Reusch Crater and the Ash Pit comprise one of the most unique highlights of Mount Kilimanjaro. Hidden within Mount Kilimanjaro, these craters are geological wonders that few climbers get to see up close.

Mount Kilimanjaro is made of three main volcanic cones—Shira, Mawenzi, and Kibo. Kibo, the highest of the three cones, is the most prominent and geologically active, containing a series of three concentric craters. These structures reflect Kilimanjaro’s complex volcanic history.

Here’s a closer look at each one:

Kibo Crater

The largest of the three, Kibo Crater spans about 1.6 miles (2.5 km) across and forms the outer rim at Kibo’s summit. This caldera was formed when the peak of Kibo collapsed inward—as volcanic pressures subsided and lava chambers beneath the surface emptied out. Over time, this loss of support underneath caused the summit to sink, creating a broad, bowl-like depression. This outer crater is geologically significant as it marks the last phase of Kibo’s peak-building eruptions.

Reusch Crater

Inside Kibo Crater lies Reusch Crater, a nearly perfect circle measuring roughly 4,265 feet (1,300 m) across. This inner crater was formed in a later phase of volcanic activity. Reusch Crater represents the collapse of a smaller lava dome within the larger Kibo Crater. It likely developed when magma beneath the surface retreated or solidified, creating a weaker structure that eventually caved-in, forming this secondary crater. This depression reflects the transition of Kibo’s volcanic activity from explosive to more centralized venting.

The Ash Pit

The Ash Pit, located at the very center of Reusch Crater, is the smallest but perhaps most interesting feature, measuring around 460 feet (140 m) wide. Geologically, this pit is an active fumarole, an opening that still emits faint sulfurous vapors. The Ash Pit is a remnant of Kibo’s last stages of volcanic activity, when hot gases and ash were ejected rather than molten lava. Over time, as volcanic activity waned, it left behind this cylindrical shaft, which plunges deeply into the mountain.

While Kibo’s last major eruption happened around 360,000 years ago, the Ash Pit continues to show traces of volcanic activity. Temperatures just beneath its floor remain at 170°F (78°C), a reminder that the volcano is not extinct, but dormant. Despite the icy conditions at the summit, snow never accumulates within the Ash Pit, melting immediately upon contact with the heated ground.

Visiting Reusch Crater and the Ash Pit

For climbers who reach the summit at Uhuru Peak, descending into Reusch Crater requires additional preparation and stamina. The trip from Uhuru Peak to the Reusch Crater adds approximately three hours to the itinerary. Only climbers in peak physical condition, with thorough acclimatization and no signs of altitude sickness, should consider this journey as part of a standard itinerary as it adds a significant chunk of time (and effort) to an already long and tiring summit day.

The most popular, and less strenuous, way to visit Reusch Crater and the Ash Pit is by using one of our Crater Camp routes. These itineraries spend a night within Kibo Crater after the summit, camping near Furtwängler Glacier. Camping in the crater allows time for climbers to make the round trip hike to the Ash Pit given that they do not have to make a long descent.

For those who undertake the journey, Reusch Crater offers a rare look at Kilimanjaro’s lesser-known features. This side excursion rewards hikers with dramatic, panoramic views of Kilimanjaro’s crater system and a close-up encounter with the Ash Pit’s sulfurous vapors.

Richard Reusch – Son of Kibo

The Reusch Crater was named in 1954 in honor of Gustav Otto Richard Reusch, a German missionary whose deep commitment to Kilimanjaro exploration was notable.

Reusch, based in the Kilimanjaro region, first reached the summit in 1926. During his ascent, he became the first to record the crater that now bears his name. Over the years, Reusch made at least 65 ascents, more than 25 of which brought him to the summit, earning him the honorary title of “Son of Kibo.”

Reusch’s legacy is rich not only for his countless expeditions but for the discovery of the frozen leopard near the summit, which remains one of the mountain’s most mysterious findings and inspired Ernest Hemingway’s famous short story, “The Snows of Kilimanjaro.” Reusch documented the moment with a photograph and preserved part of the leopard’s ear as proof.

Reusch’s influence extends beyond his mountaineering feats. He spent 30 years as a missionary in Tanganyika, where he established a seminary in Marangu, one of Kilimanjaro’s gateway towns, in 1927. This town eventually became the starting point for the Marangu Route, the first official route up Kilimanjaro. In 1929, Reusch co-founded the Mountain Club of East Africa (now known as the Kilimanjaro Mountain Club) with British geographer Clement Gillman, establishing the region’s first organized trekking and mountaineering initiatives.