Eberswalde Crater and Delta (Sub-meter-per-pixel cPROTO - detail mgnf)

Original caption:"After the sediments were deposited to form the delta, the material was further buried by other materials - probably sediments - that are no longer present. The entire package of buried material became cemented and hardened to form rock. Later, erosive processes - such as wind - stripped away the overlying rock, re-exposing the delta. Now preserved essentially as a fossil, the former floors of channels in the delta became inverted, to form ridges, by erosion. Channels can be inverted by erosion on both Earth and Mars. Usually this happens when the channel floor, or the material filling the channel, is harder to erode than the surrounding material into which the channel was cut. In some cases, the channels on Earth and Mars have been filled by lava to make them more resistant to erosion. In the case of Eberswalde, there are no lava flows; instead, the channel floors may have been rendered resistant to erosion either by being better-cemented than the surrounding material, or composed of coarser-grained sediment (such as sand and gravel as opposed to silt), or both".