Which process involves layers of sediment being compacted and cemented together?

The process in question refers to the formation of sedimentary rock, which occurs when layers of sediment accumulate over time. Compaction happens as the weight of the overlying materials exerts pressure on the lower layers of sediment. This pressure causes the particles within the sediment to be pressed together more tightly. As the sediments become compacted, water and minerals can fill the spaces between the particles and eventually lead to cementation, solidifying the sediment into rock. This geological process is key to understanding how sedimentary rocks are formed and the role of sediment layers in the rock cycle.

The other processes listed do not directly pertain to the compaction and cementation of sediment. Thermal metamorphism involves changes to rocks due to heat and pressure without melting. Convection refers to the movement within fluids (like mantle convection in the Earth) due to temperature differences and is unrelated to sedimentary processes. Subduction describes the process where one tectonic plate moves under another, leading to various geological phenomena, but it does not involve the compaction and cementation of sediment.