1. Sedimentation: Sedimentary rocks are formed from layers of sediment that accumulate over time. These sediments can be sand, silt, clay, shells, or other fragments of rock.
2. Deposition: As sediment is carried by wind, water, or ice, it eventually settles and accumulates in layers. The process of deposition creates a layering effect, with the oldest sediments at the bottom and the youngest sediments on top.
3. Compaction and Cementation: Over time, the weight of the overlying layers compresses the sediments, squeezing out water and air. Minerals dissolved in the water then precipitate out and act as a cement, binding the sediment particles together to form solid rock.
This entire process means that the layers at the bottom of a sedimentary rock were deposited first and are therefore the oldest. Conversely, the layers at the top were deposited last and are the youngest.
