Oldoinyo Lengai: Chris first adventure in Aug. 1996

The small town of Arusha (1200 m) in Tanzania was the starting point. From Arusha I took a public bus to the village of MtoWa Mbu about 100 km northwest, even partly paved. The next day journey was not so easy to get organized. So, I went to the village pub for a beer and a couple of darts games. My search for tranport got public and before dinner, I had arranged a lift. The next morning I got up with the first light and went out on the street of the village as agreed. After waiting for over an hour – I had forgotten to set the clock to “Tanzanian” time – a guy came running along and pointed to a scrap-looking Toyota pickup truck that was loaded with many goods. Well, ok. From MtoWaMbu we turned north on a bumpy dusty road and followed it to the Masai village of Selela and further on to Engaruka. Changing passengers jumped on and off, all finding uncomfortable space on the loading. This was an important service for the villages along the route to get goods and transportation.

Behind Engaruka there was no more settlement and more and more wild animals like zebras, giraffes and antelopes appeared in the open gras plains. The Toyota got stuck more and more often in the deep dust. When the driver tried to get it out, the engine of the old car increasingly failed by overheating. The rift shoulder rose steeply to the left and the stratovolcanoes Kitumbeine, Karimassi and Gelai (2942 m) could be seen to the north. In the evening after countless breakdowns, we – driver, assistant and I – gave up reaching our final destination, also because orientation was very difficult in the dark. The driver allowed us to approve a few beers, because we had no food at all. After that we fell asleep easily, lying peacefully on a tarp under the starsky, despite of scorpions, poisonous snakes and lions. We had at least reached the eastern slopes of Oldoinyo Lengai. The next morning the dust swallowing and shaking came to an end after 24 hours on the 150 km stage. Near Lake Natron (610 m) was the small Masai settlement Engarosero, where I got unloaded from the Toyota together with four live chickens, 2.5 crates of beer, many crates of Coca Cola, all kinds of plastic goods and equipment. I was welcome by the Siningo family in a simple campsite near to the village.

The ascent of Ol Doinyo Lengai on August 17, 1996

I got ready to set off for the summit of Lengai in the morning with a 25 kg backpack including 6 liters of water and a lot of useless equipment. The Masai told me, that it was customary to take a guide up the mountain. Well, I smiled and declined with many thanks, because I thought the mountain, which had been described in some literature as unclimable, was relatively easy in terms of commonly mountaineering experience. The Masai laughed and let me go.

The temperature was still pleasantly fresh in the morning, but that changed brutally around noon. In a dry river canyon I found a place in the shade – luckily without cobras and scorpions – to rest and save water. After the midday heat, I continued to climb through sticky annoyingly high grass and came across car tire tracks at approximately 1300 m. Great, but sadly I didn’t have a car. From there, the stratovolcano Lengai rose noticeably steeper on an increasingly narrow mountain ridge. Meanwhile deep canyons, that had been washed out by the rare rain in the relatively soft rock of the volcano, occured to the right and left hand side.

Night was falling, but thanks to the full moon, I was able to continue climbing without a headlamp. Despite the relative coolness of the night I was quite thirsty and sweated a lot, which was due to the steep upper volcanic flank of over 45 degrees. Then finally I reached the 2830 m high crater rim at the west side. But my enthusiasm didn’t last long, because seconds later , I found myself 2 meters deeper in a mountain crevasse that I had overlooked in the dark. Fortunately, apart from bleeding scratches on the legs, the fall went off lightly.

After this incident, I was able to enjoy the activity spectacle in the crater of Lengai for the first time. The moon had set, but in the large crater – from a size of a sports stadium – were clearly visible half a dozen of hornitos, or tall hills. The lava of the crater looked like white snow, with only a few black spots in between and suddenly, I saw a faint shimmer of red in a black lava flow. Liquid lava, only some hundred degrees hot. The source of it became evident as lava boiling and bubbling more and more violently behind a small lava dam. It hissed, gurgled and cracked softly but also somehow frightening. I climbed very carefully into the crater and approached the fluctuating activity at dawn. After exploring and taking a few photos, I used the cool morning for the descent, which didn’t take long but seemed endlessly long without water through the dry and increasingly hot savannah. In the camp, I reported about my success and the activity of Lengai, which was taken with respect by those people who came across.



