Peat is a deposit consisting of decayed or partially decayed humified plant remains. Peat plateaus are generally flat-topped expanses of peat, elevated above the general surface of a peatland, and containing segregated ice that may or may not extend downward into the underlying mineral soil. Some controversy exists as to whether peat plateaus and palsas are morphological variations of the same features, or genetically different. Layers or lenses of segregated ice occur especially in the mineral soil but they are thinner and less extensive in peat plateaus than in palsas. Flat-topped, somewhat raised peatlands without an icy core occur in non-permafrost environments but are not peat plateaus.