Christoph Weber, Email: mail@vulkanexpeditionen.de
Joerg Keller, IMPG, Albert-Ludwig-University Freiburg, Albertstrasse 23b, 79104 Freiburg, Germany Email: jkeller@uni-freiburg.de
An common expedition was organized by Chris Weber from 3rd October to 11th October 2000. A film team and four scientists, led by Joerg Keller, were members of the expedition. Joerg Keller has studied O. Lengai since his first visit in 1988 and has published several papers about O. Lengai:
3rd October to 11th October 2000
Nature of record: Observation by J. Keller, A. Zaytsev, D. Wiedenmann, J. Klaudius, D. Szczepanski, M. Szeglat, C. Weber.
Geography: GPS-Data and barometrical instruments (series of data-measurements) gave new information about the altitudes of O.Lengai. The highest summit is approximatly 2955 m (2950-2960 m). The cone peak C on the northern crater rim is approximatly 2835 m. The crater floor was on October 2000 approximately 2925 m at the Overflow NW and E.
Despite the known track up the WNW flank of Lengai, two other different descents were made during the visit.
1) The track down the eastflank (named Dorobo-Route "the ascent route of Krafft-Keller expedition in 1988") was followed by J. Keller and 2 scientists of his team on 7th October 2000 for reconnaissence. This track is difficult and should not be attempted without a guide.
2) One track starting half way between the western crater wall and the summit down the WSW flank passing the Kirurum crater (named Reck-Route) was followed by Keller/Weber including expediton members and local porters on 11th October to 12th October 2000. One overnight camp was made at the Kirurum crater along this track to give time for fieldwork.
Different craters around O. Lengai were visited beside of the summit-crater expedition, such as Lalarasi and Loolmurwak. For further information about geography around Lengai please contact J. Keller.
Renumbering: Some frequent visitors and scientists who work on Lengai have decided to change some numberings for the current cones. This is because of an easy understanding for the future and owing to changes of cones during the last years. The new cone numbers will follow a logical system as followed: a new eruption center gets always a new T-number (e.g. T49). New cones at the flank of an existing cone, and clearly fed by this, will be numbered with an "B" (T49B), following ones by "C", "D" and so on. This leads to the following renumbering:
- T52 (former T52C)
- T52B (former T52W)
- T52C (former T52E)
- T37 (former T37S)
- T37B (former T37N1)
- T37C (former T37N2)
- T37D (former T37E) and also (former T5/9)
 overview map |
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 crater: lavaflows |
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.
Lava and fumarole temperatures: Between 3rd Oct. and 9th Oct. 2000 temperature measurements were made by three different instruments and gave consistent values. The following table gives values from a digital thermometer (TM 914C with a stab feeler standard K-Type). the instrument was used in the 0-1200 Celsius mode, taking readings by inserting the feeler 10 cm into still moving and liquid lavas (10 times at various days) and as deep as possible into the fumaroles (5 times at various days). Calibration was by the Delta-T method: values are +/- 6°C in the 0-750°C range.
All values shown were recorded by four repeat measurements at one spot.
- Pahoehoe lava flow (15 m below outflow from lava pond (lake) inside T49B in an closed lava tube); 507°C
- Aa flow front in slow motion (shortly after escaping a closed lava tube near T49B, 25 cm thick); 496°C
- Fumarole 25 m NNW of T49C in a crater crack towards the rim (see map of cracks); 75°C
- Fumarole at the Overflow NW inside the old crater rim; 69°C
- Fumarole at the NW flank of T48; 95°C
According to the red glow of lava in the night of the recent visit and the visit of 1998 by Chris Weber, he has noticed, that the lava glow during a visit by Chris Weber in Aug. 1998 and Aug. 1996 was more intensive, therefore probably hotter than 530°C.
Appearance of crater: Flow 1 had still a brown appearance, but had continued to weather after the 30th July describtion. The younger Flow 2 was partly black to gray in the joints and cracks of the Aa flow field. Some smaller flows around T49 and T49B were slightly black, though probably only a few hours old. We learned from this visit and many other visits, that hydration of fresh lava flows (specially under high humidity) can cause a black surface turn into soda-white within 24 hours respectively overnight.
NW of T49B another cone belonging to the T49 eruption cluster had appeared after 30th July and is named T49C (see map). T51 was surrounded by flat Pahoehoe flows and had grown since 30th July. There was a new cone in the collapsed T48 with some small light gray looking lava flows close to the cone.
During this year many new cracks (in a maximum up to 1 m wide and 5 m deep) had opened all across the crater floor. The V-shape of cracks could lead to an expansion or doming theory of the crater floor. Most of the cracks point to the T52 and T49 eruption clusters, roughly the center of the major cone concentration. Some of the cracks break through the crater rim. Other cracks are filled up or covered by young lava flows. So the map of cracks may not show all actual cracks in the surface.
Accident: On the evening of 3rd Oct. 2000 at 2010 hours, one of our scientists (Jurgis Klaudius) stepped by accident with his left foot in a fresh but already black and solid looking lava flow (about 25 cm thick) at the westslope of T49B. This can easily happens to everyone in the night if solid and fresh black flows are all around one site. In this case it caused a serious second degree burning to Klaudius around his ankle up to his lower leg. All light plastic and gorotex parts of his sport shoe were burned away owing to about 500°C lava temperature. The leather parts and the sole were left as a framework. On 6th Oct. without any chance to get a helicopter for rescue, evacuation was necessary because of the risk of an infection. He managed to slide down the steep slopes of O. Lengai on his hands and right foot for most of the steep upper track, but was finally carried by a seat-construction and by four strong porters on their shoulders the rest of the way down. He was brought to hospital in Arusha right after the evacuation and flown out to Germany after further 24 hours. After a skin transplantation J. Klaudius is recovering very well and will not suffer lasting damage.
Warning: O. Lengai is as dangerous as any other active volcano. We have experienced explosive eruptions, suddenly appearing lava fountains, several cone collapses, lava flash floods and flows with enormous quantity.
Lava temperature of 500°C is hot enough to burn someone seriously and because of the very low viscosity, this natrocarbonatite lava is extreme fluid and can flow very fast. But most difficult is the problem of rescue at Lengai like our example shows, though even the danger of the mountain itself and the weather should be taken very seriously. We do not recommend visits on Lengai without a guide or an experienced person.
Information contact: Celia Nyamweru, Department of Anthropology, St. Lawrence University, Canton NY 13617 USA (Email: cnyamweru@stlawu.edu);
Joerg Keller, IMPG, Albert-Ludwig-University Freiburg, Albertstrasse 23b, 79104 Freiburg, Germany (Email: jkeller@uni-freiburg.de);
Christoph Weber, Volcano Expeditions International, Friesenstrasse 20, 42107 Wuppertal, Germany, Tel: 0049-202-4491897 (Email: mail@vulkanexpeditionen.de;
URL: http://www.Vulkanexpeditionen.de);
Frederick Belton, 3555 Philsdale Ave., Memphis, TN 38111 USA (Email: oldoinyolengai@hotmail.com; URL: http://www.people.memphis.edu/~fbelton/Lengai.html);
for video-film clips contact: Marc Szeglat, Duelmenerstrasse 11, 46117 Oberhausen, Germany (eMail: m.szeglat@t-online.de, URL: http://www.vulkane.net)