In geology, solifluction, also known as soil fluction or soil creep, is a type of mass wasting where waterlogge sediment slowly moves downslope over impermeable material. It can occur in any climate where the ground is saturated by water, though it is most often found in periglacial environments where the ground is permanently frozen (permafrost). A term often used for deposits formed under periglacial conditions is Gelifluction. During warm seasonal periods the surface layer (active layer) melts and literally slides across the frozen underlayer, slowly moving downslope due to frost heave that occurs normal to the slope. This type of mass wasting can occur on slopes as shallow as 0.5 degrees at a rate of between 0.5 and 15 cm per year. In Germany the solifluction deposits from the Younger Dryas are found to have a consistent thickness of 0.4–0.7 metres.