How do salt domes form beneath sedimentary rock layers?

Salt domes form through the movement of relatively plastic materials, such as rock salt, which flow due to gravitational or tectonic forces.12

The process typically follows this sequence:

• Deposition and Burial: Thick layers of salt are deposited and subsequently buried by denser sedimentary strata. Because the salt is less dense than the overlying rock, the configuration becomes gravitationally unstable.12
• Pillow Formation: The salt begins to flow from its original bed toward a central point, creating a rounded salt pillow. As salt accumulates, it domes the overlying strata, while the area of origin subsides to form a rim syncline.1
• Piercement: As the salt continues to flow, it exerts tension on the overlying rock, causing fractures and faults. Eventually, the salt pierces through the center of the domed area, forming a plug-shaped mass.1
• Upward Growth: The salt mass continues to rise, often maintaining its position near the surface as additional strata are deposited.1

This upward migration is driven by the salt's ability to flow under high pressure and temperature over long periods.1