Lava lake rises (again) in African Nyiragongo volcano

In 2002, the last time Nyiragongo volcano erupted, lava raced down its flanks into the crowded city of Goma, on the border between the Democratic Republic of the Congo and Rwanda. About 250 people died, 20% of the city was destroyed, and hundreds of thousands fled. Since then, the at-risk population living in the shadow of the volcano has more than doubled to 1.5 million.

[Nyiragongo volcano in 2020]

The 2002 eruption began after an earthquake opened up fissures in the southern flank of the volcano. The 200-meter-wide lava lake, the largest in the world, drained in a matter of hours, releasing low-silica, runny lava that flowed as fast as 60 kilometers per hour. The lava piled up in layers up to 2 meters deep in Goma and created a new delta 800 meters wide in nearby Lake Kivu.

As soon as the fissures healed, however, fresh lava began to bubble up and refill the crater lake. Activity accelerated in 2016 when a second vent began to fountain within the crater. In February 2020, Dario Tedesco, a volcanologist, led an expedition into the volcano’s crater. They found the lake rising faster than ever. The second vent was gushing an estimated 4 cubic meters of lava per second, enough to fill an Olympic swimming pool every 10 minutes. Their analysis suggests peak hazard will arrive in four years, although they believe an earthquake could trigger a crisis earlier.

[Goma in 2020]

 They believe the system may be reaching a critical point, as it did before the 2002 eruption and an earlier one in 1977. In both cases lava lake levels stabilized several years before the eruption, they argue, as the mass of molten rock weighed down on the magma below. But swarms of small earthquakes or ground deformation are clearer warning signs of restless magma. Cynthia Ebinger, an expert on Rift Valley geology says the stretching of tectonic plates in the region leads to earthquakes and fresh intrusions of magma that can also trigger eruptions.

A network of seismometers around the volcano shows high earthquake activity and several deep swarms. Scientists do not know how unusual the activity is because they lack comparable, older data. But sustained, rumbling tremors were recorded months before the 2002 eruption. Nothing like that is detected for the moment.

The network requires constant maintenance, because of vandalism, theft, and lightning damage. Several seismometers are currently out of action.

[Update 23 May 2021]: Nyiragongo Volcano Erupts to 45,000 feet: DR Congo Orders Citywide Evacuations. See here.