Eruption of Nyiragongo Volcano in May 2021 degassing of CO2 before and after eruption in the atmosphere

Abstract

The Nyiragongo volcano is located in the western part of the African Rift. The deep fractures allow the upwelling of gases before and after the eruption, especially carbon dioxide (CO2). We want to understand the behaviour of carbon dioxide before and after the eruption of the Nyiragongo volcano on 22 May 2021. The Nyiragongo volcano erupted on the evening of Saturday 22 May 2021 at 18:15 local time in Goma, about 20 km north of the city of Goma. The lava flowed in two directions from the flanks of the volcano, one flow coming to a halt in the northeastern suburbs of Goma, The other flow cut off one kilometre of the national road 4 linking Goma to Butembo, a major regional road vital for the supply of the city of Goma, causing 32 victims, the production of several volatile gases in the atmosphere, the destruction of 17 villages in the territory of Nyiragongo and the cracking of the ground in the city of Goma and Gisenyi. The Nyiragongo Volcano is infamous for its extremely fluid lava that flows like water when the lava lake flows, which is monitored by the scientific community of the Goma Volcanological Observatory (O.V.G), the lava lake is the seat of an intense gas production. CO2 is a gas that is heavier than air, asphyxiating, and deadly at a concentration of 15%. The variation of CO2 in the different sites allows us to study the behaviour of the Nyiragongo Volcano, one Month before the eruption, the CO2 showed an increasing trend in some sites and a few Months after the eruption we observed a slight decrease in all the CO2 monitoring sites. Nyiragongo is an important contributor of CO2 and SO2 to the troposphere. This 2021 eruption is similar to the one of 17 January 2002, which caused the death of about 100 people and the evacuation of several people. The most deadly eruption of Nyiragongo was in 1977, when more than 600 people died.Post-eruption seismic activity was characterised by a large number of earthquakes of magnitude 3.5 or more. A few earthquakes of magnitudes greater than 3.5 have been recorded by global seismic networks (USGS), the strongest of which had a magnitude of 5.2 in 2002.Compared to other eruptions that Nyiragongo volcano has experienced, the seismic activity before the eruption of 22 May 2021 was not too alarming. This is because there were no strong earthquakes (greater than or equal to 3.5) that preceded the eruption a few months before, as had been noted in previous eruptions. After eruption, exceptional seismic activity was noticed. Many earthquakes of magnitudes greater than or equal to 3.5 were recorded by the local seismographic network. These earthquakes were felt, the strongest having a magnitude of 5.2