Seismic and ground deformation activity continue to slow down
This is good news for Goma and its surroundings: the likelihood of a new eruption in the near future continues to decrease, although vigilance remains high.
Volcanic crisis continues, easing slowly, while possible cholera outbreaks add to worries
It can only be hoped that the suspected (and likely) magma intrusion underneath will simply stop and eventually cool without breaking towards the surface and cause an eruption.
At any rate, it would be too early to call the volcanic crisis be over: "earthquakes and ground deformation data continue to indicate the presence of magma under the urban area of Goma with an extension under Lake Kivu", according the the latest update of the dedicated site of Belgium's Royal Museum for Central Africa.
According to the latest data, the seismic and GPS deformation data suggest that the magma intrusion at depth has either halted, paused or at least shifted to (less worrying) locations towards the north, according to the institute's update. Whether deformation is occurring at the floor of Lake Kivu itself is unfortunately impossible to detect at the moment.
More measurements are on the way and will allow scientists in the near future to better evaluate the situation, hopefully allowing the displaced people from large parts of Goma to return safely.
In the meanwhile, the human situation of people on the ground remains very difficult. More than 230,000 displaced people are crowding neighboring towns and villages. Lack of clean water, food and medical supplies, as well electricity in parts of Goma, are creating catastrophic conditions in many places. To add to all this misery, health authorities are worried about outbreaks of cholera - at least 35 suspected cases have been found so far.
Plus de 230 000 personnes sont toujours déplacées suite à l'éruption du volcan Nyiragongo en République démocratique du Congo.Les humanitaires sont mobilisés & la réponse s'intensifie alors que 35 cas suspects de choléra ont été identifiés.Le pointhttps://t.co/aAC6NLhEI9 pic.twitter.com/YLQvb9wUPN— ONU humanitaire (@UNOCHA_fr) June 1, 2021
Situation remains tense
Several scientists, notably from Italy's INGV, are arriving in the area to help the underfunded Goma Volcano Observatory staff monitoring the volcano and asses the situation.
In the meanwhile, several detailed maps of the recent lava flows and their impact have been published by various agencies, e.g.:
Nyiragongo volcano (DR Congo): fears of potential catastrophic eruption trigger partial evacuation of Goma City
The reason scientists worry are both a lack in precise monitoring data, the potential of large impact of an eruption, and the continuing earthquakes that rattle the area around Goma and Gyseni, as well as ground cracks in and around Goma, which might indicate that magma is accumulating beneath the area and could well lead to a new eruption.
More than 200 tremors have been recorded in the past 2 days. According to some unconfirmed posts on social media, some of the new ground cracks expose glow beneath (likely from hot gasses if true).
According to latest findings of researchers, the recent eruption indeed drained the lava lake, but according to some sources, it has already partially refilled (or did not drain entirely).
Ash plumes are rising from the crater of the volcano, likely from internal collapses after the (partial?) drainage of the lava lake. Combined with the intense degassing activity, they create dangerously contaminated acid rain and people are urged not to use rain water for cooking, washing etc if any possible.
From a summary on reliefweb:
"Researchers observing the volcano have a limited sense of the current risk level; the situation remains highly unpredictable as several warning signs emerge of the risk of a new eruption in the next few days, including multiple cracks on the ground, emission of gas and the worrying fact that the Kivu crater seems to have refilled very quickly, indicating another possible eruption. The IRC is preparing a response to meet the escalating humanitarian needs in collaboration with the government and other NGOs. There is now a desperate need for an increase in funding through support from the international community."
There are several scenarios how the situation might evolve (adapted from Nyiragongo : de 3 scénarios présentés par l'OVG, une prochaine éruption du volcan est inévitable):
A new eruption of Nyiragongo on its southern flank, where fractures open in the area of Goma and Gisenyi cities. Lava flows would likely destroy destroy part of them.
An eruption of Nyiragongo volcano on its southern flank, but with fissures INSIDE the city and extending close to Kivu lake. Large volumes of lava destroy part of the cities of Goma and Gisenyi and reaches the lake. The amount of lava that would flow into the lake is insufficient to raise the temperature of the deep water over the entire lake by at least 1° C, there will be no lake overturn and eruption of deadly dissolved CO2 from the gas-rich deep-lake water.
An eruption of Nyiragongo volcano opening of fractures on its southern flank inside the city and/or inside the lake Kivu. Parts of Goma and Giseny would be destroyed and the heat released by lava in the lake would trigger an overturn of the deep lake water rich in dissolved CO2. This would cause a catastrophic overturn and sudden release of large quantities of CO2, a so-called limnic eruption. The gas cloud would instantly kill all people and animals at lower elevations around the lake - likely thousands of people.
The same could be triggered if a very large earthquake was to occur under the lake sufficiently disturbing the water layering...
While this is the worst scenario, it is hopefully also the least likely.
No eruption occurs. Seismic activity gradually dies down, as it is a result of internal readjustments after the recent eruption.
A pall of ash hangs over #Goma on May 25; #Nyiragongo is obscured by plume/clouds. Source of ash unclear but possibly from collapses within the Nyiragongo crater after #lava lake drainage. @CopernicusEU #Sentinel3 OLCI True Color @planet PlanetScope image of Goma-Gisenyi pic.twitter.com/sdl3PY8crs— Simon Carn (@simoncarn) May 25, 2021
Volcan Nyiragongo: risque de catastrophe majeure, exode pour fuir Goma | TVA Nouvelles https://t.co/Ge8rmabGf2— SIBOMANA Jean Bosco (@sibomanaxyz987) May 27, 2021
Nyiragongo volcano (DR Congo): death toll rises to 32, ground cracks and tremors continue to worry
Recent high-resolution INSAR radar images showed that the ground south of the volcano has risen by several centimeters during or since the eruption. The vertical displacement is highest in the area of Goma city, where numerous cracks in the ground have become visible.
This leads to fears that one possible scenario (not necessarily the most likely) could be the formation of a new dike - or lava-filled fissure - that could open in this area and produce a second, potentially catastrophic flank eruption.
Similar ground cracks were also observed during and shortly after the last flank eruptions in 1977 and 2002, but fortunately did not result in additional eruptions, but are thought to relate to adjustments of the ground after the drainage of significant volumes of magma during both eruptions. It is to be hoped that the same is true this time and that the seismic activity will gradually die down and not be followed by new lava eruptions at low elevations. More research and observations in the following days and weeks will be needed to get a bitter picture.
Goma-Nyiragongo: Les mouvements sismiques actuels sont causés par les manœuvres de la terre qui comble le vide qui s'est créé avec l'éjection de la lave, explique l'OVG https://t.co/ReUfxW0Bew pic.twitter.com/TcCevhqL4W— Oliveira Simeon (@oliveira_simeon) May 26, 2021
In the meanwhile, the death toll from the eruption has increased to 32 people, most of which died by secondary causes not the lava itself. The lava flows destroyed 2500 buildings including 3 medical centers.