Why can rock salt flow upward through surrounding rocks over geologic time?

Rock salt flows upward through surrounding rocks because it acts as a relatively plastic material when subjected to high pressure and temperature over long periods of geologic time. This movement is primarily driven by gravitational forces, tectonic forces, or a combination of both.12

Because salt has a lower density than many consolidated sedimentary rocks, such as sandstone, it becomes gravitationally unstable when buried beneath them. In this state, the lighter salt is forced upward through the denser, more brittle overlying strata. This process, known as diapirism, often begins with the salt flowing from an undeformed bed into a rounded "pillow" before eventually piercing the overlying layers to form a plug-shaped salt dome. The ability of salt to flow is comparable to the movement of glaciers, allowing it to migrate from depths as great as 15,000 meters toward the surface.123