Jan 2010: Hans Schabel climbed on Jan 16 and reported: "We gaped into the impressive jumble of debris at the bottom of the crater, saw some fumaroles near the rim, but otherwise things are quiet.
Feb 2010: Alexander Daneel, Martin Dodwell, and Frank Louw climbed on Feb 11. Alexander sent photos and reported: "You could even hear the magma moving within the bowels of the mountain and there was a small fissure that erupted every time it "growled". There also was steam coming from an area of the rim of the crater right next to the part that collapsed. The collapsed area is almost a hundred meters wide."
Panaroma of Lengai ash cone looking north. The collapse area at about one o'clock is described by Daneel as "almost a hundred meters wide." Photo courtesy Alexander Daneel.
View into crater showing vents at upper right and recent lava at lower right. Photo courtesy Frank Louw.
Feb 2010: Frank Möckel climbed on Feb 14, took pictures and wrote a report which follows:
"A group of four geologists (Frank Möckel - head of the group and organizer, in friendly and successful cooperation with Basecamp Afromaxx Ltd.-Moshi, Dr. Kerstin Nindel, Dr. Thomas Seifert and Peter Slesaczeck) from Germany investigated during February 2010 the volcano Oldoinyo Lengai and also the numerous small cones and several craters (Sinja Lalarasi cone, Armykon hill, Black Belly, Dorobo cone, Nasira cones, Kisete crater etc.) around the Lengai volcano. In the night from 14.02.2010 to 15.02.2010 we climbed the Oldoinyo Lengai over the western route, which is covered with grey ash and lapilli of the 2007-2008 explosive eruptions. The vegetation here is totally destroyed. The climbing was very hard, especially at the upper part of the volcano. Typical for the western route are many erosions gullys in different size and width. The surface of the ash cover is strongly cemented like concrete. The thickness of the concrete layer is only 0,5 to 1,0 cm. Under this solid layer the ash is still loose. This situation is very dangerous. The concrete layer could collapse when we go over. We think that the concrete layer was formed by rain or humidity. In the upper part (from about 500 m under the crater rim) of the Lengai volcano the surface is also cemented but in this section many large bombs, stones and blocks embedded. This surface is very rough. On this surface often lies sandy or gravelly material. The steep ascent (angle about 45° to 55°) of the volcano and the slippery surface makes the climbing very hard and dangerous. We went through cloud cover and with much effort we came to the pearly gates. After the pearly gates region we came directly to the new ash cone of the 2007-2008 explosive eruptions series. The new ash cone consist of pyroclastic loose material. The climbing of the new ash cone is not so hard, but a strong stormy wind is blowing here. At 06.20 in the morning we reached the rim of the new ash cone. To this time we have seen a beautiful sun rise over the Kilimanjaro from the distance. The air temperature on the crater rim was 11.4 degrees Celsius. The rim of the new ash cone is only approximate 1 m wide. On the rim we found many small bombs. We looked from the southern side (the summit of the Lengai and the south crater in the back) of the new ash cone into the deep crater (about 80 m depth) and we have seen new small black hornitos and cones additional a new black lava flow on the crater floor. The three new hornitos in the most western part of the crater floor are black and very fresh. In the middle of the crater floor stand a cone-shaped grey hornito. The new black lava flow is situated in the southern part of the crater floor. The eastern part of the crater floor is collapsed. This older lava is light grey and slightly altered. The fill up of the inside of the new ash cone with lava is small at the moment. Sampling of new lava was not possible. Momentaily no way exists to go to the crater floor of the new ash cone. We think that the new lava is natrocarbonatite, but this is not certain. In the crater and around the crater many fumaroles were observed. The gas is rich in sulphur (everywhere H2S smell). No seismic activity was noticeable. We heard no noise from the bottom of the crater. Duration of climbing: about 8 hours. Duration of descent: about 5 hours."
