A 2026 study of satellite-measured ground movement modeled a shallow magma-system source about 200 meters beneath Santiago crater at Masaya Volcano in Nicaragua. The result is an inference from surface deformation—not a satellite image of molten rock or proof that an eruption is imminent. The paper also modeled a deeper source beneath the caldera, showing that the volcano’s activity cannot be reduced to a single underground reservoir.
What did scientists find beneath Masaya?
Johnson and colleagues analyzed Sentinel-1 Interferometric Synthetic Aperture Radar (InSAR) observations from January 2018 through February 2024. Their model accounts for the observed ground deformation with two sources: a shallow one beneath Santiago crater, at about 200 meters depth, and a deeper one beneath the center of Masaya’s caldera, at about 3,200 meters. The 2026 paper describes the satellite time series and the model results.
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The shallow source is not an entirely new idea. The study builds on earlier work that had inferred a source in this location; its contribution is a newer analysis modeling both shallow and deep sources over the observation period. EarthScope Consortium’s explainer describes the shallow source as a second inferred magma reservoir at a depth of 200 meters.
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How can satellites infer something underground?
InSAR compares radar observations collected at different times to detect small changes in the distance between the ground and a satellite. Researchers use the resulting surface-deformation patterns to fit geophysical models. In this case, the authors used point-source models to represent sources that can account for the measured movement.
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So “reservoir” is an interpretation of a modeled deformation source, not a directly observed chamber with confirmed walls or a measured pool of molten rock. The approximately 200-meter figure is the modeled source depth; it is not a direct measurement of a chamber boundary. The satellite data record surface change, and the subsurface explanation depends on the model used to interpret it.
How did the shallow and deep sources change?
The modeled volume changes differed between the two sources and the study’s two time intervals:
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| Modeled source | Location and depth | 2018–2022 modeled volume change | 2022–2024 modeled volume change |
|---|---|---|---|
| Shallow source | Beneath Santiago crater; about 200 m | Decrease of about 4,000 m³ | Decrease of about 6,000 m³ |
| Deeper source | Beneath the caldera center; about 3,200 m | Decrease of about 1.3 × 10⁶ m³ | Increase of about 4.5 × 10⁵ m³ |
These are model-derived changes reported by Johnson et al. in the 2026 study, not direct measurements of magma volume. The authors interpret the deeper source’s increase during 2022–2024 as inflation associated with new magma supply from depth. During the same interval, the shallow source’s modeled volume continued to decrease.
Does the result mean Masaya will erupt soon?
No. The modeled inflation at depth is evidence about subsurface change, but by itself it does not forecast an eruption or establish its timing. The paper says more inflation may be needed before renewed effusive vent activity. The findings support monitoring and interpretation of Masaya’s magma system; they do not support calling an eruption imminent.
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What the study establishes—and what it does not
- It establishes: Sentinel-1 observations from January 2018 to February 2024 showed deformation patterns that the authors modeled using shallow and deep sources.
- It estimates: the sources’ locations, depths, and volume changes within that model.
- It does not directly show: magma underground, the exact shape or boundaries of a chamber, or a guaranteed future eruption.
The result is therefore best understood as a geodetic inference about how Masaya’s subsurface system changed—not as a satellite photograph of a newly discovered, precisely bounded magma chamber.
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