Overview of African Volcanoes: From Kilimanjaro to Nyiragongo

Historical Volcanic Eruptions in Africa

Ol Doinyo Lengaï, around 1917 and 1966-1967

Ol Doinyo Lengaï, in Tanzania, is the only volcano in the world to emit carbonatite, a lava rich in sodium and potassium carbonate, which solidifies into a unique white rock. Although its eruptions are less explosive than others, they are remarkable for their exceptional chemical nature. In 1966-1967, a major eruption covered the volcano's flanks with this white lava, attracting the attention of geologists worldwide. This volcano, sacred to the Maasai, is also known as the "Mountain of God."

Nyiragongo, 1977 and 2002

Nyiragongo, in the Democratic Republic of the Congo, is one of Africa's most active and dangerous volcanoes. In 1977, a sudden eruption caused the partial draining of its lava lake, releasing fast-moving lava flows that killed hundreds of people. In 2002, another eruption destroyed much of the city of Goma, forcing hundreds of thousands of people to flee. This volcano remains a constant threat to the region due to its proximity to densely populated areas.

Mount Cameroon, 1999 and 2000

Mount Cameroon, one of West Africa's most active volcanoes, has erupted several times, notably in 1999 and 2000. These eruptions produced spectacular lava flows, sometimes reaching the Atlantic coast. Although less deadly, they disrupted local activities and reminded people of the power of this giant, which stands over 4,000 meters tall.

Erta Ale, 2005 and 2017

Located in Ethiopia, Erta Ale is famous for its permanent lava lake, one of the few in the world. In 2005, a major eruption led to the evacuation of local populations and the death of livestock. In 2017, renewed eruptive activity caused lava flows and toxic gas emissions, affecting nomadic communities in the region. This volcano, located in the Afar Depression, is a symbol of the intense geological activity of the Great Rift Valley.

Nyamuragira, 2010 and 2011-2012

Nyamuragira, a neighbor of Nyiragongo, is one of Africa's most active volcanoes. Its eruptions, often effusive, produce vast lava fields. In 2010 and 2011-2012, lava flows threatened surrounding villages and Virunga National Park, home to mountain gorillas. These eruptions also disrupted regional air traffic due to ash emissions.

Dynamics and Danger of African Volcanoes

Volcanoes of the East African Rift

The East African Rift is a tectonic divergence zone where the continental crust thins and fractures. This favors the rise of low-viscosity basaltic magmas. It mainly features red volcanoes, such as Erta Ale or Nyamuragira, characterized by fluid lava flows that extend over vast areas. Their danger lies in the speed of the flows and the proximity to populations, but explosions are generally rare.

Volcanoes Related to Hotspots

Hotspots, such as those in Réunion, Comoros, or Cape Verde, generate shield volcanoes (Piton de la Fournaise, Karthala, Fogo). These volcanoes are particularly active and produce frequent, often effusive eruptions, but can also lead to more dangerous explosive phases. Their activity shapes iconic landscapes and fertilizes the soil, while posing a direct threat to nearby cities.

The Cameroon Volcanic Line

Mount Cameroon, rising over 4000 m, is a stratovolcano associated with the Cameroon Volcanic Line. This type of volcano is potentially explosive and can eject large amounts of ash and scoria. Its proximity to densely populated areas significantly increases the risk. The 2012 eruption reminded us of the importance of monitoring this West African volcanic giant.

Gray Volcanoes and Explosive Risks

Gray volcanoes, rich in silica and dissolved gases, have viscous lava that traps volatiles. Pressure builds up in the magma chambers, leading to spectacular explosive eruptions, accompanied by ash plumes and pyroclastic flows. The stratovolcanoes of the Virunga (Nyiragongo, Nyamuragira, Bisoke) are emblematic examples of this dynamic. These phenomena pose the most brutal volcanic threat to populations.

Secondary Risks and Human Impacts

In addition to flows and explosions, Africa has experienced indirect volcanic disasters. The most dramatic example is Lake Nyos (Cameroon, 1986), where a massive release of carbon dioxide (\(CO_2\)) asphyxiated more than 1700 people. Ash falls also disrupt crops, drinking water supplies, and public health. Modern infrastructure (roads, airports, power grids) is also vulnerable.

A Balance Between Fertility and Threat

African volcanoes illustrate a dual nature: they shape spectacular landscapes, fertilize the soil, and nourish civilizations, but they also pose a constant threat. Seismic monitoring, alert systems, and numerical modeling of volcanic plumes are now essential to protect the millions of people living near these geological giants.

Table of Main African Volcanoes

Red and Gray Volcanoes: Two Eruptive Dynamics

So-called red volcanoes correspond to effusive volcanoes, characterized by fluid lava flows and relatively low gas content. Their magma is basaltic, with low viscosity, allowing gases to escape easily. The result is spectacular but generally non-explosive activity, as seen at Piton de la Fournaise or Karthala. The landscape is dominated by vast lava fields and gentle slopes.

In contrast, gray volcanoes correspond to explosive volcanoes, where the lava is more viscous, rich in silica and dissolved gases. The buildup of pressure leads to violent eruptions, with ash plumes, pyroclastic flows, and glowing avalanches. Ol Doinyo Lengai and some stratovolcanoes in East Africa or Cameroon are examples.