Compaction

Compaction is the reduction of sediment volume as burial pressure packs grains closer together. It decreases pore space and helps transform loose sediment into sedimentary rock.

Effective stress: The part of total stress carried by a material’s solid framework after subtracting pore-fluid pressure. It governs how strongly sediment grains press against one another during burial.
Sediment: Loose mineral or organic particles transported and deposited by natural processes. Compaction acts on sediment after it accumulates and is buried.
Compaction curve: A graph relating porosity or sediment thickness to burial depth or effective stress. It quantifies how a sediment’s pore space changes as burial proceeds.
Cementation: The precipitation of minerals in sediment pores that binds grains together. Unlike compaction, cementation strengthens sediment by adding minerals between grains.
Porosity: The fraction of a material’s volume occupied by voids. Compaction reduces the pore space measured by this property.
Grain size: A measure of the diameter of particles in a sediment or rock. Particle size influences pore geometry and the way grains pack.
Compaction disequilibrium: Abnormally high pore pressure caused when rapidly buried sediment cannot expel fluid quickly enough. It reveals where rapid burial has outpaced fluid escape and normal compaction.
Lithification: The processes that turn loose sediment into solid sedimentary rock. Compaction is one pathway within lithification, alongside cementation.
Pore pressure: The pressure exerted by fluid occupying pores in rock or sediment. Elevated pore pressure can support grain loads and slow compaction.
Grain sorting: The degree to which sediment grains have similar or varied sizes. Poorly sorted grains can fill one another’s pore spaces before burial.

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