The Oldoinyo Lengai is located in the East African Gregory Rift in Tanzania at 2,751 latitude south and 35,902 longitude east. The current height of the stratovolcano is 2960 m.

Its mountain base is located in the bottem of Rift Valley at approx. 600 m altitude, with a western connection to the over 2000 m high valley shoulder. The steep volcano slopes run into Lake Natron in the north, which extends to the border with Kenya and further on.

The age of the Lengai is about 370,000 years, so far behind the last major folding phase of this part of the East African Rift 1.2 million years ago, in which several carbonatitic volcanoes were formed.

The older part of the Lengai is the dorment south crater. It erupted yellow tuffs 370,000 to 150,000 years ago. The young and still active part is the north crater. It initially ejected black tuff until around 1,250 years ago. Then the eruptiones of natron-carbonatitic lava began, which has filled the crater with mostly high viscose lava flows. For the Masai tribe living arround the volcano, Lengai is sacred mountain and the seat of their creator Engai.

G. Fischer was probably the first European to penetrate this volcano in 1883, which is located in what is now Tanzania. The first scientific report on the crater and its special lava was provided by F. Jäger in 1904. Reck made the first photographic report in 1914. From then on, several expeditions visited the Lengai, although it was not the frequently climbed volcanoes in the 19th century due to its remoteness and difficult access.

Eruption Datas Oldoinyo Lengai

The first dated major explosion of the previous century occurred in 1917. Ashes (tephra) were thrown nearly 50 km into the surrounding area and lava flows reached the base of the volcano. This eruption was numbered with the Vulkan Explosiv Index (VEI) 3.

In 1923 A. Barns observed night glow over the crater and in 1926 another explosive eruption occurred, also observed by Richard in 1940 and 1942 – for weeks, ash clouds rose over the volcano after violent explosions (VEI 3).

On August 9, 1966, what is probably the most serious explosion in historical times occurred. An ash (tephra) cloud rose over 4,000 meters into the sky and ash fell 200 km away. There were no major explosions between 1967 and 1983.

Since 1983 until today, many effusive and smaller ash (tephra) eruptions, only interrupted by a longer rest period from 1993 to 1994, have almost filled the crater. From 1999 the overflow of lava began until another very explosive phase occurred in 2007/2008. Since then, the over 130 m deep crater that was left, has been backfilled again with effusive lava.

Petrography of Ol Doinyo Lengai

Soda carbonatitic (alkali carbonatitic) minerals: Nyerereite (Na0.82K0.18) 2Ca (CO3) 2 and Gregoryite (Na0.78K0.05) Ca0.17 (CO3). This non-silicate magma is a mixture with sodium-calcium-carbonate. The inclusion of bubbles is caused by a high proportion of dissolved CO2. The temperature of the melt is relatively cold at around 600 ° C from an igneous point of view. This temperature is just enough to cause a red glow at night. The viscosity of the melt is 1-5 Pa s (basalt has approx. 100-1000 Pascal sec., Water 0.01 Pa s) and reaches flow speeds with a slight gradient of 10 km / h.



Location Date Temperature (°C)
T40 lava lake 28 August 1999 529
Pahoehoe flow in a tube near T40 1 September 1999 519
Aa flow still in motion at flat terrains (60 cm thick) 1 September 1999 516
Pahoehoe flow in a tube near T49B 3 October 2000 507
Aa flow still in slow motion at flat terrain (25 cm thick) 3 October 2000 496
Pahoehoe flow in a tube near T49G 11 February 2004 588
Pahoehoe flow in a tube near T49B 12 February 2004 579
Aa flow not in motion anymore at flat terrain (15 cm thick) 13 February 2004 490
Pahoehoe flow in slow motion (10 cm thick) flat terrain 26 June 2004 560
Pahoehoe flow (15 cm thick) in motion inside a Levée 03 February 2005 561
Aa flow not in motion anymore at flat terrain (15 cm thick) 03 February 2005 520
Aa flow not in motion anymore at flat terrain (10 cm thick) 06 February 2006 519
Pahoehoe flows (20-50 cm thick) in slow motion 23 August 2007 516

