ERUPTION AT NYIRAGONGO VOLCANO, DEMOCRATIC REPUBLIC OF CONGO
17-18 JANUARY 2002
A REPORT ON A FIELD VISIT TO ASSESS THE INITIAL HAZARDS
OF THE ERUPTION
Prepared for the World Health Organization
Dr Peter J Baxter MD
University of Cambridge
18 February 2002
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Introduction
1. The writer was a member of a French-English official scientific team sent to evaluate the initial impact of the Nyiragongo eruption on 17-18 January 2002. This report has been written at
the request of the World Health Organization. It is a summary of an initial evaluation of the
health hazards of the eruption made in the field during 22-26 January. The team over-flew the
volcano and Goma in a helicopter from Kigali on 22 January and made field observations in the
area from 23-28 January (the writer, 23-26 January). One team member remained to continue
studies on Lake Kivu until 13 February.
2. Nyiragongo is a volcano which does not erupt frequently, but it gained its notorious reputation
at its last eruption in 1977, when 40-300 villagers were killed when a set of perpendicular fissures suddenly opened on the high flanks to release exceptionally fast-moving lava flows from its
lava lake. The longest flow on that occasion travelled 10 km to within 2 km. of Goma airport.
No further major activity ensued after that event until the new eruption on 17-18 January 2002,
when lava flows entered the city of Goma. This disaster triggered an immediate response from
international agencies and governments. From the natural hazard perspective, the expansion of
populations in areas of active volcanism exposes large numbers of people to novel eruptive
threats, and this is the first time that a large city has been invaded by extensive lava flows. This
new disaster scenario required an urgent public health response to evaluate the hazards to life and
health. This assessment was made all the more urgent because of the humanitarian crisis in the
eastern Democratic Republic of Congo (DRC) that led many of the people who had fled from the
lava flows to return to the city within one or two days, despite the danger of further eruptive activity or the possible risks arising from the proximity of the cooling lava flows. On 22 January,
about 100 people died in an explosion at a gas station when a petrol leak ignited on the cooling
lava, resulting in the largest death toll to date from the eruption.
3. The writer was invited by the French government to join a team of three French volcanologists
who were assigned to leave Paris on 21 January with an official delegation of the French and
English foreign ministers, which had been previously planned as a diplomatic mission to countries in eastern Africa, including DRC and Rwanda. The assistance of the French embassies in
the two countries was invaluable in enabling the scientific team to reach Goma by the afternoon
of 23 January, completing the journey by road from Kigali, Rwanda. A French volcanologist,
Jacques Durieux and two Italian volcanologists, Dario Tedesco and Paolo Papale, had arrived the
day before for the United Nations and we joined with them to form a working group.
4. The official French-English team comprised Patrick Allard (CNRS, France), Jean-Christophe
Komorowski (IPGP, France), Michel Halbwachs (Universite de Savoie, France) and the writer,
Peter Baxter (University of Cambridge). Allard had studied the volcano some years earlier, and
Halbwachs was already working on Lake Kivu to assess the feasibility of extracting methane
stored in its depths for power generation in Rwanda. The eruption presented a new and potentially devastating possibility of the huge amounts of carbon dioxide and methane stored at the bottom of the lake being released in a gas burst, resembling the lethal event at Lake Nyos,
Cameroon, in 1986. Baxter had been a member of the international scientific response-team to
the Lake Nyos disaster, and Halbwachs had recently headed an international team which had successfully begun the operational degassing of the lake to remove its gas hazard. The eventuality of
either Nyiragongo or Nyiramuragira volcanoes erupting into Lake Kivu had, rather surprisingly,
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not been foreseen by scientists, and one of the Goma lava flows had formed a new delta at the
lake shore. The danger from the stability of the lake waters being disturbed by the entry of hot
lava at depth added substantially to the urgency of the scientific task.
The eruption of 17-18 January 2002, and subsequent eruptive events.
5. Local volcanologists informed us that from 4 January the population were aware of frequent
felt earthquakes which continued for nearly two weeks until the eruption, which began without an
increase in earthquake activity, or any other warning, at 0830 on 17 January. A fissure opened
on the east flank high up on the volcano, which drained lava from the lava lake in the crater to
form a limited lava flow that destroyed two villages. The area had been affected in 1977, when
the lake had emptied its lava over 18 km3 in less than one hour. Villagers were aware of this
event, but in any case they had been advised by the Goma Volcano Observatory since 1993 to
flee to higher ground if a new eruption occurred, which is what most of them did. As it was a
clear day, people could see the lava flows coming. The people who were killed in this and the
subsequent fissure flows were amongst the elderly, or groups such as patients left behind in a
dispensary, but even fit people were also unable to avoid being engulfed. Two children were
known to have died in one village.
