Column of lapilli and ash emanating from the 2007-2008 eruption of Oldoinyo Lengai volcano, a carbonatite-phonolite volcano in the Eastern rift focus site of GeoPRISMS Rift Initiation and Evolution program. The eruption was triggered by a fault and dike intrusion event on the nearby Gelai basaltic shield volcano. This unusual volcano formed along the hanging wall of the Natron border fault, which developed during the last 5 My. Gas emissions and nutrient-rich ash-fall deposits create a unique environment for migrating herds of wildebeest and zebra, and they document the time-space details of rift evolution. Photo credit: Cynthia Ebinger (University of Rochester)