In mechanics and geodynamics, a critical taper is the equilibrium angle made by the far end of a wedge-shaped agglomeration of material that is being pushed by the near end. The angle of the critical taper is a function of the material properties within the wedge, pore fluid pressure, and strength of the fault (or décollement) along the base of the wedge.
In geodynamics the concept is used to explain tectonic observations in accretionary wedges. Every wedge has a certain "critical angle", which depends on its material properties and the forces at work. This angle is determined by the ease by which internal deformation versus slip along the basal fault (décollement) occurs. If the wedge deforms more easily internally than along the décollement, material will pile up and the wedge will reach a steeper critical taper until such a point as the high angle of the taper makes internal deformation more difficult than sliding along the base. If the basal décollement deforms more easily than th