Two Hidden Magma Reservoirs Found Beneath Nicaragua's Masaya Volcano

"Cloud penetration is important for volcanoes because many of them, like Masaya, are in tropical areas where there is often cloud cover," explained Young Cheol Kim, who completed his doctorate at Penn State this summer. "When we look at all the different satellite images across multiple years, we can see how the distance between the satellite and the ground changes, where it is uplifting or subsiding."

Six years of that. No drilling required.

Why two reservoirs instead of one?

The pattern forced the conclusion. Early in the study period, the caldera floor subsided — likely magma draining away. Later, the same area began to rise, suggesting fresh magma arriving from a deeper source. But Santiago crater's surroundings deflated continuously, ignoring the switch entirely.

"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," Johnson said. The independent deflation near Santiago, she added, "indicates that the plumbing system is more complex and could be due to decreasing magma in a second, shallower reservoir."

So the model, and it remains a model: a deeper source feeding the main reservoir, and a separate shallow reservoir near Santiago that's losing magma. Words like "could" and "potentially" carry real weight here. Nobody has directly imaged these reservoirs. The inference rests on surface deformation patterns, which other processes can sometimes mimic.

Why Masaya deserves the attention anyway

Masaya sits near Managua, Nicaragua's capital. It's a national park and a tourist magnet, drawing visitors to its persistent lava lake. Its last major lava flow dates to 1772, which sounds reassuring until you consider its constant degassing — the volcano regularly releases high concentrations of sulfur dioxide, a harmful gas, even without any eruption.

"Having a thorough understanding of Masaya's volcanic activity and its related hazards is critical as around 2 million people live near Masaya," Johnson said.

Kim framed the monitoring logic simply: continuous tracking establishes the baseline, so scientists can spot deviations and, if needed, "warn people in a timely manner."

What's still missing

Plenty. The study covers six years — a blink for a volcano. The authors themselves call for "further long-term geodetic and modeling studies" before anyone claims effective hazard mitigation, at Masaya or at other lava-lake volcanoes like it. The links between these underground reservoirs and what actually happens at the surface remain unproven.

There's also a human footnote worth a line. Johnson did this work as an undergraduate honors thesis in Christelle Wauthier's research group before starting a Ph.D. at the University of Hawaii at Manoa, where she'll now image beneath Kilauea using seismic waves. The research was supported by National Science Foundation awards 1945417 and 2523375.

Two reservoirs, six years of radar, zero confirmed eruptions foretold. A solid step forward — and, as the authors admit, only a step.