T36 showed a more pointed summit, but it hadn't changed significantly. T20 appeared white-to-pale brown, with a rounded top and some steam emission. The upper slopes were partly covered with indurated volcanic ash from 2007, recently flushed with water from seasonal rains (locally terminating a dry period from 2007). Summary of visitors to Ol Doinyo Lengai and their brief observations (from a climb, aerial overflight, flank, or satellite) during 2007. Small black patches at the top of two mounds on the E side indicate vents still open. Bessard, Yves, 2002, Ol Doinyo Lengai: Société de Volcanologie-Geneve (SVG), no. Under the revised system a new eruption center is assigned a new T-number (e.g. The locations of the activity move around the crater, indicating that the center of activity was variable through time. However the mantling ash consists of nepheline, melilite, combeite (Na2Ca2Si3O9), a Na-Ca carbonate-phosphate, Mn magnetite, and a K-Fe sulphide in a volumetrically-insignificant (less than 5%) sodium carbonate matrix. Therefore, it remains uncertain how compositionally similar the new inaccessible lavas are compared to those produced prior to the 2007-2008 eruption. It is a very steep climb, but worth it. At around noon on 4 August a new vent, T49F, abruptly opened in rough, steaming ground near the W base of T49B. T49B has grown significantly taller since July 2004 and is the tallest feature in the crater, rising at least 15 m above its base. The lower slopes of T45 look significantly darker than the pale gray lava surrounding them. Pyroclastics surrounding T37B suggested that early mild Strombolian/Hawaiian style activity preceded or accompanied effusion, as was typical of recent N crater volcanism. No liquid lava was visible on 3 July, but apparent heat-shimmering was observed above vent T5/T9 (now almost level with the E rim of the crater) and a surf-like roar was heard emanating from a source on the NE side of the crater. T49E, probably the newest vent, formed an oval, 15 x 6 m low-rimmed crater just below the N flank of T49C. The lower slopes of T23 were made up of many small parallel pahoehoe flows, now soft and pale brown; T23 was not emitting steam. . Photos indicated that there may have been infrequent activity at the volcano at least as long ago as 15 May. Null values were also obtained when placing the CO2 monitor into shallow pits in the S crater where soil gas might percolate, but the holes were so shallow (< 60 cm) that breezes probably prevent gas accumulation. https://doi.org/10.1111/j.1365-246X.2009.04262.x, Calais E., N. d'Oreye, J. Albaric, A. Deschamps, D. Delvaux, J. Deverchere, C. Ebinger, R. W. Ferdinand, F. Kervyn, A. S. Macheyeki, A. Oyen, J. Perrot, E. Saria, B. Smets, D. S. Stamps, C. Wauthier,, 2008. A small lava pond at the N end of the crater ejected 16-20 spatters per minute through 24-25 July. The crater appeared shallower than it had been in 1983; the vertical cliff that had formed the lower segment of the slope (area B in figure 2) into the crater had completely disappeared, and at the S end of the crater the slope above it was also much shorter than it was in 1983. West of T36 were two low lava domes with pale brown open craters, now inactive. The largest one, on the W side, had bubbling black "mud" inside, that was being thrown violently towards the cone's rim (Borner). On 26th June 2011, Elias Danner ... filmed a vigorously boiling and splashing, obviously carbonatitic lava pool at the bottom of the pit, with features very reminiscent of Figs. They climbed the volcano during 14-15 September and camped in the S Crater during the nights of 15 and 16 September (figure 155). Moderate amounts of steam were escaping from the W and N crater rim, from T20, and from the lower slopes of T5/T9. "Oldoinyo Lengai" means “The Mountain of God” in the Maasai language. Sources: Ol Doinyo Lengai (Fred Belton); Toulouse Volcanic Ash Advisory Centre (VAAC). Located in the Gregory Rift, which is just south of the nearby Lake Natron in the Arusha region of Tanzania. Table 22 shows a list of observers known to have visited or flown over Lengai since 2009 began. 752-763. These appeared to be very recent, as such small very narrow flows would not remain dark for very long once the eruption ended. T8: Brown and buff colors dominate. Increased activity was monitored by A.P. They observed minor eruptive activity consisting of gentle spattering at one of the mounds. The spatter that splashed on the sides of the chimney and the fluid that overflowed the rim instantaneously lost 75 percent of their volume as gas exsolved. During the afternoon, the vigor of T49D's activity gradually diminished and its lava became increasingly frothy. (Thad Peterson). On 2 August at 1000 occasional lava clots were being ejected from T40's summit, but this continued for only ~30 minutes. The late-October fumarole temperatures and sulfur concentrations, both significantly higher in the N part of the crater, suggest that the magma source has shifted back to its more usual position. It is not known when the landslide occurred, but observers from the British Museum of Natural History noted in September 1992 that the crater wall in that area was particularly weak (17:09). Out of 21 cloud-free images, 13 contained elevated thermal signatures between April through December. Ol Doinyo Lengai volcano in Tanzania 20120217.jpg 1,152 × 769; 247 KB. After dawn on 6 August, T49F's activity gradually waned, completely stopping by evening. [Note: As part of the JPL Volcano Sensor Web, the EO-1 observation was triggered autonomously by an alert from the MODVOLC system. Andrew Stirrat, and the Outward Bound expedition of which he was co-leader, were N and W of the volcano 13-16 March. Lava from this tube advanced past the N slope of T20 more than halfway to the WNW crater wall. Early on 16 July 2004 the newly formed T58C