Giant fractures around Alba Patera
The Tantalus Fossae are a set of giant faults and fractures, located on the eastern side of Alba Patera in the Arcadia quadrangle. These faults are referred as grabens and the result of extensional forces associated with the uplift of the Alba Patera volcano. When the extension of the crust creates two parallel faults, the rock in between the faults drops down into the void created by the extension and forms a graben. The same features can also be found on the western side of Alba Patera, forming an incomplete ring around the volcano. Alba’s graben structures are up to 1000 km long and have a width of 2-10 km with depth ranging from 100 to 350 m.
Throughout the image we can spot numerous graben structures running roughly from the northeast to the southwest. These structures were not all created at the same time, but one after the other. This gives geologists the opportunity to reconstruct the events that created this astonishing landscape. The large impact crater in the image center for example is crosscut by some grabens which means, that it was already present before the volcano was uplifted what in consequence created the faults. The second largest, filled impact crater and many smaller ones, appear to superpose the faults and are therefore younger.