Vulcanology of Kilimajaro

Kilimanjaro is the largest member of an E-W belt of around twenty volcanoes near the East African Rift Valley. Other notable members in this belt located in Tanzania are: Ngorongoro caldera, Ol Donyo Lengai and Mt Meru.

Kilimanjaro is a huge stratovolcano reaching an elevation of 5,895 m. Stratovolcanoes are made by the mixing of erupted ash and cinders with lava flows which then cool to create conical formation. These types of volcanoes materialize over tens of thousands of years may often consist of several lava types including: Andesite, Basalt and Dacite.

This volcano's highest and most recent cone is called Kibo. Shira to the west and Mawenzi in the east are older 2 cones that, together with Kibo, make up Kilimanjaro. Kibo has not been active in recent history, however steam and sulfur are still emitted. At Kibo's summit is a 2.25km wide crater. It was probably active in the last 10,000 years. The typical eruption type for this sort of volcano is explosive.

Shira is topped by a large plateau where erosion has cut deeply into a remnant rim. In contrast, Mawenzi's summit is a steep rocky pinacle surrounded by cliffs of 0.5 km - 1.5 km high. Erosion has destroyed all its original crater, and a huge horseshoe shaped ridge opens to the northeast. Deep gullies with up to 45 degree gradients make many places pretty much inaccessible. A colossal series of radial dykes make up more than 30 percent of the summit of Mawenzi.

Kibo's glacier-clad summit is the highest spot in Africa this is a 1.9 x 2.7 km caldera, with an inner crater is around 1.3 km wide, and inside that a deep, 350m wide central pit. Original volcanic forms are preserved at the summit and on many of the sides. The exception is the south side where glaciers have cut into the cone. About 250 satellite cones occur on Kilimanjaro, most following SE and NW trends.

Estimates suggest that of a total volume of about 1,150 cu. miles, Mawenzi and Shira each contribute about 120 cu. mi. of andesites and basalts, Kibo has the same volume of similar but unexposed rocks, plus an additional 107 cu. miles. Interestingly, more than half of Kilimanjaro's volume is represented by older, basal basalts (672 cu. mi.), so as in Cascade stratovolcanoes - a basaltic shield is the most important, but least conspicuous element of a chemically complex volcano.

Most of Kilimanjaro was made in the Pleistocene period, but a group of younger summit craters are from the Holocene.

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