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.

 

Abstract

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.

 

References

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

Sinabung: Seismicity high

At the Sinabung on Sumatra the situation comes to a head: here the seismicity increased enormously in the last days and not only debris avalanches were registered, but above all earthquakes with low frequencies. They indicate massive magma rise. Yesterday, a good 560 of these quakes were recorded. In the first 6 hours of today, there were already 239 quakes. In addition, 112 signals testified to debris avalanches. The dome is growing and the situation is becoming more and more critical!

Pacaya: Another ash cloud

Guatemalan volcano Pacaya erupted another ash cloud today. It rose to an altitude of 3000 m and drifted in a westerly direction. Yesterday INSIVUMEH reported strombolian eruptions from McKenney crater. Incandescent tephra was spewed a good 175 m above crater level. The lava flow on the southern flank reached a length of a proud 1725 m. MIROVA indicates high thermal radiation. INSIVUMEH warns not to enter the south side of the volcano. The photo was published on February 21.

Etna paroxysm no. 7 starts

Update 10:15 am: The paroxysm has already ended and only steam is emitted. The most beautiful view was probably from the north. From the south it was very hazy. The paroxysm built up very quickly and practically without warning and lasted only about 1 hour. It was the shortest paroxysm of the series so far. Since it was practically windless, the ash cloud dominated this time. Red-hot tephra was hidden by it, and less red-hot material was erupted than usual. This is also evidenced by the relatively small lava flow that entered Valle del Bove. Towards the south, no lava at all was on its way this time.

The tremor amplitude reached a high value and was even minimally higher than during the last eruption. In summary, gas pressure was high, but less magma was erupted than in the other paroxysms. The material was more fragmented. Exact data about the height of the eruption cloud are unfortunately missing so far. The VAAC Toulouse issued 2 reports, but apparently detected the eruption only during its initial phase. Likewise values about the thermal radiation are missing. But the pictures say more than a thousand words anyway.

Update 9:30 a.m.: The paroxysm is heading towards its peak, producing a breathtaking eruption cloud. The LiveCam with the best view is linked here. Below you can see the livestream from Localteam. Unfortunately it is very hazy in the south of the volcano, so the view is a bit cloudy.

Original news: 9:15 a.m.: This morning Etna is on the move with its 7th consecutive paroxysm. Without any omens, the tremor started to increase sharply and with absolutely no wind, a lava fountain is currently (9:15 am) building up along with an ash cloud. The paroxysm came much later than the statistics would have suggested. This shows once more that nature remains unpredictable in the end.

Strong earthquake shakes Iceland

This morning Iceland was shaken by a strong earthquake of magnitude 5.7. The hypocenter was located at a depth of only 1.1 km, according to IMO. The epicenter was located on the Reykjanes Peninsula, more precisely, 3.3 km south-south-west of Keilir. This is a mountain of volcanic hyaloclasti. These are fragments of volcanic glass. Keilir is located about 10 km northeast of Grindavik and thus in the area that has been hit by inflation-related earthquakes since the beginning of last year. However, the magnitude of the current main earthquake suggests that the origin was tectonic in nature. However, it could be that the ground deformation triggered by inflation caused stresses and thus a fault zone was activated. But this is so far only speculation on my part. Therefore, I am eagerly awaiting a report from IMO to assess the situation.

There were numerous pre- and aftershocks. Among the aftershocks, there were 34 tremors with magnitudes greater than 3. IMO has so far registered a total of 378 tremors in the affected region within 48 hours.

The earthquake occurred at 10:05 UCT. It was felt in a wide radius. There are no reports of damage yet.

