Reports uranium-series ages for the hydrothermal deposits of past geothermal activity from several Quaternary volcanic centers in the northern Kenya rift valley. High-temperature continental geothermal systems; U-series data and calculated ages for geothermal silica samples; Extensive silica deposits occurring on the upper flanks and summit area of Namarunu; Correspondence between the uranium-series ages and the periods of high lake level within the rift; More.