Ol Doinyo Lengai, which translates to “Mountain of God” in Maasai, is the sole volcano that spews black lava that turns white when it cools. It may be found in northwest Tanzania, south of Lake Natron, near the southern tip of the Great Rift Valley’s eastern arm. Read more about Mount Ol Doinyo Lengai
Due to its “cold” black lava, which has a low viscosity and a low temperature (for lava) of 500°C to 700°C, Ol Doinyo Lengai is sometimes referred to as the strangest volcano in the world by geologists. The massif is regarded by hikers as one of Tanzania’s most difficult mountains. Compared to climbing Kilimanjaro, is far more difficult. The trek usually starts at midnight and climbs across volcanic ash and gravel dirt on high inclines.
When the lava cools and mingles with the atmosphere, it turns a silvery white, most lava contains a fair amount of silica, but also on Ol Doinyo Lengai, the black lava contains, among other things, a lot of sodium and calcium carbonate.
So Ol Doinyo Lengai is unique in the sense that it produces these Effusive eruptions of natural carbonatite then it likes to explode every now and then with silicate lava. So that dynamic that switches between a piece of natural carbonatite type organism and an explosive silicate organism isn’t very well understood at all. And those switches are what made this volcano particularly hazardous.
In fact, it is probably the only volcano anywhere in the solar system that still erupts in carbonatite lava. And the deficit of silica means that it lacks the skeletal strength most other lavas possess. allowing it to flow extremely quickly,
It is unique in the sense that it erupts at very low temperatures for what we expect of Lava so it erupts anywhere between 400-600 degrees Celsius. Because the explosive eruption carved out this deep 100-meter crater. No one’s been able to access the crater floor to collect samples.
Essentially, what we think happens is that there is a silicate magma reservoir somewhere below the volcano. And then from that natural carbonatite. Emissivity separates out that like oil and water at some depth within that plumbing system. So the Natural Cover monitor inherently comes from a silicate parent.
But there’s more to Ol Donyo Lengai than its strange black lava.
.It’s a religious site for the local people. And all of these different dynamics play such an important role in making the area what it is. It’s the source of what I consider the fertility of the Serengeti, the ashes from Ol Doinyo Lengai, provide the nutrients that the Serengeti depends on. So there’s this whole connection with botany and guiding the environment around it. And I think that’s what makes it so special for the local communities and why it’s so important to that. It absolutely blows your mind to be on the edge of that crater.
To gain a grip on the sharp rocks, hikers must walk slowly and occasionally on all fours.
It is the only active volcano with lava that contains carbonate. After emission, “Natro-carbonatite,” a lava abundant in sodium and potassium carbonate, experiences the modification of these minerals with moisture, which whitens the lava’s surface. Its lava is the most fluid in the entire planet and the coolest, with temperatures of just 590o Celsius, and a viscosity extremely similar to water. The lava turns entirely white as it cools. Numerous scientific research has been conducted on the distinctive terrain of a white lava volcano, the origin of its composition, the signs of previous collapses, and debris avalanches.
Recent research indicates that further collapses are a possibility, necessitating ongoing observation.
Where is Ol Doinyo Lengai?
Ol Doinyo Lengai, located in the Great Rift Valley and around 240 kilometers (149 miles) from the town of Arusha, is referred to by the Maasai inhabitants of this area as the Mountain of God. The eruption of its ferocious lava has caused some to believe that this majestic peak has a heavenly origin, despite the fact that it is an active volcano. Locals make the pilgrimage to the peak to pray to the gods for anything they desire, whether it is rain, offspring, or a suitable partner.
The walk provides views of stunning meteor showers and shooting stars if you’re brave enough to glance up from the supposedly perilous, tiny trails.
The shadows of Kilimanjaro, Meru, and the Serengeti plains then appear as you stand on the mountain’s summit as the sun rises. You might feel a little bit like a deity yourself as you gaze down at the quietness and majesty of the planet from above the clouds.
A safari in the Ngorongoro Conservation Area is frequently paired with a trek to the summit of Ol Doinyo Lengai. Before going out for the peak at dusk, most visitors spend the day swimming at the adjacent Ngare Sero Waterfall or paddling on Lake Natron to observe the breeding flamingoes. Park fees, conservation fees, and rescue costs are among the payments paid to the tour operator.