6. The population of Goma (about 500,000 people) was not advised on the need to evacuate after
this first event. Further lava flows flowed from new fissures, or fractures, which propagated
along the southern flanks of the volcano towards Goma later on that day (Figs.1-4). The two
main flows extended to the city of Goma (Fig. 5), one traversing part of the airport and the older
commercial centre before ending at the shore of Lake Kivu, where it formed a delta and lava tube
into the water. The other shorter flow stopped where it cut the main west road out of the city.
All buildings in the direct path of the flows were engulfed and destroyed. The high temperature
of the flows (> 800 0C) led to the immediate combustion of all flammable materials in their paths
and inside concrete or block structures remaining standing but in contact with the flows and subjected to the intense radiant heat of the lava. The lava in the city was fluid enough to flow inside
buildings through doors and openings and moved at a steady, walking pace, but the flows also
built up against buildings before they collapsed and became engulfed. MONEC personnel (blue
helmets) helped to warn the people to flee from the oncoming flows. Over 200,000 escaped, with
some people going west further into Congo, but most fled east across the border into Rwanda.
The majority of the evacuees started to return next day after the flows had stopped moving,
though the lava remained very hot.
7. The homes of about 100,000 people in Goma were destroyed, together with a substantial core
number of commercial buildings. About 15-20 % of the city area was covered by lava. Altogether, 47 deaths were reported in the initial event. Those who lost their homes also lost all their
possessions, as they had to leave without any warning; they were not insured.
8. Seismicity, as felt earthquakes, increased over 19-20 January, some being felt at Kigali, 150
km away. This led to fears amongst the people of a major earthquake. Some houses collapsed as
a result of these “volcanogenic” quakes, about Richter scale 4-5, and up to nine deaths and 150
injuries were reported from this cause in nearby Gisenyi in Rwanda. The seismicity and the felt
quakes waned over the next few days.
9. On the night of 21 January, a collapse and explosion occurred inside the crater, which by now
had been observed by volcanologists to have lost its lava lake. The absence of the lake implied
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that most of the stored lava had been released during the eruption. A fall of hot, deep ash (about
10 cm.) occurred on the upper south-west flank of the volcano, damaging vegetation, with a light
dusting of fine ash falling in Gisenyi and Goma.
10. By 25 January, the volcanic activity, as measured by seismicity, had declined and there had
been no further lava flows since 18 January. Volcanologists agreed that the threat of further activity had, for the time being at least, diminished. Daily life in Goma was rapidly resuming, and
the top loose surface rocks of the lava flows were being bulldozed away to open up the main
roads to pedestrian and motorized traffic previously made impassable by the flows. The lava
flows were still very hot beneath the surface, and heavy rain falling on the lava produced clouds
of steam, which also created unfounded anxiety that further activity was occurring. Reports of
sporadic, small explosions around the city over the days since the lava flows stopped were received, including during bulldozing over the flows. A pervading smell of methane gas was also
reported, strongest in certain places and buildings, including at the airport.
Acute volcanic hazard assessment
11. The hazards of lava flow eruptions are governed by geological considerations, such as the
chemical composition of the magma for a particular volcano. The lava at Nyiragongo is mafic,
i.e., it has a silica content less than 55%, and so has a lower viscosity than the silicic lavas. Mafic
lava flows occur at such familiar volcanoes as Kilauea, Hawaii and Mount Etna, Italy, but the lava at Nyiragongo differs from these and most other volcanoes around the world in having a much
lower viscosity and being capable of flowing under gravity in an unusually fluid form. The
flows are potentially much more hazardous in being difficult or impossible to out-run, with
speeds of 30 km/hr on average, and an initial velocity of 100 km/hr at the fractures. The eruptive
history of Nyiragongo is not well described, as the scientific studies have not been undertaken.
The edifice of the volcano is comprised of numerous layers of old lava flows, but the maximum
run-outs of these in the largest foreseeable eruptions of the volcano are not known.
12. The main hazards of lava flows that have been previously recognized at volcanoes include:
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Mechanical destruction and fires (lava lake temperature > 1000oC)
Fall of heavy fragments from lava fountaining and forceful spattering
Explosions when lava flows advance over vegetation (forming flammable organic
gases)
Explosions when hot lava enters water expanses: steam explosions inside lava tubes
Gases from fissures
Opening of fissures and shifting ground, with risk of subsidence
Ground instability from lava loading on steep slopes leading to landslides triggered by
heavy rain, earthquakes
Collapse events at shorelines where “new land” of lava forms on steep shore gradients
All of these hazards have arisen at this eruption.
