Ol Doinyo Lengai

East African Fault

Main article: East African Fault (rift valley)

Ol Doinho Lengai is part of the East African Fault volcanic system. Ol Doinho Lengai is not just the strangest volcano in the world, it is one of the most unusual volcanoes in the entire solar system. The reason for its originality is that this volcano plays the role of a cog in a much larger machine that transforms the Earth with its amazing geological creativity. Under East Africa, amazing processes occur that generate volcanoes and maintain living conditions for very unusual, almost alien life forms.

Пейзаж внутри Восточно-Африканской рифтовой долины (Северная Tanzania). On the left is the southern part of Lake Natron, further is the volcano Ol Doinho Lengai, on the right is the inner edge of the fault, in the background is the Ngorongoro Highlands

Eruptions

The age of the volcano is estimated at 350 000 - 400 000 years. It consists of basalts and phonolite from ancient Pleistocene times. About 30,000 years ago, the volcano began stage 2 formation. Basalts spread 40-80 km from the volcano. Their volume was 50,000 cubic kilometers. Phonoliths spread over a distance of 15 kilometers and formed 30 extrusion domes.

In other words, this volcano is capable of spewing strange magma of two kinds: superfluid and quite viscous. Thick magma can hold a large amount of gases, preventing them from quietly coming to the surface. It's worth punching through the hole in the cone of the volcano with the gas - and all these locked fumes expand dramatically, causing a very powerful explosion. Thus, more viscous magma with more silicon causes explosive eruptions, and black magma manifests itself as lava rivers, ponds and fountains.

Ol-Doinho-Lengai is active almost constantly. Her first documented observations date back to the end of the 19th century. Since then, many eruptions have been recorded: in 1880, 1882-1883, 1904, about 1907-1910, 1913, 1914-1915, 1916-1917 (ash emission at a distance of 48 km), 1921, 1926, 1940-1941, 1954, 1955, 1958, 1960-1966, 1967, 1983-1993, 1994-2006, 2007-2010, 2011-2013.

They differed in the scale of the eruptions of 1917 and 1940-1941. In the second case, ash fell at distances of up to 100 km from the volcano.

During the eruption in 1966, 50 tons of tephra were ejected from the side crater.

View of the volcano during the 1966 eruption.

The amount of black lava varies with each eruption, but is always impressive. In 2006, in two weeks, the volcano outlawed so much that it would be enough to fill more than 350 Olympic swimming pools.

In 2007, between July 12 and 18, volcanic activity in the mountains caused daily tremors in Kenya and Tanzania. The strongest earthquake reached 6 points on the Richter scale. Geologists assumed that this was a consequence of the movement of magma in Ol Doinho Lengai. The volcano erupted on September 4, 2007. The release of ash in the direction of the wind reached 18 km. The northern and western slopes were covered with lava flows. Burning ash after an explosive eruption in 2007 covered the villages of Naiobi and Kapenjiro 11 and 14 kilometers from the volcano, respectively. Activity in the volcano continued into 2008.

2008 eruption

The explosive eruptions of Ol Doinho Lengai, including the 2007 eruption, are something special. They are accompanied by loud explosions, huge plumes of ash, and sometimes also amazing flashes of lightning and rolling thunder. With each large explosion, the summit is often partially or completely redrawn, and a new crater forms on the site of a large piece of rock. After each major explosive eruption, the crater is filled with black lava. Above the active lava pool, which is directly underground, hornitoses form.

Crater

Volcanic activity changes the shape of the crater every year. It is regularly filled with lava, which quickly freezes and later collapses inside. Sometimes lava shimmers over its edges.

Volcano crater filled with frozen lava in 2006

Ornito atop a crater filled with frozen lava in 2006

2011 aerial photography

Lava and gases

In the middle of the 19th century, the first explorers of East Africa noted that Aldoinho Lengai was covered with snow, as was the peak of Kilimanjaro. In fact, this is not snow, but soda ash, which was previously used in mummification in Egypt - it was formed as a result of the contact of carbonatite lava with moist tropical air. Most volcanoes on the planet spew silicate lava. The melt contained in the Oldoinho-Lengai magma chamber is almost silicate-free and consists predominantly of sodium carbonates (more known to us as soda) and calcium. You are probably familiar with the latter - it consists of a calcareous coating inside a kettle or around a tap.

