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

Anticline

In structural geology, an anticline is a fold that is convex up and has its oldest beds at its core. The term is not to be confused with antiform, which is a purely descriptive term for any fold that is convex up. Therefore if age relationships In structural geology, an anticline is a fold that is...

  called Raymond Arches. The stratigraphy is detected by radio-echo sounding. The Raymond effect arises from the unusual flow properties of ice

Ice

Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...

. It is of importance because it provides field evidence for the flow properties of ice. In addition, it permits dating of changes in ice flow and the establishment of changes in ice thickness . The effect was first predicted by Charles F. Raymond.

Ice viscosity

Viscosity

Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher 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, implying that near the base of the ice-sheet, the viscosity increases. This diverts ice flow laterally, and is the cause of the characteristic anticlines, which are in effect draped over the high viscosity area.