Based on Frank's photos below and reports and photos of Alexander Daneel and others from previous months, it appears that there has been a return to the small eruptions of natrocarbonatite lava and cone building that were typical of Lengai prior to the 2007-2008 explosive eruption. The lava has not been sampled and its composition is unknown. However, these crater floor vents are typical of lava pond basins and spatter cones that characterize eruptions of low viscosity natrocarbonatite lava.
General view of Lengai's north crater. Photo courtesy Frank Möckel
View of crater floor. Photo courtesy Frank Möckel
Detail of a crater floor vent. Photo courtesy Frank Möckel
Detail of a crater floor vent. Photo courtesy Frank Möckel
Detail of a crater floor vent. Photo courtesy Frank Möckel
March 2010: David R. Sherrod of the US Geological Survey, Vancouver, Washington, USA, surveyed Lengai from March 12 - 14, accompanied by Kisana Mollel of Dorobo Safaris, and Olemelok Nantatwa of Engare Sero village. Many thanks to David for forwarding their survey to me, which appears below and is also available as a PDF document at Sherrod_OldonyoLengai_March12_2010(5).pdf
"Oldonyo Lengai’s North Crater was quiescent when visited Friday, 12 March 2010. The crater rim, approximately circular, ranges in diameter from 270 to 310 m (fig. 1). Crater depth is 110 to 122 m, two-thirds or more of that is the height of cliffs that rise directly from the crater floor to its throat, and the remainder is the height of the sloping crater rim (fig. 2). If the crater has not deepened since June 2009, then a depth of 80 m reported by T. Fisher is an underestimate. From its rim, the crater mouth slopes inward 30 degrees, descending at that pitch for 15–30 m before ending abruptly at the cliffs of the crater throat. Fine-grained pale gray or light-brownish gray ash, in part altered by weak solfataric steaming, mantles the upper slopes. A rockfall that occurred before April 2009 (A. Daneel’s photos in GVP monthly reports) has scalloped the northeast crater slope, leaving a shallow scar 70 m wide (figs. 3, 4). Outward-dipping beds of vent-building tephra, exposed by the scar, provide visual evidence that the mouth-coating ash is thin, only 30 cm or less in most places (fig. 4). The throat is about 200 m diameter. The crater floor has an area of 3.26 ha. It lies at an altitude slightly lower than the “Pearly Gates” traversed on the westside climbers’ route (fig. 5).
Figure 1. View north from summit of Oldonyo Lengai toward North Crater. Top of Pearly Gates lava flow visible emergingfrom fog on west slope (left). USGS photo by D. Sherrod, Mar. 13, 2010.
Figure 2. Cross section of North Crater on Mar. 12, 2010.
Figure 3. (First image above) View northeast showing large-block rockfall on crater floor and resulting scar on northeast rim. USGS photo by D. Sherrod, Mar. 13, 2010.
Figure 4. (Second image above) View north toward the rockfall scar on northeast rim. USGS photo by D. Sherrod, Mar. 12, 2010.
Figure 5. Map of North Crater Area on Mar. 12, 2010
The scene on March 12 appeared largely or entirely unchanged from that appearing in photos taken one month earlier (February 2010); at that time, pahoehoe had floored nearly half of the crater floor. The smell of H2S was weak, SO2 smell was undetectable, and steam escaped from the few cracks that cut across the crater slopes. Neither steam nor fume were notable in the deeper part of the crater. Several volcanic and erosional events, listed next, can be surmised from geologic relations on the crater floor, although none of the events is dated except by knowledge of their presence or absence during previously documented visitation. The recent lava flows and hornitos described below presumably are carbonatite, but none was sampled because they are inaccessible.
(1) Globs of lava are spattered on the throat walls. The spatter and rock alteration obscure much of the layering of strata exposed in the cliff faces.
