Erta Ale and the Danakil in 2002 and 2010

Erta Ale is part of  the Danakil range, which belongs to the 10.000 km2 Danakil depression,  an 160,000 km2 area of the African Rift system called “Afar triangle”, which occurred 60 million years ago. This geological still active African Rift system caused due to volcanoes and faults multiply cut-offs from the Red Sea 30,000-10,000 million years ago. This Afar  triangle, partly up to 120 m below zero, is an extremely hot area, so that seawater evaporated in the 60 °C desert, leaving former seabed sediments as well as  submarine volcanism, which  can be studied in the area today. In this Afar triangle, extensive flood basalt of alkali basaltic chemistry and trachyte mountains dominate the picture and created the Danakil range which lies on an N-S-fracture.

The volcano Erta Ale is a  broad, 50-km-wide isolated shield that rises from –50 to 613 m above sea-level and is  the most active volcano in the Danakil in recent times. The volcano contains a 0.7 x 1.6 km, elliptical summit crater (caldera) and another larger 1.8 x 3.1 km wide depression elongated parallel to the trend of the volcano range which is located SE of the summit. Fresh looking basaltic lava flows can be seen in the caldera and locally have overflowed its rim. Some recent fissure eruptions have occurred on the N flank. To the north of the summit caldera two long-term lava lakes have been active for 100 years or even more.

A large northern pit-crater of Erta Ale has been active possibly since 1906, at least from 1967 and has an average diameter of 350 m. From 1959 to 1960 there have been occurred  large fissure eruptions. An active lava lake has been eyewitnessed by famous volcanologist Tazieff in 1968 and the adventurer Rüdiger Nehberg discovered  in 1970, that the N-pit had risen over the edge floating outside. In 2008, the N-pit collapsed and since then lava flows have poured out into the crater’s interior from time to time.

In 2002 for example a south-pit-crater measured around 160×120 m wide, with an 90 m wide active lava lake inside approximately 80 m below the crater rim. There were also phases (2004/2005) where the lava lake had a closed, cooled “lava lid”. By 2010 the lava lake had filled part of the S-pit-crater and five years later the entire S-pit was filled up, releasing lava flows outside the pit into the vast caldera towards the south. The lava lake temperature was measured at a max. of 1187 °C.

Film expedition into the Danakil (Nov./Dez. 2002)

Erta AléWe were nine German expedition participants traveling in an old MilMi17 military helicopter of solid russian construction on our flight from Makale at 2100 m to the Erta Ale shield volcano, 610 m high in the Danakil, one of the hottest deserts in the world, which is located in the Ethiopian Afar triangle. On board this military helicopter were the pilots and soldiers, our Ethiopian tour guide Kedir, the cook Hasan, an armed Afar, around 2 tons of equipment, food and water for 6 days. Marc, our cameraman, was sitting by open sliding door of the heli and securely fixed with a rope, so he couldn’t fall out as the heli turned around. After tuff days had passed, we finally managed to have our goal in focus.

For the expedition leader Chris, the way up to this point went through negotiations and payments with the military for the air transport in Addis Ababa, the land transport with four 4×4 cars plus personnel and for the procurement of equipment. After this followed a grueling and failed approach through Danakil desert and through Afar area to Erta Ale on a land route.

The local Afar didn´t allow us to proceed for whatever reason. So we had to change our plans and use the direct airway to the volcano.

Since the Ethiopian military and the Afar tribe in the Danakil desert were often enemies of the war, our military helicopter was of course not appreciated to be seen over the Erta Ale, so the pilot flew the heli in low-flight to the volcano from the sparcely populated north. Then it was quickly unloaded and the helicopter flew away, with an appointment to pick us up again after 5 nights. At 40 degrees Celsius, the transport of the equipment over shaky and very fragile lava fields to a suitable camp site was hard work. For security reasons we were hiding some water, documents and money in rock places, right after we went to explore the active lava lake profoundly.

