Kilimanjaro

Geology

Kilimanjaro is a large volcano composed of three distinct volcanic cones: Kibo, the highest at 5895m (19,650ft); Mawenzi at 5,149 metres (16,893 ft); and Shira, the shortest at 4,005 metres (13,140 ft). Mawenzi and Shira are extinct, while Kibo is dormant and could erupt again.

Volcanic activity at the Shira centre commenced about 2.5 million years ago, with the last important phase occurring about 1.9 million years ago, just before the northern part of the edifice collapsed. Shira is topped by a broad plateau at 3,800 metres (12,500 ft), which may be a filled caldera. The remnant caldera rim has been degraded deeply by erosion. Before the caldera formed and erosion began, Shira might have been between 4,900 m (16,000 ft) and 5,200 m (17,000 ft) high.

Mawenzi

Kibo is the largest cone and is more than 15 miles (24 km) wide at the “Saddle Plateau” altitude. The last activity here has been dated to between 150,000 and 200,000 years ago and created the current Kibo summit crater. Kibo still has gas-emitting fumaroles in the crater.

Kibo is capped by an almost symmetrical cone with escarpments rising 180 metres (590 ft) to 200 metres (660 ft) on the south side. These escarpments define a 2.5-kilometre-wide (1.6 mi) caldera caused by the collapse of the summit. Within this caldera is the Inner Cone and within the crater of the Inner Cone is the Reusch Crater, which the Tanganyika government in 1954 named after Gustav Otto Richard Reusch. The Ash Pit, 350 metres (1,150 ft) deep, lies within the Reusch Crater. About 100,000 years ago, part of Kibo’s crater rim collapsed, creating the area known as the Western Breach and the Great Barranco.