Table 1. Lava temperature measured by a digital thermometer (TM 914C with a stab feeler standard K-Type). The instrument was used in the 0-1200 Celsius mode. Calibration was by the Delta-T ethod: values are +/- 6°C in the 0-750°C range, with at least 4 different measurements at one spot. These temperatures compare well with the range of the first temperature determinations on natrocarbonatites of 491-544°C by Krafft & Keller June 1988 (Science vol. 245, 1989), although occasionally higher temperatures up to 588°C have been obtained in the eantime.” Courtesy of Christoph Weber.



The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography.

Bell K, Dawson J B, 1995. Nd and Sr isotope systematics of the active carbonatite volcano, Ol Doinyo Lengai. In: Bell K, Keller J (eds), Carbonatite Volcanism, Oldoinyo Lengai and the Petrogenesis of Natrocarbonatites, Berlin: Springer-Verlag, p. 100-112.

Dawson J B, 1962. The geology of Oldoinyo Lengai. Bull Volcanol, 24: 349-387.

Dawson J B, Keller J, Nyamweru C, 1995. Historic and recent eruptive activity of Oldoinyo Lengai. In: Bell K, Keller J (eds), Carbonatite Volcanism, Oldoinyo Lengai and the Petrogenesis of Natrocarbonatites, Berlin: Springer-Verlag, p. 4-22.

Global Volcanism Program (GVP), 1996. Bulletin of Global Volcanism Network (BGVN), Smithsonian Institution

Adventurous journey to Nyiragongo in 1996

Here you can read the first part of a series about the volcanoes in the East African Rift Valley. The reports come from the volcano guide Chris Weber.

African Rift Valley East

The East African Rift system extends from the Jordan Valley through the Red Sea, southwards through East Africa and then along the Zambezi River. This system is about 6500 km long. The active continental rift volcanism in East Africa created great faults with an average width of 50-60 km. In places, parts of the earth’s crust has sunk, while in other places the edges of the trench has been lifted up.
As a result, the altitude of the bottom of the trench varies from 600-900 meters below the trench shoulders. In some areas this difference in altitude is even up to 3000 meters. Sediments and lava have partially filled the rift over millions of years.

Turning inland from the Red Sea into Ethiopia, the rift is dividing the country into the highlands to the west and lower desert to the east. Then in Kenya and Uganda two separate branches go apart and join together at their southern end in southern Tanzania along its border with Zambia. The Western Rift is also called the Albertinen Rift, including the Ruwenzori Range, plus the Mitumba and Virunga Mountains. The deepest valleys are found to the north of Kenyas capital Niarobi.

The most of the great rift lake was formed as the result of the rift-system, and lies in territories within the rift. Lake Victoria is considered to be part of the rift-valley-system, although its found actually between the two rift branches. The most rift lakes have high mineral contents as result of evaporation of water, like Lake Magadi with a high concentration of soda, meanwhile Lake Bogoria and Lake Natron are all strongly alkaline, while freshwater springs who supply the lake Naivasha do support the current biological variety. The southern section of the Rift Valley with lake Malawi hosts the third deepest freshwater lake in the world and reaches 706 metres surface to bottom.

The two major gateway-towns of the East African Rift are Nairobi in Kenya and Addis Abeba in Ethiopia.

