The chemically exotic lava flows of Tanzania's Ol Doinyo Lengai volcano have unusually low temperatures and viscosities. Its lava flows are not incandescent during daylight hours. The flows are usually only a few cm thick and travel only a few tens of meters from their source. This 1966 photo shows a small lava flow, only a meter wide, with miniature channels and levees (note the person at the top for scale). Ol Doinyo Lengai is Earth's only volcano known to erupt carbonatitic (sodium carbonate) lava flows in historical time.
The northern crater of Ol Doinyo Lengai is seen here in February 1980 from the summit of the volcano. The inner crater is a steep-walled pit that remained after the powerful explosive eruptions of 1966 and 1967. Three years after this photo was taken, another eruption began. Slow lava effusion completely filled in the inner crater. By December 1988, lava had overflowed the near southern crater rim, at the lower center of the photo.