Final answer:
Sedimentary rock formation involves compaction, which reduces sediment porosity by pressing grains closer, and cementation, where minerals precipitate to 'glue' these grains together, resulting in solid rock.
Step-by-step explanation:
The creation of sedimentary rock involves two main processes: compaction and cementation. Compaction occurs when sediments are buried and the weight of the overlying material presses them closer together, reducing the porosity by eliminating the spaces between the grains. Imagine pushing down on the contents of a full garbage can: this is akin to how layers of sediment are compacted over time. Cementation is closely related to compaction, as it also involves the reduction of pore spaces, but it occurs when minerals precipitate out of water being squeezed from the spaces between sediment grains. These minerals, often calcite, quartz, or pyrite, act like a glue to bind the grains together, turning loose sediments into solid rock.
Clastic sedimentary rocks form from weathered particles of pre-existing rock, transported and deposited by wind or water. Once these particles settle, compaction and cementation transform them into rocks such as sandstone and shale. This process contributes significantly to the geological cycle, and understanding it is essential for reconstructing past environments and locating natural resources like fossil fuels and minerals.