13. Nyiragongo’s northern neighbour, Nyamuragira, erupts more frequently with lava flows (it
had a small eruption about a year ago). In 1938 lava from this volcano went as far as Lake Kivu.
In 1977 both volcanoes erupted at the same time, and a concern of volcanologists has been that
Nyramuragira would erupt again on this occasion, but there has been no evidence of such a threat
so far. The ash from Nyiramuragira is believed to be toxic; in an eruption in 1995 thousands of
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cattle grazing in the ash fall area died. The ash fell in needle rather than round-particle form,
which may have interfered with the feeding or digestive processes of the cattle, or the ash could
have had a toxic coating of fluoride. I am not aware of any studies performed on this ash in
1995. Nyamuragira last erupted in February-March 2001.
14. The summits of the two volcanoes are about 15 km. apart and separated by a valley area.
Vast ground emissions of carbon dioxide occur here, the lowest depressions containing the skeletons of many wild animals that have been lured to their deaths by the lush grass. The area is also
known as the “Cemetery of the Elephants.” Mofettes, or small vents through which volcanic
gases (carbon dioxide) outflow independently of eruptive activity, are also found in this active
volcanic area (e.g., at Masuko). The ground carbon dioxide emissions are known to be a hazard
to local people. As recently as last December four people died from this cause whilst working in
a field.
15. The smell of gas, in particular methane, was reported in the city after the eruption. The possibility of soil gas emissions being a hazard from the eruption causing fracturing of the ground in
and around Goma required assessment. Minor explosions were also reported in the days after the
eruption (Fig.6).
16. A gas plume was visible from the helicopter arising from the Nyiragongo crater, but the altitude of the summit (3,489 m., or11, 385 ft.) is probably too high for the plume to pose an air pollution hazard to Goma. No measurements of the gas flux from the crater have been undertaken.
A major plume from the crater was visible on satellite photos during the lava flow eruptions.
Volcanic gases include sulphur dioxide, hydrogen sulphide and hydrogen chloride and hydrogen
fluoride, as well as carbon dioxide. A more relevant consideration is the emission of gases from
the fracture sites opened in the eruption from where lava has, or has not, been emitted. The fractures are lengthy and pass through, or close to, villages (Fig. 7). Lava fountains were observed
from the vents during lava emission, so the high temperatures would have driven gases upwards
in plumes, which would be unlikely to have grounded and been hazardous to local people at the
time. This type of lava rapidly degases, usually as it emerges from the vents, but some residual
degassing can occur from flows themselves, though the high temperature also results in strong
upward convection of any such emissions.
17. Massive gas releases from eruptive fractures are a potential danger in volcanic areas where
carbon dioxide is normally abundantly emitted from the ground. The risk, which is rare, is related to hydrothermal systems becoming reservoirs for carbon dioxide under high pressure (c.f., the
eruption at Dieng, Indonesia, 1979). There are no rivers draining the volcanic edifice, as it is
very porous, and Lake Kivu is relied upon as a main source of water. There was no identifiable
hydrothermal system at Nyiragongo. Lake Kivu is fed from below with magmatic carbon dioxide that is converted by fermentation processes at the bottom of the lake into methane. Organic
matter is also converted to form methane. These processes have been going on undisturbed for
possibly many thousands of years and vast quantities of the gases are now present, with the deep
waters (the lake is over 600 m. deep) containing dissolved methane and carbon dioxide (about
70:30 ratio) under pressure. Little mixing of waters occurs in the lake because of its shear walls
and the greater density of water containing dissolved gas at the bottom of the lake. Disturbance
of the stratified layers of water by an earthquake or submarine eruptive fissures opening to emit
lava into the lake could lead to destabilization and the release of a devastating cloud of gas.
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Main Field Survey Findings
18. Volcanic activity. On 22 January we over-flew the volcano in a helicopter from Kigali. Lava
flow activity had ceased in the town. Another flight was taken from Goma airport on 24 January
and visibility was good enough to visualize the crater and the origins on the flanks of the lava
flows. The crater lake was empty of lava. No new lava flow activity since 17-18 January was
seen. A heavy ash fall was apparent on the upper south-west flank of the volcano. Subsidence of
the shoreline at Lake Kivu (30-60 cm.) has occurred since the eruption, but the profile is less continuous than previously thought. The subsidence is likely to be related to stretching of the rifting,
and may be associated with continuous intrusion of magma, i.e., the recharging of the volcano.
