Definitions for "Active layer"
Keywords:  permafrost, thaw, freeze, frost, summer
Upper zone of soil that (in higher latitudes) experiences daily and seasonal freeze and thaw.
the soil above permafrost, that melts each year in the summer sun. The active layer is where plant roots and burrowing insects are found.
(Also called frost zone, mollisol.) That part of the soil included with the suprapermafrost layer (i.e., existing above permafrost) that usually freezes in winter and thaws in summer. Its bottom surface is the frost table, beneath which may lie permafrost or talik. The depth of the active layer varies anywhere from a few inches to several feet. Compare active permafrost.
Keywords:  slope
active slope - NR