Satellites Reveal Two Hidden Magma Sources Under Nicaragua's Masaya Volcano

Scientists at Penn State say satellite measurements point to two previously unrecognized magma sources beneath Masaya, an active volcano in Nicaragua known for its lava lake. The finding suggests the volcano's plumbing is more complicated than researchers had thought, according to the university and ScienceDaily.

The result matters because about 2 million people live within 13 miles of the volcano, which is also a popular tourist destination. The researchers say a better picture of what is happening underground could eventually improve monitoring and eruption forecasting.

What the satellites detected

The team analyzed six years of data from the Sentinel-1 satellite, which observes Masaya about once every 12 days. The results were published in Geophysical Research Letters.

Between 2018 and 2024, the ground inside Masaya's caldera first sank and later began to rise. The researchers say this shift could reflect changes in how much magma is stored deep underground, and that fresh magma may have entered a deep reservoir. In general, the ground can sink when magma drains from a reservoir and can rise when new magma adds pressure.

The area around the active Santiago crater and its lava lake behaved differently. It continued to sink throughout the study period. The researchers interpret that as a sign of a separate, shallower magma reservoir acting independently of the deeper one.

How the technique works

The team used interferometric synthetic aperture radar, known as InSAR. The method sends microwave signals from a satellite toward the ground and compares the returning signals taken at different times. Changes in the distance between satellite and surface reveal where the ground is rising or sinking, even by very small amounts.

Radar can collect measurements through clouds, which is a particular advantage in tropical regions such as Nicaragua. Young Cheol Kim, who completed his doctorate in geosciences at Penn State this summer, said cloud penetration is important because many volcanoes sit in tropical areas with frequent cloud cover. The approach lets scientists study processes far below the surface without observing the magma directly.

Why Masaya is closely watched

Masaya sits near Managua, the Nicaraguan capital, and has multiple overlapping craters and calderas. Calderas are large depressions that generally form when the ground collapses after magma leaves an underground chamber.

Lead author Lizzie Johnson, who earned her bachelor's degree in geosciences from Penn State in May, noted that Masaya last produced a major lava flow in 1772. Even so, she said, its steady release of gas often creates dangerously high levels of sulfur dioxide. That gas is potentially harmful and is released when magma is near or at the surface. The researchers say elevated concentrations can create hazardous conditions for visitors and nearby communities even without a major eruption. The caldera is a national park.

Scientists have studied Masaya for years, but the movement of magma through its reservoirs and passageways remains poorly understood, the researchers said. Those systems can change over time, which makes it hard to know exactly what is happening below.

Why it matters for people near the volcano

For residents and visitors, the practical value lies in earlier and better-informed warnings. Kim said continuous monitoring helps scientists establish what normal activity looks like so they can spot changes that might signal heightened activity or a possible eruption. If a warning is needed, he said, it can then be issued in a timely manner.

Johnson said the observations help scientists understand how magma moves beneath Masaya and may improve monitoring and forecasting in the future. The work does not, by itself, predict an eruption. It adds to the understanding of how the volcano's shallow and deep reservoirs may be connected or may operate separately.

What remains uncertain

The interpretation rests on ground movement seen from space, not on direct observation of magma. The researchers describe the deep-reservoir explanation as a possibility and say scientists "believe" the changes reflect shifting magma storage. The study covers 2018 to 2024, and the researchers say magma systems can change over time, which is why they stress continued monitoring.

Around Prague, based on reporting by ScienceDaily