The term
Gravity Current Intrusion denotes the
fluid mechanics phenomenon within which a fluid intrudes with a predominantly horizontal motion into a separate stratified fluid, typically along a plane of neutral buoyancy. This behaviour distinguishes the difference between gravity current intrusions and
gravity currents, as intrusions are not restrained by a well-defined boundary surface. As with
gravity currents, intrusion flow is driven within a gravity field by density differences typically small enough to allow for the
Boussinesq approximation.