In May 2021, Congo’s Mount Nyiragongo, one of the world’s most dangerous volcanoes, suddenly erupted. Lava flowed down the mountain toward the Congolese city of Goma and the Rwandan city of Gisenyi, leaving hundreds of people dead or missing and hundreds more injured. The eruption itself lasted about six hours, but in its aftermath, seismic activity in the area continued for another 10 days. Now, using data from monitoring stations installed near the volcano in 2015, an international team of researchers have pieced together how that eruption happened so suddenly, according to Science News. The data suggest that the event could have been much deadlier than it was– and highlight the need for researchers and public officials to better understand this volcano’s particular structure and hazards before the next eruption.

Nyiragongo’s last two eruptions occurred in 1977 and 2002. Both eruptions were preceded by several days of distinct seismic activity strong enough to be felt by people living around the volcano. But before the eruption on May 22, 2021, even the sensitive monitoring stations near the volcano seemed to detect no clear warning signs of magma shifting underground. 

However, there was actually a large lake of molten lava burbling in the volcano’s summit crater up until the eruption. By 2021, that lake had risen to near the top of the crater. But lake level alone isn’t typically enough to indicate the potential for an eruption. Researchers say that the trigger for the actual eruption was probably a tiny crack that formed in the volcanic cone due to the buildup of stress over time from the pressure and heat of the magma within. That would have been enough to allow the magma to push through the summit crater.

The study of natural disasters, especially how and why they occur, is a key component of understanding the geosciences. GEO 117: Natural Disasters is a course that focuses on the geological processes that underlie volcanic eruptions, and other natural phenomena such as floods, earthquakes, and landslides. The course focuses on major events in the geological and historical record as well as hazard potential for people living in areas prone to specific natural disasters, such as these volcanic eruptions.