Mountain Trekking Ol Doinyo Lengai

Ol Doinyo Lengai, a volcanic mountain, altitude 2886 meters (9524 feet), towers above the East African Rift Valley in northern Tanzania. The white deposits on the mountain surface are weathered natrocarbonatite ash and lava. To the lower left of the white cone is a narrow white streak formed by lava that has occasionally flowed out of the crater. The trek to the crater (1700m or 5600 ft). is an exceptionally demanding one.

Ol Doinyo Lengai is a unique and extremely fascinating volcano that is located in the East African Rift valley, about 120 km NW of Arusha, Tanzania. It is the only volcano in the world that throws up natrocarbonatite lava, a highly fluid lava that contains almost no silicon. Natrocarbonatite lava is also much cooler than other lavas, being only about 950 degrees F (510 degrees C) compared to the temperatures over 2000 degrees F (1100 degrees C) for basaltic lavas.

Lava with a low gas content can flow like a whitewater stream, and actually has a viscosity similar to that of water. Natrocarbonatite lava glows orange at night, but is not nearly as bright as silicon-based lavas since it is not as hot.

During the day it is not incandescent; most flows look like very fluid black oil, or brown foam, depending on the gas content. In the past, some visitors to the crater believed they were seeing mud flows. Most newly solidified lava is black and contains crystals that sparkle brightly in the sun. There are also small flows known as "squeeze-ups" that are light gray when they flow and solidify.

Contact with moisture rapidly turns natrocarbonatite lava white because of chemical reactions that occur when the lava absorbs water. Eventually the water absorption process turns lava flows into brown powder. In dry weather the whitening of flows happens over a period of a few days to a couple of weeks, depending on the thickness of the flow. In rainy weather the lava surface turns white immediately. In parts of the crater that have been inactive for several months, the ground is light brown/white and so soft that one's feet sinks into it when walking.

An early start is necessary with guides and porters through farmland, forest, scrub and grassland. It is advisable to begin the climb at the foot of the mountain on the western slope. This ideal place is 3 hours walk from Katesh township. After spending the night in the village you climb and have more time to enjoy the scenery. Summiteers usually receive certificates.