Ol Doinyo Lengai: Climbing the Active Natrocarbonatite Volcano

Ol Doinyo Lengai is the only volcano on Earth currently erupting natrocarbonatite lava, a unique substance that appears black or brown in the sun and glows dull red at night. Standing at an elevation of 2,962 meters within the East African Rift, this active stratovolcano remains a sacred site for the Maasai people who know it as the Mountain of God. Unlike the silica-rich magma found in the Ring of Fire, the lava here is rich in sodium and potassium carbonates, allowing it to remain liquid at temperatures as low as 510 degrees Celsius.

While Kilimanjaro and Meru offer traditional alpine trekking, Ol Doinyo Lengai provides a raw encounter with active geology in one of the harshest environments in East Africa. The mountain is situated near Lake Natron—a caustic, alkaline lake that serves as the primary breeding ground for 2.5 million Lesser Flamingos. This proximity creates a stark contrast between the white soda crusts of the lake and the dark, ash-covered slopes of the volcano. Hikers should expect a vertical gain of roughly 1,600 meters over a relatively short horizontal distance, making the gradient exceptionally steep compared to most commercial trekking peaks.

The Unique Geology of the Mountain of God

Understanding Natrocarbonatite Lava

Standard basaltic lavas in places like Hawaii or Iceland reach temperatures exceeding 1,100 degrees Celsius, but the magma at Ol Doinyo Lengai stays between 510 and 600 degrees Celsius. This lower temperature causes the lava to flow with a viscosity similar to water, often resulting in strange, silver-white rock formations as it cools and reacts with moisture in the air. This chemical composition means the rock is highly unstable; it erodes and dissolves quickly in the rain, which is why the crater topography changes so rapidly between seasons. When the lava first emerges it looks like black oil, but within hours of exposure to the atmosphere, it turns into a grey or white powder that resembles snow from a distance.

The Changing Crater Floor

The 2006 explosive eruption significantly altered the summit, deepening the crater and making the active hornitos—small, chimney-like vents—harder to reach for casual observers. Visitors should realize that the landscape at the top changes monthly as fresh flows solidify and collapse (a process that can happen overnight during periods of high activity). Because the mountain is seismically active, the sound of the lava bubbling inside the hornitos often resembles the sound of crashing ocean waves, a rhythmic thumping that echoes across the summit plateau. Standing on the rim provides a direct view into the throat of the volcano, where the ground can feel warm to the touch even through thick-soled hiking boots.

Logistics and Preparation for the Night Trek

Nighttime Ascents and Thermal Safety

Most hikers start their ascent from the base at midnight to avoid the punishing heat of the Rift Valley floor where temperatures frequently exceed 40 degrees Celsius during the day. The climb is a grueling 1,600-meter vertical gain over just five kilometers of horizontal distance, requiring a pace that minimizes exhaustion before the sun reaches its zenith. Reaching the summit at dawn is the primary goal—not just for the sunrise views over Lake Natron—but because the descent becomes hazardous once the equatorial sun begins to bake the exposed slopes. There is zero shade on the mountain, and the dark volcanic ash absorbs heat rapidly, making a mid-day ascent physically dangerous for most trekkers.

Essential Gear for Steep Scree Slopes

Because the upper slopes consist of loose volcanic ash and crumbling rock at a 45-degree angle, trekking poles are mandatory for safety during the descent. High-traction boots with deep lugs are essential because the dry ash behaves like fine sand, offering almost no resistance when you try to plant your feet on the way down. I have seen many hikers attempt this in standard running shoes, only to find themselves sliding uncontrollably on the return trip; a mistake that often leads to shredded clothing and skin abrasions. Since the summit at nearly 3,000 meters can be windy and freezing before dawn, a lightweight down jacket and a windproof shell are necessary layers despite the heat at the base camp.

Permits and Local Access Requirements

You must coordinate with the Engare Sero village office to pay the mandatory conservation fees, which typically cost around 35 to 40 USD per person. These fees are separate from the guide salary, and it is standard practice to hire a local Maasai guide who understands the current stability of the mountain trails. Most travelers reach the area via a six-hour drive from Arusha, often staying at campsites or lodges near the village of Engare Sero. It is wise to verify the current eruption status with local operators before departure, as the Tanzanian government occasionally restricts access to the summit during periods of heightened explosive activity.

Frequently Asked Questions

Is it safe to climb Ol Doinyo Lengai while it is erupting?

Safety depends on the type of activity; the volcano is usually in a state of effusive eruption with low-energy lava flows that stay within the crater. However, explosive ash eruptions occurred as recently as 2006 and 2008, and smaller ash vents remained active through 2021. Always check the latest seismic reports and use a local guide who can interpret the sounds and tremors of the mountain.

How difficult is the climb compared to Mount Kilimanjaro?

While much lower in elevation at 2,962 meters, the incline is significantly steeper than any section of the standard Kilimanjaro routes. The path involves scrambling over loose scree and ash on a 45-degree slope with no switchbacks. Most fit hikers complete the round trip in 6 to 10 hours, but the physical strain on the knees during the descent is intense.

What is the best month to visit the volcano?

The dry season from June to October offers the most stable climbing conditions and clearer views of the Rift Valley. During the rainy seasons of April and May, the ash slopes become incredibly slippery and muddy, making the steep ascent nearly impossible and potentially dangerous due to flash floods in the surrounding canyons. High winds are also less frequent during the mid-dry season months.

Can I see the lava glowing during the day?

No, the natrocarbonatite lava is much cooler than typical orange lava and only glows a dull, dark red that is visible in total darkness. During daylight hours, the fresh lava appears like liquid black asphalt or dark mud. To see the red glow, you must reach the crater floor or the rim well before the first light of dawn.