Control of Gravitational Potential Energy on the Distribution of Off-Rift Volcanic Activity in the Turkana Depression, East African Rift

The distribution and alignment of volcanism in continental rifts is controlled by regional extensional stresses modulated by several factors such as structural inheritance, volcano edifice loading, and rift architecture. These interactions result in complex characteristics of rift-related volcanic features, which may be difficult to interpret considering the different controlling processes. The Turkana Depression (East Africa) exemplifies these complexities, showing an anomalous location of volcanic fields (outside the area of ongoing extension), with variable vent orientation. We analyze vent distribution in the Turkana Depression and calculate the stresses resulting from Gravitational Potential Energy (GPE). Our results show that West to East variations in topography and (subordinately) crustal thickness give rise to extensional GPE-related stresses East of Lake Turkana, where recent off-rift volcanism is localized. Within each different volcanic field, local GPE-related stresses control the arrangement of volcanic vents, which therefore do not respond to the regional (plate motion-driven) stress field.