Nyiragongo is a spectacular, active stratovolcano (11,385 feet above sea level) that towers over the city of Goma, Democratic Republic of Congo (4,600 feet above sea level) and hosts the world’s largest lava lake in its summit crater. Its highly unusual lavas are extremely fluid due to having some of the lowest silica levels on the planet, and they are capable of moving with velocities of tens of miles per hour.
Nyiragongo is also a dangerous volcano. It looms just 12 miles from the major population centers of Goma and neighboring Gisenyi, Rwanda. Destructive eruptions in 1977 and 2002 claimed many lives and devastated infrastructure in this war-torn region. With accelerating population growth creating rampant urban sprawl, the next eruption of either a lava flow or explosive “parasitic cone” could create an even more disastrous humanitarian crisis in this region.
With an eye toward better understanding volcanic hazards at Nyiragongo volcano and its threat to the cities of Goma and Gisenyi, University of Wyoming PhD student Erin Phillips, fellow mountaineer and photographer John Catto, and I have just been on an expedition to the DRC. In collaboration with scientists at the Observatoire Volcanologique de Goma (OVG) and Dario Tedesco from the University of Napoli in Italy, our explicit goal was to collect samples from Nyiragongo’s lava flows and parasitic cones.
With the right samples in hand, we are now measuring those sample’s isotopes (atoms which serve as little radioactive clocks in the rocks) to provide a time line of past eruptions in order to better understand how often and with what regularity Nyiragongo is erupting. This work will be conducted in my University of Wyoming High Precision Isotope Laboratory and at Janne Blichert-Toft’s laboratory at Ecole Normale Superieure de Lyon, France.
A Volcanic Crisis Waiting to Happen?
Goma is built on the southern fracture zone of the lower flanks of Nyiragongo. Since the 1994 Rwandan genocide, more than 5.5 million people have died in the Eastern Kivu from a war that has involved genocide, rape, murder, and exploitation of children as soldiers.
Central to the stability of this region is Goma—the center for the UN peacekeeping mission and dwelling place of more than a million residents and refugees. Clearly, a volcanic crisis in this war-torn region will create a major humanitarian catastrophe.
The lava flow on which the city of Goma is built was put in place sometime between A.D. 1208 and 1374 (based on 14C ages; Tuttle et al., 1990). Because these lavas are extremely fluid, this flow (or series of flows?) is speculated to have quickly covered the area where Goma exists today. As noted by the authors of this study, “If such an eruption were to occur in the future without adequate warning, the loss of life in Goma would be extensive.”
In addition to this “prehistoric” flow (before the modern city of Goma was founded around 1941), there have been two historic eruptions. In the 1977 eruption, between 74 and 400 people lost their lives (Durieux, 2003). In 2002, approximately 170 died and 120,000 lost their homes (Tedesco et al., 2007). Goma has since rebuilt on both the 1977 and 2002 lava flows.
In addition to these lava flows, numerous (around a hundred) “parasitic cones” of unknown age surround the Nyiragongo main cone. These are the cones of debris that form when there’s an eruption from a crack on the side of the main volcano. Some of Nyiragongo’s cones have erupted within the city of Goma. In fact the Goma Volcano Observatory (abbreviated “OVG”) is located directly on one of them. Many very large flows on the flanks of Nyiragongo are clearly young based on morphology, but are again of unknown age.
Current hazard maps for this region, such as those of Favalli et al. (2009) are based only on observations of the 1977 and 2002 eruptions at Nyiragongo. These authors themselves state that “the assumption that no other lava flows were produced in the last few hundred years is questionable. This is a limitation in the present hazard evaluation, which assumes that future venting will follow patterns observed in the 1977 and 2002 eruptions.”
Clearly there is an urgent need to provide a concrete scientific framework for hazard assessment of Nyiragongo and to plan ways to mitigate its risk for Goma and Gisenyi. However, without knowledge of Nyiragongo’s magma cycles and the ages of the flows and parasitic cones in the Goma region an informed assessment is not possible.