19. Lava flows. P. Papale considers that the lava flows from the upper fracture (Shaheru area)
travelled at least tens of kilometres per hour. More people than officially reported are likely to
have been killed in the remote villages in these highly fluid flows. Flows from the Monigi vents
near Goma are likely to have been much slower, as low as 1-2 km/hr., but no precise figures on
lava flow speeds are available. In Goma, the main flows were rough or aa lava, with tongues of
smooth, or pahoehoe, lava emerging from the edges and surrounding or invading houses without
actually engulfing them as was the case with the aa flows (Fig. 8). This flow behaviour needs
much more extensive study from the hazard viewpoint, as it applies to these very fluid lavas. On
6 February another big earthquake was felt, which caused panic in Goma, and four people are
said to have died in Goma from gas poisoning near a lava flow. In Monigi, five people died near
the hot lava flow, reportedly from a release of steam following heavy rainfall.
20. Earthquakes. Earthquakes were being felt in Goma when we arrived. With only one operational seismograph, it was not possible for the volcanologists to determine the origin of these.
Quite possibly they were associated with ground movement, such as widening along the extensive fracturing system, but more recently are thought to be due to tectonic rifting. Collapse of
buildings due to the earthquakes was reported, but we did not come across any examples of these.
21. Fires on the lava flows. On 23 January, soon after arriving at Goma, we made observations
on the lava flow about 200 m. from our hotel (Hotel Masque). Blue flames were burning on one
part and we used the thermocouple to measure the temperature of the flame (500 0C). The air
near the flames contained about 2% methane, the smell of which was readily detectable in the
area. We were told that on the day before the flames had been 1.5 m. high and were orange. This
suggested that the fire was originally caused by the burning of organic matter inside the flow, and
the flames were possibly the combustion of distillates of vegetation. Such burning on the lava
was commonly sighted after the eruption. The lava surface was still quite hot, with the heat penetrating the soles of the boots.
22. Methane. Smells of methane were reported inside and outside various buildings. At the
Belgian School we measured methane levels < 1%, though a faint smell of methane was present
in some rooms. On 24 January we measured methane levels at the airport where there was concern that the restarting of flights might be too dangerous. There were strong odours of methane
near a drain system for rainwater about 200 m. from the lava flow edge, which had not been detected by workers before the eruption. Methane was found in the air along the ground at this location, but at levels < 1%. At a nearby concrete roof over a drain the methane level was 2% with
2% carbon dioxide.
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Later that day we walked along hot lava flows that had made swathes through banana plantations
and, although a trace odour of methane was detectable, measurements were well below 1%.
23. Explosions. These were a remarkable feature of this eruption, and a new observation, which
were probably linked to the flows of lava travelling through an extensive built-up area. We saw
places where inside floor tiles and outdoor paving had been displaced and shattered over small
areas. We were taken to Botembo Avenue to a row of offices where smells of methane were
common after the eruption. In one place the paving had been displaced upwards and we measured 5% carbon dioxide and 3 - 4% methane in air by the tile gaps. Inside one office by some
displaced floor tiles we found 1% carbon dioxide and 2.6% methane. Not far away was a garage
where an explosion had blown apart a concrete floor 10 cm. thick. A similar explosion of a concrete floor had occurred at our hotel. It was possible that the explosions had occurred at the time
of the felt earthquakes, but the ground movement produced by these was not severe enough to
have caused this localized type of damage. We consider it most likely that the eruption opened
pre-existing fractures which allowed deep gas to rise to the surface and form pressurized pockets.
Spontaneous ignition of the methane-containing gas mixture cannot be ruled out. The occasional
minor explosion occurred when bulldozing the lava flows, probably due to the ignition of a small
pocket of methane. As far we knew, no one had been injured or killed by the “methane” explosions.
24. Fissures. Gaping fissures with or without lava emissions were studied. Above the village of
Munigi, a fissure had opened beneath a settlement. No one had been killed, but we were told that
the fissure had widened since 18 January. Only steam at low levels was being emitted, and no
significant amounts of carbon dioxide or methane. Hydrogen sulphide was undetectable. The
fissures were very dangerous, especially for children playing close to them, as they were large
enough to fall in. At one place the fissure was 10 m. wide.
