Natrocarbonatite is a rare

carbonatite Carbonatite () is a type of intrusive or extrusive igneous rock defined by mineralogic composition consisting of greater than 50% carbonate minerals. Carbonatites may be confused with marble and may require geochemical verification. Carbonati ...

lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or ...

which erupts from the Ol Doinyo Lengai

volcano A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates ...

Tanzania Tanzania (; ), officially the United Republic of Tanzania ( sw, Jamhuri ya Muungano wa Tanzania), is a country in East Africa within the African Great Lakes region. It borders Uganda to the north; Kenya to the northeast; Comoro Islands ...

within the

East African Rift The East African Rift (EAR) or East African Rift System (EARS) is an active continental rift zone in East Africa. The EAR began developing around the onset of the Miocene, 22–25 million years ago. In the past it was considered to be part of ...

of eastern

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

. Natrocarbonatite lavas were first documented in 1962, by J B Dawson.

Composition

Whereas most lavas are rich in

silicate minerals Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide, ) is usually con ...

, the natrocarbonatite lavas of Ol Doinyo Lengai are rich in the rare sodium and potassium

carbonate mineral Carbonate minerals are those minerals containing the carbonate ion, . Carbonate divisions Anhydrous carbonates *Calcite group: trigonal ** Calcite CaCO3 ** Gaspéite (Ni,Mg,Fe2+)CO3 ** Magnesite MgCO3 **Otavite CdCO3 ** Rhodochrosite MnCO3 ...

s, nyerereite and gregoryite. Due to this unusual composition, the lava is erupted at relatively low temperatures (approximately 500-600 °C).https://www.science.org/doi/10.1126/science.245.4914.168 This temperature is so low that the molten lava appears black in sunlight, rather than having the red glow common to most lavas. It is also much more fluid than silicate lavas.

Impact

The sodium and potassium carbonate minerals of the lavas erupted at Ol Doinyo Lengai are unstable at the Earth's surface and susceptible to rapid

weathering Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs '' in situ'' (on site, with little or no movement ...

, the minerals are

anhydrous A substance is anhydrous if it contains no water. Many processes in chemistry can be impeded by the presence of water; therefore, it is important that water-free reagents and techniques are used. In practice, however, it is very difficult to achi ...

and when they come into contact with the moisture of the atmosphere, they begin to react extremely quickly. The black or dark brown lava and ash erupted begins to turn white within a few hours. The resulting volcanic landscape is different from any other in the world.

In popular culture

Notable appearances
Etnatao: Ol Doinyo Lengai Volcano Tanzania

Eruption

Ol Doinyo Lengai Volcano HDTV
(from a French TV documentary)

References

* ttp://oldoinyolengai.pbworks.com/w/page/33191422/Ol-Doinyo-Lengai,-The-Mountain-of-God OL DOINYO LENGAI - THE MOUNTAIN OF GOD Volcanology Volcanic rocks {{volcanology-stub