What is the increase in volume of rocks due to elastic and nonelastic changes during deformation called?

The increase in volume of rocks due to elastic and nonelastic changes during deformation is referred to as dilatancy. This term describes the phenomenon where a material, when subjected to stress, can expand in volume as a result of the rearrangement of its internal structure. In geological terms, dilatancy often occurs in the context of rock deformation under stress conditions, where the rocks may initially deform elastically before transitioning to non-elastic behavior, typically leading to volume changes.

Dilatancy is particularly important in understanding phenomena such as faulting and the mechanics of earthquakes. During the buildup of strain in rocks, some may exhibit elastic behavior, recovering their original volume when stress is relieved. However, upon reaching certain stress thresholds, they may undergo irreversible changes, leading to an increase in volume due to fracturing, jointing, or other rearrangements of the grain structure.

The other options refer to related but distinct concepts. Differential settlement pertains to uneven sinking or shifting of a foundation or structure, often due to variations in soil load-bearing capacity. Elastic rebound refers to the rapid release of energy after strain accumulation, resulting in an earthquake, but does not specifically indicate a change in volume during deformation. Fault creep describes a gradual, continuous movement along a fault line without