The second, which is the fact that evaporites are often less dense, or more buoyant, than the surrounding rock, which aids in its mobility and creates a Rayleigh Taylor instability. This means that the less dense substance will find a way to rise through or away from the more dense one. In salt tectonics, this occurs in three ways; the first is differential loading, where the salt flows from an area of high pressure to lower pressure, the second is gravitational spreading, where the salt spreads out laterally under its own gravitational weight, the last is thermal convection, where warmer – and thus less dense – salt rises through colder and more dense salt. This is only seen in laboratory settings due to the unlikely occurrence of salt bodies with great enough temperature variance.
