Oldonyo Lengai and Empakai Crater Trekking: Tanzania's Volcanic Adventure Beyond Kilimanjaro

Oldonyo Lengai is the only active volcano on Earth that erupts carbonatite lava. It runs black instead of red, flows almost like water, and turns white within hours. Empakai Crater sits nearby in the Ngorongoro Highlands, a caldera ringed by forest with a soda lake and flamingos on its floor. One is a brutal midnight climb. The other is a half-day walk. Together they make the best volcanic trek in Tanzania that almost nobody books, and we send far fewer people here than to Kilimanjaro.

Why Trek Volcanoes Instead of Kilimanjaro?

Kilimanjaro is the reason most trekkers come to Tanzania. It is a fine mountain and we run it constantly. But it is a long walk at altitude, it is crowded, and the summit is a sign in the snow.

These two are different. Lengai is a geological freak that scientists travel across the world to study. Empakai is a caldera with no roads and no people in it, where you walk down through forest to a lake full of flamingos. Neither takes a week. Neither has a queue.

If you have already climbed Kilimanjaro, or you want something stranger than a big hill, this is what we point you towards.

What Is Oldonyo Lengai?

Oldonyo Lengai means Mountain of God in Maasai. It stands south of Lake Natron in the Gregory Rift, part of the East African Rift system, and it is sacred to the Maasai as the dwelling place of Engai.

It is an active stratovolcano and it is genuinely unlike any other volcano on the planet.

The lava

Almost every volcano on Earth erupts silicate lava. Lengai erupts natrocarbonatite, a lava made of sodium and potassium carbonate minerals with almost no silicon. Two of those minerals, nyerereite and gregoryite, are named after Julius Nyerere and the geologist John Walter Gregory.

The consequences are strange and visible:

• It erupts far cooler than ordinary lava, cool enough that molten flows look black in daylight rather than glowing red

• It is extraordinarily fluid, closer to motor oil than the sluggish creep of normal lava

• It turns white within hours as it reacts with moisture in the air, so the crater floor looks frosted

• At night the same lava glows, because the darkness reveals what daylight washes out

This is the only place on Earth where any of that happens. Carbonatite lava was first documented here in 1962, and the eruptions in the decades since confirmed that carbonatite rock comes from magma, settling a real argument in geology.

The craters

The mountain has two summit craters. The southern one is inactive and filled with ash. The northern one is the active one, and it is where the carbonatite comes out. Small cones called hornitos sit on the floor, steaming, sometimes spilling lava.

How Hard Is the Oldonyo Lengai Trek?

Hard. This is the part we make sure people understand before they book.

Lengai is steeper and more punishing per hour than any single day on Kilimanjaro. The route is a continuous climb on loose volcanic ash and scree with no switchbacks to soften the gradient. You take two steps and slide back one. There is nothing technical about it, no ropes and no skills required, but it is relentless.

The descent is worse than the ascent for most people. Coming down loose scree on tired legs in daylight heat is where the trouble usually starts.

Some of our guests who have summited Kilimanjaro have found Lengai the tougher climb. The difference is that Kilimanjaro is days of thin air and endurance, while Lengai is one savage night. Both are hard. They are hard in different ways.

Why Does the Climb Start at Midnight?

Heat and sunrise.

The mountain sits in dry, hot Rift Valley country. There is no shade anywhere on the route. Climbing it under the sun would be miserable and, for many people, unsafe.

So you start around midnight, climb through the cool of the night with a head torch, and reach the crater rim as the sun comes up. The Rift Valley opens below you. Lake Natron sits to the north, the Ngorongoro Highlands to the south. On a clear morning you can see a long way.

Then you come down, because by mid-morning the mountain is an oven.

What Is Empakai Crater?

Empakai is a volcanic caldera in the Ngorongoro Conservation Area, north-east of the famous Ngorongoro Crater. It is smaller than its neighbour and it gets a tiny fraction of the visitors.

Steep walls covered in montane forest ring the crater. A soda lake covers much of the floor and draws flamingos. There are no roads inside and nobody lives there.

The rim is the other reason to come. On a clear day you look out over Oldonyo Lengai, the Great Rift Valley, Lake Natron, and sometimes Kilimanjaro in the distance. It is one of the best viewpoints in northern Tanzania and there is usually nobody else standing on it.

Wildlife on the slopes and floor includes buffalo, bushbuck, blue monkey and hyena. Elephant use the crater too. The birding around the lake is excellent.

How Hard Is the Empakai Crater Hike?

Moderate. This is the opposite of Lengai.

You descend from the rim through thick montane forest to the lake. The path is steep but short and the forest is beautiful, full of old trees and monkeys watching you pass. The walk back up is the work. It takes noticeably longer than the descent and it will make you sweat, but it is over quickly.

