Only minor ash eruptions were reported by local Masai after the last noteable eruptions on 8 April and 17 April 2008. Some of the evacuated local Masai had returned back to their settlements, but part of the livestock had not returned from evacuation sites yet midd of May 2008. The volcanic fall-out of pyroclastics was still visible around the volcano. Due to a heavy rain period (season) vegetation damage was not as severe, as it could have turned out by this strong explosive eruption period of O. Lengai (BGVN 33:2). Up to around 1000 m altitude the vegetation, mostly "Elefant grass", normal grass and some Akazia trees, were undamaged around the volcano, except for the western sides where severe damage of the vegetation occurred as far as 10 kilometers away from the summit. Some lahars had happened on the north and northeast of the volcano's out runs. The elderly Masai reported, that in compare to their visible observations, the recent eruption period was stronger than the 1966/1967 explosive event.

Only few effusive eruption periods on Lengai have been reported since end of March 2006 with an overflow to the west far down the slopes and the followed collaps of the central area of the crater. Evidence of lava flows have been given by remote sensing data (MODIS) analyzed by Matthieu Kervyn 20 June 2006. The volcanologist Steven Beresford has noted only some days old lava flows from hornito T37B on 13 June 2006. This activity has been confirmed by locals. Activity with surface lava flows have then returned on 20 June 2007 due to information of the local Lengai observer and guide Burra Ami Gadiye. Through July 2007 many tectonic earthquakes have been reported from the Rift Valley area around Lengai, some with epicenters as close as 20 km and only at 10 km depth. Christoph Weber has visited O. Lengai with an excursion group and noted as well many earthquakes between 18 and 24 August 2007. On midnight between 3 and 4 September 2007 activity has culminated with a very strong and gasrich eruption ("paroxysm"(1)) causing a some kilometer high eruption column and damage to the vegetation on the volcano slopes, documented on a ASTER satellite image on 4 September. Ash fall out of about 1 cm has been reported from the tourist facility Moivaro camp at the shore of Lake Natron. The access to the volcano has been closed for visitors by local authorities.

Christoph Weber arrived with a film team at the crater of O. Lengai 1100 on 02 February. C. Weber took scale of the the tallest hornito T49B with approximately 2890 m altitude (GPS) standing ~60 m above the crater floor at the NW overflow. No recent eruption had accured at T49B, but strong noisy degassing took place sometimes. Just east of T49B the hornito T56B had convecting lava deep inside and some only days old lava flows streched from three different vents at T56B towards the east as far as the E overflow. After the major collaps of T56B in 2004, this hornito (standing at approximately 2875m altitude on 02 Feb.) has nearly grown up again to its former shape and altitude. Also from T58C and the collapsed T58B hornito some days old lava flows were found on the eastern slopes passing the old and weathered T37, T37B and T45. The caldera shaped collapsed T58B had it's flat flour at ~2865m altitude with four active vents inside. Lava convection was close to the surface of T58B and inside the tall T58C.
At 1300 on 02 February a sudden increase of activity took place with two lava fountains at T58B lasting only some seconds. At the same time lava spilled out at all T58B vents, a T58C flank vent to the east and at a T56B vent. A lava flow went from T58B ~50 m towards the east. Lava spatter with lava flows inside T58B and up to ~150m towards the east occurred as well the following 3 days. From 0500 until 0730 on 06 February higher activity occurred with lava outflow at T58C. T58B showed also higher activity level from than on until C. Weber left the crater on 07 February morning.

Lava temperatur was measured with 519°C at an Aa lava flow with cooled surface and not in motion any more. Fumarol temperatures were measured as well. During an observation flight on 13 February C. Weber noticed new lava flows from T58B and T56B vents. Crater rim overflow measurements on 2 February 06 indicate no change since last reported in Bulletin v. 30, no. 4 by Fred Belton (width in meter):
NW overflow: 3 February 06 (135m)
E overflow: 3 February 06 (72m)
W overflow: 3 February 06 (20m)
N overflows: 3 February 06 (1m at each of three locations)

Various attachments for others:

Visitors on Lengai:

02 February, Chris Weber and 4 participants (until 07 Feb.) plus 2 german day visitors
03 February, non
04 February, 2 germans camping one night
05 February, 2 dutch, one german day visitors
06 February, 2 russian, 2 german dayvisitors
07 February, non