(2) Rubble from wall collapses has formed talus cones that cover more than half the crater floor. The oldest of these talus deposits comprises large blocks from the rockfall that carved the east side of the crater slopes (pre-April 2009) (fig.3). This large-block rockfall has light brown ash on it, erupted from a 3–4-m wide pit blasted through the talus debris. The several smaller ash-rimmed craters that appear in March and April 2009 photos (S. Lübben and B. Wilhelmi, respectively, posted on Fred Belton’s Web site) are now muted. Also nestled among the large-block talus field is a small hornito. It and the short pahoehoe flows that issued from it are covered by the same brown ash that coats the talus. If the hornito is a product of June 2009 activity described and pictured in various reports, then the brown ash must postdate June 2009.
(3) Young gray pahoehoe, lacking any ash cover, covers about 1.37 ha, or 40 percent of the crater floor (fig. 6). It issued from three bocas near the north crater wall (scene essentially identical to that photographed by Frank Möckel_ Oldonyo Lengai: Trip Report March 12-14, 2010.
Figure 6. View northwest toward boca and young pahoehoe on crater floor. USGS photo by D. Sherrod, Mar. 12, 2010.
The faintest of noise could be heard from the area of the three bocas in the North Crater. The sound was reminiscent of sloshing heard deep in pits on Kīlauea, although with more of a drumming percussion, like that of periodic gas release occurring every 3–10 seconds, but wind across the crater rim made it extremely difficult to resolve the crater sounds or their origin. A nighttime visit to the rim from camp was made on March 13. At that time the crater and all vents within it were dark. No incandescence was seen.
The south crater, where we camped, is now dotted by ballistic craters, features presumably resulting from the eruptive events of 2007–08 (fig. 7). The shallow impact craters, as wide as 1.5 m diameter, chiefly or entirely postdate the ashfall that accompanied the 2007–08 eruptions, judging from crater preservation and the deformation of surface beds. Craters were sparse closer to the vent, especially on steep slopes, so the sense of a directed muzzle that might be inferred from the distribution of ballistic craters may be an artifact of favorable summit slopes.
Figure 7. View south-southwest across South Crater, 0.7 km from North Crater vent. Arrows point to three of the more than 200 ballistic craters visible in the field of view. USGS photo by D. Sherrod, Mar.12, 2010.
Under current quiescent conditions, the chief hazard at the North Crater is crater rim stability. The rim’s circumference is marked by a faint footpath traced by the many visitors who wish to see as much of the crater floor as possible or who walk to the east rim on clear mornings for a better view of Mounts Kilimanjaro and Meru. Rim-collapse hazard may diminish with time, as the rim materials become better cemented; or it may increase as ongoing alteration weakens otherwise stable rock. Those who walk the rim need to watch for traces of circumferential fractures and then judge where the onstrike projection of those fractures might approach the rim. The northeast rim seemed especially unstable.
We detected no perceptible gas hazard during our visit. The summit area is well ventilated, and the smell of sulfide gas was weak. Measurements made by inserting a handheld field device* into low-temperature steaming cracks at the summit detected no CO2. Null values were also obtained when placing the CO2 monitor into shallow pits in the south crater where soil gas might percolate, but the holes were so shallow (<60 cm) that summit breezes probably prevent gas accumulation. Concentration of ground CO2 is unlikely to pose a hazard for those in closed areas (tents?), given the wind across the summit area. The North Crater’s cliff-lined walls preclude access to the only obvious topographic trap for CO2.
