At the northern end the reservoir is fronted by a series of sheer cliffs on both sides where it fills a deep rift valley.
A great rift valley also extends along the ridge over most of its length.
The park is important for the conservation of afromontane fauna, especially species endemic to the western rift valley's mountains.
Because the region was a former marine strait, several areas of the rift valley are below sea level.
There are some hot springs characteristics of a rift valley to the east.
The half grabens may have alternating polarities along the rift axis, dividing the rift valley into segments.
Over the past 7 million years, a relatively complete geologic record of over 20000ft m of fossil-bearing sediment has been deposited within the park along the rift valley's western margin.
There have been recent earthquakes along the rift valley, the most recent being in 2000.