The geological situation was as described in recent reports. The lava lake occupied about half of the crater, and the lake surface was approx. 90 m below the W rim of the S-pit crater. The remaining area in the E was covered by basalt that had a terrace (T) 45 m below the crater rim. Previous observations had located the terrace at 70 m below the rim. It was widely covered with talus; hence, the lava lake must had risen up to the present terrace level between spring 2002 and our visit. Almost no talus was found on the terrace, indicating that the lava cover was not old. Actually lava fountaining up to 20 m high occurred out of the crater lake.

We set various anchorages for a pulley system to rope down into the crater to the first terrace (T). Chris was the first to climb into the S-pit to clean the route from loose rocks. The goal of the effort was to reach the terrace and take a lava sample from the approx. 45 m deeper lying lava lake by fishing technique. When cameraman Marc had roped down into the crater to document the action, the crater edge suddenly broke off from above over a distance of perhaps 30 m. Luckily most of it fell into the lava lake.

But as some rocks of the break out unfortunately crashed onto the terrace, Marc and Chris jumped away from the spot and away from the lava lake edge, from which a huge cloud of dust rose up. We were convinced that it was a unique case, but nevertheless we quickly finished filming to get out of the crater. When Marc was hanging on the rope for the ascent, another 20 m wide rock package crashed into the lava lake and onto the platform again. Luckily both of us made our way up. After that second rock fall all other documentations were taken from the rim of the crater, as well as from the N-pit-crater and outside the wide caldera. Then our helicopter appeared as agreed. We packed everything up, made an extended sightseeing flight over the Erta Ale, then along the Danakil Range to the north to the volcano Dallol with a stop-over and finally to Makale.

Visit of Erta Ale (Visit Feb. 2010)

From 8th to 11th February 2010, Chris was back at Erta Ale with an expedition group, like he had been in 2009 as well. For expeditions Erta Ale range had always been approached from the west side where the sand desert meets the lava flows of Erta Ale around 50 m below sea level. A high base camp already 150 m above sea level was reachable by 4×4-car and the ascent to the edge of the caldera had to be continued on foot in around four hours in the relatively cool nighttime. While the descent back to the basecamp could be done in 3 hours, depending on temperature which could rise up to 50 °C in daytime at Erta Ale range.

The situation at the two active craters had changed quite a bit. The larger N-pit-crater to the north of the caldera had collapsed in 2008 and been refilled with many lava flow events since then. Lava spatter (about 15 m high strombolian activity) took place at a central located hornito in this N-pit once every day during our observation. Short lava flows occurred from this hornito towards the east and south inside the N-pit.

The elliptic S-pit still measured with about 180 m EW and 130 m NS. The upper platform (terrace T) inside the crater was  overflown by young looking lava flows. Now the lowest point from the lava lake surface to the crater rim was only about 20 meters on the W side. A 65 m wide active lava lake was located in the western half of the S-pit. Fountaining at this lava lake took place most of the time during observation, occasionally higher than the crater walls. Fresh lava spatters were found at the craters west edge.

Chris again had brought rope equipment to make an attempt to climb down into the S-pit. Since the first platform (T) was not 30 m below the old rope anchors, it seemed to be possible. Well, he managed it and got lava samples and very nice film documentations. One day later this platform (terrace T) was completely flooded with lava.


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

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

Oldoinyo Lengai: The holy mountain of the Masai (1996 until 2004)

The 2nd part of Chris Weber’s Ol Doinyo Lengai report describes what happened at the volcano in Tanzania, between the years 1996-2004.

Report on Lengai 17 August 1996

Ol Doinyo LengaiChristoph Weber climbed Lengai on 17 August and he observed a lava fountain up to 3-m-high on T37. During his entire time of visit lava still poured out. Beside activity at T37, Weber saw some quite fresh black Aa and Pahoehoe lava flows on the crater floor. He estimated the thickness of the fresh flows as typically 20-30 cm. Fresh flows were easy to distinguish because they may change from black to grayish white as they cool within days. They were often stacked, particularly on flow field F37, the one most active at that time, forming a composite of new flow material about a meter thick overall. Because of the rough irregular surfaces on some flows, their contacts with successive flows often contained considerable void space. Many of the flows were tube-fed, the tubes typically being 10- to 150-m long.