*The device, Analox Corp.’s CO2 Buddy, is specifically for personal protection and has default alarms at 0.5%, 1.5%, and 4% CO2. The manufacturer specifies that it will read down to 0.01%, but low concentrations are not reported reliably and ambient atmospheric concentrations typically read 0%"
May 2010: The following report was sent to me by Laura Carmody: Four scientists [Laura Carmody (University College London), Adrian P Jones (University College London), Matthew J Genge (Imperial College London), and Wendy Nelson (Carnegie Institution of Washington)] and two Masaai guides ascended Oldoinyo Lengai on the 18th May 2010 reaching the northern crater at around 10am and spending approximately 2 hours at the summit. Observations of the crater suggest that the volcano is in a period of reduced activity following the explosive eruption in 2007 with no lava production on the crater floor, although lava could be heard below the surface at intervals of 15 – 20 minutes. The crater floor was covered with rocky debris including tilted broken lava plates (5-10 m scale) possibly from recent magma withdrawal, and various gravity collapse material from the over-steepened and locally unstable inner crater walls. Observations of these collapses from two sites around the ash cone (north eastern and south western sectors of the rim) indicate debris scars of about 30m in width with some material appearing to have fallen en masse into the crater. There were at least three visible sites of active degassing, two from fissures on the crater rim ash cone and one from a vent on the crater floor. These plumes were white in colour and had a sulphurous smell suggesting the presence of hydrogen sulphide. The ash cone on the northwestern approach to the crater showed up to knee-deep alteration to dark brown, yellow and black soil-like products with pockets of blue and green material accompanied by a distinctive rotten eggs (sulfurous) smell. Climbing conditions were difficult with slope angles of around 55° through the pearly gates and narrow gullies to walk in.
Photo courtesy Laura Carmody
Oct 2010: Michael Dalton-Smith flew over the crater in early October and saw some magmatic activity of the type that was typical of Lengai prior to the 2007-2008 eruption.
The active vents are located in the SE part of the crater. Photo courtesy Michael Dalton-Smith
Three active vents and two lava flows are visible inside the pit crater. Photo courtesy Michael Dalton-Smith
Nov 2010: Richard Priebe sent me an account of his Nov 16 - 17 Lengai climb with his two sons:
"My boys are 8 and 9 years old. We’ve done some hiking in the past but the challenge of 1700 vertical meters was before us. My wife and I joke about the days when we would push the boys in a stroller to the base of hill. They would hope out and run/scramble all the way to the top. If there is motivation to climb they have endless energy otherwise the stroller was essential. Lava flows were enough motivation to get us to the mountain. After driving for another hour with our guide up the gentle slopes of the mountain we came to the end of the track. It was 8:00pm, the moon was shining bright and we put on our packs and headed off.
My boys were thrilled to be on Tanzania’s only active volcano! There head lamps were flashing all over as they were searching for lava flows and eruptions. I reminded them that the lava was in the crater at the summit, we had a long way to go. Nonetheless the barren landscape scared by erosion was plenty exciting. The boys were jumping between the dry stream beds stomping on the dirt watching it collapse. I knew that they needed all that energy for later and so reigned them in behind me and put a no playing rule in effect. Hiking should be fun but I didn’t want their energy used up in the first hour. The summit was our goal.
We kept a steady slow pace for the first hour and then the trail steepened and became a series of erosion tracks on the crest of a ridge. Either side had steep droops into the canyons below. The hiking was nice, cool night air, the moon shining and soft sand in the ditches we were following. After two hours Spencer (8 years) got cold. I was warm in my shorts and t-shirt so I tried to think of what was happening. Normally I hike by myself and don’t have to worry about anyone else’s needs. The guide knew the trail but didn’t have any guiding blood in him. Caring for my boys while hiking is my job so I got into gear and started thinking how to help out. I figured that if he was cold he probably needed some more fuel so we put on a sweater and ate some snacks. Every little break we took in more trail mix to keep the energy up. My Tanzanian friends have this thing against eating or drinking while exercising. I couldn’t convince them that we had a long way to go and that they needed energy. I must have really bugged them offering them food every break but they flat out refused. My boys on the other hand enjoyed our snacks and drinks.
Tate (9 years) set himself a great steady pace and stayed up front with the guide. I forced Spencer to go a lot slower. Everything in him wanted to catch up to the group but I knew that he needed better pacing. We practiced the rest step. Step forward and rest the upper foot while taking a good breath while all the weight is on the locked back leg. Take another step forward and repeat. It’s a great way to move forward at a snails pace and get lots of rest in the leg muscles along the way.
