Sedimentary rocks are formed through a multi-step process involving the breakdown and transport of other rocks or organic material. The main stages include weathering (breaking down of preexisting rocks), transport (by water, wind, or ice), deposition (where sediments settle out), sedimentation (layer accumulation), compaction (weight pressing down layers), and cementation (minerals hardening the sediments together into solid rock). These processes result in rocks that are often layered, such as sandstone, limestone, shale, and chalk. Sedimentary rocks may also contain fossils trapped within the layers as they form.