Back here on Earth, geological processes have resulted in the loss of at least 32 people. Mount Nyiragongo erupted over the weekend, sending lava and toxic gases into the city of Goma in the Democratic Republic of the Congo (DRC). The city has a population of about 1.5 million people, and an evacuation was ordered. Many of the recorded deaths were caused by traffic accidents from the resulting crush of vehicles leaving.

The glow from the lava could be seen in numerous images and news feeds, and because of the type of lava involved, it flowed rapidly into the nearby city. Piles of it reached up to three stories, buildings have been destroyed, and water supplies are threatened. Additionally, a magnitude 4.7 earthquake hit just this morning near the border between the DRC and Rwanda, increasing fears that the recently refilled crater lake, now full of lava, could crack and send even more lava into the area.

Nyiragongo is a terrifying volcano, and I always made a group in my Hazards class present on the last eruption in 2002, which killed 250 people. The eruption before that, in 1977, killed thousands, and that number is inexact at best. The volcano is considered by many volcanologists to be the most dangerous in Africa, with its fast-moving lava and proximity to millions of people. The lava is incredibly fluid, more like a Hawaiian flow than an Andean explosion, and the speed of flow has been clocked at upwards of 40 miles per hour. Additionally, Nyiragongo sends huge amounts of carbon dioxide into the atmosphere. This gas is heavier than normal air, so it stays near the ground and becomes a deadly hazard for both people and animals.

On top of everything, this latest eruption had no clear warning signals in advance.

So what is the cause of this volcano? We’ve discussed the formation of hot spot volcanoes like those in Iceland and Hawaii, which are fairly free-flowing due to the fresh magma erupting from the mantle. We’ve talked about island arc volcanoes like those in Japan and the Aleutian Islands, where one subducting plate is going under the other, the rock is melting, and causing chains of volcanoes to form. This works on land as well and creates mountain chains like the Andes. But Nyiragongo is a different beast altogether.

It turns out that a piece of Africa is trying to break apart from the full continent, and the resulting tear is called the East African Rift. The rift runs south from the Red Sea to Mozambique. The plates involved are the Nubian plate in the northwest, the Somalian plate to the southeast, and the Arabian plate to the east. They are moving away from each other, and the continental crust is thinning out, allowing fresh magma to rise up from the mantle and make its way quickly to the surface.

Now if you add in the fact that Nyiragongo is more of a mountain peak than a flat shield volcano, you get some additional gravitational influences on that fast lava flow, increasing its speed to the dangerous numbers we see in this situation.

But all the science in the world doesn’t make the loss of human life any easier, and we hope things settle in the region soon.

More Information

Earthquake Strikes Near Congo’s Mount Nyiragongo Volcano, Raising Worries of Second Eruption (Weather.com)

Are We Seeing a New Ocean Starting to Form in Africa? (Eos)

Mount Nyiragongo just erupted—here’s why it’s one of Africa’s most dangerous volcanoes (National Geographic)