NISAR observations of how magma moved beneath Ethiopia’s volcanoes
image: (a) Location of the Erta Ale and Hayli Gubbi volcanoes. The crater’s rims of Erta Ale are outlined by black ticked lines. Topographic contours are shown at 100-m intervals. Inset: Red box indicates the study area. Blue and pink boxes indicate the data coverage of Sentinel-1 and NISAR, respectively. Yellow line denotes the plate boundary [31]. Black arrows represent GPS velocities in the ITRF2014 reference frame [32]. (b-e) Pre-eruption Sentinel-2 optical image zoom in the northern caldera of Erta Ale and Hayli Gubbi. Post-eruption Sentinel-2 and Landsat-9 optical images show surface changes and collapse pits in (c–d) Erta Ale and (f–g) Hayli Gubbi. Red dashed polygons and white dashed lines indicate the newly formed pits and fractures.
Credit: 10.1016/j.geog.2026.06.002
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.
However, a single satellite 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.
“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,” said 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.
The researchers linked this pattern to two shallow dikes beneath Erta Ale. A dike is a steep crack that stores or transports magma. When magma drains from it, the surrounding rock may contract and the surface above may sink. 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 said. “Combining multiple radar missions could improve our ability to distinguish how different eruptions develop.”
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.
title: NISAR observations of contracting dike-driven crustal deformation during the 2025 Hayli Gubbi Eruption, Afar
Journal Name: Geodesy and Geodynamics