It is common for natural disasters such as volcanic eruptions, floods, and earthquakes to kill hundreds and even thousands of people. Rarely will a lake kill such a number of people. However, eruptions in some volcanic lakes such as Lake Monoun, Lake Kivu, and Lake Nyos have led to several deaths. On the evening of August 21, 1986, Lake Nyos erupted, releasing a mixture of water and white gas up to 100 meters in the air. Once the content settled on the surface of the lake, it started flowing down the valley and through the villages suffocating over 1,700 people and numerous livestock.
About Lake Nyos
Lake Nyos is a volcanic lake in the northwestern region of Cameroon, situated some 196 miles northwest of the capital Yaoundé. The lake is situated on the flank of an inactive Oku volcanic plain. Beneath the lake is a pocket of magma which causes the carbon dioxide to mix with water and change it to carbonic acid. The magma is approximately 50 miles below the lake. Lake Nyos is one of the three lakes in the world known to be saturated with carbon dioxide (the two others being Kivu and Monoun in the DRC and Cameroon respectively). The lake has a maximum length of 1.2 miles, a width of 0.75 miles, and covers an area of approximately 390 acres.
The 1986 Eruption and Effects
It is still not clear what led the eruption of Lake Nyos but some geologists think that it resulted from a landslide. However, others suspect that there must have been some volcanic eruption on the lake’s bed. The other theory is that the rainfall on one of the sides of the lake may have caused the outgassing. Another possible cause is an earthquake, but this has been ruled out as no one reported a tremor on the day of the disaster. Whatever it was, the water got saturated with carbon dioxide. About 0.29 cubic meters of gas may have been released in the process. The blue water of the lake quickly turned and the level of water dropped. A column of water and foam measuring about 330 feet formed on the surface of the water, causing a wave of about 82 feet to hit one side of the lake.
Since carbon dioxide is less dense than air, it started moving down the valley to the nearby villages. The gas had a mass of about 160 feet and traveled at a speed of 12-31 miles per hour. The gas was thick enough to suffocate the people in the villages of Nyos, Subum, Cha, and Kam, killing 1,746 people and over 3,000 livestock. About 4,000 people who fled later developed respiratory problems as a result of the gas.
The 1986 disaster led to various studies on how to prevent the disaster from recurring. The installation of a degassing column in the middle of the lake was proposed by several researchers. The idea is slowly to allow the heavily saturated water at the base of the lake to come to the surface through the pipe. A feasibility study was successfully conducted in 1995 and the first tube was installed in 2011.