🌋VolcanoAtlas

Ol Doinyo Lengai

Earth's Only Active Carbonatite Volcano

Elevation

2,962 m

Last Eruption

2017–present

Type

Stratovolcano

Country

Tanzania

Location

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Volcanic Hazards & Risk Assessment

Primary Hazards

  • Pyroclastic flows
  • Lava flows
  • Volcanic bombs and ballistics
  • Lahars and mudflows

Risk Level

Population at RiskLow
Infrastructure RiskHigh
Aviation RiskSignificant

Geological Composition & Structure

Rock Types

Primary
Unknown
Silica Content
Varied composition

Tectonic Setting

Unknown
Intraplate setting with hotspot or regional volcanic activity.

Age & Formation

Epoch
Unknown
Evidence
Unknown

Eruption Statistics & Analysis

MetricValueGlobal RankingSignificance
Total Recorded EruptionsUnknownLowModerately active volcano
Maximum VEIVEI UnknownMinorLocal impact potential
Recent Activity9 years agoVery RecentCurrently active

Monitoring & Alert Status

Monitoring Networks

Global Volcanism Program
International eruption database

Current Status

Active
Recent volcanic activity detected. Continuous monitoring in place.

Authority Sources

Smithsonian GVP
Official volcano database

Related Volcanoes

All Tanzania Volcanoes
Explore by country
Stratovolcano Volcanoes
By volcano type
Arusha Region, Gregory Rift Valley
Regional volcanoes

Interesting Facts

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Ol Doinyo Lengai is the only volcano on Earth currently erupting natrocarbonatite lava — a magma type composed of sodium and calcium carbonates rather than silicate minerals.

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Natrocarbonatite lava erupts at approximately 500–590°C (930–1,090°F), less than half the temperature of basaltic lava (~1,170°C) and the coolest lava known on the modern Earth.

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Freshly erupted carbonatite lava appears jet black but turns white within hours as it absorbs atmospheric moisture — giving the summit crater an eerie, constantly changing appearance.

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The Maasai name 'Ol Doinyo Lengai' translates to 'Mountain of God,' and the volcano holds the highest spiritual significance in Maasai culture as a dwelling place of Engai (God).

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Natrocarbonatite lava has the viscosity of motor oil at eruption temperature — approximately 1,000 times less viscous than basaltic lava — making it the most fluid lava on Earth.

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The mineral nyerereite (Na₂Ca(CO₃)₂), found only in Lengai's lavas, is named after Julius Nyerere, Tanzania's first president.

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Between 1983 and 2006, quiet carbonatite lava effusion gradually filled the Northern Crater until flows began overflowing the crater rim in 1998.

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The 2007 explosive eruption transformed the volcano overnight from effusive carbonatite to violent silicate eruptions, demonstrating a dual magmatic system that scientists had only theorized about.

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Ol Doinyo Lengai stands with approximately 2,360 m of topographic prominence above the rift valley floor — making the standard climbing route one of the steepest non-technical volcano ascents in the world.

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Lake Natron, 15 km north of the volcano, hosts up to 2.5 million lesser flamingos — the largest breeding colony of the species in the world — sustained by the lake's extreme alkalinity partly derived from volcanic carbonate minerals.

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Carbonatite volcanism was once thought to be confined to Earth's geological past until Lengai proved it persists today, making the volcano an irreplaceable natural laboratory.

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The summit crater temperature can drop below freezing at night while active carbonatite lava flows at 540°C just meters away — one of the most extreme thermal juxtapositions on any volcanic summit.