Most people in reasonable walking fitness manage Empakai without difficulty. It is the right choice if you want to get out of the safari vehicle and use your legs without committing to a mountain. Sturdy shoes matter. Trainers on a wet forest path are a bad idea.

Do You Need a Ranger?

For Empakai, yes. An armed Ngorongoro Conservation Area ranger must accompany you into the crater. This is a rule, not a suggestion, and you cannot hike it on your own.

The reason is straightforward. You are leaving a vehicle in a place where buffalo, elephant and hyena live and walking down into their crater. The rangers are trained for exactly that.

Permits go through the Ngorongoro Conservation Area Authority, and you need a 4x4 to reach the trailhead. We handle both as part of the trip.

For Lengai, you climb with a local guide. The mountain sits outside the conservation area on Maasai land, and the guides who take you up grew up beneath it.

Lengai or Empakai: Which Should You Do?

Do both if you can. They are completely different experiences and they sit close together.

If you only have appetite for one, pick honestly. Lengai punishes people who underestimate it. Empakai rewards anyone who can walk uphill.

Can You Combine Them?

Yes. They pair naturally, and this is how we usually build the trip.

The two sit in the same corner of northern Tanzania, connected by the Ngorongoro Highlands and Lake Natron. The route most of our trekkers take runs roughly like this:

• Start on the Ngorongoro Crater rim, with a game drive on the crater floor

• Walk Olmoti Crater, a short hike that works well as a warm-up

• Camp on the Empakai rim and descend to the lake with a ranger

• Trek out through Maasai country towards Lake Natron, often with Maasai guides and donkeys carrying the loads

• Reach Lake Natron, where flamingos gather in numbers against the backdrop of Lengai

• Climb Lengai at midnight as the finish

The walk between Empakai and Natron is the part people remember. You leave the conservation area, the land dries out and warms up, and you pass through villages and rolling country with the volcano ahead of you the whole way.

It also works as a bolt-on. Three or four days added to a northern circuit safari covers the highlands and Lengai without a separate trip.

When Should You Go?

The dry season. This is not a preference, it is a safety point on Lengai.

Lengai's scree is loose when dry and treacherous when wet. Rain also turns the fresh black lava white almost immediately, which is fascinating geology and a poor photograph. Empakai's forest descent gets slick, and the rim view that makes the hike worthwhile disappears into cloud.

Ask us before you fix dates. Conditions on Lengai change and we would rather move your trip than send you up a wet mountain.

Is Oldonyo Lengai Safe? It Is an Active Volcano

It is genuinely active, and it has been in near-continuous activity for decades. Its behaviour alternates between quiet phases, when carbonatite lava wells up inside the northern crater, and occasional explosive phases that throw ash.

Quiet phases are when people climb. Explosive phases are when nobody does.

This is why you climb with people who watch the mountain. Local guides and the operators who work here know what it is doing week to week. We check activity before we confirm a Lengai climb, and we will cancel one if the mountain is not behaving. Nobody sensible treats this as a fixed booking that goes ahead regardless.

What Should You Bring?

For Lengai

• Boots with real grip and ankle support, broken in, not new

• Head torch with fresh batteries and a spare

• Gloves — you will use your hands on the steep sections and the rock is sharp

• More water than you think, and something with salt in it

• A light layer for the cold night and sun protection for the descent

• Trekking poles, which help more on the way down than the way up

• Nothing you mind ruining; volcanic ash gets into everything

For Empakai

• Sturdy walking shoes with grip; the forest path is steep

• Rain jacket, because the highlands make their own weather

• Binoculars for the flamingos and the forest birds

• A warm layer for the rim, which sits high and gets cold

• Water and snacks for the crater floor

Where Does This Fit in a Tanzania Trip?

Both sit within reach of the northern circuit, so most people add them to a safari rather than building a trip around them.

Two structures we build most often:

• Safari plus highlands — Serengeti and Ngorongoro, then the highlands walk through Olmoti and Empakai to Lake Natron, finishing with Lengai

• Kilimanjaro plus Lengai — climb Kilimanjaro, recover for a few days, then take on Lengai as a very different kind of summit

The second one is for people who want two mountains and understand they are not the same problem. Kilimanjaro tests your lungs. Lengai tests your legs and your patience with loose ground.

Planning Your Volcanic Trek

These are not mountains you book off a website and turn up for. Lengai needs a check on what the volcano is doing. Empakai needs NCAA permits, a ranger and a 4x4. Both need honest conversation about fitness first.

We have arranged trekking in Tanzania since 1948. We handle permits, rangers, guides, transport and camps for both, and we will tell you plainly if Lengai is the wrong trek for you. Some people should do Empakai and skip the volcano. That is a fine trip.

Tanzania Trekking — Kilimanjaro, Meru, Oldonyo Lengai and Empakai