Ol Doinyo Lengai’s Eruption Activity
In addition to explosive activity, Ol Doinyo Lengai also experiences phases where the composition of the lava may have much more silicate material, which lowers its viscosity. Since there is no flowing lava present, this type of eruption is characterized by ash outbursts and the ejection of blocks and bombs. However, powerful lava fountains may be present during the early stages of an explosive eruption. The two most recent explosive eruptions took place in the years 2007–2008 and 1966–1967.
Many people who have observed Ol Doinyo Lengai since the middle of the 1980s have seen lava flows and, to a much lesser extent, explosive eruptions. Natrocarbonatite lava outbursts are frequently focused in one or more tiny cones that earlier lava eruptions have carved out of the crater floor.
These eruptions often take the shape of open lava lakes or pools that may or may not be overflowing, lava flows that come from openings or fissures inside or close to the cones’ bases, or lava splashes or fountains that come from the cones’ summit vents. Although the activity is not fully understood, it is believed to be a result of the crater’s plumbing, the depth of the lava there, and the gas composition of the lava. Nobody is aware of what triggers the lava to flow out at any one time or how the several crater vents are related to one another.
Although there are various possibilities, mineralogists would like to know how the lava develops under the surface and why it has such an odd chemical makeup. Last but not least, no one knows why the regular tiny lava flows gave way to explosive activity at the end of August 2007 or how that may have been connected to earthquakes that had occurred in the area during the preceding two months.
Strangest Magma on Earth: Carbonatites of Ol Doinyo Lengai
You would be hard-pushed to find a better contender than Tanzania’s Ol Doinyo Lengai if you had to choose the most unusual volcano on Earth. It is the only location on Earth where carbonatite lava is currently erupting, and it is some of the most bizarre things you will ever witness (see the excellent video above). Due to the unique composition of this lava, which is rich in calcium, sodium, and carbon dioxide, these eruptions exhibit several peculiar characteristics. The exact origin of these carbonatite lavas, however, is still up for question, and to further complicate matters, Ol Doinyo Lengai doesn’t even produce the typical carbonatite lava (if you can call any carbonatite lava “normal”).
Furthermore, it may be possible to mine rare earth elements from carbonatites, making it even more crucial to understand how they arise.
What are carbonatites?
In addition to having a lot of carbon dioxide, carbonatites are types of magmas that are rich in alkali elements including calcium, sodium, and occasionally potassium. Why is that peculiar? The majority of terrestrial magma is silicate, which means that a large portion of the magma is composed of linked chains of silicon and oxygen. Even so-called “low silica” magmas like basalt include 45 weight percent of silica (SiO2), but so-called “high silica” magmas like rhyolite can have more than 70 weight percent.
These carbonatite magmas, which are mostly composed of calcium carbonate (CaCO3), are currently so heavily enriched in alkali elements that silica content is as low as a few percent by weight! Instead, the magma’s primary constituents are calcium and carbon dioxide (and in the case of Ol Doinyo Lengai, sodium).
The behavior of the magma is affected in a noticeable way by this. Since even the runniest basaltic lava is highly viscous, silica chains in silicate magma are what gives it part of its strength.
However, carbonatite magma can have far lower viscosity than silica chains, which enables the peculiar “garden hose” eruptions that are an example of activity in the Oldoinyo Lengai crater. Additionally, carbonatite magma can erupt at significantly lower temperatures than silicate magma due to its composition and lack of structure. Carbonatite lava erupts at temperatures between 480 and 590 C, while ordinary basalt may erupt at 1100 to 1200 C. Even the coolest silicate magmas are probably a few hundred degrees warmer than that (rhyolite).
Even silicate lava weathers differently from carbonatite lava. Since they are made of carbonate minerals like calcite (or even weird minerals like nyerereite and gregoryite), they degrade quickly when exposed to moisture or even a humid environment.
As a result, the dark carbonatite lavas of Oldoinyo Lengai erupt in a distinctive hue that turns them from black to grey to stark white as they cool (see above).
