What effect does high pressure have on rock deformation?

High pressure significantly influences the physical properties and behavior of rocks during deformation. Under high-pressure conditions, which are typically found at greater depths within the Earth, rocks are subjected to increased confining stress. This stress causes rocks to deform in a ductile manner rather than breaking or fracturing, which is characteristic of brittle deformation that occurs at lower pressures.

Ductile deformation allows rocks to change shape without breaking, accommodating the stress over longer periods. This behavior is facilitated by the rearrangement of minerals and the flow of material within the rock, as the high pressure enables bonds within the minerals to be more flexible. As a result, the most accurate description of the effect of high pressure on rocks is that they deform ductilely, which allows for more gradual changes in their structure under stress.

While it might seem plausible that rocks could become denser or flow easily under pressure, the primary effect described in the context of deformation processes is the emphasis on ductility, making it a defining characteristic of rock behavior under high-pressure conditions.