Hotspot volcanoes

Here’s why Mount Nyiragongo is one of Africa’s most dangerous volcanoes

The volcano’s magma is also particularly rich in carbon dioxide, an invisible and odorless gas. This gas often quietly exudes to the surface via aquifers above deep bodies of outgassing magma. Being denser than air, the gas accumulates unnoticed in low areas. The locals call it mazukuor “evil wind”.

“We have a lot of people dying because of mazuku every year in the region,” says Smets. If the carbon dioxide-rich magma is mined by the Nyiragongo, dangerous volumes of gas can also erupt from fissures and flooded areas quite suddenly.

A volcanic ambush

Eruptions at Nyiragongo typically occur when pressure from magma buildup or an earthquake forces cracks open in the sides of the mountain, causing the lava lake to catastrophically dry out or stored magma to erupt. more deeply.

But like the volcanoes that make them, individual eruptions have their own unique behaviors and properties, and no two are the same. Monitoring volcanoes for signs of future paroxysms is therefore fraught with pitfalls, and the latest outbreak of Nyiragongo is a perfect example of these challenges.

Between eruptions, Nyiragongo’s summit crater tends to fill with magma, and it has done just that since the 2002 eruption. In 2016, a second vent opened at the summit. In 2020, volcanologists airlifted by UN peacekeepers, who were protecting the scientists from armed rebels in the area, noticed that the lava lake was filling up faster than ever. An ominous sight, but scientists can’t be sure the height of the lava lake is an indicator of the volcano’s readiness to erupt.

On May 10, 2021, the Goma Volcano Observatory detected an increase in seismic activity at the summit. This may have suggested that magma was moving at shallow depths, but it was not an infallible warning sign of an upcoming eruption.

The observatory’s efforts to keep tabs on Nyiragongo have been somewhat thwarted lately. Some of its seismic stations had been subject to theft and vandalism, with the risk of violence leaving many unrepaired. The observatory also lost financial support from the World Bank last year due to allegations of embezzlement.

Therefore, for several months the remote sensors did not have an internet connection and regular on-site measurements of the volcano were not possible. Despite these persistent problems, the observatory, with a small budget from the DRC government and in cooperation with other international partners, continued its efforts to monitor Nyiragongo.

But in the end, the volcano erupted unexpectedly, providing no clear geological indication that it was about to erupt. “There was absolutely no precursor for this eruption,” Smets says. “No one could have detected this eruption” in advance.

This weekend’s eruption surprised a town haunted by the ancient underworld of Nyiragongo. Luckily, the lava missed Goma. Sunday morning the eruption had has lost its intensity. The lava stopped less than 300 meters from the edge of Goma, leaving behind a frozen and hissing river of volcanic rock.