Let’s talk volcanoes

Let’s talk volcanoes

“The fastest lava flow ever recorded occurred here when Nyiragongo erupted in 1977 and its crater emptied in under an hour.”

The Democratic Republic of the Congo (DRC) is home to two exceptionally active volcanoes, Nyamuragira and Nyiragongo of the Virunga National Park. Fiery and volatile, these dramatic volcanic giants are very much alive and like to let you know it. It is believed Nyiragongo has erupted at least 34 times since 1882 all the while menacingly exhaling smoky ash clouds across the skies of neighbouring Goma. This city sits on the shore of Lake Kivu and its foundations largely consist of the solidified remains of Nyiragongo’s past lava flows.  

In 2002, Nyiragongo violently erupted with some reports suggesting that up to 40% of the structures in Goma were destroyed. Three lava streams cut through the jungle and into the city displacing around 200,000 people eventually flowing into Lake Kivu and poisoning the water. To make matters worse, neighbouring Mount Nyamuragira erupted six months later, then in 2006 and again in 2010. It is possible to hike to the original lava vent created by Nyiragongo’s 2002 eruption and the size of it really gives you an idea of the scale of the event.  

The fastest lava flow ever recorded occurred here when Nyiragongo erupted in 1977 when its crater emptied in under an hour. Lava rushed towards Goma at speeds of up to 60km per hour and reportedly killed around 2,000 people and destroyed around 400 houses. These volcanoes are seriously active.  

The 1977 disaster led to Nyiragongo’s classification as a Decade Volcano, a list of 16 volcanoes known for particularly destructive eruptions near large human populations. They are designated by IAVCEI (the International Association of Volcanology and Chemistry of the Earth's Interior). 

A new vent inside Nyiragongo’s caldera, possibly two, opened up in 2016 leading to the highest level of activity since the major eruption of 2002. This heightened activity brought the volcano’s potential hazards back into the spotlight and some researchers have theorised another eruption could happen again in the near future.

Alongside the obvious dangers of the Decade Volcanos themselves, volcanologists are concerned a limnic eruption could occur here on the shores  of Lake Kivu. These are rare natural disasters that occur when toxic clouds of CO2 are released from CO2-saturated lakes, a process known as outgassing, following a trigger event. These deadly gas clouds are called ‘mazuku’ in Swahili meaning ‘evil wind’. 

“The World Health Organisation warns that the continuing tectonic rifting could lead to catastrophic loss of life in the region.”

Limnic eruptions are rare due to the specific components that must come together.  A source of CO2 must exist, the water must be deep enough for sufficient pressure to dissolve large quantities of CO2 and the lake must be meromictic, meaning its layers do not mix.  The vast majority of lakes in the world are holomictic, so their waters do mix and therefore dissolved gasses do not accumulate. 

Lake Kivu is one of only three known lakes to be saturated with CO2 in this way, the others being Lake Monoun and Lake Nyos, both in Cameroon. Under ordinary circumstances, the CO2 of these lakes is dissolved due to the high pressure and cooler waters at the base of the lake, which prevents the CO2 from escaping. A trigger is therefore required to set off an eruption, such as volcanic activity or tectonic plate shifting.

This disaster famously occurred in 1986 at Lake Nyos where between 100,000 and 300,000 tons of CO2 was suddenly released killing 1,700 people and 3,500 livestock. It was the first known large-scale asphyxiation caused by a natural event. The trigger for the explosion was believed to be a landslide. Lake Kivu is however 2,000 times larger than Lake Nyos. Put simply, very large lakes dissolve very large quantities of CO2 and a limnic eruption of this kind on Lake Kivu could instead impact two million people living along its shores. 

The gas composition at Lake Kivu is predominantly CO2 and methane due to local volcanic activity and pockets of magma underneath the lake bed. Geologists have discovered from the lake’s fossil records that local extinction events have occurred around the lake every 1,000 years or so, which are thought to be due to limnic eruptions resulting in mazuku. 

The World Health Organisation warns that continuing tectonic plate shifting could lead to catastrophic loss of life in the region. In Cameroon, degassing tubes now siphon water from the deepest layers of Lake Nyos allowing the CO2 to escape in safe quantities. The political and humanitarian situation in Goma, however, has resulted in both slow progress with similar degassing projects on Lake Kivu as well as a concerning lack of satisfactory evacuation measures for what many believe could be an impending disaster. 

There are some energy projects, so far predominantly led by Rwanda, which extract methane from the lake bed. Lake Kivu is much larger than those in Cameroon and degassing is therefore significantly more expensive here. During the process, small quantities of CO2 are also extracted but it is not known whether sufficient CO2 will be siphoned to prevent a limnic eruption. These projects are already risky given that CO2 can alter small amounts of the deep lake water to carbonic acid, which over time may erode the lake bed equipment. The failure of this equipment or an explosion during extraction could itself trigger a limnic eruption. Multi-state co-operation cannot be overstated. 

In March 2020, Rwanda and DRC signed an agreement regarding how to develop the lake’s gas resources. This was a significant breakthrough following several years of methane gas mining agreements that struggled to progress to implementation. Goma will be a recipient of the resulting gas resources that it so desperately needs. It is hoped this agreement will be a driving force to move multiple projects forward in tandem and minimise disruption to the lake’s marine life and the shore’s inhabitants.