Report on Lengai 6 August 1998

Observation of the crater from 6 August 1998, 0800 until 7 August 0800 by Chris Weber. On 6 August at 0800 an eruption started at hornito T37N1. This hornito has a platform about 5 m above the surrounding area while it is highest peak at the northern flank is about 8 m high. A little splatter cone had build up on this platform where foaming white to pale grey carbonatite lava splashed out and fed short lava flows with a few meters length down the west-slope of T37N1. Most of the lava went into older lava tubes west of this hornito. The vasiculation of the gas rich lava was high. The activity stopped around 1100 with a 4 m drop of the lava level in T37N1.

On the same day at 1400 lava splashed out of two openings close to it is peak of hornito T48. The black degassed very liquid lava fed little lava flows reaching 8 m of length down the east-slope. The activity stopped shortly after 1600.

On 7 August at 0408 a loud explosion blew of the top and northside of hornito T49 after several earthquakes during the night. The earthquakes seamed to have shallow and deeper hypocenter in the volcano. Rocks of this hornito up to 1 m3 were thrown or rolled a few meters to the north by this explosion. Right after the explosion a lava fountain (fire curtain) approximately 15 m high continued until 0413 with a loud turbojet-noise. Pahoehoe lava with little viscosity (1-5 Pa s) which splashed down north of the hornito traveled fast to the north and west.. The 10-20 cm thin flow stopped moving shortly after the end of the eruption. The amount of erupted lava was about 70-100 m3. Lava pearls up to 4 mm diameter and fine ash were transported at least over 200 m by the wind in northwest direction. The fountain had a dark red glow. The hornito lost less than one meter of the 6 m elevation., whish it had before the explosion.

At 0615 on 7 August hornito T44 started activity for an unknown time. Black liquid lava splashed out of it is 6 m high peak and splattered on the flanks of the cone. No lava flow was observed until 0815.

T40 degassed with mild turbojet-noise. The lowest point [ X ] of the crater-rim over the crater-floor in northwest was 20 cm.


Report on Lengai 3 until 11 Oktober 2000

Eruptive activity: On 3rd Oct. from 1200 until 1350 hours spattering occurred in the saddle between T49 and T49B out of a small vent. Two little lava flows were observed at the northern and southern flank of T49 during that time. At 1350 the west side of T49B collapsed and released out of an approximately 6 m wide and 5 m high gap a sudden flash flood of lava. Parts of the collapsed wall of T49B were washed towards the west as big blocks. Within a few seconds the flow had reached halfway between the cone and the NW Overflow. After 5 minutes the flow had reached its final extent about 40 m short of the NW Overflow (See map of flows: Flow 4A). The lava flow was up to 5 centimeter thick and later Aa flows were several decimeters thick.

Until 8th Oct. lava spattering and many small lava flows (formed from overflowing the vent, as spatter fed flows or emitted from small new vents and fissures) had nearly closed the gap in the west wall of cone T49B. Only close to the top of T49B spattering occurred on the evening of 8th Oct. On the morning of 9th Oct. at 1035 hours nearly the same west flank of new lava collapsed in the same manner as on 3rd Oct., leaving a 7 m wide and 7 m high gap. Lava went in a flash flood within seconds towards the NW and stopped just 10 m before the NW Overflow. The flow covered the Flow 4A and is shown in the flow map as Flow 4B.

During the afternoon of 9th Oct. T48 had strong degassing and for only 10 minutes ejection of tear-drop lapilli occured. After this event T48 went quiet for the rest of our visit. Right after sunset of 9th Oct. at 1810 hours a crack opened at the SSW base of T49C with a sudden noisy gas jet followed by a 10 minutes spraying of lava droplets and sperical lapilli up to approximately 10 m high. A small lava flows (Flow 4C) were emitted too and moved NW. From there on until our descent on 11th October no flows were observed, meanwhile the lava lake inside T49B was still in motion and heavily splashing and degassing.

