It is considered the most dangerous volcano in Africa, but its monitoring has now been undermined. From its height of 3,470 meters, Nyiragongo, located in the Democratic Republic of Congo, about fifteen kilometers north of the city of Goma and Lake Kivu, and west of the Rwandan border, is usually monitored by twelve stations of the Goma Volcanological Observatory (OVG). Today there are only five left.
The other seven, stations responsible for studying earthquakes linked to the movements of magma in the ground, were in fact closed and dismantled as a security measure due to the occupation of the areas where they were installed by the rebels. of the M23.
This rebel militia, mainly made up of Tutsis and supported according to the UN by neighboring Rwanda, took up arms again at the end of 2021 after several years of dormancy and has since seized large parts of the North Kivu region, in the eastern DR Congo.
While Kinshasa accuses Rwanda and its M23 "proxies" of wanting to take control of the minerals of eastern Congo, the M23 claims, for its part, to defend a threatened segment of the population and demands negotiations that the DR Congo refuses, ruling out discussing with “terrorists”.
Since October 2023, clashes have intensified, particularly in the Nyiragongo region, where the eponymous volcano is located, between the M23 and local fighters, auxiliaries of the Congolese army.
Also read: What are the main armed groups active in eastern DR Congo?
Placed on yellow alert - the alert level at which it was maintained on March 18 by the OVG - the Nyiragongo must be subject to reinforced surveillance, just like its twin in the Virunga park: the Nyamulagira.
The OVG, deprived of part of its observation data, is worried. Just like the populations who live nearby, marked by the last eruption of Nyiragongo, in May 2021. A surprise that even the Observatory could not have seen coming. The lava flows caused the death of 32 people and displaced more than 500,000 people.
“Every time the [security] situation deteriorates, volcano monitoring suffers”
“Some of our stations found themselves in areas with reduced security, so we preferred to uninstall them and bring them back to the OVG for their safety,” explains Charles Balagizi, scientific director of the OVG at the microphone of TV5 Monde, specifying that the seven uninstalled stations are seismology stations. Those for geochemistry (making it possible to monitor gas emissions) and those used to control soil deformation are, for the moment, still operational.
But without these seismology stations “we can have observation biases”, explains to France 24 Benoît Smets, volcanologist at the Royal Museum for Central Africa (AfricaMuseum), a Belgian scientific research institute, and at the University of Brussels , who worked for several years alongside the OVG. “When we want to locate the source of earthquakes, the fact of no longer having a closed system, with instruments all around the volcano, increases the location error, and we can underestimate or overestimate its activity” .
A situation which is, however, not unprecedented. “Each time the [security] situation degenerates, the monitoring of volcanoes suffers, because it is necessary to protect the equipment which is quite expensive, and to ensure the safety of the sentries who guard the monitoring stations,” adds the researcher, specialist in volcanoes in this region plagued by armed conflicts for 30 years.
“On all the activities that are in the militarized zone, we no longer control anything 100%,” adds Georges Mavonga, general director of the OVG, to TV5 Monde, indicating an area in which three stations were installed which contributed to monitoring of Nyamulagira.
In its latest information bulletin, the OVG also specifies that during the study period (from March 8 to 16, 2024), the seismo-volcanic activity concentrated on either side of the large fracture connecting the two active volcanoes, "was more concentrated in the Nyamulagira field than in that of Nyiragongo".
“The volcano is active, no immediate danger, the population can lead a normal life,” the notice board detailing the alert levels set up by the OVG tells the people of Goma.
The yellow level at which Nyiragongo has been maintained does not in fact indicate an imminent risk of eruption. Based on the same color code (green, yellow, orange, red) as that used for other volcanoes, in Hawaii or on Reunion Island, it makes it possible to specify to the population that the volcano is active. “There is nothing that directly threatens the population, but as the volcanoes are active, we must remain vigilant and monitor their activity,” specifies Benoît Smets.
But three years after the last eruption of Nyiragongo, scientists remain vigilant. As of 2021, the volcano had only shown an obvious precursor shortly before erupting.
ReportersIn Goma, the issue of the Nyiragongo volcano remains burning
“An active and unpredictable volcano in a very densely populated region”
Typically, volcanic eruptions involve a build-up of pressure and a surge of magma toward the surface. Processes that produce geophysical and geochemical signals that can be detected and interpreted as eruption precursors.
But “on May 22, 2021, Mount Nyiragongo, an open-vent volcano (mouth of the volcano through which the lava comes out, Editor’s note) with a persistent lava lake perched [at the top of] its crater, shook up this interpretation,” explained the researchers from the OVG and the AfricaMuseum in a publication published in August 2022 in the journal Nature.
A precursor is a detected anomaly which can lead to an eruption, explains Benoît Smets. “In 2021, nothing had happened 30 minutes before the eruption, so it was impossible to detect in advance that the volcano was heading toward an eruption.”
Also, he adds, "the problem of lacking functional stations is that we risk not seeing any change coming which would indicate the arrival of a dangerous eruption".
General view taken on May 22, 2021 from the island of Tchegera, outside Goma, on Lake Kivu, eastern DR Congo, showing the eruption of the Nyiragongo volcano. © Alex Miles, AFP
Aerial view showing lava flows that engulfed buildings in the village of Bushara, near Goma, on May 23, 2021, after the volcanic eruption of Mount Nyiragongo, which sent thousands of people fleeing overnight in the eastern DR Congo. © Justin Katumwa, AFP
An effusive volcano, Nyiragongo - just like its neighbor Nyamulagira - is characterized by its "lava lake", a basin filled with molten lava which remains liquid. “These volcanoes are therefore almost continuously erupting,” explains Benoît Smets.
The activity of this lava lake is punctuated by eruptions on the flanks of the volcano which create flows. This is particularly what is monitored when yellow vigilance is implemented, specifies the researcher. “This involves monitoring whether eruptive activity threatens the population, in inhabited areas, through cracks that open on the flanks of the volcano emitting lava flows.”
The composition of Nyiragongo, making its lava extremely fluid, produces some of the fastest flows in the world. Those of Nyamulagira, slower but more abundant, can spread over several tens of kilometers in length.
But the major difference between these two volcanoes in the Great Rift Valley is the threat they pose, or not, to populations. Nyamulagira is located in the middle of Virunga Park, further threatening the fauna and flora. For Nyiragongo, one of the most active and dangerous in Africa, "the danger comes from the fact that a population of more than a million inhabitants lives at its feet", recalls Benoît Smets. “We therefore have a mix between a very active and unpredictable volcano, and a very densely populated region.”
Before 2021, Nyiragongo experienced two major eruptions: in January 1977 - it began 50 years earlier - and in January 2002. During this last eruption, 250 people died and 120,000 were left homeless. shelter in Goma.
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