Continental Rift Volcanism

The East African Rift is the most important example of continental rift volcanism. Another good example is the Upper Rhein Graben (rift) in Germany. But much more widespread or predominant on Earth is the mid-ocean rift volcanism usually deep down in the oceans. This is the same geophysical principle of earth plates drifting apart, but differs in the uplifting rock melt (magma).
Continental rift volcanism arises where convection currents in the interior of the earth drive the continental lithospheric plates (earth’s crustal plates) apart. The so formed fracture gaps are then filled up with volcanic products from the earth’s interior. Volcanoes arise and floods of magma pour into the fractures as viscose lava flows.
This process can stretch over hundreds of millions of years and might be accompanied by epochs of immobility. With the current examples of the East African Rift and the Upper Rhein Rift, which today are apparently subject to a small spreading scale, nevertheless, one day the subcontinent could migrate apart so that a new ocean is created.

Adventures around the volcanoes of East Africa

The Virunga volcanoes (1996 and 2011)

Part 1: Gorillas of Zaire (Rep. Kongo)

After I had eaten dust being whirled up by some UN trucks with goods for the refugees in Goma, while sitting on an open pickup truck which had given me a lift, public transport stopped finally at the frontier-post between Uganda and East Zaire. So I had to hire a local guide to continue on foot. We went through lush farmland up on the slopes of Sabinyo volcano.
This mountain and the neighboring Virunga volcanoes of Muhavura, Gahinga, just north of Sabinyo, and Visoke, Karisimbi (the highest with 4507m) and Mikeno to the south, give home to the last about remaining 600 mountain gorillas (Gorilla beringe). They hide at higher altitudes of those volcanoes in the tropical so called cloud forest, forming a fairly tale scenic atmosphere.
One day of hard and rough walking along narrow footpaths, luckily free of landmines, brought me up to the cloud forest line of Mikeno. There I had to pay a 130 US fee cash at the basic ranger station to take off the next day visiting the gorillas with an armed patrol. Well, good invested money, to keep the primates protected against poachers, hungry sodliers or refugees. Therefore most of the gorilla families have armed rangers living with them all along the time.
It was early morning when we took off into the mysterious jungle, following the gorillas tracks through thick forest for hours. Finally we arrived at an opening where a big family group of 25 gorillas were feeding and relaxing. A half ton silver back, hat of this group, washed from time to time, while gorilla babies were coming closer to check my photo equipment and my laces. After two hours or so, we left these nice creatures excited and fascinated.
I walked down from these volcanoes and met the paved road to Goma, when an overloaded pickup truck stopped to pick me up. Our truck got stopped three times on a few kilometers and on the third stop zairen soldiers ordered me to hop of. The driver of the truck said sorry drove off. I know, that the zaire soldiers got paid by their government in invalided money such as the Zaire and that’s because of hunger they kill wild animals and steal in villages, even once they looted and ruined Goma.
So, I was quite nervous when some lousy looking soldiers escorted me in a dark hut of the road, standing in front of a greening hire raked officer. I explained, that the only reason to come here was the attempt to climb the volcano Nyiragongo, that´s why I was wearing military boots. I knew ahead, that these shoes would have had brought some trouble to me in East Africa. So I had to pay my way out by little cash and cigarettes. John, a local translator for care-oganisations and journalist told me some days later in Goma, that it’s impossibile to get any kind of good shoes around Goma.
In the surrounding of Goma huge refugee camps with kilometers of space hosted some hundreds of thousands of Hutus who had started an exodus from Ruanda into Zaire in the 1970’s after first massacres took place by the Tutsi minority. Then, after many incidences 1994, the Hutu took revenge and killed 75 percent of the Tutsi and moderate Hutus. Alone in June and July up to 1 million people were killed. Finally, the rebel group RPF took over in Ruanda and installed a Tutsi government again, causing countless Hutu to flee out of the country.