Frequently Asked Questions

What makes Ol Doinyo Lengai unique among volcanoes?
Ol Doinyo Lengai is the only volcano on Earth currently erupting natrocarbonatite lava — a magma type composed of sodium and calcium carbonates rather than the silicate minerals found in virtually all other volcanic lavas. This extremely rare lava erupts at just 500–590°C, roughly half the temperature of basaltic lava, and appears black when molten rather than red-orange. It also has extraordinarily low viscosity, flowing almost like water. Within hours of eruption, the lava absorbs atmospheric moisture and turns white, giving the summit an unearthly appearance. No other active volcano produces anything like it.
Is Ol Doinyo Lengai still active?
Yes, Ol Doinyo Lengai is very much active. The volcano has been in near-continuous eruptive activity since 1983, alternating between quiet phases of natrocarbonatite lava effusion in the summit crater and periodic explosive eruptions that produce ash columns. The most recent confirmed eruption began in April 2017 and continues into 2025, with ongoing carbonatite lava emission and intermittent ash activity at the Northern Crater. Satellite monitoring regularly detects thermal anomalies at the summit.
Can you climb Ol Doinyo Lengai?
Yes, Ol Doinyo Lengai is climbable and has become a popular adventure tourism objective in northern Tanzania. The standard route ascends from the Maasai village of Engare Sero on the southern side, with climbers typically departing at midnight to reach the summit for sunrise. The climb covers approximately 2,000 m of elevation gain over 8–10 hours and involves steep, loose volcanic scree — it is physically demanding but non-technical. A local Maasai guide is required. The summit crater offers an extraordinary view of active carbonatite lava, unlike anything else on the planet.
Why is the lava at Ol Doinyo Lengai black and then white?
Natrocarbonatite lava erupts at approximately 540°C — too cool to glow red in daylight — so it appears jet black when fresh. The lava is composed of sodium and calcium carbonate minerals, which are chemically unstable in the presence of atmospheric moisture. Within hours of exposure, the carbonatite absorbs water and undergoes rapid chemical weathering, transforming from dark grey-black to brilliant white. This gives the summit crater a striking appearance: fresh black lava flows surrounded by white-weathered older flows, with the contrast constantly shifting as new lava is erupted.
What does Ol Doinyo Lengai mean?
Ol Doinyo Lengai translates to 'Mountain of God' in the Maa language spoken by the Maasai people of East Africa. 'Ol Doinyo' means 'mountain' and 'Lengai' (also written 'Le Ngai' or 'L'Engai') means 'God.' The volcano is the most sacred peak in Maasai cosmology, believed to be a dwelling place of Engai, the supreme deity. Maasai warriors traditionally make pilgrimages to the summit as spiritual rites of passage.
How dangerous is Ol Doinyo Lengai?
Ol Doinyo Lengai poses moderate direct hazard, mitigated by its remote location in the sparsely populated Gregory Rift Valley. During explosive phases like 2007–2008, ashfall can affect Maasai communities within 20–30 km, contaminating water and pasture. Pyroclastic flows, though generally limited to upper flanks, threaten climbers. The steep, unconsolidated slopes are prone to landslides. The most significant risk is the unpredictable transition from quiet effusive activity to explosive eruptions, which can occur suddenly — as demonstrated in September 2007 when decades of calm carbonatite lava emission gave way to violent VEI 3 explosions within days.
When did Ol Doinyo Lengai last erupt?
Ol Doinyo Lengai has been in a state of ongoing eruption since April 2017, with natrocarbonatite lava effusion and intermittent ash emissions from the Northern Crater continuing into 2025. Before that, a major explosive eruption (VEI 3) occurred from September 2007 through 2010, followed by a return to effusive carbonatite activity from 2011 onward. The volcano has been in near-continuous activity since 1983, making it one of the most persistently active volcanoes in Africa.
Where is Ol Doinyo Lengai located?
Ol Doinyo Lengai is located in the Arusha Region of northern Tanzania, in the Gregory Rift Valley approximately 15 km south of Lake Natron and 160 km west-northwest of the city of Arusha. It stands within the eastern branch of the East African Rift System. The volcano is accessible from Arusha via the town of Mto wa Mbu and the Maasai village of Engare Sero at its southern base. Its summit is visible across the flat rift valley floor from distances exceeding 50 km.