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Kilimanjaro

Cosmonaut Oleg Artemyev captured this gorgeous view of the Kilimanjaro volcanic complex sticking its head above a sea of clouds earlier this month. From this vantage point you can see both the central volcanic crater at the summit and the highest point in Africa, on the rim of that crater. The high point just to the edge of the crater is called Uhuru peak and a recent survey assessed it to reach 5891 meters above sea level.

Kilimanjaro is the culmination of 3 volcanic complexes built up over the last 2 million years. Lavas on the slopes of the main peak, partially buried by more recent activity, show that there was a volcano developed here between 2.3 and 1.9 million years ago. That volcano, known as Shira, remains as a ridge on the slope of the largest peak today. 1.9 million years ago, that volcano collapsed to form a caldera, prior to nearly a million years of quiet at this site, and during that time the former peak partially eroded away.

950,000 years ago, volcanism restarted at the site seen off to the left edge of this image, a summit called Mawenzi. This peak was built up out of lava flows between 950,000 and 488,000 years ago. Eruptions at this peak ceased after a major collapse and avalanche event, which triggered lahars that flowed down the slopes.

The main peak of Kilimanjaro is known as Kibo. Activity on it may have started as early as 1 million years ago, but the youngest well-exposed activity is about 463,000 years old. It is likely that both Kibo and Mawenzi were erupting simultaneously as those 463,000 year old rocks are at roughly the same elevation as the summit of Mawenzi – meaning the volcano had to grow to that height by that time. These eruptions have partially buried the remnants of Shira, leaving it only weakly exposed. The main summit grew through a series of explosive, crater and caldera forming eruptions, intrusive lava flows, and dome formations. The flat summit of this peak is thought to have formed in an eruption about 200,000 years ago, associated with an intrusion of igneous rocks, a dome collapse, and lahars that probably involved melting glaciers at the summit.

Smaller cinder cones have formed since this last main volcano-building event, and these dot the landscape around the main mountain.

-JBB

Image credit: https://twitter.com/OlegMKS/status/1028582780358283264

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