Study Identifies Two Active Magma Reservoirs Beneath Nicaragua's Masaya Volcano

A new study has identified two active magma reservoirs beneath Masaya volcano in western Nicaragua, based on analysis of satellite radar imagery spanning 2018 to 2024. The findings, published in Geophysical Research Letters, provide insights into the shallow plumbing system of this persistently active basaltic volcano located near a large population center (ScienceAlert; DOI: 10.1029/2026GL123214).

Masaya is a shield volcano complex within a caldera approximately 6 by 11 kilometers in size, situated about 20 kilometers southeast of Nicaragua's capital, Managua, according to the Smithsonian Institution's Global Volcanism Program (volcano.si.edu). The researchers note that the volcano "sits within 20 km of 2 million people and is a popular tourist destination due to its lava lake," making understanding of its magma processes important for hazard assessment (ScienceAlert).

Modern activity at Masaya has primarily involved passive degassing, lava lake formation in the Santiago crater since late 2015, and occasional vent-clearing explosions, as described in the study. Despite its shield morphology typically associated with effusive eruptions of fluid basaltic lava, the volcano has a history of more explosive behavior, including multiple caldera-forming Plinian eruptions. It has not produced a major lava flow since 1772, with that event largely confined to the caldera (ScienceAlert; volcano.si.edu).

The team, led by researchers including Elizabeth Johnson, analyzed Sentinel-1 Interferometric Synthetic Aperture Radar (InSAR) time series data. They observed that the ground north of the Santiago crater subsided slightly from 2018 until mid-2022 before uplifting from mid-2022 to 2024. Concurrently, the area surrounding the crater showed consistent deflation throughout the period. Modeling of these deformation patterns indicates two distinct active magma chambers, in an arrangement the authors describe as "interestingly similar to what is inferred at Kīlauea" (ScienceAlert).

Both Masaya and Kīlauea are basaltic systems with semi-persistent lava lakes and occasional explosive summit activity. Previous research had suggested multiple magma sources beneath Masaya, but details of the plumbing system remained incomplete (prior study DOI: 10.1002/2017GL076769).

Chronic gas emissions from Masaya, particularly sulfur dioxide, regularly exceed World Health Organization air quality standards in surrounding areas, posing potential public health concerns in addition to eruptive hazards (ScienceAlert). The volcano has been nearly continuously active since the mid-16th century and attracts tourists, while fertile volcanic soils have supported nearby settlement.

The authors conclude that further long-term geodetic and modeling studies will enhance understanding of transitions between intrusive, effusive, and eruptive activity, supporting more effective hazard monitoring and mitigation at Masaya and similar lava-lake-hosting basaltic volcanoes (DOI: 10.1029/2026GL123214).