Working on Nyiragongo: Collecting the Right Samples
On two previous research expeditions to Nyiragongo in 2007 and in 2010 (this time supported by a grant from the National Geographic Society), Dario Tedesco, Jacques Dureiux, John Catto, and I collected a suite of samples from the vertical walls in the summit crater, the outer flanks of the volcano, and even magma samples from the lava lake (as reported in National Geographic magazine). This has given us a head start on understanding both the volcano’s long-term and short-term eruptive history as reflected in the crater walls.
The primary objective of this year’s research expedition, funded by the National Science Foundation, was to sample the parasitic cones that surround Nyiragongo at last, both in the city and in the surrounding countryside.
Sampling in the city was easy. For example, the excavation for the new OVG building on the side of Mount Goma, one of Nyiragongo’s parasitic cones, exposed the tephra (rock and ash) we were seeking. On another occasion, we found ourselves on the local chief’s property near the village of Monigi, on the outskirts of Goma. After crossing onto his property we were taken, by armed guards, to see him during his genteel Sunday afternoon gathering. After a jovial conversation we were provided with one of his shepherds and his enthusiastic son as our escorts to sample the tephra and lavas of the Bushwaga cone that we were seeking.
Collecting samples from cones and lava flows in the countryside was a little more difficult. Our travels often involved long bumpy four-wheel-drive roads and sometimes our objectives required long interesting treks into an outback that was rarely visited by anybody except those trying to eke out an existence gathering firewood or poaching charcoal from the deep interior of the Virunga National Park. But in almost all instances, because of our official affiliation with OVG, our driver Kuru’s diplomacy, and the persistent memory of Nyiragongo’s historical and deadly eruptions, the situation was rarely restive and everybody in the villages we visited were supportive of our scientific objectives. Nonetheless, no matter how lofty our goals and benevolent and diplomatic we wished ourselves to be, for those whose needs and concerns are more immediate we were still primarily Mzungus, “wandering white-skinned people of means,” that simply changed the pace and course of their day.
As a final part of our Nyiragongo expedition, PhD student Erin Phillips and I climbed to the summit of Nyiragongo with a small group of porters, a cook, and two armed park guards/rangers. This overnight trip enabled us to complete the Nyiragongo sampling I started in 2010 when I collected a dozen samples from the lava lake and the crater walls. It also provided an important opportunity for Erin to see Nyiragongo’s spectacular crater and lava lake firsthand.
The lava lake has changed dramatically since 2010; it is now smaller and has sunken deep into a crater on the third, lower terrace, whereas in 2010 it was perched about 30-50 feet above the third terrace, walled in by a spatter cone. Today it would be hard to get right to the edge of the lake to get a fresh sample like I did in 2010, but you could get a great gas sample right now. I guess I am not surprised it has all changed; it is after all a volcano: one of Earth’s “crucibles of change.”
An Unexpected Journey Into the Summit Crater of Nyamulagira
About ten miles northwest of Nyiragongo is Nyamulagira (also spelled Nyamuragira), a shield volcano that is often referred to as Africa’s most active volcano, and correctly so. There have been 28 confirmed eruptive events at Nyamulagira since 1938 and it has erupted regularly since the 1980s, with eruptions occurring every one to four years. It has been considered a lesser hazard for humans simply because of its remote location, but that is rapidly changing as the area between Goma and Sake (a village 15 miles to the west), becomes increasingly more populated and developed.
Although very near to Nyiragongo, Nyamulagira’s chemistry is significantly different, erupting with more ordinary alkaline lavas (about 43 percent silica), that form a classic shield volcano with low-angle slopes. Why is it that these two volcanoes are so close to each other and yet so chemically different? Do they come from different mantle sources, involve different magmatic process, or both?
For the first time in over fifty years Nyamulagira now also hosts a massive lava lake in its summit crater, so a unique opportunity and highlight of this trip was flying into the active crater for three days. In stark contrast to the lush green crater I saw when I flew here in 2010, the crater is now devoid of living vegetation (except for a few small flowers starting to appear here and there), has many young flows covering its surface, and now contains a large degassing lava lake.
