South of Lake Natron in the eastern rift valley of  North Tanzania, lies Mount Ol Doinyo Lengai (locally regarded as the  sacred Mountain of God in the Maa Language), an active volcano. At  2878meters, Mt. Ol Doinyo Lengai is the only known volcano in the world  that sometimes erupts natrocarbonatite lava, a highly fluid lava that  contains almost no silicon. Natrocarbonatite lava (most fluid lava) is  also much cooler than other lavas.  During the day most of this lava  flows look like fluid black oil. Some feel the lava flows resemble mud  like-flows.  Natrocarbonatite lava turns white when in contact with  moisture.  During rainy periods, the lava turns white almost immediately  whilst this whitening takes longer during the dry periods.

Mount Ol Doinyo Lengai also has phases of explosive  activity during which the composition of the lava may contain much more  silicate material. With this type of eruption, initial phases of the  eruption may include strong lava fountains but usually there is no fluid  lava and ash eruptions accompanied by ejection of rocks and explosions  occurs.  The two most recent eruptions of this type occurred during  1966-1967 and 2007-2008.  Almost without fail, about every seven years  Ol doinyo Lengai erupts and plumes of smoke billow out of the crater. At  other times it is possible to walk down into the crater, almost to the  edge of the molten lava flows.

Views in the north from its summit crater lies the  hot barren salt flats of Lake Natron stretch into the distance, beyond  lies the Kenyan border. The day temperatures by the lake often exceed  40°C and a few animals survive here with the flamingo making its home  here as breeding grounds, nesting on the salty surface on upraised  mounds. The view on the east is dominated by Mt Kilimanjaro and to the west the forested escarpments and hills comprising the western slopes of the Great African Rift Valley.

To the south stretches the Crater Highlands, Ngorongoro being one of the prime wildlife conservation areas in Africa.

The  ascent of Ol doinyo Lengai is demanding on account of the day time  heat, lack of water, steep and unstable slopes of ash and crumbly rocks.  An early start is recommended and the best approach is from the west  where the morning sun can be avoided for a while