HiRISE: The side of Chasma Boreale

Chasma Boreale is the 560-kilometer long valley that cuts through the Northern Polar layered deposits of Mars. The section that it exposes show fine scaled layering and a major unconformity, where the azimuth of the beds changes markedly. This is is characteristic of the polar layered deposits. The formation of the unconformity suggests a time when the lower sediments were being eroded rather than deposited…. [More at link]