(SOURCE: Guardian (c)ippmedia ,Date: 2006-04-01 10:44:07)
By (c)Adam Ihucha, Arusha
Hundreds of villagers living around Mount Oldonyo Lengai in Ngorongoro District have been forced to flee their homes after the volcano erupted on Thursday, 30th. Eyewitnesses said they heard a rumbling noise before the volcano began discharging ash and lava, prompting local residents to flee the area in their hundreds. District officials estimated that about 3,000 people from Nayobi, Magadini, Engaruka, Malambo, Ngaresero, Gelai Bomba and Kitumbeine villages left their homes within a few hours of the eruption, adding that most of them trekked to villages in neighbouring districts. Ngaresero resident Ibrahim ole Sakay said alarm bells were sounded after smoke was seen coming from the peak of the mountain, adding that people panicked after lava began pouring out of the volcano. 'People had to flee their homes in order to save their lives?it was the only sensible thing to do because a volcano eruption can easily obliterate whole villages and communities,' he said. He added that the eruption destroyed vegetation and polluted water sources, but no casualties were reported. 'Thank God, nobody was injured although smoke is still visible at the top of the mountain,' he said, adding that it was unlikely that those who fled their homes would return while smoke was still bellowing from the peak. Ngorongoro District Commissioner Assey Msangi told The Guardian by telephone that it was not unusual for minor eruptions to occur at the mountain. 'I have not yet received an official report, but eruptions are a common phenomenon at Mount Oldonyo Lengai because they occur almost every year,' he said. Mt Oldonyo Lengai is located in the Rift Valley, about 120 kilometres northwest of Arusha. It is the only volcanic mountain in the world that discharges the highly fluid natrocarbonatite lava that usually contains almost no silicon. Natrocarbonatite lava is also much cooler than other lavas; averaging only about 950 degrees F (510 degrees C) compared to temperatures of over 2,000 degrees F (1,100 degrees C)?for basaltic lavas. At about 370,000 years old, Oldonyo Lengai is the youngest big volcano in this part of the Rift Valley.

(based on information sources from Celia Nyamweru, Fred Belton, and others)
...The eyewitness David Peterson reported to Celia Nyamweru, that a smoke column was visible on 28 March 2006, which propably marks the start of a bigger eruption on Oldoinyo Lengai. This ash column could have been triggered by a violent degassing (lava fountain up to strombolian and explosive eruption) or a mayor collapse of the hornitos T56B and T58B because of flank uplift by lava. Both phenomena occurred during recent years and were described for example by F. Belton (Bulletin v. 30, no. 4) and C. Weber (Bulletin v. 29, no. 2) and may come together in one single event. This type of eruption is not comparable with the last big explosive eruption period of 1966/67.
On 30 March a lava flow on the lower slopes of O. Lengai was observed. Aerial views on O. Lengai indicated that a large lava flow had traveled from T58C (and T58B?) to the southeast and clockwise over the south part of the crater. At the west overflow the lava escaped on the outer flank of O. Lengai running down mainly inside a gorge (deep erosion gully/korongo) until approximately 1000 meters altitude. Some vegetation at the crater rim and along the gully was ignited by this lava, but because of rainy season the fire was not very severe or prolonged. During the first days of April no activity was observed on the outer flanks of O. Lengai. Reports of evacuations of the Maasai communities around O. Lengai during the first days of April were not confirmed, though the Tanzanian government's recommendation to evacuate was reported by the local media (e.g. Guardian, Arusha, by Adam Ihucha, 1 April).
Michael Dalton-Smith flew over O. Lengai on April 4 and reported to F. Belton that fresh looking black lava covered the already grey lava flows from 30 March inside the gully on the western slope. Visitors who climbed Lengai later on reported about a big lava channel, 5 meters wide and 2,5 meters deep, starting from the hornito T58C, following the flow field to the south west and then continuing outside the crater at the west overflow where there was a channel 8 meters wide and 3 meters, probably deepened by thermal erosion. The collapsed hornito area at T56B and T58B measured about 30 meters north to south and 15 meters east to west with an active lava lake inside. The tall hornitos T58C (partly collapsed to the southeast) , T49B and T57B were mostly not affected by the collapse, and as well the west part of T56B remained standing.

• BLOG for Pambau (http://blogs.stlawu.edu/lengai)!

• Celia Nyamweru: Scientific info about Lengai by Celia Nyamweru, St. Lawrence Univ. (http://it.stlawu.edu/~cnya/)



• Fred Belton: Many Infos about Lengai and Fred guides also tours (http://www.oldoinyolengai.org)



• Bulletin of Global Volcanism Network, GVN, Smithsonian Institution, USA (http://www.volcano.si.edu/)