Decken Glacier

The Decken Glacier is one of the great glaciers on the southern face of Kibo, Mount Kilimanjaro’s highest cone. Descending from the Southern Ice Field beside its neighbour the Kersten Glacier, it bears the name of the very explorer who led the first serious European expedition to study Kilimanjaro — making it one of the most historically significant glaciers on the mountain.

Set on the sunlit southern side above the main climbing routes, the Decken Glacier is both a spectacular sight and a monument to the age when Kilimanjaro was first mapped and measured.

Overview of the Decken Glacier

The Decken Glacier is an outlet glacier fed by the Southern Ice Field, flowing down the southern flank of Kibo. It sits among the famous cluster of southern glaciers — alongside the Kersten, Heim, Rebmann and Ratzel glaciers — that together form the wall of ice seen from the southern approaches.

Because it faces the sun and the climbing routes, the Decken Glacier is among the most visible of Kilimanjaro’s glaciers, its layered vertical ice walls glowing in the dawn light on summit morning.

Where Is the Decken Glacier Located?

The Decken Glacier descends the southern face of Kibo, flowing from the Southern Ice Field above 5,700 metres, on the side of the mountain that overlooks the Machame, Umbwe and Barafu approaches.

Key location details:

• Mountain: Mount Kilimanjaro (Kilimanjaro National Park)
• Position: Southern face of Kibo
• Source: Southern Ice Field
• Neighbouring glacier: Kersten Glacier
• Elevation: from about 5,700 m down the southern face
• Status: prominent, retreating southern glacier

Named for the First Scientific Explorer of Kilimanjaro

The Decken Glacier is named after Baron Carl Claus von der Decken (1833–1865), the German explorer who led the first serious European scientific expeditions to Kilimanjaro in 1861 and 1862. Accompanied by the young scientist Otto Kersten — for whom the neighbouring Kersten Glacier is named — von der Decken climbed onto the mountain’s slopes and confirmed, from his own observations, that the summit of an equatorial African mountain was truly covered in snow and ice.

His work helped settle a debate that had followed the missionary Johannes Rebmann’s first report of Kilimanjaro’s snows in 1848, which many in Europe had refused to believe. Von der Decken’s expeditions brought back measurements and scientific description that established Kilimanjaro on the map of the world. He died young, in 1865, while exploring the Juba River in Somalia — but his name endures on the ice of the mountain he helped reveal.

Size, Elevation, and Conditions

The Decken Glacier lies in Kilimanjaro’s arctic summit zone, where the air stays permanently below freezing while the equatorial sun is fierce — especially on this sun-facing southern aspect.

Conditions on the ice:

• Surface temperatures remain below freezing year-round, from a few degrees below zero by day to well under −15 °C on cold, clear nights.
• Its southern face is exposed to intense direct sunlight, which erodes the vertical ice walls.
• Precipitation falls as snow and graupel and often disappears within days.
• The glacier has no active accumulation zone, so it loses more ice than it gains.

A Retreating Glacier: Ice Loss on Kilimanjaro

The Decken Glacier is part of one of the world’s most studied examples of tropical glacier loss. Almost 85 percent of Kilimanjaro’s ice cover disappeared between 1912 and 2011, shrinking from about 11.4 km² to under 1 km².

Key facts about the retreat:

• Average annual ice loss was about 1.1 percent from 1912 to 1953, rising to 1.4 percent (1953–1989) and 2.5 percent (1989–2007).
• Of the ice still present in 2000, nearly 40 percent had gone by 2011.
• The southern glaciers, including the Decken, have thinned and retreated, and some once-connected ice has fragmented.
• One 2013 assessment estimated most of Kilimanjaro’s ice will vanish by around 2040, and that it is highly unlikely any ice body will remain after 2060.

Why the Decken Glacier Is Retreating

The causes of Kilimanjaro’s ice loss are subtler than simple warming. Research points to a decline in atmospheric moisture — lower specific humidity following a sharp climate shift at the end of the 19th century — rather than rising air temperature as the main long-term driver. No clear warming trend was found at the elevation of these glaciers between 1948 and 2005.

Because the summit air stays below freezing, the ice rarely melts from the top. Instead it is lost mainly through solar radiation striking the vertical ice walls and through sublimation, where ice turns directly to vapour in the dry, sunlit air. On the sun-facing southern face, this process is especially effective.

Seeing the Decken Glacier

The Decken Glacier is one of the more accessible of Kilimanjaro’s glaciers to view, because it sits directly above the southern summit approaches.

• Climbers ascending from Barafu toward Uhuru Peak pass beneath the southern glaciers, with the Decken among them.
• The Machame Route, Lemosho Route and Umbwe Route all bring trekkers up the southern side toward this ice.
• From Stella Point on the crater rim, the southern ice cliffs spread out below in the sunrise.

Why the Decken Glacier Matters

Few glaciers carry as much history as the Decken. Named for the man who led the first scientific expeditions to Kilimanjaro, it is a direct link to the moment when the mountain’s snows passed from rumour into established fact. Its retreat today adds a second layer of meaning — a glacier named at the dawn of Kilimanjaro science now stands as evidence of a changing climate.

What the Experience Feels Like

To stand at the crater rim at dawn and look upon the Decken Glacier is to see the mountain much as its first explorers hoped to — a wall of ancient ice glowing above equatorial Africa. After a long, cold night-time ascent, the sight of these southern ice cliffs in the rising sun is one of the great rewards of a Kilimanjaro climb.

Frequently Asked Questions About the Decken Glacier

Where is the Decken Glacier on Mount Kilimanjaro?

The Decken Glacier descends the southern face of Kibo, flowing from the Southern Ice Field above 5,700 m, on the side of the mountain facing the main southern climbing routes.

Who is the Decken Glacier named after?

It is named after Baron Carl Claus von der Decken (1833–1865), the German explorer who led the first serious European scientific expeditions to Kilimanjaro in 1861 and 1862.

Why is von der Decken important to Kilimanjaro’s history?

His expeditions confirmed, through scientific observation, that Kilimanjaro’s equatorial summit was covered in snow and ice — settling a debate that had followed Johannes Rebmann’s disputed first report in 1848.

Is the Decken Glacier retreating?

Yes. Along with the rest of Kilimanjaro’s ice, it has retreated sharply — nearly 85 percent of the mountain’s ice was lost between 1912 and 2011, and most is projected to be gone by around 2040.

Can you see the Decken Glacier when climbing Kilimanjaro?

Yes. It is one of the visible southern glaciers, seen at close range on the final ascent from Barafu toward Stella Point and Uhuru Peak.

Need help with Kilimanjaro National Park?

If you’d like help understanding Kilimanjaro National Park, choosing a southern route that brings you close to the historic summit glaciers, or planning a safe and well-paced climb toward features like the Decken Glacier, we’re happy to guide you through the options and logistics so you can experience the roof of Africa at its most spectacular.