Two volcanic centres are reported, a southern one (Pic Chongui, , with a breached crater to the NW, and a northern centre (Mont M'Tsapéré, ) with a breached crater to the south-east. Mont Bénara is on the curving ridge between these two peaks, approximately at the contact point of the two structures. Volcanic activity started about 7.7 million years ago in the south, ceasing about 2.7 million years ago. In the north, activity started about 4.7 million years ago and lasted until about 1.4 million years ago. Both centres had several phases of activity. The most recent age reported for an ash band is 7000 year BP.