In other words, most magma or lava contains a fair amount of silica, a substance consisting of one silicon atom and two oxygen atoms. Silica likes to join in long chains that form a kind of lava skeleton, and the more silica chains, the more lava is like resin. Basalt, as in Yellowstone's large and deep reservoir, has a low silica content, so it's quite fluid. Rhyolite, which is in Yellowstone's small and shallow reservoir, is more than two-thirds silica, making it very viscous and thick. However, the black lava of the Lengai volcano has so little silicon that it flows very quickly.

Viscosity of different types of lava

The composition of Oldoinho's lava was analyzed in 2008:

The origin of the unusual composition of the lava is unknown. Ol Doinho Lengai is the only active volcano in the world that spews carbonatite lava.

When melted, it is black, secondly, it has a low temperature - only 500-600 degrees, and thirdly, after cooling it easily collapses under the influence of water.

This paradox is simply explained: there are very few silicates in the Ol-Doinho-Lengai lava, but there are many carbonates. Therefore, Ol Doinho Lengai is a natural unique - a real carbonatite volcano.

Due to the specific chemical composition of lava, this volcano is heated to only 510 ° C (the temperature of basalt lavas of most volcanoes is 800-1200 ° C) and has low viscosity. This lava is the coldest on Earth, but also exclusively fluid. Such lava looks like black liquid mud, and when frozen, it looks more like cement than the usual volcanic basalt.

Natrocarbonatites are volcanic or intrusive rocks, mainly consisting of sodium, potassium and calcium carbonates, many of which dissolve in water. These are mainly nerereite (Na2Ca (CO3) 2) and gregoriite (Na2K2CaCO3). These minerals are unstable and react easily with atmospheric moisture and various gases. In just a few days, the surface of the fresh lava flow is covered with a crust of newly formed minerals, and after some time, the original minerals are difficult to find even in the depths of the lava flow. This feature makes it difficult to sample and study natrocarbonatites.

Photographs of cuts (rock plates 30 μm thick) in polarized light showing the processes of destruction of the original minerals of nerereite (b) and gregorite (c). a is the core of nachcolite (NaHCO3). In the photo b and c, crystals of nerereite (Nr) under the action of water turn into pyrssonite (Na2Ca (CO3) 2·2H2O) (Pr), and gregoriite (Gr) - into shortitol (Na2Ca2 (CO3) 3) (Sh) and nachcolite (Nh).

During the solidification of such lava, unique rocks are formed. Geologists gave them a complex name - gregorite-nerereite carbonatites (in honor of the first researcher of the East African rift system John Gregory and the first president of Tanzania Julius Nyerere).

Carbonatites are characterized by high calcium concentrations. And besides, in them, a lot of phosphorus, mainly in the form of the mineral apatite, and rare lands were revealed. Therefore, carbonatites are considered agrochemical raw materials.

Volcano crater in 2000. Four days after the outpouring, the color of the natrocarbonatite flow changes from black to white, which reflects the dissolution rate of the minerals of the original lavas

Another common element coming to the surface in the Aldoinho-Lengai eruptions and degassing (the release of gas from magma) is chlorine. In combination with sodium from lavas, another "kitchen" chemical compound is obtained - table salt (NaCl), more precisely, its crystalline form is the mineral halite.

Fumaroles on the slope of the volcano, from which mainly water vapor emerges, enriched with sulfur, carbon dioxide, chlorine, fluorine and other compounds. February 2016 TAdviser Expedition

In a 2009 study, volcanologists collected gas samples from an African volcano in an attempt to find the cause of a unique carbon-based lava. The results surprised scientists, as the composition of the gases did not differ from those emitted along the mid-ocean ridges, despite the fact that the volcano is located deep on the continent, far from any deep-sea ridges.

As a result, scientists suggested that the volcano owes its unusual lava to the melting of minerals in the upper mantle of the Earth. According to study co-author David Hilton, professor of geochemistry at the Scripps Oceanographic Institute at UC San Diego, the chemical composition of the gases indicates that carbon dioxide enters the volcano directly from the planet's upper mantle.

Ol-Doinho-Lengai is not just a chemical curiosity. It also suffers from an identity crisis. This volcano is surprisingly steep. High, sheer volcanoes can only occur if very thick, viscous magma bursts out of the vent, which litters the surrounding landscape, accumulates and forms a steep cone. But the black lava of this mountain spreads too far and too thin a layer to form a cone-shaped mountain. Most of the volcano's magma is not carbonatite, but material containing a decent amount of skeletal silica chains, making it sticky enough to create steep slopes^[1].

