Sedimentary rocks are formed through the process of sedimentation, in which sediment is deposited in layers over time and then lithified or converted into rock through the process of compaction and cementation. The sedimentation process begins with the weathering and weathering of pre-existing rocks, breaking them down into smaller fragments. These fragments, or sediments, can be transported by water, wind, ice or gravity to a place where they are deposited.
Once the sediment is deposited, it can be compacted and cemented by the weight of the overlying layers or by the precipitation of minerals from solution. The compaction process involves squeezing the sediment particles, which reduces the volume of the sediment and increases its density. The cementation process involves the bonding of sediment particles by precipitation of minerals, such as quartz or calcite, from solution.
The type of sedimentary rock that forms depends on the size and type of sediment that is deposited, as well as the conditions under which it is deposited. For example, sandstone is a clastic sedimentary rock that forms from the consolidation of sand-sized particles, while limestone is a chemical sedimentary rock that forms from the precipitation of calcite from solution.
Sedimentary rocks are often found in layers or strata, and these layers can be used to infer relative ages.