Science1 publisher2 min readPublished
Modeling pins Ol Doinyo Lengai's 2024 bulge on a million cubic meters of new magma
D. Sarah Stamps's team attributes a short-lived swelling at Tanzania's Ol Doinyo Lengai to about 1 million cubic meters of magma roughly three kilometers down, a figure that comes out of numerical modeling of surface motion.
The Scientist · Science desk
What happened
- In 2024, D. Sarah Stamps' team detected and tracked a short-lived bulge in the ground around Ol Doinyo Lengai, an active volcano in northern Tanzania, and then set out to find its subsurface cause.
- The published answer is an influx of 1 million cubic meters of magma into an existing reservoir about 2.9 kilometers underground, a volume of roughly 400 Olympic-size swimming pools.
- Stamps said the amount is modest and not a cause for concern, and the account presents the episode as a demonstration that Virginia Tech's early-stage alert system for volcanic activity works.
- The monitoring rests on six GNSS instruments installed in 2016 that track horizontal and vertical surface motion to within 1 millimeter, two broadband seismic stations, and episodic benchmark surveys.
- Stamps said the volcano's last explosive eruption was preceded by a magnitude 5.9 earthquake, and that a significant quake followed by surface deformation changes would concern her more than this intrusion.
Compiled by The ScientistSomething wrong?How this is made
Why it matters
- capability Putting a depth and a volume on a passing bulge is what lets a monitoring group hand the Tanzania Geological Survey something specific before an explosive phase, since that agency is the one making evacuation calls.
- contradiction The paper's title places the inflation in the 2022-2023 uplift episode while the account of it dates the detection to 2024, so a reader cannot tell from the record which episode the million cubic meters belongs to.
- decision A detection only becomes an evacuation timetable once the delay between precursor and eruption is known, and Stamps said working out this volcano's time delay is part of why the team keeps monitoring.
- constraint Stamps said her team is the only one running continuous ground-based GNSS and consistent seismic monitoring at the volcano. If those stations stop, no second source carries the continuous ground record.
Surface motion is what the instruments record. The magma volume is inferred from it. "With as much certainty as we can get from numerical modeling, we found that the signal was due to an influx of magma into an existing magma reservoir about 3 kilometers (1.9 miles) underground," Stamps said [5]. The write-up attaches no uncertainty range to the volume [21].
Timing is harder to check. The paper appeared in Frontiers in Earth Science in September 2026 [20], about three years after the end of the uplift episode named in its own title and about two years after the detection as described [16][17].
The continuous network comes to eight stations in all [15], and Stamps said the team has "now collected over a decade of observations. We have a better understanding of what magma movements underground match what we observe over this time period" [14]. For the continuous instruments, that record runs about ten years to publication [19].
Usefulness depends on the discriminator that comes with a modeled volume. Stamps said that in this case "there's a little more magma being injected into a system that we know exists, but the detected magma does not appear to be moving closer to the crater" [7]. So the model is being asked for a location and a trend, not just a number, and validating a location and a trend on one episode is harder.
On the longer clock, Stamps said, "On average, there's an explosive eruption every 10 to 15 years. We do expect one within our lifetime, and we hope that our monitoring and modeling efforts will be worthwhile" [11].
What to watch
- Successive models placing the reservoir shallower over time, the second indicator Stamps named as concerning.
- Independent reproduction of the depth and volume from satellite geodesy. That would test the modeling chain against a second dataset.
- A reported interval between deformation onset and a modeled attribution, the interval an alert system's usefulness turns on.