Dropped off by a UN helicopter and unescorted by armed guards, we were a simple party of nine: two Congolese from OVG (Mathieu Yalire Mapendano and Honoré Ciraba), three Italians (Dario Tedesco, Giovanni Giuffrida, and Gabriele Erba), one German (Nicole Bobrowski), and three U.S. citizens (John Catto, Erin Phillips, and myself). Despite lots of heavy rain it was an amazingly productive and simple trip. Three of us wandered about the crater all day collecting lavas from the recent flows. Four of the group measured gases emitted from the new lava lake, two of whom rappelled partway down to a lower terrace in the active crater to better collect these gases. The two scientists from OVG made important measurements and observations to put the crater’s changes into its historical context.
Even in the depths of Nyamulagira’s crater, in the middle of Virunga National Park and deep in the high African jungle, we were reminded of our vulnerability to the persistent civil war that plagues the DRC. On the second afternoon, an extended period of heavy and small-arms fire from a nearby battle on the side of the volcano flanks riled everyone’s concern. It quickly became obvious, however, that this skirmish was outside the crater and not an issue for our group to be too concerned over.
Epilogue: Working in the DRC
Sample collection on Nyiragongo and Nyamulagira is always interesting. The toxic gases can get overwhelming when working close to the immense lava lakes, and when inside their craters there is the ever present, but not often conscious, fear of an eruption that could either be large and deadly, or small and simply exciting. There is also the awkward and tedious process of traveling long distances across young, jumbled `a`a lava flows, with a high potential of twisting your ankle or shredding your skin if you fall. But unlike most other volcanoes, these two also present the dangers of ongoing civil strife, which here in the DRC has resulted in more than 5.5 million deaths since 1994. It creates an edge that goes beyond a normal day’s work on an active volcano.
The samples we have collected over the three field expeditions are numerous and cover a range of areas, morphologies, and apparent eruption times. It is now the responsibility of PhD student, Erin Phillips, to use isotopic clocks to determine the explicit eruption ages of these lava flows and to help us all better understand the basic science of these two volcanoes: Why are they where they are? Why are they so different, and what does that mean about the sources and processes responsible for their genesis and evolution? Besides helping to predict the next eruption, answering these questions is fundamental to our understanding of alkaline volcanism both in the African rift and globally.
Chakrabarti, R., K.W.W. Sims, A.R Basu, M. Reagan, and J. Durieux, 2009, Timescales of Magmatic Processes and Eruption Ages of the Nyiragongo volcanics from 238U –230Th-226Ra-210Pb disequilibria, Earth and Planetary Science Letters, v. 288, doi:10.1016/j.epsl.2009.09.017.
Durieux, J., 2003a, Volcano Nyiragongo (D.R. Congo): Evolution of the crater lava lakes from the discovery to the present, Acta Vulcanologica, v. 15 (1-2).
Durieux, J., 2003b, Nyiragongo: The January 10th 1977 eruption, Acta Vulcanologica, v. 15 (1-2).
Favalli, M., G.D. Chirico, P. Papale, M.T. Pareschi, and E. Boschi, 2009, Lava flow hazard at Nyiragongo volcano, D.R.C., Bulletin of Volcanology, v. 71.
Head, E.M., A.M. Shaw, P.J. Wallace, K.W.W. Sims, and S.A. Carn, 2011, Insight into volatile behavior at Nyamuragira volcano (D.R. Congo, Africa) through olivine-hosted melt inclusions, Geochemistry, Geophysics, Geosystems, v. 12, doi:10.1029/2011GC003699.
Tedesco, D., O. Vaselli, P. Papale, S.A. Carn, M. Voltaggio, G.M. Sawyer, J. Durieux, M. Kaserek, and F. Tassi, 2007, January 2002 volcano-tectonic eruption of Nyiragongo volcano, Democratic Republic of Congo, Journal of Geophysical Research, v. 112.
Tuttle, M.L., J.P. Lockwood, and W.C. Evans, 1990, Natural hazards associated with Lake Kivu and adjoining areas of the Birunga Volcanic Field, Rwanda and Zaire, Central Africa, U.S. Geological Survey Open File Report 90-691.