Part 2: Nyiragongo volcano hike

There was little to say about Goma itself, because this ruined town was a total mess with hotels and restaurants closed, shops emty and an UN oganisation (pease and aid force) behind many high fence lines. After one night in Goma without any food except Coca Cola, and went out on the road again ot reach the foot of Nyiragongo. It was out of the question to clime up the volcano without guide an armed force, because of gang (bandits) actyvities around volcanoes such as RPF rebels and others.
So I went to the national park headquarter asking for help. Two remained officers were surprised to see me as a visitor, but the very nice Mr. Kivuya Wa Viui agreed to join me up the volcano after a long conversation and after paying the 100 US fee for hiking the mountain, plus some extra for my guide. Maybe the only incoming for Kivuya since many mounth. At a nearby zairen military post we founed luckely a solution get a well armed group. The chef officer was so amazed of my crazy wish to clime Nyiragogo, that he ordered a docent soldiers for this expedition.
I wasn’t really sure about of putting my life and my army boots into the hand of a group of Rambos with no shoes. Well, there was one more problem, my leeck of any food. But after checking this jung guys out and the fact, that this forest are hiding places for Hutu and Titsi, gave me no other option. For this evening Mr. Kivuay gave me some food and a place to lay dowen my sleeping bag.
Our expedition started by early morning it was best armed with an amazing viorty of weaponds. Soon we entered the jungle at its best with heat, humidity crying monkeys and crazy loud zikades. During a brack, I pulled out my foto camera and instandly watched into the soldies big eyes. Well, for sure it was in their eyes a fortioned. But they made jokes about in the next minute and asked for a group picture all together. Then they gave me some of their food, an unkowen paste of sweet rood.
We walked up a slippy path under combat conditions with one little group well ahead of us, when suddenly loud gun fire started. I stopped breathing, went down and listened, meanwhile some soldiers rushed up the path. The exosting trecking was forgotten for the monemt. I look to Kivuay next to me. He was shaking his head and asked a soldier with whispering voice. Then he greened to me and explained, that it was just a salute for a shot comrade a while ago. Well thanks, thought I.
We reached a hut half an hour below the crater rim after 5 hrs. of tracking. Me and the armed ranger Kivuay agreed that the soldiers would retuned slowly back down the volcano. No, rebels, they said, not asking for a single Dollar. Well, only bush land was on the upper slopes of 3470 m high Nyiragongo, and it was quite cold already. Mr. Kivuay and I went up to the crater rim for some hours, so that I could document the geological situation of the volcano.
For this night we returned to a little and cold hut with open door and window. It was aufull only wirh a bed of leaves. The following morning we went up again for some pictures, then we started our descent. Half way douwn Kivuay pulled me of the track deep into the bushes and me getting doon and being quide, so did I. Some sldiers pass by. At the ranger post Kivuay explaned to me, that he was afrait of frandly fire. I left my body with an extra tip, paid my way via Goma to the frontier of Ruanda.

Part 3: Through Ruanda

Crossing for Zaire into Ruanda these days mend unpacking the backpack at cable military checkpoint and explaining my reason of travel, as well why I carried a meter long bush knife (sometimes I asked myself too) and what I’m supposed to do with my photo camera. I maganed anrgy and swetting to anwers this and reached the border town Gisenyi, got a hotl and some food, A riseing dawn I wend out to take a few pitures of destroyed military machenery from  the Ruanades conflic, well knowing that I had to be carefully by doing this. But the treets were emty in my opinion, so I took pictures.
When I start to walk back two military guys came across towards me. Oh oh, I thought. They said, ‘it’s forbidden to take pictures in Gisenyi’ and asked for my camera. I said no and that I was only taking pictures of the sun set over lake Kivu. They escorted me to a closed by police station. A nother military showed and after a discusion they aksed the film roll in my camera. To give the roll away with the of Nyiragogo and Gorillas away was out of the question. We argued I asked of higher rank officer again and again They agreed and two of them wend of.
That was my chance. I said ‘I need to go to toilet’ and to my surprise they had one in the station, even a real flushing one, and let me go. I closed the door, pulled out my camera, flushed the toilet, pushed the rewind button the camera motor did so, took the film roll out, a new inside, closed, flushed again and wend out. The militaries igrored me and the matter facted, that I was swetting like hell. Soon after, an argry officer showed amd asked for the film roll. Well, I took it out and handed over to him, than I left. The laugh was on my side for right now.
There was for sure no photo shop to develop my film roll, to make sure I left Gisenyi at dusk without breakfast on a big truck towards the frontier of Tanzania. Counless military stops and the frontier paper work took me all day long. Luckyly I got a nother truck on the tanzanien side, where a million refugees camped along the road since over two years. In one center of those elend I had to hopp of the truck already by night. So far safe, but hungry and tyred.
The nice truck driver asked for me around where to spend the night. An english speaking guy showed me a splace in a tent and a bessar cinemar where I could founde food and a coke. Maybe 50 relativly previleged or so, wathched quite silently the movie ‘Over the top’ with the actor Silvester Stallone on a small TV. Entrance fee of the cine was a quarter of a Dollar. This unreal, real situation made me some tears comming into me eyes. I left this burned, sad and tortured land towards the Serengeti, crossed the national park and reached the  town Arusha, an urban paradise in compare.