Impact of ash on the environment

volcano and its extinct counterparts emitted huge amounts of volcanic ash, which settled on nearby plains, making the soil extremely fertile," says Dmitry Chernyakhovsky, candidate of geographical sciences. - Herds of large animals grazed on the obese pastures of the Rift Valley. Fierce competition for this valuable resource could cause, among other factors, the accelerated evolution of our ancestors - hominids, it is in East Africa. "

In support of his hypothesis, the scientist recalls that only 50 kilometers from the volcano, in the Alduvai Gorge, in the 1960s, anthropologists Louis and Mary Liki discovered the remains of Homo habilis (a skillful person). It was here about two million years ago that our ancestors began to make stone tools for cutting animal carcasses.

However, considering that the age of Ol-Doinho-Lengai is estimated at 350-400 thousand years, and the lifetime of Homo habilis was 2.3-1.5 million years ago, this volcano itself could not have influenced human evolution and, probably, we can only talk about "its extinct brothers." See Kilimanjaro.

Until today, thanks to volcanic ash, the surrounding plains retain a grandiose diversity of fauna. It is in this region that one of the main sights of the animal world unfolds - the annual migration of the Gnu antelopes.

Footprints in Engare Cero

In 2008, scientists learned from a local resident about numerous traces of Homo sapiens and ungulates between 5 and 19 thousand years old on the coast of Lake Natron, located at the foot of the volcano (see below). Initially, it was assumed that the traces are much older (120 thousand years), but radiocarbon dating indicated a relatively young age.

Prints of ancient people near Engare Sero/ ©Liutkus -Pierce et al., 2016

The site near the village of Engare Sero has retained a record number of traces. When the excavations were completed, scientists counted over 400 petrified prints of bare legs on a space of no more than a tennis court. A new detailed analysis of these traces was carried out by Kevin Hatala from the American Chatham University and his colleagues. Their article was published in the journal Scientific Reports^[2].

One of the traces of Engare-Sero/ ©William Harcourt-Smith

In total, 408 fossilized traces dated 10-12 thousand years old were found in Engar Sero. Many of them anthropologists traced in whole chains, determining who and how could leave these prints. Thus, 17 chains of traces were associated with a slowly moving group of 14 adult women, two men and one boy. The authors suggest that this group was engaged in gathering.

Trace chains traced in Engare-Sero/ ©Hatala et al., 2020

In early and traditional human communities, it was a "command" and generally a "women's" affair. "In modern communities, such as the Hadza and Ache," the scholars write, "groups of women engage in gathering together, only sometimes they are visited by adult men."

It seems that this feature has been preserved in them since a very distant antiquity: it is not for nothing that the lion's share of traces in Engare Sero is female, but there are no children at all.

In the opposite direction (approximately northeast), six more trace chains are traced, apparently unrelated to each other. The nature of the tracks suggests that these people moved separately, quickly and at different speeds. Two women and a man were moving at medium speed, another man and one woman were moving quickly. Finally, another chain was left behind by a woman who fled.

Researches

In 1855, Ol-Doinho-Lengai first appeared on a map compiled by two missionaries. One of the names they gave to this volcano is "Snow Mountain." However, they did not actually see snow, but black lava cooled by streams of humid air.

In an 1870 account, one of the Arab merchants named Sadi described the peak as follows: "It is either the color of gold, then white, like silver, and then again black."

When Western explorers began climbing to the top of the volcano in the early 20th century, they noticed mud rapidly oozing from its slopes, which seemed to settle into a white layer of salt-like matter. That's how they described the volcano's carbonatite lava - a spectacle so bizarre they thought it was anything but lava.

Scientists first descended into craters only in 1960, when this part of Tanzania modern-day was still called Tanganyika, and only Britain a year remained before independence from. John Barry Dawson, a scientist at the Tanganyika Geological Survey, gained some black lava and in his groundbreaking 1962 study showed that this strange substance consists of calcium, sodium, potassium, water and. carbon dioxide

Ascension

As of 2016, it is possible to climb the volcano accompanied by a local masaya guide.

The climb is carried out at night - from 00 to 5 in the morning - as the scorching sun interferes with the day. Start from a height of 1100 meters, the final point is about 3000 meters above sea level.

Of the girls, only one in five make it to the summit, according to one of the guides.

Caldera view in February 2016 at 5:20 am after sunrise. TAdviser expedition.

"The rim of the crater is 30 to 60 centimeters across. And on both sides are steep slopes. Falling on one side will leave you in a crater filled with lava. And from the outside there is a deep abyss. On the left is death by liquid fire, and on the right is death by blunt force. I moved almost on all fours, "said British researcher Genge. Representatives of TAdviser carefully traveled all the way along the edge of the crater in an upright position. The view is impressive.

