Ol Doinyo Lengai is an active volcano

Volcano

2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...

 located in the north of Tanzania

Tanzania

The United Republic of Tanzania is a country in East Africa bordered by Kenya and Uganda to the north, Rwanda, Burundi, and the Democratic Republic of the Congo to the west, and Zambia, Malawi, and Mozambique to the south. The country's eastern borders lie on the Indian Ocean.Tanzania is a state...

 and is part of the volcanic system of the Great Rift Valley

Great Rift Valley

The Great Rift Valley is a name given in the late 19th century by British explorer John Walter Gregory to the continuous geographic trench, approximately in length, that runs from northern Syria in Southwest Asia to central Mozambique in South East Africa...

 in Eastern Africa

Africa

Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

. It is located in the eastern Rift Valley

Great Rift Valley

The Great Rift Valley is a name given in the late 19th century by British explorer John Walter Gregory to the continuous geographic trench, approximately in length, that runs from northern Syria in Southwest Asia to central Mozambique in South East Africa...

, south of both Lake Natron

Lake Natron

Lake Natron is a salt lake located in northern Tanzania, close to the Kenyan border, in the eastern branch of Africa's Great Rift Valley. The lake is fed by the Ewaso Ng'iro River but also by mineral-rich hot springs and is quite shallow, less than three meters deep, and varies in width depending...

 and Kenya

Kenya

Kenya , officially known as the Republic of Kenya, is a country in East Africa that lies on the equator, with the Indian Ocean to its south-east...

. It is unique among active volcanoes in that it produces natrocarbonatite

Natrocarbonatite

Natrocarbonatite is a rare carbonatite lava which erupts from the Ol Doinyo Lengai volcano in Tanzania within the Great Rift Valley of eastern Africa. Whereas most lavas are rich in silicate minerals, the natrocarbonatite lavas of Ol Doinyo Lengai are rich in the rare sodium and potassium carbonate...

 lava

Lava

Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...

, a unique occurrence of volcanic carbonatite

Carbonatite

Carbonatites are intrusive or extrusive igneous rocks defined by mineralogic composition consisting of greater than 50 percent carbonate minerals. Carbonatites may be confused with marble, and may require geochemical verification....

. Further, the temperature of its lava as it emerges is only around 510 °C (950 °F). A few older extinct carbonatite volcanoes are located nearby, including Homa Mountain.
"Ol Doinyo Lengai" means "The Mountain of God" in the Maasai language

Maasai language

The Maasai language is an Eastern Nilotic language spoken in Southern Kenya and Northern Tanzania by the Maasai people, numbering about 800,000...

 of the native people.
The record of eruptions on the mountain dates to 1883, and flows were also recorded between 1904 and 1910 and again between 1913 and 1915.