25. Lake Kivu. M. Halbwachs arranged for divers and a submersible to study the lava delta and
lava tube. The lava tube extended to a depth of 80 m. There was no obvious evidence of instability of the water, such as discolouration or finding raised sediments. A submersible was used to
make additional observations from 7 February. Yellow flames had been reported to be burning
on the lake well away from the lava flow, the colour suggesting that methane might have been the
gas. We were told of smells and unpleasant experiences whilst swimming on Lake Kivu before
the eruption, which were being ascribed to gas emissions. These reports need to be followed up
by a survey of gas concentrations at the lake surface, but we had insufficient time to do this. Further investigations at the lake using a submersible have continued under Halbwachs. A slight
temperature anomaly was found in a 3 metre thick water level at 80 m. depth which extended for
some distance from the lava delta. Further data on the lake waters are being processed.
26. Drinking water. Suitable lake water samples were obtained and the results of analyses for
cations and anions are awaited, but the drinking water was unlikely to be contaminated by the
lava flow, which was small in relation to the huge size of the lake. We would not expect the lava
flow to emit excessive toxic minerals into the water, but water quality will need further monitoring. Water from Lake Kivu was piped to the main villages, such as Monigi, but the sources of
water for the remote villages (Fig. 3) needs to be confirmed, especially as there are few, if any,
springs and no rivers on the flanks of the volcano.
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27. Air quality. The indoor air of buildings might be affected by the ground gas emissions as
described above. Plume gases emitted from the crater are unlikely to be a concern. However, the
scraping away of the top surface of the lava flows by bulldozers and the subsequent action of traffic will generate much dust, which could become a respiratory health hazard as well as a nuisance. The dust made airborne by human activity would be best reduced by frequent rainfall, but
the dry seasons may lead to the drying out of the lava flows and the resuspension of clouds of fine dust over the city. Particle in air monitoring should be undertaken if this happens.
Conclusions on the field hazard assessment
28. Mortality. The loss of life in the main lava flow event (47 deaths as officially reported) was
low. However, many more deaths could have occurred but have gone unrecorded in the villages
high up on the volcano where the volcano flows were very fast. The eruption occurred during
daylight hours, and a short but sufficient warning of the encroaching lava was given to the population of Goma, so that they were able to evacuate the city in time. The humanitarian crisis dictated that people returned to the shattered city as soon as the flows had stopped and before they
had cooled sufficiently.
29. Methane. Methane gas pervaded the city air at mostly low, non-dangerous levels. This gas
came partly from lava flows burning vegetation inside the hot lava, but mainly from ground
emissions associated with fractures bringing up methane and carbon dioxide from deeper in the
crust. Fires on the lava flows were possibly due to the burning of organic distillates, or methane.
The flammability limits of methane in air are 5.0-13.4 % by volume. Methane has an oily or hydrocarbon smell, but it is not toxic. The main danger is from fire and explosion. Rarely, when in
the presence of other products of fermentation, it can ignite spontaneously, but in most instances
a flame, or spark, is needed.
30. Explosions. Explosions were due to localized pressurization of methane and carbon dioxide
from deep sources, probably sediment layers, acting against an impermeable layer, such as concrete. The gases moved along fractures in the course of the eruption or as a result of earthquake
activity. Spontaneous ignition of a methane gas mixture as a cause of the explosions cannot be
ruled out.
31. Carbon dioxide hazard. No obvious hazard from carbon dioxide emissions from fractures or
soils was found or reported. This assessment may change when magma begins to recharge the
volcano and refill the lava lake, and further evaluation of this hazard is urgently needed. The
presence of carbon dioxide is usually undetectable by the senses, and it is a toxic gas in its own
right. 5-10% concentrations and above are highly dangerous when inhaled.
32. Ambient air quality. Air quality in Goma and the impacted villages was not severely affected during, or in the aftermath, of the eruption. Toxic emissions would have been present in the
fires triggered by the lava flows in Goma, with smoke inhalation being a risk for people escaping.
No information was available on this.
33. Ash. Ash fall was not a significant problem. However, future ash falls from the two volcanoes should be studied, as it appears that the ash may well have toxic properties or at least be a
hazard to grazing animals. A collapse of a rock platform in the crater was probably responsible
for the ash emission episode marked by a modest explosion. A major phreatic explosive eruption
did not occur a result of the draining of the lava lake. Abundant ash falls might present an acute
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respiratory hazard, depending upon the proportion of respirable particles. Toxic ash should not
be a hazard to humans, but vegetables should be washed to remove ash before consumption.
