It’s Science Wednesday! This past Saturday (May 22), Mount Nyiragongo in the Democratic Republic of the Congo in central Africa erupted for the first time in nearly 20 years. This active stratovolcano stands 11,385 feet tall (3470 m) and has a main crater about 2 kilometers wide. Inside the crater is an active lava lake – this was suspected for a long time but not scientifically confirmed until 1948 during an expedition to peer inside (imagine the excitement, but also the terror!). Prior to a major eruption in 1977, the lava lake was 2000 feet/600 meters deep! Through time, the lake has fluctuated quite a bit in size, depth and temperature.
For those mineralogically inclined, the lava at Nyiragongo contains nepheline, leucite, kalsilite and clinopyroxene. For those not so inclined, this essentially means that the lava is made up of a lot less silica (silicon and oxygen, also known as silicon dioxide). Instead, it is richer in iron and magnesium. The more silica, the more “sticky” or, resistant to flow and the slower the lava flows. As Nyiragongo’s lava composition has very low silica, the lava is fluid and fast-moving instead. The consequences of this were seen in 1977 when the crater walls of the volcano fractured and the lava lake drained in less than an hour. Lava flowed down the flanks of the volcano up to 37 mph (60 km/hr), overwhelming villages and killing hundreds. In 2002, another eruption killed hundreds and left more than 100,000 homeless.
Experts say that activity at the volcano for the past five years was very similar to that before big eruptions in 1977 and 2002. So, what happened if we knew this was coming? Unfortunately, funding was cut to the Goma Volcano Observatory (OVG) – researchers have been unable to pay for an internet connection to run remote sensors or fuel to transport scientists to the volcano for several months now. Data need to be downloaded manually onto memory cards/sticks during the handful of occasions that visits are made to the volcano. That, compounded with the difficulty of predicting what factors would ultimately win out to create an eruption (the lava lake started rapidly filling in 2020 but nothing happened; seismic activity was detected on the summit on May 10, but then it took two weeks for the eruption to occur), makes it very challenging to forecast.
Over 1000 houses have been destroyed and 17 villages in the vicinity have been impacted during this latest eruption. One of the lava flows stopped just 0.7 miles (1.2 km) from the city of Goma, home to over 670,000 people. So, what is there to do when you live in the shadow of such a dangerous volcano? Perhaps this recent close encounter with widespread destruction will spark a renewed mitigation effort, leading to more robust scientific work on the ground, more active monitoring, and renewed city planning in the most at-risk areas.
For more on this volcano, check out the Smithsonian Institution’s Global Volcanism Program: https://volcano.si.edu/volcano.cfm?vn=223030
Photo: rock from Nyiragongo, given to me by Laurie Kelley