Accident: Jürgis steped into a little lava flow in October 2000.

In the evening Oct. 3rd, 2000 small lava flows were to be seen again at Hornito T49, so that I called the geologist of the IMPG team, Jürgis Klaudius, who was already resting in his tent, to have a look. He was curious and to hurry up, he put on his sneakers instead of his mountain boots, and jumped out of the tent. We went to the lava flow in the dark and then a scream from Jürgis followed. He briefly had stepped into a 20 cm high lava flow at a temperature of about 500 degrees, which was flowing across a flat terrain and just looking black in the dusk. All light plastic and gorotex parts of his sport shoe were burned, the leather parts and the sole were left as a framework.
The consequences were quite fatal. Despite my good first aid and quick treatment of the burned injuries, Jürgis had to be evacuated from the mountain after two more days with his infected foot on 6th August. Since an attempted air rescue by heli failed because of non capacity, only the rescue down the steep mountain slope remained. In the steep upper part, over 45 degree, Jürgis had to slide down on his butt with his injured foot forward wrapped into bandage. This was painful and distroyed his trousers. In the middle of the way down, two of us gave him a support and when it got flatter, the four of us rescuers shouldered the tired man piggyback changing every 10 minutes one after another. For this descent we needed about 8 hours instead 4 hours or so.

Following, Jürgis, me and driver Mike had an 8 hour drive through the night into hospital in Arusha. Next morning I had already rebooked the flight from Jürgis towards Germany and then Mike and I started our journey back to the Lengai, where I made the ascent with a load of 30 kg luggage early in the following morning. Later on when Jürgis had returned to Germany a succesfull skin transplantation took place. Luckily everything went fine again without immobility consequences.


Report on Lengai 18 until 22 Oktober 2002

By the arrival 18th June the fresh looking and still black lava flows were visible from T49B on a length of 120 meters towards western directions. From T46 black lava flows streched towards NW, W, SW, and South on a length of 20 to 80 meters. The hornito T37B was covered with still black lava and propably had erupted recently. The flanks of T48 as far as to T44 were covered with black lava lapilli also propably from recent activity. The diameter of the T49 base (eruption center) increased strongly compared to august 2001.

A new eruptioncenter was clearly visible half way between T46 and the West overflow an could be numbered as T54. The eruption site of T54 was an open lava pond with an overflow of about 40 meters towards the west. Black lava had covered older lava flows who had left the crater on his west side in Febuary 2002. A lava lake bubeling deep inside T48 was clearly heard during the days of our observation. The fumarolic activity and its temperature (> 125°C) increased also from summer 2001 until summer 2002. Three recognizable relativly deep released single vibrations occured during our visit

Activity and small lava flows were observed from T49B. On 18th June lava spattering from the top of T49B went on in intervals of intensitiy from 14:00 until 19:00 hours. The maximum height of the lava fountains of was arround 3 meters. A litle lava flow went from the top towards the norh east for about 50 meters. During the day of 19th June spattering occurred with a duration everedge of 30 minutes followed by one and a half our breaks of now activity until 04:15 hours in the afternoon. No more activity outside hornito T49B and other hornitos was observed until 22nd June. On 22nd June arround 10 m3 collapsed from the wall below the summit of T49B into the crater.


Report on Lengai 10 until 14 February 2004

On 10 February 2004, Chris Weber and others visited Lengai for 5 days. The summit of the tallest hornito in the center area of the active crater at Oldoinyo Lengai was at approximately 2886 m altitude (GPS), standing about 33 m above the surrounding crater floor to the north. This tallest hornito at the T49 location (T56B) was not active anymore, while T48B (T58B) had a lava lake deep inside it’s hornito, clearly indicated by noises and tremor. The activity had changed to the common effusive and lava lake activity. This occured at the old T49 eruption center, also indicated by the activity of T49B during observation and an active new vent (numbered T49G by C. Weber) at the north flank of T49 (T56B), about half way up from its base to the north side.

