The Pleistocene Kilimanjaro Volcano

TANZANIA

Aerial view looking west of the Kibo inner cone with central ash pit and collapsed rim (centre right), known as the Western Breach. Note the glaciation around the edges leading up to the Uhuru summit ridge (back right) (Photo credit G. Pearson).

Geological Period

Quaternary

Main geological interest

Volcanology
Geomorphology and active geological processes

Location

Tanzania.
2°45’00.0″S, 37°00’00.0″E

The highest stratovolcano of the East African Rift that maintains a glacier on its summit.

It is a spectacular landscape whose snowcapped summits and the majestic volcanic landscape forms a strong contrast with the surrounding plains. The Kilimanjaro region is World Heritage site registered by UNESCO in 1987. Its highly alkaline volcanic products and the later lahar deposits due to the interaction of the glaciers with the erupting volcanoes from its summit craters form a particular suite of rocks (phonolites, tephri-phonolites, phono-tephrites and tephrites). The rapidly retreating glaciers and the snows capping the summit are unique phenomenon as they occur near the equator (Kaser et al., 2004); these glaciers provided a unique opportunity to investigate the climate of the late Pleistocene; in addition, the various archives (lake deposits, pit bogs, glaciers) at pristine locations at high altitudes provided important climate records (Barker et al., 2010; Courtney Mustaphi et al., 2021).

Resistant lava flows with associated ash layers, viewed from the Kibo Barranco on the southern edge of the mountain (Photo credit G. Pearson).

Mt. Kilimanjaro is the highest mountain in Africa (5895m a.s.l. at its peak). It is a 40×60 km elliptic volcanic edifice with three centres/ peaks (Shira, Kibo, and Mawenzi from West to East) equally spaced along a N110°E-striking axis (Kent, 1944). It is a polyphased volcano successively built since ~2.5 Ma years ago. According to Nonnotte et al. (2008) the oldest phases of volcanic activity begun at ~2.5 Ma in the Shira vent while the latest important phases occurred around 1.9 Ma, before the collapse of the Northern part of the edifice. Magmatic activity then shifted eastwards in the Mawenzi and Kibo twin centres where initial volcanism is dated at ~1 Ma. the most recent Mawenzi rocks (492 ka and 448 ka) close to the present summit, are linked to the final stage of edification for this centre. The present cone at Kibo was built at 274 to 170 ka ago (Nonnotte et al., 2008). However, volcanism might have continued until 150 ka. The volcanic products are highly alkaline (mostly phonolites, tephri-phonolites, phono-tephrites and tephrites, with few trachy-basalts). The summit of Kilimanjaro is covered by a rapidly retreating glaciers, whose age might date back to the late Pleistocene (Nonnotte et al., 2008; Cullen et al., 2013).

Mount Kilimanjaro has been investigated since the 1950s. Its geology and particularly the glaciers at the summit have been a subject of continued investigation. The climate archives at the summit and high-altitude ranges of the volcano have also been well researched.

Geological map of Mt. Kilimanjaro (Modified from Nonnotte et al., 2008).

Barker, P.A. et al. (2011) ‘Seasonality in equatorial climate over the past 25 k.y. revealed by oxygen isotope records from Mount Kilimanjaro’, Geology, 39(12), pp. 1111–1114. Available at: https://doi.org/10.1130/G32419.1.

Kaser, G. et al. (2004) ‘Modern glacier retreat on Kilimanjaro as evidence of climate change: observations and facts: GLACIERS AND CLIMATE CHANGE’, International Journal of Climatology, 24(3), pp. 329–339. Available at: https://doi.org/10.1002/joc.1008.

Kent, P.E. (1944) ‘Kilimanjaro: An Active Volcano’, Nature, 153(3885), pp. 454–455. Available at: https://doi.org/10.1038/153454a0.

Mustaphi, C.J.C. et al. (2021) ‘A 3000-year record of vegetation changes and fire at a high-elevation wetland on Kilimanjaro, Tanzania’, Quaternary Research, 99, pp. 34–62. Available at: https://doi.org/10.1017/qua.2020.76.

N.J., C. et al. (2013) ‘A century of ice retreat on Kilimanjaro: The mapping reloaded’, The Cryosphere, 7, pp. 419–431. Available at: https://doi.org/10.5194/tc-7-419-2013.

Nonnotte, P. et al. (2008) ‘New K–Ar age determinations of Kilimanjaro volcano in the North Tanzanian diverging rift, East Africa’, Journal of Volcanology and Geothermal Research, 173(1), pp. 99–112. Available at: https://doi.org/10.1016/j.jvolgeores.2007.12.042.

Asfawossen Asrat
Botswana International University of Science and Technology, Palapye, Botswana

The Pleistocene Kilimanjaro Volcano

TANZANIA

Geological Period

Main geological interest

Location

The highest stratovolcano of the East African Rift that maintains a glacier on its summit.

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