The 3470 m high strato volcano Nyiragongo is part of the Virunga mountains, which consist of 8 volcanoes. One of Africa’s most notable active volcanoes contained a lava lake from time to time in its deep summit crater.This lava lake was exsisting for half a century before outer flanks draining catastrophically in 1977. The steep slopes of a volcano are in contrast to the lower profile of the neighboring shield volcano Nyamuragira to the north. The 1.2 km wide summit crater has benches in the steep walled. Mark levels of former lava lakes, which have been observed since the late 19th century are found. The older strato volcanoes of Baruta and Shaheru are overlapped by the recent Nyiragongo and partially still seen on the north and south. Around 100 parasitic cones are located along radial fissures as far as Lake Kivu to the south. Many cones are buried by lava flows already, that extend long distances down the flanks, In 1977, the extremely fluid lava flows caused many fatalities on the south-east flank. The fluid lava flows towards the south in January 2002, destroyed a major portions of the city of Goma at lake Kivu.

Activity Reports

Observation on 3 August 1996.

Christoph Weber visited the volcano on 3 August 1996 and made a rough sketch map. Weber also saw no new activity. Features in the crater area included a spatter cone, a feature bordered on its S side with a light gray lava flow (dark shading 1). This flow was apparently the last erupted prior to the visit and it still showed fresh-looking flow channels. Weak fumaroles were located along the SE crater’s wall at concentric fractures ~50-150 m below the crater rim. Weber also relayed that seismologist Mahinda Kasereka had seen typical seismicity around this time interval

Members of an SVE excursion who climbed Nyiragongo during the second week of April 1996 found also no visible eruptive activity. They heard from local residents that the eruption that began in June 1994 (BGVN 19:06-19:08) had ended in September 1995. Whether the eruption actually ceased in September 1995 is ambiguous because Dario Tedesco learned that in November 1995 and in February-March 1996 observers saw glow above the crater at night. Also, Tedesco learned that some tourists spending the night near the summit during this same post-September interval allegedly saw minor activity. Some sustained seismic activity was reported in September through early December 1995 (BGVN 21:01).

Figure below: Nyiragongo sketch map showing the crater in August 1996. Symbols are as follows: 1) Spatter cone with last lava flows (shaded); 2) spatter half-cone; 3) first platform (or bench, ~175 m below the crater rim); 4) surface of chilled lava lake and associated lava flows (~275 m below the rim); and 5) dikes. Courtesy of Christoph Weber.

Observations in January 2011. Chris Weber visited Nyiragongo with an expedition group from 19 until 22 Jan. 2011. Lava lake activity of the last years  continued into January. The first platform from the eastern crater rim at 3420 m was still ~175 m below and marked the post-1977 level. The lowest platform inside the crater was at 3020 m (level of post-2002), which made a total of ~400 m. A high dynamics lava lake, consisted of the lava fountains, measured roughly 200 diameter and was hosted behind an 20 m high ring wall built by lava spattering.


The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography.
Krafft M, 1990. Fuhrer zu den Virunga-Vulkanen. Stuttgart: Ferdinand Enke
Global Volcanism Program (GVP), 1996. Bulletin of Global Volcanism Network (BGVN), Smithsonian Institution