NISAR observations of how magma moved beneath Ethiopia’s volcanoes
image: A comparison of pre- and post-eruption optical images shows two distinct new collapse pits, one situated within the crater and the other along its rim.
Credit: Xu, W., Bai, C., Luo, X., Wang, X., Xie, L., Jiang, H., & Xu, X.
Magma moving beneath a volcano can make the ground rise, sink or shift sideways. Measuring these changes gives scientists clues about where magma is stored and how it travels.
A study published in Geodesy and Geodynamics used satellite radar to examine the November 2025 eruption of Hayli Gubbi in Ethiopia’s Afar Depression. Hayli Gubbi and nearby Erta Ale are separate volcanoes within the same volcanic zone, where three tectonic plates are pulling apart.
The research is among the first to use the NASA–ISRO Synthetic Aperture Radar mission, or NISAR, to investigate an eruption. Radar satellites send signals to the ground and record their return. Comparing measurements from different times can reveal movements as small as a few centimeters. A single satellite, however, cannot show the full direction of movement.
To address this issue, the researchers combined NISAR’s left-looking radar view with right-looking observations from Europe’s Sentinel-1 satellites to reconstruct ground movement in three dimensions. Like photographs taken from different angles, the combined observations allowed the team to measure movement from east to west, north to south, and up or down. The findings show how three-dimensional satellite measurements can reveal hidden magma pathways and eruption-related faulting, supporting monitoring and hazard assessment across volcanic rift zones.
“By viewing the volcanoes from complementary directions, we reconstructed the three-dimensional deformation field and measured all three components of ground movement at centimeter scale,” says corresponding author Wenbin Xu from Central South University, China.
Although the eruption occurred at Hayli Gubbi, the strongest ground movement was detected at Erta Ale. “Images showed two new collapse pits and cracks at Hayli Gubbi, while Erta Ale’s summit crater partially collapsed. Radar data showed the ground at Erta Ale sinking and moving inward,” Xu shares.
The researchers linked this pattern to two shallow dikes beneath Erta Ale. “A dike is a steep crack that stores or transports magma, Xu explains. “When magma drains from it, the surrounding rock may contract and the surface above may sink.”
Notably, both dikes were centered about 1 km underground and resemble structures involved in earlier eruptions, suggesting they are persistent parts of the area’s magma network.
Stress changes associated with the eruption also appear to have reactivated nine faults near Erta Ale. Compared with a larger eruption earlier in 2025, the November event was more localized and relied mainly on shallow magma storage. The researchers suggest that deep magma involvement may be associated with more extensive dike propagation and stronger tectonic activity, while shallow reservoirs may produce smaller, concentrated events.
“NISAR adds an important new perspective for observing volcanoes that are difficult to monitor from the ground,” Xu says. “Combining multiple radar missions could improve our ability to distinguish how different eruptions develop.”
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Contact the author:
Wenbin Xu (School of Geosciences and Info-Physics, Central South University), Changsha, China
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