The trail began at 1180m. By midnight we had hit 2000m everyone was getting tired and the night was getting long. Clouds rolled in and we lost visibility. My Tanzanian buddies were really starting to slow down and we moved at my snails pace together. At 2:30am and having risen to 2400m the mud was slick from the rain. Ol Doinyo Lengai is a massive mountain but isn’t rock. The whole area is hard packed dirt with small rocks stuck in. Those rocks are all lose. The erosion ditches are soft sand but this was giving way to hard packed mud. Visibility was low and we were starting to slip a lot. There were a few really tough sections and I began to wonder what I’d gotten us into. My two Tanzanian friends were flat on their bellies trying to inch worm their way up. Every step their feet were slipping. I was close to my boys giving them support and reminding them not to lean into the slope. The others up ahead got stuck and couldn’t go any further. After situating my guys in a safe crack I went around to look for a better route. I quickly realized what was happening as these guys were grasping at anything for dear life. I walked out beside them and put my hand down for them to step on. I couldn’t convince them to stand up straight. Their leaning into the hillside was causing them to slip making it nearly impossible to carry on. They proved to be very determined and tough as they pushed through the difficult section and carried on. I was very impressed with their attitudes as they wanted to quit and were hating life but carried on. Later one of them was trying to express how much he hated the difficult sections. The best he could come up with was “I’d rather been seen washing dishes for my wife than be on that mountain again” (washing dishes obviously being a female role in our area of Tanzania).
I was completely amazed at my young boys pushing on and being driven to see lava glowing at night. Tate stayed up ahead with the guide the entire trip, the two others would go for 3 minutes and then lie down and sleep. Spencer and I would soon catch up, wake the others and push them to keep going. Soon my GPS topo map showed we were at the summit and in the crater but were obviously still climbing. Visibility was against us and we couldn’t see even 40m ahead. After 9 hours of hiking and being 4:40am I simply couldn’t wake my friends again and left them to enjoy their cold bitter sleep. The terrain changed and became slick mud. It was weird stuff. It look like solid lava rock but you sunk in a foot deep where it had a different layer of super slick below. The boys and I pushed on another 50m elevation gain and it was too much. My topo map had said we were at the summit a long way back and we were still rising. We couldn’t do it anymore. The boys were exhausted and wanted to go back home. It was time to wait things out for morning. I situated them with the guide and went another 3 minutes where I hit the summit. It was so foggy and visibility so poor that hauling the boys up there was not worth it. No lava in sight just a drop down the other side.
There aren’t really any level places on the entire mountain. I took the boys down as ways to where our other friends were sound asleep and kicked away at the mud levelling a small area. We put on our toques wrapped up in garbage bags and ponchos. I opened up those hand warmer packs and stuff their shirts full and we tried to catch a bit of sleep. It was nearly 5am. The sun rises at quarter to 6. The boys were too cold. I went back and forth cuddling them to keep them warm. The rain pelted down on us and the wind was fierce. Being in Tanzania for the past few years I haven’t shivered like that in a while.
Finally when the light was enough I woke everyone up so we could keep moving and try to warm up a bit. (I’m guessing it was 10 degrees Celsius, cold for Africans). My boys and I head up to a ridge while my other friends headed back down. We made our way for another 50 minutes to the rim of the crater. The visibility remained poor and we didn’t see any lava flows. The boys were tired enough to take their losses and head back home. “At least we made it to the top” they said. What an amazing sense of accomplishment. We let out a few loud cheers celebrating the victory. We now call lava “Wava, waaaa! we didn’t see any lava”. Hearing the boys talk I think it might be better that we didn’t have visibility. They had created in their minds such an amazing world of ash cones, lava pool and lava creeks. It might have been a let down to see what just looks like mud.
