Raymond Effect

Raymond Effect is a flow effect in ice sheets, occurring at flow divides, which gives rise to disturbances in the stratigraphy, showing unusual arches or anticlines called Raymond Arches.^[1] The stratigraphy is detected by radio-echo sounding. The Raymond Effect arises from the unusual flow properties of ice, as its viscosity decreases with stress.^[2] It is of importance because it provides field evidence for the flow properties of ice.^[3] In addition, it permits dating of changes in ice flow and the establishment of changes in ice thickness.^[4] The effect was first predicted by Charles F. Raymond.^[5] Raymond Arches and the Raymond Effect have been observed at numerous other ice divides e.g. Siple Dome,^[6] Fletcher Ice Rise, Berkner Island,^[7][8] Roosevelt Island,^[4][8] and Korff Ice Rise.^[9]

Ice viscosity is stress-dependent, and in zones where the (deviatoric) stresses are low, the viscosity becomes very high. Near the base of ice-sheets, stress is proportional to the surface slope, at least when averaged over a suitable horizontal distance. At the flow divide, the surface slope is zero, and calculations show that the viscosity increases.^[5] This diverts ice flow laterally, and is the cause of the characteristic anticlines, which are in effect draped over the high viscosity area.