Volcano update 23.02.21: Etna paroxysm

EtnaThe 5th Etna paroxysm in direct succession was also the one that produced the strongest tremor signal. The height of the lava fountain was comparable to that of the last eruption, reaching heights of between 800 – 1000 m. Thus, this paroxysm was also among the strongest representatives of its kind. The VAAC detected volcanic ash at an altitude of 10,000 m. The tephra rained down on the volcanic flanks in the communities and meanwhile covered whole streets. Lava flows flowed in different directions. The largest flowed into the Valle del Bove. Towards the south a moderate flow was on its way and even in the northern direction some lava flowed. It is striking from the course of the tremor that there was a further peak after the actual paroxysm. The associated infrasound signals manifested themselves around 4:00 UCT. Less pronounced tremor peaks can also be detected during the last two paroxysms. Currently, the volcano has not yet calmed down completely and is emitting small ash eruptions. Intense afterglow can be seen on the thermal cams.

Etna: New paroxysm at the start

Update 9:50 a.m.: The paroxysm is now probably almost unstoppable. On the LiveCam you can already see a small lava fountain rising at the New Southeast Crater. The eruption is developing very fast and is already heading towards the peak phase. And this again in the most beautiful volcano watching weather!

Original message 9:15 a.m.: Currently, it looks as if another paroxysm is at the start at Etna in Sicily. Around 9:15 CET, not only the tremor increased significantly, but continuous strombolian eruptions started and the lava output increased significantly. Of course, the eruption can still stall, but so far it looks like a paroxysm is approaching fairly quickly.

Etna: New paroxysm on 17 February

Etna

Last night, Etna in Sicily produced another paroxysm. Virtually without warning, the tremor shot up at 21.15 UCT (22.15 CET) and already an hour later the eruption was heading towards its peak. A lava fountain was again produced from New Southeast Crater and multiple lava flows were underway. This time, the lava flowed not only into Valle del Bove, but also in a southerly direction. VAAC detected volcanic ash at an altitude of 10,000 m. The tremor amplitude was a bit larger than during the February 16 paroxysm. MIROVA registered an extremely high thermal radiation with a power of 17,000 MW! Indeed a very extreme value and I don’t remember to have seen something like that at Etna in recent times. Even now it is quite hot in the area of New Southeast Crater, which can be seen nicely on ThermalCam. In the latest Sentinel satellite photo from February 16, hot vents can be seen in all 4 summit craters.

This eruption confirms once again that it is virtually impossible to predict these paroxysms by statistics. Yesterday I postulated an eruption interval of almost 4 weeks, this time the next eruption came after 28 hours. It would not be atypical if we would see more outbreaks in the short term, but of course the break interval may lengthen again, or shorten even further.

In Our FB group, numerous media were shared again

Etna: Paroxysm of 16.02.21

After Tuesday’s paroxysm, Etna is in a hangover mood today. The tremor has fallen to a multi-week low, moving at the base of the yellow range. The tremor curve gives a good indication of how short-lived the peak phase of the paroxysm was. This one was a moderate representative of its kind: the lava fountain reached a maximum height of just over 500 m and the main phase lasted less than an hour. What made the eruption special were the good visibility conditions and that it occurred at dusk. Accordingly, many media were shared in the social networks, some of which I would like to present to you here. From a posting by volcanologist Boris Behncke, it can also be seen that not only photos and videos were shared on social media, but also a lot of fake news that worried residents of the region. As spectacular as the paroxysm looked, it was not an unusual event that heralds a major disaster like a strong earthquake, or a flank eruption. A flank eruption will of course occur again sooner or later on Etna, and the Damocles sword of a strong earthquake always hovers over Sicily, but there is no direct link between yesterday’s eruption and possible tectonic earthquakes in Sicily.

Strong earthquake Mw 7.6 shakes Loyalty Islands

The Loyalty Islands region has just been shaken (13:19:57 UTC) by a strong earthquake of magnitude 7.6. The epicenter was located 401 km east of Tadine on New Caledonia. The earthquake focus was located at a depth of only 2 km. Should the information be confirmed, then in my opinion a tsunami is imminent. The strong earthquake was preceded by several quakes with magnitudes between 6.2 and 5.7.