The Only Carbonatite Volcano Erupting Today
Every other active volcano on Earth — Kilauea, Etna, Fuji, all of them — erupts silicate rock, built around silicon and oxygen. Ol Doinyo Lengai erupts natrocarbonatite: a lava made chiefly of sodium and potassium carbonate minerals, nyerereite and gregoryite (Natrocarbonatite). It is the only volcano known to produce this lava in historical time — which makes Lengai, in a very literal sense, the strangest active volcano on the planet.
That odd chemistry drives everything else about it. With almost no silica — the ingredient that makes most lava thick and sticky — natrocarbonatite is the coolest and most fluid lava on Earth. Field measurements put its eruption temperature at roughly 500–590 °C, with instrument readings as low as 491 °C; for comparison, basaltic lava pours out around 1,100 °C. Its viscosity is so low it's often described as moving like water or thin oil, curling into ropey strands and running fast across the crater floor.
The one statistic to quote
Ol Doinyo Lengai is the only volcano on Earth erupting natrocarbonatite lava in recorded history, and at roughly 500–590 °C it is the coolest lava ever measured — about half the temperature of ordinary basalt (~1,100 °C). That is why it flows out black rather than glowing red.
The Black Lava That Turns White
Lava glows because it is hot — the red-orange you picture is thermal radiation. Rock has to be around 700 °C before it glows visibly red in daylight, and Lengai's lava never gets that hot. So in sunlight its fresh flows look black or dark brown, like moving asphalt, and only at night do they show a faint, dull orange glow. Visitors who expect a river of fire are often startled to find what looks like spilled oil creeping across the crater.
Then it changes colour. The nyerereite and gregoryite that make up the fresh lava are chemically unstable in open air: within hours to a few days they react with atmospheric moisture and break down, drawing pale, washing-soda-like sodium-carbonate compounds to the surface. The black crust weathers to a chalky grey-white, so Lengai's summit looks oddly snow-dusted — in equatorial Africa, at a crater that is anything but cold. It is one of the most genuinely photogenic, under-documented sights in volcanology, and the reason the volcano keeps turning up in “weirdest places on Earth” lists.
The Mountain of God
“Ol Doinyo Lengai” means “Mountain of God”in the Maasai language, and it's easy to see why it earned the name: a steep, almost perfectly symmetrical cone rising straight off the rift floor to about 2,962 metres, just south of the flamingo-pink soda flats of Lake Natron and northeast of the Ngorongoro Crater. It sits on the East African Rift, the same continental split that feeds Erta Ale in Ethiopia and Nyiragongo in DR Congo — except that here the rifting taps an unusually carbonate-rich magma source, which is what produces the one-of-a-kind lava.
The connection to Lake Natron isn't a coincidence either. The sodium carbonate that makes Natron so caustic — and so deadly to most animals that enter it — is chemically kin to the minerals Lengai erupts. The volcano has been quietly salting this corner of the rift for millennia, and the Maasai regard the mountain as the dwelling of the god Engai.
When Lengai Turned Explosive
For most of its recorded history Lengai has done one thing: quietly ooze carbonatite across its North Crater floor. Our Smithsonian GVP record shows a long effusive run from 1983 that slowly filled the crater until lava spilled over the rim in late 1998. But the volcano is not only gentle. In 2007–2008 it broke pattern with months of genuinely explosive eruptions — a VEI 3phase that threw ash over the surrounding plains and excavated a deep new pit where the filled crater had been. It wasn't the first time, either: the 1960s episodes also ended explosively. The data below shows the two speeds Lengai runs at.
| Eruption | VEI | Style | Notes |
|---|---|---|---|
| 2017–2025 CE | 0 | Effusive (natrocarbonatite) | The current, quiet phase: small lava flows and spatter rebuilding the floor of the North Crater after the 2007–08 blasts reshaped it. |
| 2011–2016 CE | 0 | Effusive | Return to gentle carbonatite effusion inside the deepened North Crater. |
| 2007–2010 CE | 3 | Explosive | The dramatic exception: months of ash eruptions that excavated a deep new crater and dusted the surrounding plains. |
| 1994–2006 CE | 1 | Effusive | A long run of lava flows that slowly filled the North Crater until lava overflowed the rim by late 1998. |
| 1983–1993 CE | 2 | Effusive + minor explosive | Sustained carbonatite effusion with occasional small ash bursts. |
| 1967 CE | 3 | Explosive | Ash eruption from the North Crater. |
| 1960–1966 CE | 3 | Effusive + explosive | Quiet lava emission that ended in explosive activity in 1966, famously photographed with grazing wildebeest below. |
Source: VolcanoDB analysis of Smithsonian Global Volcanism Program records for Ol Doinyo Lengai (id 137): 27 recorded eruptions — 8 VEI 0, 7 VEI 2, 5 VEI 3, 2 VEI 1 and 5 unrated; highest on record is VEI 3. Selected rows shown; see the full data page for the complete history.
Since the 2007–08 blasts, Lengai has gone back to quiet effusion, slowly refilling the deepened North Crater — the phase our record logs continuing through 2025. That alternation matters for anyone planning to visit: the mountain can switch from a gentle lava spectacle to an ash-throwing hazard, and the summit you climb today is not the same shape it was twenty years ago.
Climbing the Mountain of God
Lengai is one of the very few active volcanoes in East Africa you can actually climb, and that draws a steady trickle of hikers to the villages around Lake Natron. It is not a gentle walk. The standard ascent is a steep, loose, overnight push — climbers set off around midnight to reach the crater rim at dawn before the equatorial sun turns the bare slope into an oven. There is no shade and no water on the mountain.
What waits at the top depends on the volcano's mood. In a quiet effusive phase you may see fresh black natrocarbonatite flows and small spatter cones (hornitos) on the crater floor; in a lull you may see only the white-crusted aftermath of earlier activity; and in an explosive phase the summit is simply off-limits. Nothing is guaranteed, the surface can be hot and fragile underfoot, and a qualified local guide is essential. Before you commit, check the volcano's current state on our active volcanoes tracker and the live erupting-now dashboard.