's deformation, particularly whether the shallow Santiago crater reservoir continues to deflate without causing an eruption.
Development of more detailed computer models linking the two magma reservoirs, which could clarify how magma moves during periods of unrest.
Whether similar dual-reservoir patterns are detected at other active volcanoes hosting lava lakes, such as those in Hawaii or the Democratic Republic of Congo.

Sources

Something strange is happening beneath a volcano near 2 million people · Latest Science News -- ScienceDaily

Checked

10 claims in this story checked against 1 source: 6 supported.

Show each claim

Partly supportedHeadline: scientists 'discovered' two hidden magma sources beneath Masaya. The source reports evidence of two previously unrecognized sources, not a definitive discovery.Latest Science News -- ScienceDaily: “Scientists at Penn State have uncovered evidence of two previously unrecognized magma sources beneath Nicaragua's active Masaya volcano”
SupportedAbout 2 million people live within 13 miles of Masaya.Latest Science News -- ScienceDaily: “approximately 2 million people live within 13 miles of the volcano”
SupportedThe separate magma reservoirs behave in opposite ways.Latest Science News -- ScienceDaily: “This would help explain why different sections of the same volcano moved in opposite directions.”
SupportedThe findings are based on six years of satellite observations and were published in Geophysical Research Letters.Latest Science News -- ScienceDaily: “Using six years of satellite observations, researchers tracked subtle changes in the ground around Masaya.”
Partly supportedThe shallower reservoir near Santiago crater was losing magma.Latest Science News -- ScienceDaily: “a shallower reservoir near Santiago crater may be losing magma”
SupportedJohnson: '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,'Latest Science News -- ScienceDaily: “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,”
SupportedJohnson: the area around Santiago crater 'deflated over the entire study period' and the plumbing system 'could be due to decreasing magma in a second, shallower reservoir'.Latest Science News -- ScienceDaily: “This indicates that the plumbing system is more complex and could be due to decreasing magma in a second, shallower reservoir.”
Partly supportedKim: 'Doing continuous monitoring allows us to understand the baseline activity and see if things are changing'.Latest Science News -- ScienceDaily: “Doing continuous monitoring allows us to understand the baseline activity and identify see if things are changing,”
SupportedThe researchers stressed that their observations did not indicate any immediate danger to surrounding communities.Latest Science News -- ScienceDaily: “The researchers emphasized that their observations did not reveal any immediate danger to communities surrounding Masaya.”
Not in the sourcesThe Sentinel-1 satellite was operated by the European Space Agency.Latest Science News -- ScienceDaily: “the Sentinel-1 satellite, which observes the volcano approximately once every 12 days”