34. Lava flows. Lava flows erupting from fractures in the town and/or adjacent areas with little
warning could be very hazardous in a future eruption. However, a further eruption of Nyrigongo
does not appear to be imminent and may be dependent on refilling of the lava lake, or other evidence of an uplift of magma.
35. Volcanic hazard assessment. The group of volcanologists agrees that the eruption is linked
to tectonic activity on the rift system, as well volcanic activity. Possibly, rifting caused the fractures on the volcano though which the lava stored at high level erupted, rather than ascending
magma breaking open the flanks. The present on-going subsidence, with the recent strong shocks
felt by the population, is probably due to tectonic rifting. If further fracturing continues as a result of this process it might increase the risk of future lava fissures arising in Goma, and also
fracturing at Lake Kivu, with the potential for the destabilisation of its gas-laden waters. An
eruption of Nyamuragira is likely in the foreseeable future as it erupts frequently anyway. A hazard assessment must take into account the classical effusive and mildly explosive activity of both
volcanoes. Both volcanoes are also characterized by the opening of long, gaping fissures through
which lava emerges at different locations, and these emissions merge to form flows several hundred metres wide.
Disaster scenarios
36. The fracturing of the ground could readily extend into Goma in a future eruption, with lava
pouring out of the ground inside the city. This would not leave time for warning in the city, as in
the present eruption when the lava flows moved slowly enough to permit escape. The fracturing
could occur along lines that prevent many thousands of people from escaping and cause many
deaths in the ensuing fires ignited by the hot lava. The risk of the fires becoming confluent and
out of control (“super fires”) would also add to the loss of life, from heat and toxic smoke and
combustion gases.
37. Lake Kivu could become destabilized by an eruption if severe earthquakes occurred beneath
the lake, or the fractures and lava discharge involved the lake itself. An overturning of the waters
could lead to a gas burst with a large cloud of carbon dioxide and methane flowing into low-lying
areas around the lake. Many thousands of people around the lake would be at risk of asphyxia in
such a discharge, as the cloud would displace the air before it was eventually dispersed by the
wind.
Mitigation measures
38. Volcano monitoring: forecasts and warnings. A seismic network is going to be installed
soon with the assistance of the US Geological Survey. Volcanologists at the Goma Observatory
are on alert for signs of a sudden resumption of activity, including changes in the waters at Lake
Kivu. The development of new fissures and lava flows would require an urgent assessment of
the risk to Goma.
39. Risk assessment. A full risk assessment of a future eruption of Nyrigongo and its impact on
Lake Kivu will be required by a team of scientists. Nyamuragira volcano and its activity will also need to be included. The potential for loss of life directly as a result of volcanic activity is on
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a level that must now be regarded as highly significant even in a region (eastern DRC) where 2.5
million people have died from malnutrition and infectious diseases, due to the collapse of the
health system and food insecurity, between 1998 and 2001. In 1995, the late Haroun Tazieff, the
French volcanologist, proclaimed during the Rwandan refugee crisis that the number of victims
of volcanic activity would be at least two to three orders of magnitude smaller than the number
that would be claimed by a large scale displacement of the (then) one million refugees in the refugee camp close to the town of Goma (Nature 1995; 376: 394). His eruption forecast has now
been overtaken by events, as have the refugee and humanitarian problems. The potential for a
much larger loss of life from the volcano, both in absolute and relative terms, now makes the
need for a new risk assessment essential. The devastating cholera and dysentery epidemics in the
refugee movements in July 1994, in which 50,000 died in the first month after the influx (Lancet
1995; 345: 338-344), should not be allowed to recur in future displacements of the populations,
e.g., in an evacuation in a volcanic crisis, with the appropriate involvement of international agencies.
40. Lake Kivu and the gas hazard. The French/English team plan for A. Woods, a fluid dynamics expert at Cambridge University and who has a special interest in volcanic flow problems, to
make an initial evaluation of the stability of the lake in relation to thermal inputs from lava flows
using data provided by K. Tietze, a limnologist who has studied Lake Kivu for many years in collaboration with Halbwachs. This would be a major contribution to the initial risk assessment.
41. Humanitarian crisis. The humanitarian crisis and conflict situation in eastern DRC must be
incorporated in such an assessment. The health impact of the present volcanic emergency, leading to the disruption to life in Goma and its surroundings, should be reviewed, e.g., the consequences of this “salient” or sudden, disruptive event for water and food supplies and outbreaks of
infectious diseases, such as cholera, dysentery and malaria. Emergency planning for a future
eruption needs to consider the efficacy of warnings and the response to calls for evacuation in a
community that is attempting to survive under a host of different threats, the volcano being but
one of these. About 2 million people are already internally displaced in DRC, with some 310,000
as refugees in other countries (WHO data). The benefits of volcano emergency management
planning and associated recommendations need to be justified within this context. This places a
special challenge on scientists, policy makers and humanitarian agencies alike.
