OF THE RIFT VALLEY 
439 
is cut through a lava flow, which is comparatively modern ; 
yet it was much earlier than the time of the greater Naivasha, 
and must be at least Pliocene in date. The climatic variations 
indicated by the glacial history of Kenya, and the variations 
of the lakes, were probably not due to a progressive desiccation, 
but to alternations of drier and wetter periods. Thus on the 
floor of the Endariki Valley is a deep, young gorge, now being 
cut out by floods after storms (Fig. 5) ; but this gorge is being 
made by the re-excavation of an old gorge which has been 
filled by loess — a wind-carried deposit — during some recent 
period drier than the present or than during the formation of 
the original gorge. 
With so many well-preserved craters along the Rift Valley, 
and such abundant evidence of recent volcanic activity, it is 
natural to inquire as to the chances of renewed eruptions. 
In some countries, where the craters are equally well preserved, 
the volcanoes may safely be certified as dead. Along the 
Rift Valley there are, however, symptoms that the volcanoes 
are only dormant ; for steam vents and hot springs are 
abundant. Vents discharge carbonic dioxide ; and, still more 
significant, some fumaroles still give forth sulphur, as in the 
Njorowa Gorge (Fig. 6). These may be the dying efforts of the 
volcanic forces ; they indicate the possibility — not necessarily 
the probability — of renewed eruptions. Fresh outbreaks 
depend rather on whether the earth-movements along the 
Rift Valley faults have entirely ceased. The frequent earth- 
quakes along the Rift Valley suggest that the movements are 
still in progress. I have been told of subsidences and changes 
of level since the railway survey in the neighbourhood of 
Naivasha and Kijabe ; the evidence, so far as I know, is not 
conclusive, but is sufficient to call for careful investigation. 
If the Rift Valley faulting is renewed, then fresh volcanic 
outbreaks are possible and on a much larger scale than the 
known eruptions of the Teleki Volcano, about 1888, or the 
recent outbreak on the northern peninsula projecting into 
Lake Rudolf, or the eruption of Doenyo Ngai in German 
East Africa, described by Mr. Hobley in the Society’s 
Journal. 1 
1 Vol. VI., No. 13, pp. 339-43. 