Now, if you are familiar with some of the characteristics of volcanoes, you would be aware that low-viscosity lava is not likely to erupt violently. This is due to the fact that gas bubbles in the lava may escape without being stuck, which would induce fragmentation. So it makes sense that Ol Doinyo Lengai would only erupt when lava flows because of its low viscosity. The amount of carbon dioxide that may be dissolved in the magma, however, is probably the reason why the volcano has had both explosive and effusive eruptions over the previous ten years.
No matter how viscous the lava is, the more carbon dioxide (or any other gas) you can pack into it, the more probable it is to explode explosively. Ol Doinyo Lengai saw a remarkable explosive eruption in 2008 (see below), which resulted in an ash plume with carbonatite ash falls and tephra being discovered. You can notice that part of the lava seems silvery in the eruption video (above), and this hue hides the fact that there are many bubbles present even in these apparently calm outbursts.
No matter how viscous the lava is, the more carbon dioxide (or any other gas) you can pack into it, the more probable it is to explode explosively. Ol Doinyo Lengai saw a remarkable explosive eruption in 2008, which resulted in an ash plume with carbonatite ash falls and tephra being discovered. You can notice that part of the lava seems silvery in the eruption video (above), and this hue hides the fact that there are many bubbles present even in these apparently calm outbursts.
So where does this strange carbonatite magma come from?
There are two theories about the ultimate source of carbonatite magma, which is a difficult topic to answer:
- Straight off the mantle
- A magma composed of an alkaline silicate separates into liquid. I said that the only spot on earth where carbonatite magma is erupting at the moment is Ol Doinyo Lengai. However, there are several places across the world where we may discover deposits indicative of carbonatite volcanism, thus it is not the only one (although over a third are in Africa, many associated with the East African Rift). There are also other places where we discover carbonatite magma that solidified below (plutonic), however, it is challenging to determine which hypothesis can adequately explain the presence of carbonatites.
In regions known as kimberlites, the first hypothesis—in which carbonatite magmas emerge directly from a mantle source—is preferred. Diamonds are brought up from depths of 100–200 km (lower crust and upper mantle) by intense explosive eruptions that create these craters. The presence of diamonds in kimberlites indicates the presence of a carbon-rich source in the upper mantle and lower crust. These appear to be a distinct class of explosive carbonatites, with their intense eruptions being driven by the magma’s very volatile (CO2) concentration.
The most plausible scenario at Ol Doinyo Lengai appears to be the separation of an alkaline silicate magma from a carbonatite liquid.
It is possible for alkaline silicate magmas (such as basanite or phonolite) to become sufficiently abundant in alkali elements and carbon dioxide that they become immiscible, which is when they separate from the silicate magma. Comparable to combining oil and vinegar While the two can be combined to form a solution if you let them stand the oil will float on top of the vinegar once they separate.
This is roughly what would happen if a body of crystallizing alkaline silicate magma ponded in the crust, enhancing the remaining magma with alkali elements and carbon dioxide. It is possible that this separation is taking place because some of the carbonatite lavas that erupted at Ol Doinyo Lengai include blebs of silicate magma. The copious lava flows of the volcano are made possible by this separation, which also permits some passive degassing of the carbonatite. However, even if it originated from the ponding of alkaline silicate melts, both models’ carbonatite magma doesn’t appear to interact with the continental crust, at least based on an examination of the trace element and isotopic composition of carbonatites.
The fact that Ol Doinyo Lengai hasn’t always been spewing carbonatites is one of its most intriguing features (or natrocarbonatites, due to the enrichment in sodium). In its previous history, alkaline silicate volcanism produced phonolite tuffs, then “regular” carbonatites (calcium-enriched carbonatites), and finally natrocarbonatites (Ca and Na enriched). In actuality, Ol Doinyo Lengai’s most recent natrocarbonatite volcanism has only been taking place for a few thousand years. This indicates to me that the carbonatite liquids are still being separated from the volcano’s feeding source.
Some of the oddest magmas on Earth are carbonatites. One of the great puzzles in petrology is how even their ultimate source came to be.
Given that they are one of the richest sources of rare earth elements (REE), a necessary component for many contemporary electronics, carbonatites are now of particular importance to comprehend. In reality, the world’s biggest REE deposit is in China, and the sole operational REE mine in the United States is located in a carbonatite deposit. This means that in addition to being a geological anomaly, they might also be a significant resource.