Ceraunius Fossae

This VIS image shows part of Cerunius Fossae. The linear depressions are fault bounded features called graben. Graben are formed by extension of the crust and faulting. When large amounts of pressure or tension are applied to rocks on timescales that are fast enough that the rock cannot respond by deforming, the rock breaks along faults. In the case of a graben, two parallel faults are formed by extension of the crust and the rock in between the faults drops downward into the space created by the extension. The largest graben in this THEMIS image trends from almost north/south. Because the faults defining the graben are formed perpendicular to the direction of the applied stress, we know that extensional forces were pulling the crust apart in the east/west direction. Ceraunius Fossae is located on the southern part of Alba Mons and is 1166km (724 miles) long.