Mysterious Movements Detected in Nicaragua's Masaya Volcano Threatening Millions

Scientists have uncovered a perplexing phenomenon beneath one of Central America’s most active volcanoes, Nicaragua’s Masaya. A recent six-year satellite investigation reveals that two magma reservoirs located under the volcano are behaving in opposite ways, complicating efforts to predict potential eruptions and posing risks to millions of nearby residents.

The deeper reservoir, situated approximately two miles below the surface, has been expanding since mid-2022, suggesting an influx of molten rock from deep within Earth. However, a second, shallower reservoir located just 650 feet beneath Masaya’s active Santiago crater has continued to contract throughout the observation period.

This dual behavior was discovered by researchers at Pennsylvania State University using radar observations collected by the European Space Agency’s Sentinel-1 satellites between January 2018 and February 2024. The team employed interferometric synthetic aperture radar (InSAR) technology, which measures minute changes in ground movement to track volcanic activity.

The findings, published in Geophysical Research Letters, highlight a previously unrecognized complexity within Masaya’s underground magma system. This dual reservoir behavior complicates efforts to anticipate eruptions and poses significant challenges for volcano monitoring and hazard assessment.

Masaya is situated just 12 miles southeast of Managua, the capital city with a population of around two million people living within a 12-mile radius. The volcano's persistent degassing often produces dangerously high concentrations of sulfur dioxide, posing a continuous threat to public health.

Lizzie Johnson, lead author and Penn State graduate, emphasized in a press release that understanding Masaya’s volcanic activity is crucial due to its proximity to densely populated areas and tourist attractions. Despite the last major lava flow occurring in 1772, the volcano remains an active site of both scientific interest and public concern.

Historically, Masaya has experienced powerful prehistoric explosive eruptions and a significant lava flow in the late 18th century. More recently, it has been known for its persistent sulfur dioxide emissions and intermittent lava lake within Santiago crater, which draws tourists to the surrounding national park.

The satellite data revealed that from January 2018 to mid-2022, the central portion of Masaya’s caldera moved approximately 1.2 inches away from the satellites, indicating a gradual loss of pressure in an underground magma reservoir. However, around mid-2022, this trend reversed as the ground began moving toward the satellites, signaling renewed expansion within the deeper reservoir.

Computer modeling placed the expanding reservoir at about 10,500 feet beneath the caldera and estimated it had lost roughly 1.3 million cubic meters between 2018 and 2022 before gaining approximately 450,000 cubic meters through early 2024.

These findings underscore the need for continued research into volcanic systems like Masaya to better understand their complex behaviors and improve eruption prediction models. The dual reservoir dynamics observed at Masaya could have implications for monitoring similar volcanoes worldwide, potentially enhancing global volcano risk management strategies.