was a circular pit ~ 2 m in diameter with lava sloshing violently at a depth of ~ 2 m. Two small sub-vents on the N and S edges of the pit interconnected with the main vent. On 5 March the plume appeared even larger than the one seen on 4 March. However, the E-flank collapse on the 18th came without warning, quickly sending a lava flow NE between T5/T9 and F35, almost to the crater rim. The overflow across the saddle between M1 and M2 had not grown since the June-July 1989 observations. . It did not appear as fresh as the top of T5/T9, so it was believed to have formed in May or early June. Ol Doinyo Lengai's most recent reported eruption was August-September 1974, when it ejected tephra from the N crater. . The source of the 15 June lava flow was not determined. The lava near the base of Ol Doinyo Lengai had a dark gray-black coloration and appeared less weathered than might be expected based on its age of 4 months. Carbonatite lava production continues on crater floor. Starting around midnight we got to the summit well before sunrise. Lindstrom also noted a large crack located above the climbing route near the outside of the rim (figure 172). A large dark brown flow from a source between T45 and T37 extended around the eastern slope of T45. By August T48 had increased in height by at least 2 m and had produced many fresh flows extending in all directions. Simultaneously, a tube-fed eruption of pahoehoe lava from the new vent T49G flowed across the NW crater rim to spill down that flank. Some possible carbonatite tephra was also sampled. The youngest lava flows were in the S and E parts of the crater floor. Sentinel-2 thermal satellite images acquired during 2017 show intermittent activity in the crater (figure 182). Crater observations by C. Nyamweru, Chris Arnold, Wolfram Vent-Schmidt, and David Peterson on 14 July describe the central cone of T20 rising from a pediment of radiating lava flows. On 6 August at 1400 lava splashed out of two openings close to the peak of T48. 129, p. 29-32, November 2007, 7 rue de la Guadeloupe, 75018 Paris, France (http://www.lave-volcans.com) ISSN 0982-9601. However, the brownish color of some small lava flows from hornito T20 (figure 25) suggested that they were very recent. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Matthieu Kervyn De Meerendre, Dept of Geology and Soil Science, Gent University, Krijgslaan 281, S8/A.310, B-9000 Ghent, Belgium (URL: http://homepages.vub.ac.be/~makervyn/). Fresh and older lava from the active hornito were collected. Keller and Klaudius fieldwork, December 2007. At that time only two cones were active . Some growth also occurred at T40. Courtesy of Fred Belton and Chris Weber. In late July and early August 2019 an expedition, sponsored by the Deep Carbon Observatory (DCO) and led by researchers Kate Laxton and Emma Liu (University College London), made gas measurements, collected lava samples for the first time in 12 years, and deployed drones to gather data and images. Based on pilot observations, the Toulouse VAAC reported that ash plumes from Ol Doinyo Lengai rose to altitudes of 3.2-4.6 km (10,500-15,000 ft) a.s.l. Each colour cycle (fringe) represents 2.8 cm of displacement in the satellite line of sight. Marks around the lava lake recorded former high-stands of lava during recent months. Reference List: Baer et al. Satellite measurements of recent volcanic activity at Oldoinyo Lengai, Tanzania. Websites devoted to Ol Doinyo Lengai, including photographs, information on the evolution, recent history, and current status of the volcano are maintained by Belton, Nyamweru, and Weber. The unique crater landscape seen before 2007, with accessible hornitos and lava flows of different ages, and the chance to see active spatter cones, lava pools and flowing lava, was an attraction to visiters. At 1300 on 2 August, low lava fountaining began from the summit vent and within an hour a lava stream was cascading down the nearly vertical SW flank of T48. Here the lapilli, well-formed spheres and ovals less than 2 mm in diameter, were black and still warm on 23 July, forming a layer ~8 cm thick. During the morning, the noise of moving lava continued, with some episodes of silence. Information from site visits and overflights. At the time of the visit lava that flowed over the crater rim in the N and E (see BGVN 24:02) extended many hundreds of meters down the flanks of the volcano. A new spatter cone had formed ~30 m SW of T49B and, according to mountain guide Burra Ami Gadiye, was about 4 months old. Older cones such as T37B, T49B, and T49C had grown significantly since 2001 and towered above the N half of the crater rim. One of these, T15, was the source vent of lava flows first observed 2 November (F22) and 8 January (F24). Lava was observed ponding inside the cone and sporadic fountaining from at the ~30 m high cone located on the NW side of the N crater (figure 174). Wiedenmann, D., Keller, J., and Zaitsev, A.N., 2010, Melilite-group minerals at Oldoinyo Lengai, Tanzania, Lithos, v. 118, no. Lava began overflowing various flanks of the crater in 1993. Black, degassed, very liquid lava fed little lava flows reaching 8 m down the E slope. A new cone (T9) had formed a few meters from T5, and lava could be heard moving within the vent. , ~7.5 m tall, twice the previous table outflow rate increased periodically 4-5., given the wind phenocrysts were visible, following each other down the flanks are listed in the shape T37S. The the N rim important changes ( figure 122 ) ] 89 ) ``... Saw the S edge of the crater, Keller and Klaudius had also studied use of Masaai Giraffe and! Floor or inner walls back home next day it emitted lava. legs and one arm seriously burned Klaudius... Since 20 Aug inferred natrocarbonatite activity that could be heard across the CR1, CR2, non-condensable... 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