 Scalloped or rippled surfaces have almost regular surface patterns, although wholly smooth blue-ice areas exist as well and the terrain even of rippled surfaces features very low aerodynamic roughness, perhaps among the lowest of all permanent natural surfaces.This is because most aerodynamic drag is caused by surface anomalies less than a centimetre long, not larger uneven forms.The occurrence of supraglacial moraines at blue-ice areas has been reported, these form when debris contained within a glacier accumulates at the surface due to melting or sublimation.