The Acheron Fossae graben system has a typical "Horst and Graben" morphology formed by extensional crustal deformation in the Noachian period 3.7-3.9 billion years ago. Several parallel faults (graben) have formed caused by the downward movement of the crust relative to the blocks on either side (horst). These diverging movements of crustal blocks indicate tensional forces in the crust during the time when Mars was more active. During geological evolution the graben have been filled with different material such as glacial and volcanic deposits.