The first 400m of descent was tough and I was worried at how many times my guys were tripping. We had a long way to go. We then came to the loose sand areas and it all became fun and games from there. We wore the bottoms out of our pants and we slid 1100m down. It was one of the greatest boot skiing areas ever and definitely became a highlight of the entire trip. Our guide became very worried as these young boys scouted down the mountain, looking for jumps and doing combat roles up and over the ridge as they found a new line. By 11am we were back on leveler ground and the boys got their chance to play in the dirt knocking over chunks of mud and collapsing drainage ditches. At noon we were back at the vehicle and everyone fell asleep as we drove 3 hours to a small hotel.
Being good Tanzanians my friends wore their nicest clothes for this trip, being poor subsistence farmers they only own two pairs of clothes, a nice set and a work set. I handed them a bit of money and they happily headed to the market to buy a new outfit. On the ride home the next day my Tanzanian friends had the highlight of their trip when a herd of wildebeest crossed the road, later we saw 3 giraffe followed by 2 large elephants. Ol Doinyo Lengai, Tanzania’s only active volcano. What an amazing time to spend with my boys as they accomplished an amazing task hiking 1700 vertical meters up in the cold rain with no visibility through the entire night. I was wondering what their take would be but it was all smiles and happy times as they related the events to mom and sister back home."
For a video of Richard's kids scooting down Lengai, see http://www.youtube.com/watch?v=Mom-YtmAng4
Nov 2010: Arpakwa Sikorei and Andrew Kinzer wrote: "One night after our field work on Biodiversity assessment in Lake Natron climbed the Mountain on 19 November 2010, it was in the night we start by 12:00am; While in the middle of the mountain it was raining very heavily and become very cold as you compared with the normal weather of the area which is actually very hot, since it was rains in the top, then the water flows down via a very big gorge in both our right and left hands and make a lot of noise, many people get worries and scared and some decided not climbing anymore some of them are some group of visitors we meet on the way while climbing the mountain, for me it was more better since it’s not very hot but hard to climb, no longer any crowing vegetation is all destroyed by the past eruption, it’s only strong sandy which is hard to climb since it is slippery, We reached just near the top by 5:00am and we break/rested like 40 minutes waiting the morning sunrise so that we can be in the top while not dark. Just few meters like 50-100m to the top the mountain become more hard and very slippery, the lava ash remains become very, very wet and more slippery as compare to the sand parts down the mountain, this part covered with a strong kind of cement like concrete but wet so is easier to get slippery and risk your life, many people get scared, we finally rich to the top by 6:00am and it was a bit cloudy and more cooled, I were my Maasai red cloth (shuka) and just tire in my neck and heard so that to prevent myself from cooled. We stay for like 5-8 minutes in the top and we run down. while in the top we observed smalls cone, and small slightly steam kind of eruption indicate the most dangerous areas for eruptions, but we didn’t hear any kind of big effusions, bombs and or blocks embedded or stones this time as compared to other time back. Like 2006-2007 when I visited this mountain. Except that you can hardly hear a sound like windy blowing in the big hole indicate that there are big holes inside the crater formed after eruption. While coming back it was really very hard trying to scratch the ground while descending to avoid skippering down without control yourself. Failure to do that then you can slide down and risk your life for stones, and very dip gorges like big gullies formed after eruption."
Nov 2010: Ben Wilhelmi flew over the crater in late November and sent me the following photo. Ben pointed out a small pond of water and area of green vegetation seen in the lower part of the photo, between the base of the cone and the summit ridge-in the photo it appears as a brown circular area just above the dark slope of the summit ridge. The green is not apparent due to the low light level in that part of the image.
Photo courtesy Ben Wilhelmi
Dec 2010: Dave Simpson, a guide working in Kenya, flew over Lengai on Dec 6 and sent me the following shot looking straight into the crater. No evidence of recent activity is visible.
Photo courtesy Dave Simpson