On the evening of May 22, 2021, the Nyiragongo volcano erupted, leaving the residents of Goma no time to understand what was happening. Less than 40 minutes elapsed between the first abnormal tremors and the appearance of lava flows, according to research from the Royal Museum for Central Africa.
This speed, unusual even for such a closely monitored volcano, raises a fundamental question about the ability of alert systems to protect a city of over a million people.
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Nyiragongo: shallow magma storage that changes the game
Most articles dedicated to Nyiragongo remind us of its affiliation with the East African Rift and the exceptional fluidity of its lava. These elements have been known for decades. What is less understood is the precise mechanism that triggered the 2021 eruption.
A study published in 2025 in the Journal of Volcanology and Geothermal Research describes a stress change of about 10.5 MPa as a direct triggering factor. Specifically, researchers observed a significant increase in b-sismic values (an indicator of micro-fractures caused by the rise of magma), followed by a sharp drop just before and during the eruption.
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This scenario reflects a rapid transition from the accumulation of mechanical stress to its sudden release. The magma was already stored at a very shallow depth, which explains the almost total absence of classical precursory signals. For seismologists, this type of configuration makes forecasting extremely difficult, as traditional models rely on weeks or even months of detectable anomalies.
Field reports diverge on this point: some local volcanologists claim to have noted weak signals in the days prior, while others believe that the available data did not allow for a conclusion of an imminent eruption. This uncertainty fuels a scientific debate that goes far beyond the case of Nyiragongo.
Goma Volcanological Observatory: monitoring under pressure
To understand the eruption of the Nyiragongo volcano in Congo, it is also necessary to examine the conditions under which the Goma Volcanological Observatory (OVG) was operating at the time of the events.
The OVG suffered from chronic underfunding before the 2021 eruption. Several of its seismic stations were out of service due to lack of maintenance or spare parts. The security context in North Kivu, marked by the presence of armed groups in areas near the volcano, also complicated access to field equipment.
The World Bank had financed part of the monitoring stations. After the 2002 eruption, the observatory received a renewed international focus, but this support gradually diminished over the years. By 2021, the observatory was operating with resources far below the necessary standards for a volcano of this danger level.
This surveillance deficit had direct consequences on the alert chain. The cascading malfunctions, documented by several media outlets after the disaster, show that the problem was not only technical but also institutional, linked to tensions between the central government of the DRC, provincial authorities, and international partners.
Impacts of the eruption on the population of Goma and North Kivu
The lava flow poured out to the northeast of Goma, destroying homes, school infrastructure, and the city’s main water reservoir. The figures reported by UNICEF allow us to gauge the extent of the damage:
- More than 3,500 houses destroyed, as well as 7 schools and 4 health centers, according to the field assessment conducted the day after the eruption.
- Approximately 234,000 people displaced in the following days, mainly towards Sake, Minova, and Rutshuru, east of Goma.
- Nearly 200,000 people deprived of access to drinking water, in a city already weakened by recurring epidemics (cholera, measles).
The massive displacement of people compounded an existing humanitarian crisis. North Kivu was already hosting hundreds of thousands of internally displaced persons due to armed conflict. The eruption exacerbated the pressure on overcrowded shelter sites and health services on the brink of collapse.
UNICEF deployed its rapid response mechanism in Sake to distribute emergency items (buckets, jerry cans, hygiene items, drinking water). The humanitarian response was swift, but it highlighted Goma’s dependence on international aid for fundamental needs such as access to water.
Testimonies and communication crisis after the Nyiragongo eruption
Several testimonies collected after the eruption describe a common scene: families awakened in the middle of the night by red glows and tremors, with no official evacuation instructions. JRS (Jesuit Refugee Service) documented the difficulties families faced in the following days, including loss of housing, separation from loved ones, and total lack of bearings.
Communication between the OVG, local authorities, and the population has faced severe criticism. Early warning channels, when they existed, did not function in a coordinated manner. Some residents learned of the eruption through social media or by simply observing the sky, not through an official message.
This communication failure is not unique to 2021. During the 2002 eruption, which destroyed part of downtown Goma, similar gaps had been identified. The available data do not allow us to conclude that significant structural progress has been made between the two events on this specific issue.
Volcanic risk in Goma: a threat that remains active
Nyiragongo permanently holds a lava lake in its crater, one of the few in the world alongside those of Erta Ale in Ethiopia and Erebus in Antarctica. This lava lake is an indicator of continuous magmatic supply, meaning that the risk of a new eruption is not hypothetical but structural.
The immediate proximity of Goma, whose urbanization has expanded towards the slopes of the volcano over the decades, amplifies vulnerability. Unlike other dangerous volcanoes located in sparsely populated areas, Nyiragongo directly threatens a dense urban area, in a context of armed conflict that limits evacuation capabilities.
The data from the 2025 study on shallow magmatic storage reinforce a finding: Nyiragongo can erupt with very few precursory signals. As long as the observatory does not have a dense monitoring network, sustainably funded and independent of security fluctuations, the population of Goma will remain exposed to a risk that science can describe but not yet reliably anticipate.