42. Sustainability. In justification, the volcano has introduced a new layer of complexity in an
already “complex emergency”. Volcanic crises are not one-off events (e.g., like an earthquake or
flood), as is commonly supposed, but usually present long-term sustainability issues arising, for
example, from the threat of on-going volcanic activity and devastation, as is the case here. The
commercial and transport importance of Goma to the region may not be the same after the severe
damage caused by the lava flows. Rebuilding on the lava in the city may not be an option, and a
decline in economic activity there would have implications for the viability of the region.
Recommendations
43. Hazard assessment. The preliminary findings presented here were sufficient to determine if
immediate hazards to health were arising from the volcanic activity. The on-going hazards need
to be assessed, including the implications of renewed volcanic activity affecting Goma and Lake
Kivu. This is likely to be a lengthy process, leading to a range of mitigation options for emergency and strategic planning, but it should be started without delay. The assessment should
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begin with a review of the impact of the 17 January eruption and its overall consequences for the
health and safety of the population. A re-assessment of the volcanic health hazards is required
now that the initial activity has declined (Appendix 1). Of special importance is to evaluate further the ground gas emissions, including their extent and severity in association with the invisible
faults of the ground in Goma, and the hazard of explosions.
44. Contingency planning. The Alert Level at the time of writing is Yellow, meaning that a further eruption is not imminent. Ground shocks are still occurring occasionally, suggesting to the
volcanologists that rifting may still be happening, but not a rapid rise in magma. In any volcanic
crisis the state of the activity can suddenly change and move from a quiet into a threatening
mode. There is an urgent need to develop a contingency plan on the actions that may be needed
in the event of a rapid increase in the hazard level of the volcano. This will require multi-sector
involvement, together with the Goma Volcano Observatory and other scientists. D. Tedesco is
returning to Goma and will be working on a contingency plan.
45. Vulnerability assessment. The natural hazards and their implications for policy need to be
assessed in a broader context than just technical aspects of mitigation and epidemiological risk
factors. A vulnerability assessment should be undertaken which includes the political and social
aspects of the complex emergency, as well as the infrastructural and community characteristics of
Goma and the region at risk from the only two active volcanoes (Nyiragongo and Nyamuragira)
in the Virunga range. The location of stores of flammable substances is an obvious example of
infrastructural vulnerability in the light of the petroleum explosion killing 100 people. The human
vulnerability assessment should be co-ordinated by WHO (Appendix 2).
46. Human risk assessment. An innovative approach is required to policy-making to ensure it is
underpinned by evidence science in the face of uncertainty about the future impact of the volcanic activity. For example, the value of subjective probabilistic methods for dealing with scientific
uncertainty in the absence of frequency data, e.g., for forecasting volcanic activity and human
casualties, has been previously shown in the continuing volcanic crisis in Montserrat. The use of
these methodologies should be considered to support policy making in the Nyiragongo crisis,
where a large population is at risk from volcanic activity. The critical issues include decision
making if the volcanic hazard level rises and if there is a need for a precautionary evacuation of a
population out of a danger area. The displacement of large numbers of people may lead to more
deaths from infectious diseases and malnutrition than taking the risk of leaving the population in
place, unless the volcanic activity becomes immediately threatening, when people will selfevacuate, but not necessarily in sufficient time to minimise loss of life. The evaluation of the
hazard of a massive gas release from Lake Kivu, including its mode of dispersion, will also need
to be part of this risk assessment.
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Acknowledgments
I thank the French Ministry for Foreign Affairs for making my visit possible. I am indebted to
my French and Italian volcanological colleagues for their information and advice.
Jean-Christophe Komorowski prepared the map (Figure 1). We thank M. Jose Gohy and the
French Embassy, Kigali, for invaluable logistic support.
Figures
Fig. 1. Map of volcano and Goma (prepared by Jean-Christophe Komorowski).
Fig. 2. Ground fissure through village, risk of subsidence.
Fig. 3. Mountain village built on 1977 lava flow.
Fig. 4. Ground fissure, with lava reaching surface.
Fig. 5. Cooling lava flow in city of Goma.
Fig. 6. Site of gas explosion in street of Goma.
