lengai

The rarest lava on Earth

Nearly all volcanoes on Earth erupt silicate lava–that is, lava which primarily forms minerals containing silicon and oxygen. Some rare exceptions to this can be seen in carbonatites, igneous rocks that consist primarily of carbonate minerals–usually dominated by calcite or dolomite, and often with silicate minerals mixed in. Only one volcano erupts carbonatite lava today: Ol Doinyo Lengai, a rift volcano in Tanzania (see crater in picture).

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Ol Doinyo Lengai

The Maasai call this volcano “Mountain of God” and it’s certainly an awesome landmark in a spectacular landscape. Looking like a child’s drawing of a perfect conical volcano, it rears up from the Great Rift Valley floor to an altitude of 2740m (8987ft) above sea level and 99 miles away from Kilimanjaro. In Tanzania, the walls of the Northern Rift are studded with huge volcanoes that are mostly inactive now. Lengai reminds us of what once was. Its steep sides have been eroded by rainwater run-off into deep fissures and canyons that, from a distance, form beautiful abstract patterns of light and shade. At the top, there’s an active crater divided from an inactive one by a high, sheer wall.

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Ol doinyo lengai, Tanzania. 

The image below is of Ol doinyo lengai, an active volcano, located in Tanzania. 

The name means mountain of God in Masai, and the volcano is fed by the East African rift system. 

Although strato volcanoes are very common, the geological processes here are unique. This is the only volcano in the world that erupts naturocarbonatite lava (although extinct volcanoes of the same type are located close by). This kind of lava is erupted at a low temperature, just 510 degrees Celsius. This results in strange rock formations as the lava cools more rapidly than usual. 

The last major eruptive phase ended in 2009, but geological activity is still common underground- the movement of rock within the magma chamber results in strong earthquakes and carbonatite lava began erupting again in 2013.

-LL

Image; Carsten Peter

Geology: More unpredictable than a hungry Jeremy Clarkson

When you first start learning about geology you are given a few basic rules to help you along the way. As you progress you begin to discover exceptions to these rules, and as you delve even deeper you simple throw the rule book out of the window. Below are some examples of how I learnt the hard way that geology is about as simple as teaching a cat to do the Macarena.

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