Caldera Trail in February 2016 TAdviser Expedition.

Apart from the force of attraction, there are many other ways Ol-Doinho-Lengai can kill you: an explosive eruption at the summit; avalanches of debris that had been dumped down the slope for many millennia; small pyroclastic flows and bursts that have repeatedly washed the slopes with hot gas and volcanic matter; odorless lakes of invisible carbon dioxide that can cause asphyxiation - they accumulate on top as they are denser than the surrounding atmosphere...

If you are not careful, you will be ambushed by a hornithos. "Gornitos begins to fill with magma, then its side part can fall, and all the lava will pour out in the form of a tsunami," Genge said. Even actress Angelina Jolie did not show proper skill: at the end of the film "Lara Croft: Tomb Raider 2 - Cradle of Life" you can see how the heroine gets out of the partially collapsed cornitos on top of Ol Doinho Lengai. "I can't imagine a worse place, a more dangerous place to shoot a movie starring a superstar," Genge argues.

In fact, despite the risk, those who climb Ol Doinho Lengai, accompanied by Maasai guides and other Tanzanians with experience climbing various volcanoes, including Kilimanjaro, may feel safe. Accidents are few, but remarkable: in 2007, a Maasai porter fell through the bottom of the crater into a burning reservoir with black lava. Despite severe burns, he still survived - and this is perhaps the only case when someone fell into the lava and survived.

Based on the results of the ascent, a certificate is issued.

Mythology

Mythology of the Maasai

The authors of the popular 2001 edition of volcanoes reported that the Maasai living in the vicinity of the Ol Doinho Lengai volcano believe that Engai, the deity of the sky, lives on top of it. The Masai are supposedly "in holy awe" of this mountain, and among the Masai diviners, few have the right to climb to the top to chat with Engai and convey his revelations ^[3].

In 2016, during the TAdviser expedition to the top of the volcano, the masai guide calmly slept for half an hour waiting for dawn right on the edge of a crater less than a meter wide, no longer experiencing any trepidation.

Ngai, Engbi, in Maasai mythology (Kenya and Tanzania) is the deity of heaven, a thunderbolt who simultaneously performs as a tribal god of war (he is asked for good luck in military campaigns). In myths, Ngai appears in various hypostases: Engai-Narok (Engai Black) and Engai-Nanokye (Engai Red).

• Engai-Narok - a kind, loving deity of people, manifests itself in the blue sky. His voice is distant waves of thunder.
• The evil deity Engai-Nanyokye manifests himself in lightning and loved ones, deafening ramps of thunder; it kills with lightning. A black sheep is sacrificed to him.

In some variants, these are not two hypostases of the same deity (which is made "red" in the morning and evening), but two brothers. Engai-Nanokye, seeking to exterminate people, refuses to submit to the power of Engai-Narok.

According to another option, Ngai performs in three hypostases:

• Ngai-Nanyugi ("red god") - red, like the morning and evening dawn;
• Ngai-Set ("white god") is a cloudy sky;
• Ngai Narok ("black god") - cloudless, blue sky. Prayers go to Ngai Narok.

According to one version, there were once four gods:

• black good god (actually an enriched ancestor);
• white god (distant heavenly deity);
• the red evil god and
• gray god.

The black god lived lonely on a snow peak, other gods gave him a young man as companions. When the black god and the young man married the women of the surrounding people and gave birth to the Maasai, the gray and red gods, annoyed by the fact that people had spread, sent a drought. Then the young man went to heaven and, having conquered the gods, took out the rain there - the drought stopped. The young man is considered the ancestor of the Maasai. Later, the red, gray and black gods died, only white remained.

In one probably later myth, instead of Ngai, ^[4]

Kikuyu and Kamba mythology

Ngai in the mythology of the Bantu-speaking peoples of Kikuyu (Gikuyu) and Kamba (Kenya), who borrowed the name of the deity, thunderbolt, rain deity from the Maasai. Rain, lightning, thunder, rainbow - manifestations of Ngai. The health and lives of people and animals depend on it. Natural disasters, droughts, epidemics, etc. are explained by Ngai's anger. For his propitiation, sacrifices are made. Ngai was worshipped, the Kikuyu become the face of the mountain.

Descending to the ground, Ngai stops to relax in his temporary dwellings on the high mountains, most often on Mount Kenya (in the Kikuyu language - Kere-Nyaga, "mountain of radiance"), which he himself created. Accordingly, Kikuyu call it Mwene-Nyaga ("shining"). Ngai dwellings are also on the "mountain of the big rain" (to the east), the "mountain of the clear sky" (to the south), the "mountain of sleep or secret refuge" (to the west).