Fig. 7. Cooling lava flow from major vent in a fracture at Monigi village.
Fig. 8. Pahoehoe lava flow, with devastated building.
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APPENDIX 1
Health hazard assessment
1. Determine from the volcanologists, including the Goma Volcano Observatory, the most recent
state of the volcano and its latest activity, including seismicity, felt earthquakes and any extension of the fracture system, and the latest observations on Lake Kivu.
2. Assess the latest accounts of explosions, deaths, gassings, fires, smells in and around Goma
and the villages.
3. Re-evaluate the ground gas emissions (carbon dioxide, methane and carbon monoxide) along
fault lines in Goma and the fissures in the upper villages.
4. Study the behaviour of the lava flows in a field survey of their distribution around houses, and
consider the implications for future eruptions into Goma.
5. Obtain more data on the “methane” explosions around the city, their location and timing.
6. Collect drinking water samples to repeat routine anion and cation estimations to monitor the
any contamination from lava entering the lake, or the effects of the volcanic activity. Confirm
the sources of water supplies in remote areas.
7. Check ambient air quality in Goma. The levels of fine particles from drying out of the lava
flows and human activity generating dust can be measured in real time using a DustTrak instrument. Diffusion tubes will provide a useful check on sulfur dioxide levels (plume grounding).
8. Collect ash samples from the recent fall on the upper flanks and check the properties of the
ash.
9. Observe houses where people are reported to have died in “volcanogenic” earthquakes, to confirm the nature of damage and to consider the risk of local building typologies in future eruptions.
10. Collate information on epidemiological surveillance of the stressed populations, to determine
if the rapid displacement triggered any further outbreaks of infectious diseases.
11. Survey the town for vulnerability issues which might heighten the risk of casualties in future
lava flows.
12. Location and state of present hospitals and clinics, including level of care.
13. Obtain general information on the nutritional status and health problems identified as ongoing amongst refugees/displaced peoples.
14. Evaluate reports of gas emissions on Lake Kivu - carbon dioxide and methane measurements out on the lake surface.
15. Confirm the numbers and causes of death and injury in the eruptive events of January 17/18,
2002.
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APPENDIX 2
Vulnerability Assessment
The concept of a vulnerability assessment is well known in disaster mitigation work, but methodologies for incorporating hazard (probability), vulnerability and human lives in a risk assessment
format have not been often used. Advances in numerical modelling, computer power and Bayesian statistics now enable probabilistic risk assessments to be used in volcanic risk management.
The methodology was first used in the Montserrat crisis in 1997 for advising the UK government
on whether the hazard of the Soufriere Hills volcano was sufficient to warrant evacuation of the
island. The technique was used to underpin judgment, not to replace it. A group of scientists defined the main eruption scenarios that would endanger life, assigned probabilities to each of
these, and central values and ranges for casualties were estimated, using an elicitation process.
The results underwent a Monte Carlo simulation to produce a summary FN curve displaying
probability of N or more deaths over the next six months, with the calculation of individual and
societal risk values for different locations of the population around the volcano. The methodology and its application is now generally recognized as being a leading development in volcanology.
The method may not be directly applicable to the Nyragongo crisis, but the need for a framework
for a formal risk assessment incorporating a wide range of scientific opinion now exists. The
complexity of the humanitarian crisis needs to be incorporated in decision-making, and the risk
from the volcano weighed against the health risks associated with relocating people in large
numbers, either in the long-term or during periods of volcanic unrest, as a precautionary measure.
A formal method is more likely to lead to a realistic assessment of risk rather than relying on one
or two expert opinions.
Some key steps to beginning this process are suggested as follows:

An evaluation of the events and health impacts on the population of the latest eruption
and its hazards. This information can rapidly perish and should be collected soon.

Assess the current vulnerability of the population in the aftermath of the eruption to determine what new threats to health have emerged as a consequence of the activity, e.g.,
the lava flows and disruption to the infrastructure of Goma, and to life in affected villages; the health impact as a result of thousands of people displaced since their homes were
destroyed.

Review the status of the volcanic hazards identified in the initial assessment undertaken
by the international team of scientists and as indicated in my main report.

Develop a framework for a formal evaluation of human, community and political vulnerability to be co-ordinated by WHO. The assessment can be used to inform the development of future mitigation measures, such as forecasts and warnings, community
preparedness, infrastructure and land-use planning, emergency response and evacuation
planning. The data will also provide an essential input to a formal scientific risk assessment as described in the text of the report.
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