Abstract
The active volcano, Oldoinyo Lengai in the Eastern Rift in northern Tanganyika consists mainly of yellow ijolitic pyroclasts with interbedded relatively thin phonolite and nephelinite lavas, overlain by nephelinitic pyroclasts and younger ashes with marked unconformity. Ejected blocks in the pyroclasts are of rocks of the urtite-jacupirangite series with or without wollastonite, wollastonitite, fenite, carbonite, biotite pyroxenite and various lavas.
Observations were made of minor activity during September–October 1960 when it was noted that soda-rich carbonate lava was extruded on the crater-floor in addition to minor emissions of ash.
From examination of the rock sequence it appears that the volcano is waning and there has been a change from earlier dominantly gas eruptions to the more recent minor emissions of lava.
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Dawson, J.B. The geology of Oldoinyo Lengai. Bull Volcanol 24, 349–387 (1962). https://doi.org/10.1007/BF02599356
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DOI: https://doi.org/10.1007/BF02599356