This new activity propably caused two collapses (depression) in the north flank of T49 (T56B), already visible since January 2004 (first described by B. Donth). The T49G vent, hosted at the upper collaps, had a steady degassing lava lake with many overflows during the visit of C. Weber. Lava penetrated the lower collaps at T49 and lava flows reached as far as to the NW overflow. On 12 and 13 February T49B spattered lava for some hours, feeding lava flows to the west (T51), finally escaped into a lava tube system. The lava temperature very close to the lava lake was measured at 588°C. Aa lava flows not in motion anymore at flat terrain were measured between 480°C and 500°C.


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

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 soldiers 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 and drove off. I know, that the zairen 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 journalists told me some days later in Goma, that it’s impossible 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 Rwanda into Zaire in the 1970’s after first massacres took place by the Tutsi minority. Then, after many incidences in 1994, the Hutu took revenge and killed 75 percent of the Tutsi and moderate Hutus. Only in June and July up to 1 million people were killed. Finally, the rebel group RPF took over in Rwanda 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 empty and a UN organization (peace and aid force) behind many high fence lines. After one night in Goma without any food except Coca-Cola, I went out on the road again to reach the foot of Nyiragongo. It was out of the question to climb up the volcano without guide and armed force, because of gang (bandits) activities 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 month. At a nearby zairen military post we found luckily a solution to get a well armed group. The chef officer was so amazed of my crazy wish to clime Nyiragogo, that he ordered a dozen 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 leek of any food. But after checking this young guys out and the fact, that this forests are hiding places for Hutu and Tutsi, gave me no other option. For this evening Mr. Kivuay gave me some food and a place to lay down my sleeping bag.

Our expedition started by early morning, and it was my best armed ever with an amazing variety of weapons. Soon we entered the jungle at its best with heat, humidity, crying monkeys and crazy loud zikades. During a break, I pulled out my photo camera and instantly watched into the soldiers big eyes. Well, for sure it was in their eyes a fortune. 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 unknown 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 exhausting tracking was forgotten for the moment. I looked 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 hours of tracking. Me and the armed ranger Kivuay agreed that the soldiers would return 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 awful only with a bed of leaves. The following morning we went up again for some pictures, then we started our descent. Halfway down Kivuay pulled me of the track deep into the bushes and me getting down and being quite, so did I. Some soldiers passed by. At the ranger post Kivuay explained to me, that he was afraid of friendly fire. I left my body with an extra tip, paid my way via Goma to the frontier of Rwanda.

Part 3: Through Ruanda

Crossing for Zaire into Rwanda these days meant 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 managed angrily and sweatingly to answer this and reached the border town Gisenyi, got a hotel and some food. At rising dawn I went out to take a few pictures of destroyed military machinery from Rwandas conflicts, well knowing that I had to be careful by doing this. But the streets were empty in my opinion, so I took pictures.

When I started 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. Another military showed up and after a discussion they asked at least for the film roll in my camera. To give the roll away with the of Nyiragogo and Gorillas was out of the question. We argued I asked of higher rank officer again, and again They agreed and two of them went out and off.

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 went out. The militaries ignored me and the matter of fact, that I was sweating like hell. Soon after, an angry officer showed up and asked for the film roll. Well, I took it out and handed it over to him, then I left. The laugh was on my side for right now.

There was for sure no photo shop to develop my film roll, nevertheless I didn´t sleep well that night. I left Gisenyi at dusk without breakfast on a big truck towards the frontier of Tanzania. Countless military stops and the frontier paper work took me all day long. Luckily I got another truck on the Tanzanian side, where a million refugees camped along the road since over two years. In one center of those disaster camps I had to hop off the truck already by night. So far safe, but hungry and tired.

The nice truck driver asked for me around where to spend the night. An English-speaking guy showed me a place in a tent and a bizarre  cinema where I found food and a coke-cola. Maybe 50 relatively privileged or so, watched quite silently the movie ‘Over the top’ with the actor Sylvester Stallone on a small TV. The Entrance fee of the cine was a quarter of a Dollar. This unreal situation made me some tears coming into my 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