Ngai appears in myths as a cultural demiurge hero. When humanity first began to populate the land, Ngai called on Kikuyu and gave him his share - the country where Kikuyu began to live. From Ngai, Kikuyu received his wife Moombi. Ngai taught Kikuyu how to seek his help. Ngai then sent suitors for Kikuyu's nine daughters. The nine families formed laid the foundation for the nine main Kikuyu clans. They formed one large family; their common generic name was "Moombi children" (or "Moombi tribe"). Ngai taught people how to mine iron; established that kikuyu and kamba should be engaged in agriculture, Maasai - cattle breeding, ndorobo - hunting. Ngai is similar to Leza^[5]

European missionaries adapted the word God for Maasai, Kamba and Kikuyu, taking precisely the name of the existing rain deity Ngai.

Natron Lake

Washing the chemical elements of the volcano into the lake

During the rainy period, sodium, potassium, chlorine and other elements are washed out of the rocks of the volcano and demolished to its foot, where Lake Natron^[6] are located].

The water in Natron is alkaline - with an average pH of about 10-12 (the pH of ordinary drinking water is 7). The water temperature due to its shallow depth during the day often reaches 40 ° C, and in the hot springs of the northwest coast - 60 ° C. The concentration of mineral salts is so high that even fresh water from lake feeding springs has a sweet taste due to small concentrations of sodium ions, and this taste does not change even after boiling.

Because of its salty-alkaline environment, the lake kills animals and birds that decided to swim in it and turns them into statues. The term "mummification" is appropriate here, because sodium carbonate was used by the ancient Egyptians in their burials.

The liquid in it is so caustic that it can eat away at various textile and plastic products.

Cyanobacteria and small flamingos

The reservoir is covered with a crust of salt, which periodically turns red and pink due to the vital activity of microorganisms - cyanobacteria (Spirulina, Cyanospira), which give the water a red color during the active breeding season. They feed on a few invertebrates - for example, artemy crustacean (Artemia salina) and small flamingos (Phoenicoparrus minor).

Small flamingos

For small flamingos, Lake Natron is the only permanent nesting site. Up to 75% of the world's small flamingo population is born here. The source of their pink color carotenoid astaxanthin enters their body along with cyanobacteria. They nest on seasonal islands of salt (which protrude on the surface of the lake during the dry period), reliably protected from any terrestrial predators by salt waters and impassable mud of the lake.

On the banks of Natron, according to plans for January 2020, they want to build a potash plant (potassium carbonate or potassium carbonate). The plant would pump water from the lake and extract potassium carbonate to convert it into washing powder.

At the same time, the chances of small flamingos to continue breeding in the lake after the construction of chemical production are almost zero. Moreover, this can lead to the complete extinction of these birds in East Africa.

Alkaline cichlides

In more fresh springs along the shores live fish from the family of cichlovs - alcolapia (Alcolapia), which are also found in some lagoons and swampy areas of Lake Natron.

Alkaline cichlid, scientific name Alcolapia alcalica, belongs to the family Cichlidae. The main feature of this fish is the ability to live in an environment that will be deadly for most species: high temperature, alkaline and extremely mineralized water composition.

Similar volcanoes

There are several hundred extinct carbonatite volcanoes in the world that either project above the planet's surface or are buried under centuries-old geological deposits. But that number pales in comparison to hundreds of thousands of "ordinary" volcanoes active, dormant or extinct on Earth.

There is some evidence that volcanoes on Venus, which is also called the "evil twin" of Earth, volcanoes also once spewed sodium carbonatite lava^[7]

Russia

In Russia, carbonatites were found in the famous Khibinsky massif in the Murmansk region, which is a frozen deep part of the volcano, which was clearly not inferior in scale to Ol-Doinho-Lengai. Its deposits for 2018 are being developed by the Kirov branch of Apatit JSC (part of PhosAgro).

Uganda

Tororo Volcanic Massif in Uganda. Just like Ol-Doinho-Lengai spewed not silicate, but carbonate lava. According to data from 1976, there is not enough limestone in Africa, so rare volcanic rocks - carbonatites - are intensively developed for the manufacture of cement. Not far from the carbonatite volcano, a large cement plant for that time was built, which by the mid-1970s had already developed a significant part of this unique natural ^[8].

See also

• Kilimanjaro
• Phlegrean Fields (Campi Flegrei)
• Teide

Notes