While absolute dates of eruptions are generally not known, it’s possible to use different techniques to figure out the relative order of events, including the superposition of lava flows, the interaction between lavas and water lakes that were probably formed during the African humid period, the color of the lavas as a function of weathering, silicic ash that has been found in lakes downwind of Afar, or the few lava flows whose absolute ages are known from historical accounts or surface-exposure dating.